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2020 Volume 31 Issue 10
2020, 31(10): 2525-2538
doi: 10.1016/j.cclet.2020.05.011
Abstract:
From emerging pollutants to emerged threat, researchers are continuously looking for promising technologies for wastewater treatment. Adsorption has been identified as the most convenient approach for treating wastewater at low-cost and with high-efficiency. Recently, graphene and its derivatives have gained heightened attention as novel adsorbents because of their unique molecular structure and outstanding physicochemical properties. Heavy metals, dyes, polycyclic aromatic hydrocarbons (PAHs) and other pollutants, which are widely concerned recently, all show different adsorption behaviors. Numerous functional groups, resonating and delocalized π-electron system of graphene derivatives lead to the formation of various adsorptive interactions i.e., π-π interactions, electrostatic interactions, H-bonding, etc. with these venomous pollutants, and quarantine them in solution. The pristine form of graphene subsidiaries tends to exhibit low sorption efficiency due to high propensity of agglomeration, lack of selectivity, hydrophobicity and difficulty in phase separation after treatment. Therefore, designing of efficient graphene composites through the surface modification with numerous functional groups, polymers or nanoparticles is an ongoing challenge. Complex graphene composites are increasingly reported, but the fate of pollutants and adsorption mechanisms are still far to be fully clarified. This review summarizes the recent progresses in the application of graphene-based adsorbents for eliminating a wide range of organic and inorganic pollutants from wastewater. A critical explanation is provided on the synthesis of graphene adsorbents, systematic adsorption and desorption mechanisms along with their pollutant removal performances under different experimental conditions. A brief perspective on upcoming research needs and challenges involved in the designing of high-quality graphene-based adsorbents are highlighted.
From emerging pollutants to emerged threat, researchers are continuously looking for promising technologies for wastewater treatment. Adsorption has been identified as the most convenient approach for treating wastewater at low-cost and with high-efficiency. Recently, graphene and its derivatives have gained heightened attention as novel adsorbents because of their unique molecular structure and outstanding physicochemical properties. Heavy metals, dyes, polycyclic aromatic hydrocarbons (PAHs) and other pollutants, which are widely concerned recently, all show different adsorption behaviors. Numerous functional groups, resonating and delocalized π-electron system of graphene derivatives lead to the formation of various adsorptive interactions i.e., π-π interactions, electrostatic interactions, H-bonding, etc. with these venomous pollutants, and quarantine them in solution. The pristine form of graphene subsidiaries tends to exhibit low sorption efficiency due to high propensity of agglomeration, lack of selectivity, hydrophobicity and difficulty in phase separation after treatment. Therefore, designing of efficient graphene composites through the surface modification with numerous functional groups, polymers or nanoparticles is an ongoing challenge. Complex graphene composites are increasingly reported, but the fate of pollutants and adsorption mechanisms are still far to be fully clarified. This review summarizes the recent progresses in the application of graphene-based adsorbents for eliminating a wide range of organic and inorganic pollutants from wastewater. A critical explanation is provided on the synthesis of graphene adsorbents, systematic adsorption and desorption mechanisms along with their pollutant removal performances under different experimental conditions. A brief perspective on upcoming research needs and challenges involved in the designing of high-quality graphene-based adsorbents are highlighted.
2020, 31(10): 2539-2548
doi: 10.1016/j.cclet.2020.03.011
Abstract:
Global climate change, growing population, and environmental pollution underscore the need for a greater focus on providing advanced water treatment technologies. Although electrochemical based-processes are becoming promising solutions, they still face challenges owing to mass transport and upscaling which hinder the exploitation of this technology. Electrode design and reactor configuration are key factors for achieving operational improvements. The electroactive membrane has proven to be a breakthrough technology integrating electrochemistry and membrane separation with an enhanced mass transport by convection. In this review article, we discuss recent progress in environmental applications of electroactive membranes with particular focus on those composed of carbon nanotubes (CNT) due to their intriguing physicochemical properties. Their applications in degradation of refractory contaminants, detoxification and sequestration of toxic heavy metal ions, and membrane fouling alleviations are systematically reviewed. We then discuss the existing limitations and opportunities for future research. The development of advanced electroactive systems depends on interdisciplinary collaborations in the areas of materials, electrochemistry, membrane development, and environmental sciences.
Global climate change, growing population, and environmental pollution underscore the need for a greater focus on providing advanced water treatment technologies. Although electrochemical based-processes are becoming promising solutions, they still face challenges owing to mass transport and upscaling which hinder the exploitation of this technology. Electrode design and reactor configuration are key factors for achieving operational improvements. The electroactive membrane has proven to be a breakthrough technology integrating electrochemistry and membrane separation with an enhanced mass transport by convection. In this review article, we discuss recent progress in environmental applications of electroactive membranes with particular focus on those composed of carbon nanotubes (CNT) due to their intriguing physicochemical properties. Their applications in degradation of refractory contaminants, detoxification and sequestration of toxic heavy metal ions, and membrane fouling alleviations are systematically reviewed. We then discuss the existing limitations and opportunities for future research. The development of advanced electroactive systems depends on interdisciplinary collaborations in the areas of materials, electrochemistry, membrane development, and environmental sciences.
2020, 31(10): 2549-2555
doi: 10.1016/j.cclet.2020.04.012
Abstract:
The selective catalytic reduction (SCR) of NOx by NH3 is one of the most mature technologies for NOx treatment. Catalysts are the main factors affecting denitrification efficiency. Zeolites as low-temperature NH3-SCR catalysts have been extensively studied in the past few years. In this work, the mechanism of zeolites for NH3-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared. The effects of sulfur and water poisoning on zeolite catalysts in NH3-SCR reaction were also analyzed. Several ways to address the problems in low-temperature NH3-SCR reaction were discussed. Hopefully, this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.
The selective catalytic reduction (SCR) of NOx by NH3 is one of the most mature technologies for NOx treatment. Catalysts are the main factors affecting denitrification efficiency. Zeolites as low-temperature NH3-SCR catalysts have been extensively studied in the past few years. In this work, the mechanism of zeolites for NH3-SCR reaction was reviewed and the denitrification performances of zeolite catalysts prepared by different methods were compared. The effects of sulfur and water poisoning on zeolite catalysts in NH3-SCR reaction were also analyzed. Several ways to address the problems in low-temperature NH3-SCR reaction were discussed. Hopefully, this review could provide a fundamental understanding of SCR reaction on zeolite catalysts and pave the way toward similar studies to realize its commercial applications.
2020, 31(10): 2556-2566
doi: 10.1016/j.cclet.2020.08.036
Abstract:
Photocatalyst is the most widespread method in advanced oxidation technologies, but due to the photo-induced electron combine easily with hole and the wavelength of adsorption is limited which will affect some practical applications. Carbon quantum dots (CQDs) is non-toxic and harmless green materials, it has the ability to improve the photocatalytic effect which is attributed to its good electrical and optical properties. Their up-conversion effect, photosensitization and electrical conductivity are assistants which help promote the photocatalytic effect in environmental applications. The key mechanisms of CQDs to improve photocatalysis can be roughly divided into three categories: 1) Up-conversion effect converts the incident light into the emitted light with high energy to solve the problem which is the light absorption range; 2) CQDs act as a photosensitizer instead of valence band to provide electrons to the conduction band of semiconductor; 3) CQDs can be used as the internal or external electronic conductor in materials to alleviate the trend of electron and hole separation. However, CQDs and CQDs-based photocatalysts have different views to solve environmental problems, so it is necessary to integrate different views. Therefore, this review is mainly aimed at the recent researches about the preparation processes of CQD, CQDs-based photocatalysts, and their ability to remove environmental pollutants, with a special emphasis on the mechanism for depredating pollutants. Furthermore, this paper analyzes and discusses the prospects and challenges of CQDs in the environmental field.
Photocatalyst is the most widespread method in advanced oxidation technologies, but due to the photo-induced electron combine easily with hole and the wavelength of adsorption is limited which will affect some practical applications. Carbon quantum dots (CQDs) is non-toxic and harmless green materials, it has the ability to improve the photocatalytic effect which is attributed to its good electrical and optical properties. Their up-conversion effect, photosensitization and electrical conductivity are assistants which help promote the photocatalytic effect in environmental applications. The key mechanisms of CQDs to improve photocatalysis can be roughly divided into three categories: 1) Up-conversion effect converts the incident light into the emitted light with high energy to solve the problem which is the light absorption range; 2) CQDs act as a photosensitizer instead of valence band to provide electrons to the conduction band of semiconductor; 3) CQDs can be used as the internal or external electronic conductor in materials to alleviate the trend of electron and hole separation. However, CQDs and CQDs-based photocatalysts have different views to solve environmental problems, so it is necessary to integrate different views. Therefore, this review is mainly aimed at the recent researches about the preparation processes of CQD, CQDs-based photocatalysts, and their ability to remove environmental pollutants, with a special emphasis on the mechanism for depredating pollutants. Furthermore, this paper analyzes and discusses the prospects and challenges of CQDs in the environmental field.
2020, 31(10): 2567-2574
doi: 10.1016/j.cclet.2020.07.036
Abstract:
Sulfur-driven autotrophic denitrification (SDAD), a process suited for the treatment of nitrogen and sulfur-polluted wastewater without extra supplement of organic carbon, is a promising biological nitrogen removal process. However, the SDAD process was affected by many factors such as various electron donors, organic carbon and exogenous substances (e.g., antibiotics and heavy metal), which prevent further application. Thus, we conducted a detailed review of previous studies on such influence factors and its current application. Besides, a comparative analysis was adopted to recognize the current challenges and future needs for feasible application, so as to ultimately perfect the SDAD process and extend its application scope.
Sulfur-driven autotrophic denitrification (SDAD), a process suited for the treatment of nitrogen and sulfur-polluted wastewater without extra supplement of organic carbon, is a promising biological nitrogen removal process. However, the SDAD process was affected by many factors such as various electron donors, organic carbon and exogenous substances (e.g., antibiotics and heavy metal), which prevent further application. Thus, we conducted a detailed review of previous studies on such influence factors and its current application. Besides, a comparative analysis was adopted to recognize the current challenges and future needs for feasible application, so as to ultimately perfect the SDAD process and extend its application scope.
2020, 31(10): 2575-2582
doi: 10.1016/j.cclet.2020.07.050
Abstract:
Heavy metal complexes with high mobility are widely distributed in wastewater from modern industries, which are more stable and refractory than free heavy metal ions. Their removals from wastewater draw increasing attentions and various technologies have been developed, among which advanced oxidation processes (AOPs) are more effectively and promising. Progresses on five representative types of AOPs, including Fenton (like) oxidation, electrochemical oxidation, photocatalytic oxidation, ozonation and discharge plasma oxidation for heavy metal complexes degradation are summarized in this review. Their rationales, advantages, applications, challenges and prospects are introduced independently. Combi-nations among these AOPs, such as electrochemical Fenton oxidation and photoelectrocatalytic oxidation, are also comprehensively highlighted. Future efforts should be made to reduce acid requirement and scale up for practical applications of AOPs for heavy metal complex degradation efficiently and cost-effectively.
Heavy metal complexes with high mobility are widely distributed in wastewater from modern industries, which are more stable and refractory than free heavy metal ions. Their removals from wastewater draw increasing attentions and various technologies have been developed, among which advanced oxidation processes (AOPs) are more effectively and promising. Progresses on five representative types of AOPs, including Fenton (like) oxidation, electrochemical oxidation, photocatalytic oxidation, ozonation and discharge plasma oxidation for heavy metal complexes degradation are summarized in this review. Their rationales, advantages, applications, challenges and prospects are introduced independently. Combi-nations among these AOPs, such as electrochemical Fenton oxidation and photoelectrocatalytic oxidation, are also comprehensively highlighted. Future efforts should be made to reduce acid requirement and scale up for practical applications of AOPs for heavy metal complex degradation efficiently and cost-effectively.
2020, 31(10): 2583-2590
doi: 10.1016/j.cclet.2020.08.018
Abstract:
Bi/semiconductor photocatalysts have extensively been applied in the production of hydrogen, CO2 reduction and environmental remediation in recent years. This short review summarizes the role of Bi metal as a plasma photocatalyst and cocatalyst. As a cocatalyst, Bi metal can be electron/hole trappers, charge transfer mediators, or oxygen vacancy coordinators. In addition, the preparation methods of the Bi/semiconductor photocatalysts are also reviewed. Challenges and future research directions related to Bi/semiconductor photocatalysts are discussed and summarized, including the use of advanced characterization techniques to refine the reaction mechanism, the difficulties of preparing Bi single atom catalyst, and the improvement of the reduction ability of Bi-based photocatalysts. This review helps understand the reaction mechanisms of the composite photocatalytic systems containing Bi metal and proposes new perspectives for designing the photocatalysts which can control air pollution via a reductive process.
Bi/semiconductor photocatalysts have extensively been applied in the production of hydrogen, CO2 reduction and environmental remediation in recent years. This short review summarizes the role of Bi metal as a plasma photocatalyst and cocatalyst. As a cocatalyst, Bi metal can be electron/hole trappers, charge transfer mediators, or oxygen vacancy coordinators. In addition, the preparation methods of the Bi/semiconductor photocatalysts are also reviewed. Challenges and future research directions related to Bi/semiconductor photocatalysts are discussed and summarized, including the use of advanced characterization techniques to refine the reaction mechanism, the difficulties of preparing Bi single atom catalyst, and the improvement of the reduction ability of Bi-based photocatalysts. This review helps understand the reaction mechanisms of the composite photocatalytic systems containing Bi metal and proposes new perspectives for designing the photocatalysts which can control air pollution via a reductive process.
2020, 31(10): 2591-2602
doi: 10.1016/j.cclet.2020.08.019
Abstract:
Algae are potential feedstock for the production of bioenergy and valuable chemicals. After the extraction of specific value-added products, algal residues can be further converted into biogas, biofuel, and biochar through various thermochemical treatments such as conventional pyrolysis, microwave pyrolysis, hydrothermal conversion, and torrefaction. The compositions and physicochemical characteristics of algal biochar that determine the subsequent applications are comprehensively discussed. Algal biochar carbonized at high-temperature showed remarkable performance for use as supercapacitors, CO2 adsorbents, and persulfate activation, due to its graphitic carbon structure, high electron transport, and specific surface area. The algal biochar produced by pyrolysis at moderate-temperature exhibits high performance for adsorption of pollutants due to combination of miscellaneous functional groups and porous structures, whereas coal fuel can be obtained from algae via torrefaction by pyrolysis at relatively low-temperature. The aim of this review is to study the production of algal biochar in a cost-effective and environmental-friendly method and to reduce the environmental pollution associated with bioenergy generation, achieving zero emission energy production.
Algae are potential feedstock for the production of bioenergy and valuable chemicals. After the extraction of specific value-added products, algal residues can be further converted into biogas, biofuel, and biochar through various thermochemical treatments such as conventional pyrolysis, microwave pyrolysis, hydrothermal conversion, and torrefaction. The compositions and physicochemical characteristics of algal biochar that determine the subsequent applications are comprehensively discussed. Algal biochar carbonized at high-temperature showed remarkable performance for use as supercapacitors, CO2 adsorbents, and persulfate activation, due to its graphitic carbon structure, high electron transport, and specific surface area. The algal biochar produced by pyrolysis at moderate-temperature exhibits high performance for adsorption of pollutants due to combination of miscellaneous functional groups and porous structures, whereas coal fuel can be obtained from algae via torrefaction by pyrolysis at relatively low-temperature. The aim of this review is to study the production of algal biochar in a cost-effective and environmental-friendly method and to reduce the environmental pollution associated with bioenergy generation, achieving zero emission energy production.
2020, 31(10): 2603-2613
doi: 10.1016/j.cclet.2020.04.057
Abstract:
Antibiotic resistance genes (ARGs) in aquatic environments, which seriously endanger human health and ecological safety, have become a worldwide concern due to their easy diffusion and proliferation. Wastewater treatment plants (WWTPs), which receive resistant bacteria and ARGs from a wide variety of sources (i.e., livestock farms, hospitals, antibiotic manufactures, and households), are regarded as important emission sources of aquatic ARGs. This review presents a quantitative profile of the majority sources of ARGs in the influent of WWTPs and discusses the potential factors that affect the concentration distribution of ARGs. Specifically, a noteworthy existence of ARGs, which ranged from 1E + 05 to 1E + 11 copies/mL, was detected in livestock breeding wastewater, and household wastewater (caused by the unlimited utilization of antibiotics) was determined to be the predominant contributor of ARGs in WWTPs. We summarized the selective pressure on ARGs and determined the positive correlation of the concentration of ARGs and the existence of many containments, including antibiotics, heavy metals (Zn and Cu were frequently reported), quaternary ammonium compounds, etc. In the last section, physical, chemical, and biological treatments for the removal of ARGs and their effluent in WWTPs are discussed and prospective future studies are summarized.
Antibiotic resistance genes (ARGs) in aquatic environments, which seriously endanger human health and ecological safety, have become a worldwide concern due to their easy diffusion and proliferation. Wastewater treatment plants (WWTPs), which receive resistant bacteria and ARGs from a wide variety of sources (i.e., livestock farms, hospitals, antibiotic manufactures, and households), are regarded as important emission sources of aquatic ARGs. This review presents a quantitative profile of the majority sources of ARGs in the influent of WWTPs and discusses the potential factors that affect the concentration distribution of ARGs. Specifically, a noteworthy existence of ARGs, which ranged from 1E + 05 to 1E + 11 copies/mL, was detected in livestock breeding wastewater, and household wastewater (caused by the unlimited utilization of antibiotics) was determined to be the predominant contributor of ARGs in WWTPs. We summarized the selective pressure on ARGs and determined the positive correlation of the concentration of ARGs and the existence of many containments, including antibiotics, heavy metals (Zn and Cu were frequently reported), quaternary ammonium compounds, etc. In the last section, physical, chemical, and biological treatments for the removal of ARGs and their effluent in WWTPs are discussed and prospective future studies are summarized.
2020, 31(10): 2614-2618
doi: 10.1016/j.cclet.2020.08.014
Abstract:
Activated persulfate oxidation is an emerging advanced oxidation process for organic pollutant degradation. Own to different molecular structures and oxidation potentials, persulfate (PDS) and peroxymonosulfate (PMS) may show different degradation performances due to various catalytic mechanisms even by the same catalysts. In this study, the nitrogen-doped mesoporous carbon (N-OMC) was applied to activate PDS and PMS for degrading a model organic pollutant phenol to reveal their activation mechanisms. Results show that both PDS and PMS could be efficiently activated by N-OMC. The degradation of phenol fitted well with pseudo-first-order kinetics, whose kinetic constants increased with the increase of pH, PDS/PMS dosage, and N-OMC dosage. Based on quenching experiments and electron spin resonance spin-trapping technique, the N-OMC was found to activate PDS and PMS via non-radical process of electron transfer and singlet oxygen formation, respectively, instead of the commonly observed radical process. This work will be useful to understand the activation processes of PDS and PMS, and benefit for the development of catalysts for pollutant degradation.
Activated persulfate oxidation is an emerging advanced oxidation process for organic pollutant degradation. Own to different molecular structures and oxidation potentials, persulfate (PDS) and peroxymonosulfate (PMS) may show different degradation performances due to various catalytic mechanisms even by the same catalysts. In this study, the nitrogen-doped mesoporous carbon (N-OMC) was applied to activate PDS and PMS for degrading a model organic pollutant phenol to reveal their activation mechanisms. Results show that both PDS and PMS could be efficiently activated by N-OMC. The degradation of phenol fitted well with pseudo-first-order kinetics, whose kinetic constants increased with the increase of pH, PDS/PMS dosage, and N-OMC dosage. Based on quenching experiments and electron spin resonance spin-trapping technique, the N-OMC was found to activate PDS and PMS via non-radical process of electron transfer and singlet oxygen formation, respectively, instead of the commonly observed radical process. This work will be useful to understand the activation processes of PDS and PMS, and benefit for the development of catalysts for pollutant degradation.
2020, 31(10): 2619-2622
doi: 10.1016/j.cclet.2020.01.038
Abstract:
Developing an effective and mechanically durable biomimetic membrane for the separation of highly emulsified aqueous oil is significant but challenging owing to its low water flux and serious membrane fouling. In this work, a biomimetic membrane with superhydrophobicity and superoleophilicity was rationally developed via co-electrospinning of polysulfonamide/polyacrylonitrile (PSA/PAN) emulsion solution, followed by decorating of α-Fe2O3 nanowire onto the membrane surface to create membrane roughness, and grafting of 1H, 1H, 2H, 2H-perfluorododecyltrichlorosilane (FTCS) to lower membrane surface free energy. Benefiting from the nanowire-wrapped rough membrane structure and the low surface free energy FTCS, the resultant membrane showed superhydrophobicity with a high water contact angle (WCA) of 156°, superoleophilicity with a low oil contact angle (OCA) of 0°, which can separate the highly emulsified aqueous oil with an ultrahigh permeation flux over 7000 L m-2 h-1 and high separation efficiency of about 99%. Significantly, the biomimetic membrane also displayed robust stability for long-term separation owing to its advantage of antifouling property, showing great potential applications in large-scale aqueous oil treatment.
Developing an effective and mechanically durable biomimetic membrane for the separation of highly emulsified aqueous oil is significant but challenging owing to its low water flux and serious membrane fouling. In this work, a biomimetic membrane with superhydrophobicity and superoleophilicity was rationally developed via co-electrospinning of polysulfonamide/polyacrylonitrile (PSA/PAN) emulsion solution, followed by decorating of α-Fe2O3 nanowire onto the membrane surface to create membrane roughness, and grafting of 1H, 1H, 2H, 2H-perfluorododecyltrichlorosilane (FTCS) to lower membrane surface free energy. Benefiting from the nanowire-wrapped rough membrane structure and the low surface free energy FTCS, the resultant membrane showed superhydrophobicity with a high water contact angle (WCA) of 156°, superoleophilicity with a low oil contact angle (OCA) of 0°, which can separate the highly emulsified aqueous oil with an ultrahigh permeation flux over 7000 L m-2 h-1 and high separation efficiency of about 99%. Significantly, the biomimetic membrane also displayed robust stability for long-term separation owing to its advantage of antifouling property, showing great potential applications in large-scale aqueous oil treatment.
2020, 31(10): 2623-2626
doi: 10.1016/j.cclet.2020.02.008
Abstract:
At present, the assessment of photooxidation system mainly focuses on the photodegradation efficiency of target pollutant, lacking of the toxicity assessment in the photocatalysis process. Here, photodecomposition of bisphenol A (BPA) was used to investigate the performance of several cyclodextrin modified photocatalysts. Moreover, the comprehensive toxicity changes of BPA under different photocatalytic oxidation conditions were conducted. The β-cyclodextrin (β-CD) modified photocatalyst, including titanium dioxide (CM-β-CD-TiO2), carbon nitride (CM-β-CD-C3N4) and cadmium sulfide (SH-β-CD-AM/CdS) exhibit high degradation rate and mineralization efficiency of BPA. The highest total organic carbon (TOC) removal of BPA observed in the oxidation system of SH-β-CD-AM/CdS nanoreactor (73.4%). The main oxidation intermediates in these systems were detected, and the comprehension toxicity of BPA and its oxidation intermediates in different system were compared by toxicity estimation software tool (T.E.S.T.) based on quantitative structure-activity relationship (QSAR) prediction. The results show that β-CD can facilitate the photodecomposition of the target contaminant. However, many oxidation intermediates with high comprehensive toxicity, even in the oxidation system with high BPA removal, can still be detected. Therefore, not only decomposition of target contaminant but also the comprehensive toxicity of oxidation intermediates should be regarded as index to evaluate a photocatalysis technology.
At present, the assessment of photooxidation system mainly focuses on the photodegradation efficiency of target pollutant, lacking of the toxicity assessment in the photocatalysis process. Here, photodecomposition of bisphenol A (BPA) was used to investigate the performance of several cyclodextrin modified photocatalysts. Moreover, the comprehensive toxicity changes of BPA under different photocatalytic oxidation conditions were conducted. The β-cyclodextrin (β-CD) modified photocatalyst, including titanium dioxide (CM-β-CD-TiO2), carbon nitride (CM-β-CD-C3N4) and cadmium sulfide (SH-β-CD-AM/CdS) exhibit high degradation rate and mineralization efficiency of BPA. The highest total organic carbon (TOC) removal of BPA observed in the oxidation system of SH-β-CD-AM/CdS nanoreactor (73.4%). The main oxidation intermediates in these systems were detected, and the comprehension toxicity of BPA and its oxidation intermediates in different system were compared by toxicity estimation software tool (T.E.S.T.) based on quantitative structure-activity relationship (QSAR) prediction. The results show that β-CD can facilitate the photodecomposition of the target contaminant. However, many oxidation intermediates with high comprehensive toxicity, even in the oxidation system with high BPA removal, can still be detected. Therefore, not only decomposition of target contaminant but also the comprehensive toxicity of oxidation intermediates should be regarded as index to evaluate a photocatalysis technology.
2020, 31(10): 2627-2633
doi: 10.1016/j.cclet.2020.05.031
Abstract:
Hydrogenation of CO2 to value-added chemicals has attracted much attention all through the world. In2O3 with cubic bixbyite-type (denoted as c-In2O3) is well known for its high CO2 hydrogenation activity and CH3OH selectivity at high temperature. However, the other structure of In2O3 with rhombohedral corundum-type (denoted as rh-In2O3) rarely been investigated as catalyst. Herein, c-In2O3 and rh-In2O3 were prepared and comparatively studied for CO2 hydrogenation. The results indicated that c-In2O3 showed higher CO2 conversion activity than rh-In2O3 due to the impressive reducibility and reactivity. Whereas rh-In2O3 had higher CH3OH selectivity due to weaker CH3OH and stronger CO adsorption on rh-In2O3. Although c-In2O3 and rh-In2O3 catalysts showed different CO2 hydrogenation performance, in-situ diffuse reflectance infrared Fourier transform spectroscopy showed CO2 can be reduced to CO through redox cycling and hydrogenation to CH3OH through formate path.
Hydrogenation of CO2 to value-added chemicals has attracted much attention all through the world. In2O3 with cubic bixbyite-type (denoted as c-In2O3) is well known for its high CO2 hydrogenation activity and CH3OH selectivity at high temperature. However, the other structure of In2O3 with rhombohedral corundum-type (denoted as rh-In2O3) rarely been investigated as catalyst. Herein, c-In2O3 and rh-In2O3 were prepared and comparatively studied for CO2 hydrogenation. The results indicated that c-In2O3 showed higher CO2 conversion activity than rh-In2O3 due to the impressive reducibility and reactivity. Whereas rh-In2O3 had higher CH3OH selectivity due to weaker CH3OH and stronger CO adsorption on rh-In2O3. Although c-In2O3 and rh-In2O3 catalysts showed different CO2 hydrogenation performance, in-situ diffuse reflectance infrared Fourier transform spectroscopy showed CO2 can be reduced to CO through redox cycling and hydrogenation to CH3OH through formate path.
2020, 31(10): 2634-2640
doi: 10.1016/j.cclet.2020.08.007
Abstract:
It is generally recognized that the formation and accumulation of iron oxides on the surface of zero-valent iron (Fe0) resulting in significant decrease of contaminant degradation rates during the long-term reactions. However, in this study, we found that the removal efficiencies of p-nitrophenol (PNP) by micro zero-valent iron (mFe0) could maintain at the satisfactory level in the process of continuous reactions (20 cycles). The removal rate constant (0.1779 min-1) of the 5th cycle was 6.74 times higher than that of the 1st reaction (0.0264 min-1), even the 20th cycle (0.0371 min-1) was higher than that of the 1st reaction. Interestingly, almost no dissolved iron was detected in the solution, and the total iron concentrations decreased dramatically with the process of continuous reactions. The results of scanning electron microscope and energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD) revealed that the structure and composition of corrosion products change from amorphous to highly crystal with the increase of the number of cycles. The corrosion products were mainly magnetite (Fe3O4) and a small part of maghemite (γ-Fe2O3), which were in the form of microspheres on the surface of mFe0. The formation of surface oxidation shell hindered the release of Fe2+. X-ray photoelectron spectroscopy (XPS) results illustrated that partial Fe3O4 could be converted into γ-Fe2O3. Electrochemical analysis proved that the electron transfer rate of mFe0 increased with the formation of the oxides shell. However, the consumption of iron core and thicker oxide film weakened the electron transfer rate. Besides, the quenching experiments indicated that the reaction activity of mFe0 could be enhanced with the addition of scavengers. This study deepened the understanding of the structural transformation and radical production of mFe0 in continuous reactions.
It is generally recognized that the formation and accumulation of iron oxides on the surface of zero-valent iron (Fe0) resulting in significant decrease of contaminant degradation rates during the long-term reactions. However, in this study, we found that the removal efficiencies of p-nitrophenol (PNP) by micro zero-valent iron (mFe0) could maintain at the satisfactory level in the process of continuous reactions (20 cycles). The removal rate constant (0.1779 min-1) of the 5th cycle was 6.74 times higher than that of the 1st reaction (0.0264 min-1), even the 20th cycle (0.0371 min-1) was higher than that of the 1st reaction. Interestingly, almost no dissolved iron was detected in the solution, and the total iron concentrations decreased dramatically with the process of continuous reactions. The results of scanning electron microscope and energy dispersive spectrometry (SEM-EDS) and X-ray diffraction (XRD) revealed that the structure and composition of corrosion products change from amorphous to highly crystal with the increase of the number of cycles. The corrosion products were mainly magnetite (Fe3O4) and a small part of maghemite (γ-Fe2O3), which were in the form of microspheres on the surface of mFe0. The formation of surface oxidation shell hindered the release of Fe2+. X-ray photoelectron spectroscopy (XPS) results illustrated that partial Fe3O4 could be converted into γ-Fe2O3. Electrochemical analysis proved that the electron transfer rate of mFe0 increased with the formation of the oxides shell. However, the consumption of iron core and thicker oxide film weakened the electron transfer rate. Besides, the quenching experiments indicated that the reaction activity of mFe0 could be enhanced with the addition of scavengers. This study deepened the understanding of the structural transformation and radical production of mFe0 in continuous reactions.
2020, 31(10): 2641-2644
doi: 10.1016/j.cclet.2020.02.029
Abstract:
The high cost and low reserves of noble metals greatly hinder their practical applications in new energy production and conversion. The exploration of cost-effective alternative electrocatalysts with the ability to drive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is extremely significant to promote overall water splitting. Herein, ultrathin CoSe2/CNTs nanocomposites have been synthesized by a facile two-step method, where the ultrathin Co-MOF (metal organic-framework) decorated with cable-like carbon nanotubes (CNTs) (Co-MOF/CNTs) was initially fabricated, and followed a low-temperature selenization process. The ultrathin CoSe2 nanosheets as well as the superior conductivity of CNTs synergistically resulted in abundant active sites and enhanced conductivity to boost the electrocatalytic activity. The as-prepared CoSe2/CNTs electrocatalysts exhibited an overpotential of 190 mV and 300 mV vs. reversible hydrogen electrode (RHE) at a current density of 10 mA/cm2 for the HER and OER in alkaline solution, respectively, and demonstrated superior durability. Furthermore, the as-prepared bifunctional CoSe2/CNTs electrocatalysts can act as cathode and anode in an electrolyzer, showing a cell voltage of 1.75 V at 10 mA/cm2 for overall water splitting.
The high cost and low reserves of noble metals greatly hinder their practical applications in new energy production and conversion. The exploration of cost-effective alternative electrocatalysts with the ability to drive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is extremely significant to promote overall water splitting. Herein, ultrathin CoSe2/CNTs nanocomposites have been synthesized by a facile two-step method, where the ultrathin Co-MOF (metal organic-framework) decorated with cable-like carbon nanotubes (CNTs) (Co-MOF/CNTs) was initially fabricated, and followed a low-temperature selenization process. The ultrathin CoSe2 nanosheets as well as the superior conductivity of CNTs synergistically resulted in abundant active sites and enhanced conductivity to boost the electrocatalytic activity. The as-prepared CoSe2/CNTs electrocatalysts exhibited an overpotential of 190 mV and 300 mV vs. reversible hydrogen electrode (RHE) at a current density of 10 mA/cm2 for the HER and OER in alkaline solution, respectively, and demonstrated superior durability. Furthermore, the as-prepared bifunctional CoSe2/CNTs electrocatalysts can act as cathode and anode in an electrolyzer, showing a cell voltage of 1.75 V at 10 mA/cm2 for overall water splitting.
2020, 31(10): 2645-2650
doi: 10.1016/j.cclet.2020.02.048
Abstract:
The binary Ag3PO4/MIL-125-NH2 (AMN-X) composites were synthesized through ion exchange-solution method, and the ternary Ag/Ag3PO4/MIL-125-NH2 (AAMN-X) Z-scheme heterojunctions were prepared via the photo chemical reduction deposition strategy. The photocatalytic hexavalent chromium (Cr(Ⅵ)) sequestration over AMN-X and AAMN-X were investigated under visible light. AAMN-120 accomplished superior reduction performance due to that Ag nanoparticles (NPs) act as electrons transfer bridge to enhance the separation efficiency of photogenerated e--h+ pairs, in which the reaction rates (k value) were 2.77 and 124.2 fold higher than those of individual MIL-125-NH2 and Ag3PO4, respectively. The influences of different pH values, small organic acids and coexisting ions on the photocatalytic performance of AAMN-120 were also investigated. In addition, the AAMN-120 heterojunction expressed great reusability and stability in cycling experiments. The mechanism of photocatalytic Cr(Ⅵ) was investigated and verified through photoluminescence (PL), electrochemistry, electron spin resonance (ESR), active species capture, and Pt element deposition experiments.
The binary Ag3PO4/MIL-125-NH2 (AMN-X) composites were synthesized through ion exchange-solution method, and the ternary Ag/Ag3PO4/MIL-125-NH2 (AAMN-X) Z-scheme heterojunctions were prepared via the photo chemical reduction deposition strategy. The photocatalytic hexavalent chromium (Cr(Ⅵ)) sequestration over AMN-X and AAMN-X were investigated under visible light. AAMN-120 accomplished superior reduction performance due to that Ag nanoparticles (NPs) act as electrons transfer bridge to enhance the separation efficiency of photogenerated e--h+ pairs, in which the reaction rates (k value) were 2.77 and 124.2 fold higher than those of individual MIL-125-NH2 and Ag3PO4, respectively. The influences of different pH values, small organic acids and coexisting ions on the photocatalytic performance of AAMN-120 were also investigated. In addition, the AAMN-120 heterojunction expressed great reusability and stability in cycling experiments. The mechanism of photocatalytic Cr(Ⅵ) was investigated and verified through photoluminescence (PL), electrochemistry, electron spin resonance (ESR), active species capture, and Pt element deposition experiments.
2020, 31(10): 2651-2656
doi: 10.1016/j.cclet.2020.03.033
Abstract:
Graphene oxide (GO) membranes show great potential in molecular separation for water treatment. However, the inferior stability of GO membranes is a major bottleneck for practical applications. In this study, bio-inspired polydopamine (PDA) deposition is reported for enhancing the stability of GO membranes. Through simple and mild immersion, PDA is self-polymerized on GO membranes. The blocking of PDA chains to membrane defects improves the rejections for various molecules. Because the inherently strong adhesion and crosslinking of PDA greatly strengthen the interactions of substrates to GO layers and the binding force of GO nanosheets, the prepared PDA-GO membranes exhibit impressive long-term stability in cross-flow filtration, and maintain good nanofiltration performance at various feed pressures, tangential velocities, and even after external scratching. Moreover, because the deposited PDA layers obstruct the direct contact between GO and contaminants, the antifouling property of the PDA-GO membranes increases substantially, with recovery ratio about 98%.
Graphene oxide (GO) membranes show great potential in molecular separation for water treatment. However, the inferior stability of GO membranes is a major bottleneck for practical applications. In this study, bio-inspired polydopamine (PDA) deposition is reported for enhancing the stability of GO membranes. Through simple and mild immersion, PDA is self-polymerized on GO membranes. The blocking of PDA chains to membrane defects improves the rejections for various molecules. Because the inherently strong adhesion and crosslinking of PDA greatly strengthen the interactions of substrates to GO layers and the binding force of GO nanosheets, the prepared PDA-GO membranes exhibit impressive long-term stability in cross-flow filtration, and maintain good nanofiltration performance at various feed pressures, tangential velocities, and even after external scratching. Moreover, because the deposited PDA layers obstruct the direct contact between GO and contaminants, the antifouling property of the PDA-GO membranes increases substantially, with recovery ratio about 98%.
2020, 31(10): 2657-2660
doi: 10.1016/j.cclet.2020.08.008
Abstract:
Acetylene black (AB), as a kind of carbon material with large specific surface area, low density, strong electron transferability, is supposed to have great potential for application in advanced oxidation processes (AOPs). In this study, AB was utilized as a peroxydisulfate (PDS) activator for the catalytic degradation of sulfamethoxazole (SMX) in aqueous media. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) techniques, zeta potential and Raman spectra were employed to characterize the features of AB. To verify the excellent performance of AB/PDS systems, a series of control experiments were carried out. Compared to graphite/PDS and biochar/PDS system, AB/PDS system could complete degradation of SMX within 15 min. Besides, the effects of key factors including AB dosage, PDS dosage, initial pH and SMX concentration on SMX degradation in AB/PDS system were elucidated systematically. Furthermore, through the radical quenching experiments, it was proved that singlet oxygen (1O2) was dominantly responsible for the degradation of SMX. Finally, based on the experiment results and comprehensive analysis, a probable reaction mechanism of AB/PDS system for SMX degradation was proposed. This work suggests that AB has a good potential for tackling the hazardous pollutants in environmental remediation.
Acetylene black (AB), as a kind of carbon material with large specific surface area, low density, strong electron transferability, is supposed to have great potential for application in advanced oxidation processes (AOPs). In this study, AB was utilized as a peroxydisulfate (PDS) activator for the catalytic degradation of sulfamethoxazole (SMX) in aqueous media. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) techniques, zeta potential and Raman spectra were employed to characterize the features of AB. To verify the excellent performance of AB/PDS systems, a series of control experiments were carried out. Compared to graphite/PDS and biochar/PDS system, AB/PDS system could complete degradation of SMX within 15 min. Besides, the effects of key factors including AB dosage, PDS dosage, initial pH and SMX concentration on SMX degradation in AB/PDS system were elucidated systematically. Furthermore, through the radical quenching experiments, it was proved that singlet oxygen (1O2) was dominantly responsible for the degradation of SMX. Finally, based on the experiment results and comprehensive analysis, a probable reaction mechanism of AB/PDS system for SMX degradation was proposed. This work suggests that AB has a good potential for tackling the hazardous pollutants in environmental remediation.
2020, 31(10): 2661-2667
doi: 10.1016/j.cclet.2020.03.068
Abstract:
This study aimed to construct a photoelectrocatalytic (PEC) reaction system based on the self-made reduced TiO2 NTAs (r-TNAs) photoanode and activated carbon/Polytetrafluoroethylene (AC/PTFE) cathode. It would be observed clearly that the degradation rate constant of carbamazepine (CBZ) over r-TNAs(photoanode)-AC/PTFE(cathode) PEC system (0.04961 min-1) was even higher than that of r-TNAs(photoanode)-Pt(cathode) PEC system (0.04602 min-1) with the assistance of visible light irradiation and +0.4 V external potential. Besides, in order to obtain optimized conditions, the influence of key parameters such as pH value, electric current density and electrolyte concentration were studied. Most importantly, photoelectrochemical (PECH) properties, reactive oxide species contribution, ·OH formation rate and CBZ degradation pathway were determined. The results illustrated that the excellent PEC degradation performance depended on the excellent photocatalytic property of r-TNAs photoanode and electron transfer property of photoelectrodes in r-TNAs(photoanode)-AC/PTFE(cathode) PEC system. Therefore, the study demonstrated that the r-TNAs(photoanode)-AC/PTFE(cathode) PEC system could be expected to replace metal-catalyzed cathodes depending on its excellent PEC performance activity and low cost as well as the reaction system possessed objective and practical application prospect.
This study aimed to construct a photoelectrocatalytic (PEC) reaction system based on the self-made reduced TiO2 NTAs (r-TNAs) photoanode and activated carbon/Polytetrafluoroethylene (AC/PTFE) cathode. It would be observed clearly that the degradation rate constant of carbamazepine (CBZ) over r-TNAs(photoanode)-AC/PTFE(cathode) PEC system (0.04961 min-1) was even higher than that of r-TNAs(photoanode)-Pt(cathode) PEC system (0.04602 min-1) with the assistance of visible light irradiation and +0.4 V external potential. Besides, in order to obtain optimized conditions, the influence of key parameters such as pH value, electric current density and electrolyte concentration were studied. Most importantly, photoelectrochemical (PECH) properties, reactive oxide species contribution, ·OH formation rate and CBZ degradation pathway were determined. The results illustrated that the excellent PEC degradation performance depended on the excellent photocatalytic property of r-TNAs photoanode and electron transfer property of photoelectrodes in r-TNAs(photoanode)-AC/PTFE(cathode) PEC system. Therefore, the study demonstrated that the r-TNAs(photoanode)-AC/PTFE(cathode) PEC system could be expected to replace metal-catalyzed cathodes depending on its excellent PEC performance activity and low cost as well as the reaction system possessed objective and practical application prospect.
2020, 31(10): 2668-2672
doi: 10.1016/j.cclet.2020.08.003
Abstract:
Graphitic carbon nitride (g-C3N4) as a metal-free candidate of photocatalyst has received worldwide attention because of its great potentials in solar light-induced degradation and hydrogen evolution, yet the industrial application is seriously hindered by the small specific surface area and rapid recombination rate of carriers. Herein, we demonstrate that porous g-C3N4 (HCl-CNU-X) can be prepared via the co-polymerization of acidified melamine and a green bubble template (urea). Transmission electron microscopy and nitrogen sorption characterization results show that the prepared HCl-CNU-X possesses an in-plane porous structure and large specific surface area, enabling the exposure of more accessible active sites. As a result, HCl-CNU-X exhibits both enhanced photocatalytic tetracycline hydrochloride degradation and higher hydrogen evolution than bulk g-C3N4. The boosted photocatalytic performance was ascribed to the formation of the porous structure, which dramatically promotes the separation of charge-carriers and facilitates the electron transfer. This work demonstrates that the acidification of nitrogen-rich precursors combined with a bubble-template can develop a new paradigm of highly porous photocatalysts for environmental remediation and water splitting.
Graphitic carbon nitride (g-C3N4) as a metal-free candidate of photocatalyst has received worldwide attention because of its great potentials in solar light-induced degradation and hydrogen evolution, yet the industrial application is seriously hindered by the small specific surface area and rapid recombination rate of carriers. Herein, we demonstrate that porous g-C3N4 (HCl-CNU-X) can be prepared via the co-polymerization of acidified melamine and a green bubble template (urea). Transmission electron microscopy and nitrogen sorption characterization results show that the prepared HCl-CNU-X possesses an in-plane porous structure and large specific surface area, enabling the exposure of more accessible active sites. As a result, HCl-CNU-X exhibits both enhanced photocatalytic tetracycline hydrochloride degradation and higher hydrogen evolution than bulk g-C3N4. The boosted photocatalytic performance was ascribed to the formation of the porous structure, which dramatically promotes the separation of charge-carriers and facilitates the electron transfer. This work demonstrates that the acidification of nitrogen-rich precursors combined with a bubble-template can develop a new paradigm of highly porous photocatalysts for environmental remediation and water splitting.
2020, 31(10): 2673-2677
doi: 10.1016/j.cclet.2020.03.073
Abstract:
Electrochemical degradation of sulfamethoxazole (SMX) and its metabolite acetyl-sulfamethoxazole (Ac-SMX) by Ti/SnO2-Sb/Er-PbO2 were investigated. Results indicated that the electrochemical degradation of SMX and Ac-SMX followed pseudo-first-order kinetics. The rate constants of SMX and Ac-SMX were 0.268 and 0.072 min-1 at optimal current density of 10 and 14 mA/cm2, respectively. Transformation products of SMX and Ac-SMX were identified and the possible degradation pathways, including the cleavage of S-N bond, opening ring of isoxazole and nitration of amino group, were proposed. Total organic carbon removal of SMX was nearly 63.2% after 3 h electrochemical degradation. 22.4% nitrogen of SMX was transformed to NO3-, and 98.8% sulfur of SMX was released as SO42-. According to quantitative structure-activity relationship model, toxicities of SMX and Ac-SMX to aquatic organisms significantly decreased after electrochemical degradation. Electric energy consumption for 90% SMX and Ac-SMX degradation was determined to be 0.58-8.97 and 6.88-44.19 Wh/L at different experimental conditions, respectively. Compared with parent compound SMX, the metabolite Ac-SMX is more refractory and toxic, which emphasizes the importance of taking its metabolites into account when investigating the disposal of pharmaceuticals from wastewater.
Electrochemical degradation of sulfamethoxazole (SMX) and its metabolite acetyl-sulfamethoxazole (Ac-SMX) by Ti/SnO2-Sb/Er-PbO2 were investigated. Results indicated that the electrochemical degradation of SMX and Ac-SMX followed pseudo-first-order kinetics. The rate constants of SMX and Ac-SMX were 0.268 and 0.072 min-1 at optimal current density of 10 and 14 mA/cm2, respectively. Transformation products of SMX and Ac-SMX were identified and the possible degradation pathways, including the cleavage of S-N bond, opening ring of isoxazole and nitration of amino group, were proposed. Total organic carbon removal of SMX was nearly 63.2% after 3 h electrochemical degradation. 22.4% nitrogen of SMX was transformed to NO3-, and 98.8% sulfur of SMX was released as SO42-. According to quantitative structure-activity relationship model, toxicities of SMX and Ac-SMX to aquatic organisms significantly decreased after electrochemical degradation. Electric energy consumption for 90% SMX and Ac-SMX degradation was determined to be 0.58-8.97 and 6.88-44.19 Wh/L at different experimental conditions, respectively. Compared with parent compound SMX, the metabolite Ac-SMX is more refractory and toxic, which emphasizes the importance of taking its metabolites into account when investigating the disposal of pharmaceuticals from wastewater.
2020, 31(10): 2678-2682
doi: 10.1016/j.cclet.2020.06.005
Abstract:
In this work, the reduction of mercury ions (Hg2+) to elemental mercury (Hg0) was easily achieved using highly reductive carbon dots (r-CDs), which synthesized from sucrose by a simple and cost-effective method. After a careful mechanistic study, the reduction was probably accomplished with the large numbers of electrons contained in r-CDs rather than the oxidation of its functional groups. Additionally, a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay showed that the r-CDs were nontoxic to wildlife and human beings. Consequently, the r-CDs were used as an alternative to toxic reductants (SnCl2 or NaBH4) for the sensitive and in situ determination of mercury by cold vapor generation (CVG) coupled to a miniature point discharge optical emission spectrometer (μPD-OES). Limit of detection of 0.05 μg/L was obtained for Hg2+, with relative standard deviation (RSD) less than 5.4% at a concentration of 5 μg/L. The accuracy of r-CDs induced CVG-μPD-OES was validated by the determination of mercury in a certified reference material (DOLT-5, dogfish liver) and five natural water samples collected from different rivers and lakes in Chengdu City. Since r-CDs are nontoxic and prepared from abundant and inexpensive sucrose, the r-CDs induced CVG-μPD-OES retains the great potential for the inexpensive and environmentally friendly field analysis of mercury in natural water. The accuracy of the proposed method was validated by the analysis of a certified reference material and several water samples with satisfactory results.
In this work, the reduction of mercury ions (Hg2+) to elemental mercury (Hg0) was easily achieved using highly reductive carbon dots (r-CDs), which synthesized from sucrose by a simple and cost-effective method. After a careful mechanistic study, the reduction was probably accomplished with the large numbers of electrons contained in r-CDs rather than the oxidation of its functional groups. Additionally, a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay showed that the r-CDs were nontoxic to wildlife and human beings. Consequently, the r-CDs were used as an alternative to toxic reductants (SnCl2 or NaBH4) for the sensitive and in situ determination of mercury by cold vapor generation (CVG) coupled to a miniature point discharge optical emission spectrometer (μPD-OES). Limit of detection of 0.05 μg/L was obtained for Hg2+, with relative standard deviation (RSD) less than 5.4% at a concentration of 5 μg/L. The accuracy of r-CDs induced CVG-μPD-OES was validated by the determination of mercury in a certified reference material (DOLT-5, dogfish liver) and five natural water samples collected from different rivers and lakes in Chengdu City. Since r-CDs are nontoxic and prepared from abundant and inexpensive sucrose, the r-CDs induced CVG-μPD-OES retains the great potential for the inexpensive and environmentally friendly field analysis of mercury in natural water. The accuracy of the proposed method was validated by the analysis of a certified reference material and several water samples with satisfactory results.
2020, 31(10): 2683-2688
doi: 10.1016/j.cclet.2020.04.011
Abstract:
Metal organic frameworks (MOFs) has broad application prospect in separation, catalysis, and adsorption. By a facile green method, we successfully fabricated prGO@cHKUST-1 composite membrane with the modification of dopamine and orientated growth of MOFs. Mg/Al-layered double hydroxides (Mg/Al-LDHs) was used as a modulator to obtain cubic HKUST-1 (cHKUST-1) with excellent morphology and special properties. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) etc. characterization illustrated successful synthesis of cHKUST-1 and composite membranes. Cubic HKUST-1 can tune the inter-layer spacing of graphene oxide (GO) leading increase in hydrophilicity and flux of the membrane. Meanwhile, the reduction effect of PDA and intercalation effect of MOFs could change the stacked way of GO layers, forming several fuzzy pores and more active sites on membrane surface. The prGO@cHKUST-1 membrane has an excellent rejection for methylene blue (MB) (99.5%) and Congo red (CR) (71.2%). Moreover, the modified membrane exhibited 10 and 5 times higher permeation flux than that of original GO membrane and prGO membrane, respectively. Thus, using orientated growth of MOFs to synthesize GO based composite membrane will provide useful insights in ultrahigh permeation flux membranes of dye and oil-water emulsion separation.
Metal organic frameworks (MOFs) has broad application prospect in separation, catalysis, and adsorption. By a facile green method, we successfully fabricated prGO@cHKUST-1 composite membrane with the modification of dopamine and orientated growth of MOFs. Mg/Al-layered double hydroxides (Mg/Al-LDHs) was used as a modulator to obtain cubic HKUST-1 (cHKUST-1) with excellent morphology and special properties. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) etc. characterization illustrated successful synthesis of cHKUST-1 and composite membranes. Cubic HKUST-1 can tune the inter-layer spacing of graphene oxide (GO) leading increase in hydrophilicity and flux of the membrane. Meanwhile, the reduction effect of PDA and intercalation effect of MOFs could change the stacked way of GO layers, forming several fuzzy pores and more active sites on membrane surface. The prGO@cHKUST-1 membrane has an excellent rejection for methylene blue (MB) (99.5%) and Congo red (CR) (71.2%). Moreover, the modified membrane exhibited 10 and 5 times higher permeation flux than that of original GO membrane and prGO membrane, respectively. Thus, using orientated growth of MOFs to synthesize GO based composite membrane will provide useful insights in ultrahigh permeation flux membranes of dye and oil-water emulsion separation.
2020, 31(10): 2689-2692
doi: 10.1016/j.cclet.2020.07.032
Abstract:
Largely limited by the high dissociation energy of the O—O bond, the photocatalytic molecular oxygen activation is highly challenged, which restrains the application of photocatalytic oxidation technology for atmospheric pollutants removal. Herein, we design and fabricate the InP QDs/g-C3N4 compounds. The introduction of InP QDs promotes the charge transfer within the interface resulting in the effective separation of photo-generated carriers. Furthermore, InP QDs greatly facilitates the activation of molecular oxygen and promote the formation of O2·- under visible-light illumination. These conclusions are identified by experimental and calculation results. Hence, NO can be combined with the O2·- to form O—O—N—O intermediate to direct conversion into NO3-. As a result, the NO removal ratio of g-C3N4 has a onefold increase after InP QDs loaded and the generation of NO2 is effectively inhibited. This work may provide a strategy to design highly efficient materials for molecular oxygen activation.
Largely limited by the high dissociation energy of the O—O bond, the photocatalytic molecular oxygen activation is highly challenged, which restrains the application of photocatalytic oxidation technology for atmospheric pollutants removal. Herein, we design and fabricate the InP QDs/g-C3N4 compounds. The introduction of InP QDs promotes the charge transfer within the interface resulting in the effective separation of photo-generated carriers. Furthermore, InP QDs greatly facilitates the activation of molecular oxygen and promote the formation of O2·- under visible-light illumination. These conclusions are identified by experimental and calculation results. Hence, NO can be combined with the O2·- to form O—O—N—O intermediate to direct conversion into NO3-. As a result, the NO removal ratio of g-C3N4 has a onefold increase after InP QDs loaded and the generation of NO2 is effectively inhibited. This work may provide a strategy to design highly efficient materials for molecular oxygen activation.
2020, 31(10): 2693-2697
doi: 10.1016/j.cclet.2020.04.001
Abstract:
Composting can enhance the nutrient elements cycling and reduce carbon dioxide production. However, little information is available regarding the application of compost for the remediation of the contaminated soil. In this study, we assess the response of the redox capacities (electron accepting capacities (EAC) and electron donating capacities (EDC)) of compost-derived humic acids (HAs) to the bioreduction of hexavalent chromium (Cr(VI)), especially in presence of hematite. The result showed that the compost-derived HAs played an important role in the bioreduction of Cr(VI) in presence and absence of hematite under the anoxic, neutral (pH 7) and motionless conditions. Based on the pseudo-first order kinetic model, the rate constants of Cr(VI) reduction increased by 1.36–2.0 times when compost-derived HAs was added. The redox capacity originating from the polysaccharide structure of compost-derived HAs made them effective in the direct Cr(VI) reduction (without MR-1) at pH 7. Meanwhile, the reduction rates were inversely proportional to the composting treatment time. When iron mineral (Fe2O3) and compost-derived HAs were both present, the rate constants of Cr(VI) reduction increased by 2.35–5.09, which were higher than the rate of Cr(VI) reduction in HA-only systems, indicating that the hematite played a crucial role in the bioreduction process of Cr(VI). EAC and quinonoid structures played a major role in enhancing the bioreduction of Cr(VI) when iron mineral and compost-derived HAs coexisted in the system. The results can extend the application fields of compost and will provide a new insight for the remediation of Cr(VI)-contaminated soil.
Composting can enhance the nutrient elements cycling and reduce carbon dioxide production. However, little information is available regarding the application of compost for the remediation of the contaminated soil. In this study, we assess the response of the redox capacities (electron accepting capacities (EAC) and electron donating capacities (EDC)) of compost-derived humic acids (HAs) to the bioreduction of hexavalent chromium (Cr(VI)), especially in presence of hematite. The result showed that the compost-derived HAs played an important role in the bioreduction of Cr(VI) in presence and absence of hematite under the anoxic, neutral (pH 7) and motionless conditions. Based on the pseudo-first order kinetic model, the rate constants of Cr(VI) reduction increased by 1.36–2.0 times when compost-derived HAs was added. The redox capacity originating from the polysaccharide structure of compost-derived HAs made them effective in the direct Cr(VI) reduction (without MR-1) at pH 7. Meanwhile, the reduction rates were inversely proportional to the composting treatment time. When iron mineral (Fe2O3) and compost-derived HAs were both present, the rate constants of Cr(VI) reduction increased by 2.35–5.09, which were higher than the rate of Cr(VI) reduction in HA-only systems, indicating that the hematite played a crucial role in the bioreduction process of Cr(VI). EAC and quinonoid structures played a major role in enhancing the bioreduction of Cr(VI) when iron mineral and compost-derived HAs coexisted in the system. The results can extend the application fields of compost and will provide a new insight for the remediation of Cr(VI)-contaminated soil.
2020, 31(10): 2698-2704
doi: 10.1016/j.cclet.2020.07.003
Abstract:
Multiple pollutants including pathogenic microorganism contaminations and emerging organic contaminations (EOCs) have shown a growing threat to the environment, especially the natural waters. However, the control and removal of pathogenic microorganism contaminations and EOCs have been greatly limited since limited knowledge of their environmental behaviors. Thus, a novel and efficient photocatalyst Ag2O/BiOBr heterojunction was synthesized and used for removal of multiple pollutants including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), tetracycline and acetaminophen under visible light. The results showed that there were valid electron transfer pathways between BiOBr and Ag2O, the main electron transfer direction was the BiOBr to Ag2O. Photo-generated electrons were stored in Ag2O and thus separation efficiency between holes and photo-generated electrons was obviously enhanced. Active oxygen species were highly produced and eventually end up with the high efficiency of removal of multiple pollutants. For Ag2O/BiOBr with Ag2O content at 3% (the best performance) under visible light, log decrease of E. coli was 7.16 (removal efficiency was 100%) in 120 min, log decrease of S. aureus was 7.23 (removal efficiency was 100%) in 160 min, C/C0 of tetracycline was 0.06 in 180 min, C/C0 of acetaminophen was 0.17 in 180 min. This work could provide a promising candidate in the actual contaminated natural waters for cleaning multiple pollutants.
Multiple pollutants including pathogenic microorganism contaminations and emerging organic contaminations (EOCs) have shown a growing threat to the environment, especially the natural waters. However, the control and removal of pathogenic microorganism contaminations and EOCs have been greatly limited since limited knowledge of their environmental behaviors. Thus, a novel and efficient photocatalyst Ag2O/BiOBr heterojunction was synthesized and used for removal of multiple pollutants including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), tetracycline and acetaminophen under visible light. The results showed that there were valid electron transfer pathways between BiOBr and Ag2O, the main electron transfer direction was the BiOBr to Ag2O. Photo-generated electrons were stored in Ag2O and thus separation efficiency between holes and photo-generated electrons was obviously enhanced. Active oxygen species were highly produced and eventually end up with the high efficiency of removal of multiple pollutants. For Ag2O/BiOBr with Ag2O content at 3% (the best performance) under visible light, log decrease of E. coli was 7.16 (removal efficiency was 100%) in 120 min, log decrease of S. aureus was 7.23 (removal efficiency was 100%) in 160 min, C/C0 of tetracycline was 0.06 in 180 min, C/C0 of acetaminophen was 0.17 in 180 min. This work could provide a promising candidate in the actual contaminated natural waters for cleaning multiple pollutants.
2020, 31(10): 2705-2711
doi: 10.1016/j.cclet.2020.04.026
Abstract:
In this study, α-Bi2O3/g-C3N4 nanocomposite with direct Z-scheme was successfully prepared through calcination of BiOCOOH/g-C3N4 precursor at different temperature. Meanwhile, the effect of calcination temperature on the physicochemical properties of α-Bi2O3/g-C3N4 was studied. All results confirmed that calcination temperature greatly influences structural, morphology, surface states, photoelectrochemical property and photocatalytic (PC) performance of α-Bi2O3/g-C3N4 composite. Furthermore, the α-Bi2O3/g-C3N4 composite was applied as photocatalyst to degrade amido black 10B dye under visible light irradiation. It was found that the composite synthesized at 400 ℃ exhibited the highest PC performance due to the intense visible light absorbance and high separation efficiency of electron and hole pairs. Besides, the possible PC mechanism was proposed that the photo-generated charge carrier migration in α-Bi2O3/g-C3N4 photocatalyst followed a Z-scheme structure. Finally, the stability test also manifest that the α-Bi2O3/g-C3N4 composite photocatalyst has good stability and reusability, which was a promising candidate for wastewater treatment.
In this study, α-Bi2O3/g-C3N4 nanocomposite with direct Z-scheme was successfully prepared through calcination of BiOCOOH/g-C3N4 precursor at different temperature. Meanwhile, the effect of calcination temperature on the physicochemical properties of α-Bi2O3/g-C3N4 was studied. All results confirmed that calcination temperature greatly influences structural, morphology, surface states, photoelectrochemical property and photocatalytic (PC) performance of α-Bi2O3/g-C3N4 composite. Furthermore, the α-Bi2O3/g-C3N4 composite was applied as photocatalyst to degrade amido black 10B dye under visible light irradiation. It was found that the composite synthesized at 400 ℃ exhibited the highest PC performance due to the intense visible light absorbance and high separation efficiency of electron and hole pairs. Besides, the possible PC mechanism was proposed that the photo-generated charge carrier migration in α-Bi2O3/g-C3N4 photocatalyst followed a Z-scheme structure. Finally, the stability test also manifest that the α-Bi2O3/g-C3N4 composite photocatalyst has good stability and reusability, which was a promising candidate for wastewater treatment.
2020, 31(10): 2712-2716
doi: 10.1016/j.cclet.2020.04.037
Abstract:
The heterogeneous reaction of SO2 on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere. To this day, there are no reported studies that assess the impact of atmospheric CO2 in sulfate production on mineral dust surfaces. In this work, we investigate the impact of CO2 on SO2 uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). CO2 is demonstrated to suppress the heterogeneous oxidation of SO2 on alpha-Al2O3. Compared to that measured in the CO2-free case, the uptake coefficient is decreased by nearly 57% when Al2O3 particles are exposed to the gas flow with atmospheric CO2 at a relative humidity (RH) of 25%. It is also found that there is a balance between the yield of active moiety —OH provided by Al(OH)3(CO)(OH)2 clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO2-derived (bi)carbonate species. This work, for the first time, reveals a negative effect of atmospheric CO2 on the sulfate formation, which potentially decreases solar-radiation scattering and further exacerbates global warming.
The heterogeneous reaction of SO2 on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere. To this day, there are no reported studies that assess the impact of atmospheric CO2 in sulfate production on mineral dust surfaces. In this work, we investigate the impact of CO2 on SO2 uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). CO2 is demonstrated to suppress the heterogeneous oxidation of SO2 on alpha-Al2O3. Compared to that measured in the CO2-free case, the uptake coefficient is decreased by nearly 57% when Al2O3 particles are exposed to the gas flow with atmospheric CO2 at a relative humidity (RH) of 25%. It is also found that there is a balance between the yield of active moiety —OH provided by Al(OH)3(CO)(OH)2 clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO2-derived (bi)carbonate species. This work, for the first time, reveals a negative effect of atmospheric CO2 on the sulfate formation, which potentially decreases solar-radiation scattering and further exacerbates global warming.
2020, 31(10): 2717-2720
doi: 10.1016/j.cclet.2020.04.044
Abstract:
The development in technology of synthetic azo dyes, has led to excessive water resources pollution. Even at lower concentration they can impart the quality of water and human life. Herein, we have developed a novel synthesis strategy via introducing salicylic acid (SA) for the synthesis of a leachy crystalline material H-MIL-53(Fe) with hierarchical pores (HP) and exposed coordination unsaturated sites (CUS), which had higher surface area and larger pore volume than the as synthesized MIL-53(Fe). Due to these characteristics, H-MIL-53(Fe) was competent removal of orange G (OG, one of the frequently used azo dyes) with equilibrium in 300 min and the maximum adsorption capacity of 163.9 mg/g. The adsorption mechanism of OG onto H-MIL-53(Fe) was mostly based on electrostatic attraction between CUS of H-MIL-53(Fe) along with HP as active species to OG diffusion and bind. By comparing H-MIL-53(Fe) with other adsorbents for OG adsorption, it is undoubtedly that H-MIL-53(Fe) can be used as a promising adsorbent for OG removal from aqueous solutions.
The development in technology of synthetic azo dyes, has led to excessive water resources pollution. Even at lower concentration they can impart the quality of water and human life. Herein, we have developed a novel synthesis strategy via introducing salicylic acid (SA) for the synthesis of a leachy crystalline material H-MIL-53(Fe) with hierarchical pores (HP) and exposed coordination unsaturated sites (CUS), which had higher surface area and larger pore volume than the as synthesized MIL-53(Fe). Due to these characteristics, H-MIL-53(Fe) was competent removal of orange G (OG, one of the frequently used azo dyes) with equilibrium in 300 min and the maximum adsorption capacity of 163.9 mg/g. The adsorption mechanism of OG onto H-MIL-53(Fe) was mostly based on electrostatic attraction between CUS of H-MIL-53(Fe) along with HP as active species to OG diffusion and bind. By comparing H-MIL-53(Fe) with other adsorbents for OG adsorption, it is undoubtedly that H-MIL-53(Fe) can be used as a promising adsorbent for OG removal from aqueous solutions.
2020, 31(10): 2721-2724
doi: 10.1016/j.cclet.2020.05.001
Abstract:
The contamination of antibiotics in aqueous environment causes increasing concerns recently. Light-assisted activation of peroxydisulfate (PDS) has been demonstrated as an efficient technology for removal of contamination in water. Herein, a hollow sphere of CuWO4 (h-CuWO4) was employed as a visible light-activated photocatalyst for the activation of PDS, and following with high removal efficiency (98%) of antibiotic sulfamethoxazole (SMX). Under visible light irradiation, the degradation rate on hollow structures system is nearly 2 times higher than the traditional solid CuWO4 spheres. Furthermore, the underlying mechanism and detailed pathway of SMX degradation were proposed based on density functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC–MS). This work provides a new feasible way for advanced oxidation processes to remove antibiotics SMX in heterogeneous system, and open up new application possibilities of CuWO4-based materials.
The contamination of antibiotics in aqueous environment causes increasing concerns recently. Light-assisted activation of peroxydisulfate (PDS) has been demonstrated as an efficient technology for removal of contamination in water. Herein, a hollow sphere of CuWO4 (h-CuWO4) was employed as a visible light-activated photocatalyst for the activation of PDS, and following with high removal efficiency (98%) of antibiotic sulfamethoxazole (SMX). Under visible light irradiation, the degradation rate on hollow structures system is nearly 2 times higher than the traditional solid CuWO4 spheres. Furthermore, the underlying mechanism and detailed pathway of SMX degradation were proposed based on density functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC–MS). This work provides a new feasible way for advanced oxidation processes to remove antibiotics SMX in heterogeneous system, and open up new application possibilities of CuWO4-based materials.
2020, 31(10): 2725-2729
doi: 10.1016/j.cclet.2020.05.024
Abstract:
The porous g-C3N4 (PCN) nanosheets are successfully synthesized and further modified with nano-sized Ag by a simple wet-chemical process. Interestingly, the Ag-modified porous g-C3N4 (Ag-PCN) nanosheets exhibit competitive fluorescence detection performance of chloride ion (Cl-) in aqueous solution. Under the optimized conditions, the concentration of Cl- could be quantitative analyzed with the Ag-PCN in a wide detection range from 0.5 mmol/L to 0.1 mol/L, with a low detection limitation of 0.06 mmol/L. It is confirmed that the fluorescence of PCN could be effectively decayed by the photoinduced charge transfer via the adsorbed Cl- for trapping holes, mainly by means of the time-resolved fluorescence and surface photovoltage spectra. The porous structure and modified Ag promote the adsorption of Cl- on resulting Ag-PCN, leading to excellent fluorescence detection for Cl-. This work provides a feasible route to develop a fluorescence detection of Cl- with g-C3N4 nanosheets in environment water.
The porous g-C3N4 (PCN) nanosheets are successfully synthesized and further modified with nano-sized Ag by a simple wet-chemical process. Interestingly, the Ag-modified porous g-C3N4 (Ag-PCN) nanosheets exhibit competitive fluorescence detection performance of chloride ion (Cl-) in aqueous solution. Under the optimized conditions, the concentration of Cl- could be quantitative analyzed with the Ag-PCN in a wide detection range from 0.5 mmol/L to 0.1 mol/L, with a low detection limitation of 0.06 mmol/L. It is confirmed that the fluorescence of PCN could be effectively decayed by the photoinduced charge transfer via the adsorbed Cl- for trapping holes, mainly by means of the time-resolved fluorescence and surface photovoltage spectra. The porous structure and modified Ag promote the adsorption of Cl- on resulting Ag-PCN, leading to excellent fluorescence detection for Cl-. This work provides a feasible route to develop a fluorescence detection of Cl- with g-C3N4 nanosheets in environment water.
2020, 31(10): 2730-2736
doi: 10.1016/j.cclet.2020.02.033
Abstract:
In this study, Fe2O3/Mn2O3 composite was synthesized by a facile two-step technique, and several methods were carried out to characterize it. Then, the decomposition experiments of tartrazine (TTZ), a kind of refractory organic pollutant, were conducted under various environmental condition to detect the catalyst performance, such as reaction system, the dosage of catalyst, peroxymonosulfate (PMS) concentration, initial pH, different natural water substances. The results exhibited that Fe2O3/Mn2O3 composite with the mole rate 2:3 had the best PMS activation performance and the removal efficiency was 97.3% within 30 min. Besides, the optimum degradation conditions of TTZ were also discussed, that is catalyst dosage (0.6 g/L), PMS concentration (0.8 g/L) and the initial pH 11. In addition, proved by the natural water substances adding experiments, HPO42-, HCO3-, NO3- and NOM (nature organic matter) could slow down the experiments progressing, but Cl- could boost it. Then inhibitor experiments indicated both the HO· and SO4·- played a vital role in the experiments. Reusability and ions leaching experiments as well as the used catalyst physical characterization images exhibited the excellent stability and cyclicity of the Fe2O3/Mn2O3 composite. Finally, based on the XPS (X-ray photoelectron spectroscopy) and the experiments results, the possible mechanism of TTZ degradation was proposed. This system might provide a novel thought for the decomposition of refractory organic pollutant and had potential in promotion of actual sewage treatment technology.
In this study, Fe2O3/Mn2O3 composite was synthesized by a facile two-step technique, and several methods were carried out to characterize it. Then, the decomposition experiments of tartrazine (TTZ), a kind of refractory organic pollutant, were conducted under various environmental condition to detect the catalyst performance, such as reaction system, the dosage of catalyst, peroxymonosulfate (PMS) concentration, initial pH, different natural water substances. The results exhibited that Fe2O3/Mn2O3 composite with the mole rate 2:3 had the best PMS activation performance and the removal efficiency was 97.3% within 30 min. Besides, the optimum degradation conditions of TTZ were also discussed, that is catalyst dosage (0.6 g/L), PMS concentration (0.8 g/L) and the initial pH 11. In addition, proved by the natural water substances adding experiments, HPO42-, HCO3-, NO3- and NOM (nature organic matter) could slow down the experiments progressing, but Cl- could boost it. Then inhibitor experiments indicated both the HO· and SO4·- played a vital role in the experiments. Reusability and ions leaching experiments as well as the used catalyst physical characterization images exhibited the excellent stability and cyclicity of the Fe2O3/Mn2O3 composite. Finally, based on the XPS (X-ray photoelectron spectroscopy) and the experiments results, the possible mechanism of TTZ degradation was proposed. This system might provide a novel thought for the decomposition of refractory organic pollutant and had potential in promotion of actual sewage treatment technology.
2020, 31(10): 2737-2741
doi: 10.1016/j.cclet.2020.03.081
Abstract:
One of the core issues in the photocatalytic oxidation of nitric oxide is the effective conversion of NO into the final product (nitrate). More than just improving the visible light photocatalytic performance of BiOCl, we aim to inhibit the generation of toxic by-product NO2 during this process. In this study, we demonstrate that the oxygen vacancies (OVs) modulate its surface photogenerated carrier transfer to inflect the NO conversion pathway by a facile mixed solvent method to induce OVs on the surface of BiOCl. The photocatalytic NO removal efficiency under visible light increased from 5.6% to 36.4%. In addition, the production rate of NO2 is effectively controlled. The effects of OVs on the generation of reactive oxygen species, electronic transfer, optical properties, and photocatalytic NO oxidation are investigated by combining density functional theory (DFT) theoretical calculations, the in situ FTIR spectra and experimental characterization. The OVs on the surface of BiOCl speed the trapping and transfer of localized electrons to activate the O2, producing O2·-, which avoid NO2 formation, resulting in complete oxidation of NO (NO + O2·- → NO3-). These findings can serve as the basis for controlling and blocking the generation of highly toxic intermediates through regulating the reactive species during the NO oxidation. It also can help us to understand the role of OV on the BiOCl surface and application of photocatalytic technology for safe air purification.
One of the core issues in the photocatalytic oxidation of nitric oxide is the effective conversion of NO into the final product (nitrate). More than just improving the visible light photocatalytic performance of BiOCl, we aim to inhibit the generation of toxic by-product NO2 during this process. In this study, we demonstrate that the oxygen vacancies (OVs) modulate its surface photogenerated carrier transfer to inflect the NO conversion pathway by a facile mixed solvent method to induce OVs on the surface of BiOCl. The photocatalytic NO removal efficiency under visible light increased from 5.6% to 36.4%. In addition, the production rate of NO2 is effectively controlled. The effects of OVs on the generation of reactive oxygen species, electronic transfer, optical properties, and photocatalytic NO oxidation are investigated by combining density functional theory (DFT) theoretical calculations, the in situ FTIR spectra and experimental characterization. The OVs on the surface of BiOCl speed the trapping and transfer of localized electrons to activate the O2, producing O2·-, which avoid NO2 formation, resulting in complete oxidation of NO (NO + O2·- → NO3-). These findings can serve as the basis for controlling and blocking the generation of highly toxic intermediates through regulating the reactive species during the NO oxidation. It also can help us to understand the role of OV on the BiOCl surface and application of photocatalytic technology for safe air purification.
2020, 31(10): 2742-2746
doi: 10.1016/j.cclet.2020.04.036
Abstract:
Schiff base functionalized polyamidoamine (PAMAM) dendrimer/silica were prepared for the adsorption of aqueous Mn(Ⅱ) and Co(Ⅱ). The effects that influence the adsorption were investigated systematically and the adsorption mechanism was illustrated by theoretical calculation. The optimum adsorption pH are 4 and 6 for Mn(Ⅱ) and Co(Ⅱ). Adsorption kinetics follow pseudo-second-order model and the rate-controlling step is film diffusion process. Adsorption isotherm shows that high initial metal ion concentration facilitates the uptake of metal ions. The adsorption capacity increases first and then decreases in the temperature range of 15–35 ℃. Density functional theory (DFT) calculation demonstrates that Schiff base functionalized PAMAM dendrimer tends to coordinate Mn(Ⅱ) and Co(Ⅱ) with the oxygen atoms of hydroxyl and carbonyl groups, nitrogen of tertiary amine and imino groups. The imino and tertiary amine groups mainly dominate the adsorption. The reproducibility of the adsorbents indicates they can be regenerated by 5% thiourea and 0.5 mol/L HNO3 solution efficiently.
Schiff base functionalized polyamidoamine (PAMAM) dendrimer/silica were prepared for the adsorption of aqueous Mn(Ⅱ) and Co(Ⅱ). The effects that influence the adsorption were investigated systematically and the adsorption mechanism was illustrated by theoretical calculation. The optimum adsorption pH are 4 and 6 for Mn(Ⅱ) and Co(Ⅱ). Adsorption kinetics follow pseudo-second-order model and the rate-controlling step is film diffusion process. Adsorption isotherm shows that high initial metal ion concentration facilitates the uptake of metal ions. The adsorption capacity increases first and then decreases in the temperature range of 15–35 ℃. Density functional theory (DFT) calculation demonstrates that Schiff base functionalized PAMAM dendrimer tends to coordinate Mn(Ⅱ) and Co(Ⅱ) with the oxygen atoms of hydroxyl and carbonyl groups, nitrogen of tertiary amine and imino groups. The imino and tertiary amine groups mainly dominate the adsorption. The reproducibility of the adsorbents indicates they can be regenerated by 5% thiourea and 0.5 mol/L HNO3 solution efficiently.
2020, 31(10): 2747-2751
doi: 10.1016/j.cclet.2020.06.016
Abstract:
Graphitic carbon nitride (g-C3N4)-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy. In this work, we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C3N4/CeO2 nanosheets with abundant oxygen vacancies (g-C3N4/CeO2-x). The hydrothermal-roasting and incomplete-sealed state can (ⅰ) generate an in-situ reducing atmosphere (CO, N2, NH3) to tune the concentration of oxygen vacancies in CeO2; (ⅱ) beneficial to prevent continuous growth of g-C3N4 and results in honeycomb-like g-C3N4/CeO2-x hybrid nanosheets. What is more, the g-C3N4/CeO2-x photocatalyst exhibited extended photoresponse range, increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs. As a proof-of-concept application, the optimized g-C3N4/CeO2-x nanosheets could achieve 98% removal efficiency for Cr(Ⅵ) under visible light irradiation (λ ≥ 420 nm) within 2.5 h, which is significantly better than those of pure g-C3N4 and CeO2. This work provides a new idea for more rationally designing and constructing g-C3N4-based catalysts for efficient extended photochemical application.
Graphitic carbon nitride (g-C3N4)-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy. In this work, we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C3N4/CeO2 nanosheets with abundant oxygen vacancies (g-C3N4/CeO2-x). The hydrothermal-roasting and incomplete-sealed state can (ⅰ) generate an in-situ reducing atmosphere (CO, N2, NH3) to tune the concentration of oxygen vacancies in CeO2; (ⅱ) beneficial to prevent continuous growth of g-C3N4 and results in honeycomb-like g-C3N4/CeO2-x hybrid nanosheets. What is more, the g-C3N4/CeO2-x photocatalyst exhibited extended photoresponse range, increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs. As a proof-of-concept application, the optimized g-C3N4/CeO2-x nanosheets could achieve 98% removal efficiency for Cr(Ⅵ) under visible light irradiation (λ ≥ 420 nm) within 2.5 h, which is significantly better than those of pure g-C3N4 and CeO2. This work provides a new idea for more rationally designing and constructing g-C3N4-based catalysts for efficient extended photochemical application.
2020, 31(10): 2752-2756
doi: 10.1016/j.cclet.2020.06.021
Abstract:
Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals. This article proposes a novel composite electrode based on a polyaniline (PANi) framework doped with bismuth nanoparticle@graphene oxide multi-walled carbon nanotubes (Bi NPs@GO-MWCNTs) for the simultaneous detection of multiple heavy metal ions. Composite electrodes are prepared on screen-printed electrodes (SPCEs) using an efficient dispensing technique. We used a SM200SX-3A dispenser to load a laboratory-specific ink with optimized viscosity and adhesion to draw a pattern on the work area. The SPCE was used as substrate to facilitate cost-effective and more convenient real-time detection technology. Electrochemical techniques, such as cyclic voltammetry and differential pulse voltammetry, were used to demonstrate the sensing capabilities of the proposed sensor. The sensitivity, limit of detection, and linear range of the PANi-Bi NPs@GO-MWCNT electrode are 2.57×102 μA L μmol-1 cm-2, 0.01 nmol/L, and 0.01 nmol/L–5 mmol/L and 0.15×10-1 μA L μmol-1 cm-2, 0.5 nmol/L, and 0.5 nmol/L–5 mmol/L for mercury ion (Hg(Ⅱ)) and copper ion (Cu(Ⅱ)) detection, respectively. In addition, the electrode exhibits a good selectivity and repeatability for Hg(Ⅱ) and Cu(Ⅱ) sensing when tested in a complex heavy metal ion solution. The constructed electrode system exhibits a detection performance superior to similar methods and also increases the types of heavy metal ions that can be detected. Therefore, the proposed device can be used as an efficient sensor for the detection of multiple heavy metal ions in complex environments.
Electrochemical analysis is a promising technique for detecting biotoxic and non-biodegradable heavy metals. This article proposes a novel composite electrode based on a polyaniline (PANi) framework doped with bismuth nanoparticle@graphene oxide multi-walled carbon nanotubes (Bi NPs@GO-MWCNTs) for the simultaneous detection of multiple heavy metal ions. Composite electrodes are prepared on screen-printed electrodes (SPCEs) using an efficient dispensing technique. We used a SM200SX-3A dispenser to load a laboratory-specific ink with optimized viscosity and adhesion to draw a pattern on the work area. The SPCE was used as substrate to facilitate cost-effective and more convenient real-time detection technology. Electrochemical techniques, such as cyclic voltammetry and differential pulse voltammetry, were used to demonstrate the sensing capabilities of the proposed sensor. The sensitivity, limit of detection, and linear range of the PANi-Bi NPs@GO-MWCNT electrode are 2.57×102 μA L μmol-1 cm-2, 0.01 nmol/L, and 0.01 nmol/L–5 mmol/L and 0.15×10-1 μA L μmol-1 cm-2, 0.5 nmol/L, and 0.5 nmol/L–5 mmol/L for mercury ion (Hg(Ⅱ)) and copper ion (Cu(Ⅱ)) detection, respectively. In addition, the electrode exhibits a good selectivity and repeatability for Hg(Ⅱ) and Cu(Ⅱ) sensing when tested in a complex heavy metal ion solution. The constructed electrode system exhibits a detection performance superior to similar methods and also increases the types of heavy metal ions that can be detected. Therefore, the proposed device can be used as an efficient sensor for the detection of multiple heavy metal ions in complex environments.
2020, 31(10): 2757-2761
doi: 10.1016/j.cclet.2020.01.032
Abstract:
In this study, a carbon quantum dots modified maghemite catalyst (CQDs@γ-Fe2O3) has been synthesized by a one-step solvothermal method for efficient persulfate (PDS) activation under visible light irradiation. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) characterization indicated that the formation of heterojunction structure between CQDs and γ-Fe2O3 effectively reduced the catalyst band gap (Eg), favoring the separation rate of electrons and holes, leading to remarkable efficient sulfamethoxazole (SMX) degradation as compared to the dark-CQDs@γ-Fe2O3/PDS and vis-γ-Fe2O3/PDS systems. The evolution of dissolved irons also demonstrated that CQDs could accelerate the in-situ reduction of surface-bounded Fe3+. Electron paramagnetic resonance (EPR) and radical scavenging experiments demonstrated that both ·OH and SO4·- were generated in the reaction system, while ·OH was relatively more dominant than SO4·- for SMX degradation. Finally, the reaction mechanism in the vis-CQDs@γ-Fe2O3/PDS system was proposed involving an effective and accelerated heterogeneous-homogeneous iron cycle. CQDs would enrich the photo-generated electrons from γ-Fe2O3, causing efficient interfacial generation of surface-bond Fe2+ and reduction of adsorbed Fe3+. This visible light induced iron cycle would eventually lead to effective activation of PDS as well as the efficient degradation of SMX.
In this study, a carbon quantum dots modified maghemite catalyst (CQDs@γ-Fe2O3) has been synthesized by a one-step solvothermal method for efficient persulfate (PDS) activation under visible light irradiation. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS) characterization indicated that the formation of heterojunction structure between CQDs and γ-Fe2O3 effectively reduced the catalyst band gap (Eg), favoring the separation rate of electrons and holes, leading to remarkable efficient sulfamethoxazole (SMX) degradation as compared to the dark-CQDs@γ-Fe2O3/PDS and vis-γ-Fe2O3/PDS systems. The evolution of dissolved irons also demonstrated that CQDs could accelerate the in-situ reduction of surface-bounded Fe3+. Electron paramagnetic resonance (EPR) and radical scavenging experiments demonstrated that both ·OH and SO4·- were generated in the reaction system, while ·OH was relatively more dominant than SO4·- for SMX degradation. Finally, the reaction mechanism in the vis-CQDs@γ-Fe2O3/PDS system was proposed involving an effective and accelerated heterogeneous-homogeneous iron cycle. CQDs would enrich the photo-generated electrons from γ-Fe2O3, causing efficient interfacial generation of surface-bond Fe2+ and reduction of adsorbed Fe3+. This visible light induced iron cycle would eventually lead to effective activation of PDS as well as the efficient degradation of SMX.
2020, 31(10): 2762-2768
doi: 10.1016/j.cclet.2020.04.022
Abstract:
Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal's electrocatalytic hydrodechlorination performance in converting 2, 4-dichlorophenol (2, 4-DCP) to phenol. The specific activity of the Pd nanoparticles (Pd NPs) on defective polymer carbon nitride (Pd/PCN-x) reaches 0.09 min-1 m-2Pd, which is 1.5 times that of the Pd NPs supported on the perfect PCN (Pd/PCN-0). The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites, limiting the dechlorination progress. The PCN-x containing -C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs, and promote the preferential adsorption of 2, 4-DCP rather than phenol, resulting in an enhanced dechlorination efficiency.
Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal's electrocatalytic hydrodechlorination performance in converting 2, 4-dichlorophenol (2, 4-DCP) to phenol. The specific activity of the Pd nanoparticles (Pd NPs) on defective polymer carbon nitride (Pd/PCN-x) reaches 0.09 min-1 m-2Pd, which is 1.5 times that of the Pd NPs supported on the perfect PCN (Pd/PCN-0). The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites, limiting the dechlorination progress. The PCN-x containing -C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs, and promote the preferential adsorption of 2, 4-DCP rather than phenol, resulting in an enhanced dechlorination efficiency.
2020, 31(10): 2769-2773
doi: 10.1016/j.cclet.2020.06.040
Abstract:
This study demonstrated interesting ultrafast activation of molecular O2 by copper oxide (CuO) particles and very rapid elimination of aqueous 2, 4-dichlorophenol (2, 4-DCP) within reaction time of 30 s. Electron paramagnetic resonance (EPR) characterization indicated that ·OH, Cu3+, 1O2 and O2·- were generated in the CuO/O2 systems, wherein O2·- would be the main reactive species responsible for 2, 4-DCP degradation. It was further found that the catalytic ability of CuO for O2 activation was highly size dependent and nano-CuO was far reactive than micro-CuO. H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) analyses revealed that both the quantity and the reactivity of the surface reaction sites (surface Cu+ and O2) could determine the catalytic ability of CuO affecting efficient Cu+-based molecular oxygen activation. Moreover, the O2 activation ability of CuO would depend on not only the dimension, but also crystalline factors, for example, the exposed facets.
This study demonstrated interesting ultrafast activation of molecular O2 by copper oxide (CuO) particles and very rapid elimination of aqueous 2, 4-dichlorophenol (2, 4-DCP) within reaction time of 30 s. Electron paramagnetic resonance (EPR) characterization indicated that ·OH, Cu3+, 1O2 and O2·- were generated in the CuO/O2 systems, wherein O2·- would be the main reactive species responsible for 2, 4-DCP degradation. It was further found that the catalytic ability of CuO for O2 activation was highly size dependent and nano-CuO was far reactive than micro-CuO. H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) analyses revealed that both the quantity and the reactivity of the surface reaction sites (surface Cu+ and O2) could determine the catalytic ability of CuO affecting efficient Cu+-based molecular oxygen activation. Moreover, the O2 activation ability of CuO would depend on not only the dimension, but also crystalline factors, for example, the exposed facets.
2020, 31(10): 2774-2778
doi: 10.1016/j.cclet.2020.07.019
Abstract:
The rapid recombination of photoinduced electron-hole pairs as well as the deficiency of high-energy carriers restricted the redox ability and products selectivity. Herein, the heterojunction of SnS2-decorated three-dimensional ordered macropores (3DOM)-SrTiO3 catalysts were in-situ constructed to provide transmit channel for high-energy electron transmission. The suitable band edges of SnS2 and SrTiO3 contribute to the Z-scheme transfer of photogenerated carrier. The 3DOM structure of SrTiO3-based catalyst possesses the slow light effect for enhancing light adsorption efficiency, and the surface alkalis strontium is benefit to the boosting adsorption for CO2. The in-situ introduced SnS2 decorated on the macroporous wall surface of 3DOM-SrTiO3 altered the primary product from CO to CH4. The Z-scheme electron transfer from SnS2 combining with the holes in SrTiO3 occurred under full spectrum photoexcitation, which improved the excitation and utilization of photogenerated electrons for CO2 multi-electrons reduction. As a result, (SnS2)3/3DOM-SrTiO3 catalyst exhibits higher activity for photocatalytic CO2 reduction to CH4 compared with single SnS2 or 3DOM-SrTiO3, i.e., its yield and selectivity of CH4 are 12.5 μmol g-1 h-1 and 74.9%, respectively. The present work proposed the theoretical foundation of Z-scheme heterojunction construction for enhancing photocatalytic activity and selectivity for CO2 conversion.
The rapid recombination of photoinduced electron-hole pairs as well as the deficiency of high-energy carriers restricted the redox ability and products selectivity. Herein, the heterojunction of SnS2-decorated three-dimensional ordered macropores (3DOM)-SrTiO3 catalysts were in-situ constructed to provide transmit channel for high-energy electron transmission. The suitable band edges of SnS2 and SrTiO3 contribute to the Z-scheme transfer of photogenerated carrier. The 3DOM structure of SrTiO3-based catalyst possesses the slow light effect for enhancing light adsorption efficiency, and the surface alkalis strontium is benefit to the boosting adsorption for CO2. The in-situ introduced SnS2 decorated on the macroporous wall surface of 3DOM-SrTiO3 altered the primary product from CO to CH4. The Z-scheme electron transfer from SnS2 combining with the holes in SrTiO3 occurred under full spectrum photoexcitation, which improved the excitation and utilization of photogenerated electrons for CO2 multi-electrons reduction. As a result, (SnS2)3/3DOM-SrTiO3 catalyst exhibits higher activity for photocatalytic CO2 reduction to CH4 compared with single SnS2 or 3DOM-SrTiO3, i.e., its yield and selectivity of CH4 are 12.5 μmol g-1 h-1 and 74.9%, respectively. The present work proposed the theoretical foundation of Z-scheme heterojunction construction for enhancing photocatalytic activity and selectivity for CO2 conversion.
2020, 31(10): 2779-2783
doi: 10.1016/j.cclet.2020.07.024
Abstract:
The removal efficiency of pollutants in Fe(0) electrocoagulation (EC) has been associated closely with the speciation of generated Fe(II)/Fe(III) oxides during this process, which is very complicated and can be affected by various factors. In this work, in-situ Raman, X-ray diffraction and some other techniques have been used to study the speciation of Fe under different conditions and to establish a relationship between Fe speciation and Sb(V) removal efficiency. Results indicated that concentration of dissolved oxygen (DO) is a key factor influencing Fe(0) EC. It was found that green rusts (GRs) were formed and were then transformed into magnetite at lower DO concentration, and Sb(V) removal efficiency reached 99.9% after 30 min of EC. In contrast, γ-FeOOH was formed at high DO concentration, and the removal efficiency of Sb(V) after 30 min of EC was only 72.8%. In the presence of sulfite and phosphate with low concentrations, GRs can be stabilized and benefit the removal of Sb(V). We believe this work will provide some new insights on the mechanism of Fe(0) EC and the effective removal of other pollutants during Fe(0) EC process.
The removal efficiency of pollutants in Fe(0) electrocoagulation (EC) has been associated closely with the speciation of generated Fe(II)/Fe(III) oxides during this process, which is very complicated and can be affected by various factors. In this work, in-situ Raman, X-ray diffraction and some other techniques have been used to study the speciation of Fe under different conditions and to establish a relationship between Fe speciation and Sb(V) removal efficiency. Results indicated that concentration of dissolved oxygen (DO) is a key factor influencing Fe(0) EC. It was found that green rusts (GRs) were formed and were then transformed into magnetite at lower DO concentration, and Sb(V) removal efficiency reached 99.9% after 30 min of EC. In contrast, γ-FeOOH was formed at high DO concentration, and the removal efficiency of Sb(V) after 30 min of EC was only 72.8%. In the presence of sulfite and phosphate with low concentrations, GRs can be stabilized and benefit the removal of Sb(V). We believe this work will provide some new insights on the mechanism of Fe(0) EC and the effective removal of other pollutants during Fe(0) EC process.
2020, 31(10): 2784-2788
doi: 10.1016/j.cclet.2020.07.033
Abstract:
Efficient generation of singlet oxygen (1O2) by an excitonic energy transfer process is highly desired on a semiconductor photocatalyst for selective oxidation of methyl phenyl sulfide (MPS). Herein, it is demonstrated that a large amount of 1O2 is produced on pristine graphitic carbon nitride (CN) nanosheet compared with bismuth oxybromide (BiOBr) and commercial P25 titanium dioxide (TiO2). This leads to a certain photoactivity of CN for MPS oxidation. The observed ~77% selectivity for CN depends on the competitive results of excitonic energy transfer for 1O2 formation and charge carrier separation for superoxide radical (O2·-) production, which are based on the phosphorescence spectra and electron paramagnetic resonance signals, respectively. Moreover, ultrathin CN nanosheets are synthesized by thermal treatment with the cyanuric acid-melamine hydrogen bonded aggregates as precursors. It is confirmed that the amount of produced 1O2 could be increased by decreasing the thickness of resultant CN nanosheets. The optimized ultrathin CN nanosheet (~4 nm) exhibits excellent photoactivity with high selectivity (~99%). It is suggested that the excitonic energy transfer for 1O2 formation is close related to the intrinsic exciton binding energy and the two-dimensional quantum confinement effect. This work establishes a basic mechanistic understanding on the excitonic processes in CN, and develops a feasible route to design CN-based photocatalysts for efficient 1O2 generation.
Efficient generation of singlet oxygen (1O2) by an excitonic energy transfer process is highly desired on a semiconductor photocatalyst for selective oxidation of methyl phenyl sulfide (MPS). Herein, it is demonstrated that a large amount of 1O2 is produced on pristine graphitic carbon nitride (CN) nanosheet compared with bismuth oxybromide (BiOBr) and commercial P25 titanium dioxide (TiO2). This leads to a certain photoactivity of CN for MPS oxidation. The observed ~77% selectivity for CN depends on the competitive results of excitonic energy transfer for 1O2 formation and charge carrier separation for superoxide radical (O2·-) production, which are based on the phosphorescence spectra and electron paramagnetic resonance signals, respectively. Moreover, ultrathin CN nanosheets are synthesized by thermal treatment with the cyanuric acid-melamine hydrogen bonded aggregates as precursors. It is confirmed that the amount of produced 1O2 could be increased by decreasing the thickness of resultant CN nanosheets. The optimized ultrathin CN nanosheet (~4 nm) exhibits excellent photoactivity with high selectivity (~99%). It is suggested that the excitonic energy transfer for 1O2 formation is close related to the intrinsic exciton binding energy and the two-dimensional quantum confinement effect. This work establishes a basic mechanistic understanding on the excitonic processes in CN, and develops a feasible route to design CN-based photocatalysts for efficient 1O2 generation.
2020, 31(10): 2789-2794
doi: 10.1016/j.cclet.2020.07.043
Abstract:
In order to efficiently remove tetracycline in wastewater through the synergistic effect of adsorption and photocatalytic degradation, a series of novel composite materials (Cu doped g-C3N4) were synthesized by two-pot hydrothermal method. It was found that the composite materials with optimized ratio (Cu/CN-1) displayed outstanding adsorption and photocatalytic performance as compared with pure g-C3N4 photocatalyst. The removal efficiency of tetracycline (TC, 50 mg/L) reached almost 99% within 30 min by Cu/CN-1 through the synergy of adsorption and photocatalysis under visible-light irradiation, which was the highest removal efficiency ever reported. The adsorption kinetics and isotherms of TC on the Cu/CN-1 were well fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. Moreover, it was confirmed that the main effective reactive groups were O2·- and h+ in photocatalytic process. The Cu/CN-1 exhibited high stability and excellent reusability after five cycle experiments. Finally, the mechanism of synergy between Cu and g-C3N4 was proposed: on the one hand, the decoration of Cu particles significantly increased the adsorption sites of Cu/CN-1 to tetracycline, on the other hand, the modification of Cu particles effectively inhibits charge recombination and broadens the visible light absorption range of the photocatalyst.This study provided a promising photocatalyst to be used for TC removal in the actual wastewater.
In order to efficiently remove tetracycline in wastewater through the synergistic effect of adsorption and photocatalytic degradation, a series of novel composite materials (Cu doped g-C3N4) were synthesized by two-pot hydrothermal method. It was found that the composite materials with optimized ratio (Cu/CN-1) displayed outstanding adsorption and photocatalytic performance as compared with pure g-C3N4 photocatalyst. The removal efficiency of tetracycline (TC, 50 mg/L) reached almost 99% within 30 min by Cu/CN-1 through the synergy of adsorption and photocatalysis under visible-light irradiation, which was the highest removal efficiency ever reported. The adsorption kinetics and isotherms of TC on the Cu/CN-1 were well fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. Moreover, it was confirmed that the main effective reactive groups were O2·- and h+ in photocatalytic process. The Cu/CN-1 exhibited high stability and excellent reusability after five cycle experiments. Finally, the mechanism of synergy between Cu and g-C3N4 was proposed: on the one hand, the decoration of Cu particles significantly increased the adsorption sites of Cu/CN-1 to tetracycline, on the other hand, the modification of Cu particles effectively inhibits charge recombination and broadens the visible light absorption range of the photocatalyst.This study provided a promising photocatalyst to be used for TC removal in the actual wastewater.
2020, 31(10): 2795-2798
doi: 10.1016/j.cclet.2020.07.046
Abstract:
The development of photocatalysts for hydrogen evolution is a promising alternative to industrial hydrogen evolution; however, generation of high active, recyclable, inexpensive heterojunctions are still challenging. Herein, a novel strategy was developed to synthesize non-noble metal co-catalyst/solid solution heterojunctions using metal-organic frameworks (MOFs) as a precursor template. By adjusting the content of MOFs, a series of Cu1.8S/ZnxCd1-xS heterojunctions were obtained, and the Cu1.8S(3.7%)/Zn0.35Cd0.65S sample exhibits a maximum hydrogen evolution rate of 14.27 mmol h-1 g-1 with an apparent quantum yield of 3.7% at 420 nm under visible-light irradiation. Subsequently, the relationship between the heterojunction and photocatalytic activity were investigated by detailed characterizations and density functional theory (DFT) calculations, which reveal that loading Cu1.8S can efficiently extend the light absorption, meanwhile, the electrons can efficiently transfer from Zn0.35Cd0.65S to Cu1.8S, thus resulting more photogenerated electrons participating in surface reactions. This result can be valuable inspirations for the exploitation of advanced materials using rationally designed nanostructures for solar energy conversion.
The development of photocatalysts for hydrogen evolution is a promising alternative to industrial hydrogen evolution; however, generation of high active, recyclable, inexpensive heterojunctions are still challenging. Herein, a novel strategy was developed to synthesize non-noble metal co-catalyst/solid solution heterojunctions using metal-organic frameworks (MOFs) as a precursor template. By adjusting the content of MOFs, a series of Cu1.8S/ZnxCd1-xS heterojunctions were obtained, and the Cu1.8S(3.7%)/Zn0.35Cd0.65S sample exhibits a maximum hydrogen evolution rate of 14.27 mmol h-1 g-1 with an apparent quantum yield of 3.7% at 420 nm under visible-light irradiation. Subsequently, the relationship between the heterojunction and photocatalytic activity were investigated by detailed characterizations and density functional theory (DFT) calculations, which reveal that loading Cu1.8S can efficiently extend the light absorption, meanwhile, the electrons can efficiently transfer from Zn0.35Cd0.65S to Cu1.8S, thus resulting more photogenerated electrons participating in surface reactions. This result can be valuable inspirations for the exploitation of advanced materials using rationally designed nanostructures for solar energy conversion.
2020, 31(10): 2799-2802
doi: 10.1016/j.cclet.2020.07.051
Abstract:
A low-pressure reactor (LPR) was developed for the measurement of ambient organic peroxy (RO2) radicals with the use of the laser-induced fluorescence (LIF) instrument. The reactor converts all the ROx (=RO2 + HO2 + RO + OH) radicals into HO2 radicals. It can conduct different measurement modes through altering the reagent gases, achieving the speciated measurement of RO2 and RO2# (RO2 radicals derived from the long-chain alkane, alkene and aromatic hydrocarbon). An example of field measurement results was given, with a maximum concentration of 1.88×108 molecule/cm3 for RO2 and 1.18×108 molecule/cm3 for RO2#. Also, this instrument quantifies the local ozone production rates directly, which can help to deduce the regional ozone control strategy from an experimental perspective. The new device can serve as a potent tool for both the exploration of frontier chemistry and the diagnosis of the control strategies.
A low-pressure reactor (LPR) was developed for the measurement of ambient organic peroxy (RO2) radicals with the use of the laser-induced fluorescence (LIF) instrument. The reactor converts all the ROx (=RO2 + HO2 + RO + OH) radicals into HO2 radicals. It can conduct different measurement modes through altering the reagent gases, achieving the speciated measurement of RO2 and RO2# (RO2 radicals derived from the long-chain alkane, alkene and aromatic hydrocarbon). An example of field measurement results was given, with a maximum concentration of 1.88×108 molecule/cm3 for RO2 and 1.18×108 molecule/cm3 for RO2#. Also, this instrument quantifies the local ozone production rates directly, which can help to deduce the regional ozone control strategy from an experimental perspective. The new device can serve as a potent tool for both the exploration of frontier chemistry and the diagnosis of the control strategies.
2020, 31(10): 2803-2808
doi: 10.1016/j.cclet.2020.08.002
Abstract:
Although MoS2 has been proved to be a very ideal cocatalyst in advanced oxidation process (AOPs), the activation process of peroxymonosulfate (PMS) is still inseparable from metal ions which inevitably brings the risk of secondary pollution and it is not conducive to large-scale industrial application. In this study, the commercial MoS2, as a durable and efficient catalyst, was used for directly activating PMS to degrade aromatic organic pollutant. The commercial MoS2/PMS catalytic system demonstrated excellent removal efficiency of phenol and the total organic carbon (TOC) residual rate reach to 25%. The degradation rate was significantly reduced if the used MoS2 was directly carried out the next cycle experiment without any post-treatment. Interestingly, the commercial MoS2 after post-treated with H2O2 can exhibit good stability and recyclability for cyclic degradation of phenol. Furthermore, the mechanism for the activation of PMS had been investigated by density functional theory (DFT) calculation. The renewable Mo4+ exposed on the surface of MoS2 was deduced as the primary active site, which realized the direct activation of PMS and avoided secondary pollution. Taking into account the reaction cost and efficient activity, the development of commercial MoS2 catalytic system is expected to be applied in industrial wastewater.
Although MoS2 has been proved to be a very ideal cocatalyst in advanced oxidation process (AOPs), the activation process of peroxymonosulfate (PMS) is still inseparable from metal ions which inevitably brings the risk of secondary pollution and it is not conducive to large-scale industrial application. In this study, the commercial MoS2, as a durable and efficient catalyst, was used for directly activating PMS to degrade aromatic organic pollutant. The commercial MoS2/PMS catalytic system demonstrated excellent removal efficiency of phenol and the total organic carbon (TOC) residual rate reach to 25%. The degradation rate was significantly reduced if the used MoS2 was directly carried out the next cycle experiment without any post-treatment. Interestingly, the commercial MoS2 after post-treated with H2O2 can exhibit good stability and recyclability for cyclic degradation of phenol. Furthermore, the mechanism for the activation of PMS had been investigated by density functional theory (DFT) calculation. The renewable Mo4+ exposed on the surface of MoS2 was deduced as the primary active site, which realized the direct activation of PMS and avoided secondary pollution. Taking into account the reaction cost and efficient activity, the development of commercial MoS2 catalytic system is expected to be applied in industrial wastewater.
2020, 31(10): 2809-2813
doi: 10.1016/j.cclet.2020.07.052
Abstract:
Due to the relatively sluggish charge carrier separation in metal sulfides, the photocatalytic activity of them is still far lower than expected. Herein, sulfur vacancies and in-plane SnS2/SnO2 heterojunction were successfully introduced into the SnS2 nanosheets through high energy ball-milling. These defective structures were studied by the electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope analyses. The sulfur vacancies and in-plane heterojunctions strongly accelerate the separation of photoexcited electron-hole pairs, as confirmed by the photoluminescence emission spectra and time-resolved photoluminescence decay spectra. The introduction of sulfur vacancies and in-plane heterojunction in SnS2 nanosheets results in roughly six times higher photodegrading rate for methyl orange and four times higher photocatalytic reduction rate of Cr6+ than those of pure SnS2 nanosheets.
Due to the relatively sluggish charge carrier separation in metal sulfides, the photocatalytic activity of them is still far lower than expected. Herein, sulfur vacancies and in-plane SnS2/SnO2 heterojunction were successfully introduced into the SnS2 nanosheets through high energy ball-milling. These defective structures were studied by the electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope analyses. The sulfur vacancies and in-plane heterojunctions strongly accelerate the separation of photoexcited electron-hole pairs, as confirmed by the photoluminescence emission spectra and time-resolved photoluminescence decay spectra. The introduction of sulfur vacancies and in-plane heterojunction in SnS2 nanosheets results in roughly six times higher photodegrading rate for methyl orange and four times higher photocatalytic reduction rate of Cr6+ than those of pure SnS2 nanosheets.
2020, 31(10): 2814-2818
doi: 10.1016/j.cclet.2020.03.055
Abstract:
An innovative method for the ultrasensitive detection of mercury by solution anode glow discharge atomic emission spectroscopy (SAGD-AES) coupled with hydride generation (HG) was first investigated. In this method, the mercury vapor generated by the HG was transmitted to the SAGD through the miniature hollow tungsten tube for excitation and detected by a miniaturized spectrograph. A thorough parametric evaluation of the HG and SAGD system was performed, including the type and concentration of carrier acid, He flow rate, concentrations of NaBH4, discharge current and discharge gap. Under optimal operating conditions, the detection limit for Hg2+ achieved 0.03 μg/L, with a relative standard deviation of 1.1% at the Hg2+ concentration of 5 μg/L. Moreover, the correlation coefficient of the calibration curve was 0.9996 in the range between 0.1 and 10 μg/L. The accuracy and practicability of HG-SAGD-AES were verified by measuring GBW09101b (human hair), GBW10029 (fish), soil and rice samples. The results showed good agreement with the certified values and values from direct mercury analyzer (DMA).
An innovative method for the ultrasensitive detection of mercury by solution anode glow discharge atomic emission spectroscopy (SAGD-AES) coupled with hydride generation (HG) was first investigated. In this method, the mercury vapor generated by the HG was transmitted to the SAGD through the miniature hollow tungsten tube for excitation and detected by a miniaturized spectrograph. A thorough parametric evaluation of the HG and SAGD system was performed, including the type and concentration of carrier acid, He flow rate, concentrations of NaBH4, discharge current and discharge gap. Under optimal operating conditions, the detection limit for Hg2+ achieved 0.03 μg/L, with a relative standard deviation of 1.1% at the Hg2+ concentration of 5 μg/L. Moreover, the correlation coefficient of the calibration curve was 0.9996 in the range between 0.1 and 10 μg/L. The accuracy and practicability of HG-SAGD-AES were verified by measuring GBW09101b (human hair), GBW10029 (fish), soil and rice samples. The results showed good agreement with the certified values and values from direct mercury analyzer (DMA).
2020, 31(10): 2819-2824
doi: 10.1016/j.cclet.2020.08.004
Abstract:
Macroporous 3D carbon doped with nitrogen confined Mo catalyst (MoOx@CN) had been prepared by a facile one-step pyrolysis technique using silica as a template and was employed for oxidative desulfurization (ODS) of dibenzothiophene (DBT) in model fuel with H2O2 as oxidant. The effect of different operating conditions (i.e., reaction temperature and time, catalyst dosage, H2O2/DBT (O/S) molar ratio) were also systematic investigated. Under the optimal reaction condition, MoOx@CN catalyst exhibited highly excellent ODS performance toward DBT, the highest sulfur removal efficiency can be up to 99.9% and sulfur content was wiped out from 800 ppm to 10 ppm. Due to the robust 3D structure promoting rapid transfer, in addition to the increased number of active sites induced by the Mo vacancies, the catalyst, prepared using chitosan and ammonium heptamolybdate in a mass ratio of 1:0.5, displayed rapid kinetics and low activation energy in the oxidation of dibenzothiophene. Moreover, it exhibited excellent recyclability after five cycles without any obvious decrease in catalytic activity for the oxidative desulfurization reaction.
Macroporous 3D carbon doped with nitrogen confined Mo catalyst (MoOx@CN) had been prepared by a facile one-step pyrolysis technique using silica as a template and was employed for oxidative desulfurization (ODS) of dibenzothiophene (DBT) in model fuel with H2O2 as oxidant. The effect of different operating conditions (i.e., reaction temperature and time, catalyst dosage, H2O2/DBT (O/S) molar ratio) were also systematic investigated. Under the optimal reaction condition, MoOx@CN catalyst exhibited highly excellent ODS performance toward DBT, the highest sulfur removal efficiency can be up to 99.9% and sulfur content was wiped out from 800 ppm to 10 ppm. Due to the robust 3D structure promoting rapid transfer, in addition to the increased number of active sites induced by the Mo vacancies, the catalyst, prepared using chitosan and ammonium heptamolybdate in a mass ratio of 1:0.5, displayed rapid kinetics and low activation energy in the oxidation of dibenzothiophene. Moreover, it exhibited excellent recyclability after five cycles without any obvious decrease in catalytic activity for the oxidative desulfurization reaction.
2020, 31(10): 2825-2830
doi: 10.1016/j.cclet.2020.06.029
Abstract:
This study evaluated the removal of multiple pollutants, i.e., polybrominated diphenyl ethers (PBDEs), novel halogenated flame retardants (HFRs), sulfonamide antibiotics (SAs), and heavy metals (HMs), by a full-scale reversed A2/O process in a sewage treatment plant (STP) in Guangzhou, China. The reversed A2/O process demonstrated high removal efficiencies (REs) for total PBDEs (60.5%±4.3%), novel HFRs (98.4%±2.8%) and HMs (70.1%±1.2%), and a relatively low RE for SAs (25.0%±2.3%). BDE 209, the dominant PBDE congener, showed a high residual concentration (13.41±5.18 ng/L) in the suspended particulate matter (SPM) of treated effluents. Some novel HFRs, dechlorane plus (DP) and decabromodiphenyl ethane (DBDPE), were detected in the SPM of the raw sewage (7.50±4.14 ng/L and 11.52±11.65 ng/L, respectively). The removal of SAs was mainly through biodegradation in the activated sludge bioreactors(ASBs).Of the HMs, Mn and Ni exhibited the lowest REs (47.5%±2.2% and 35.0%±2.6%, respectively), while Cr and Cu showed the highest removal (REs > 80%). In terms of treatment units in the reversed A2/O process, ASBs showed the highest RE (27.8%) for the multiple pollutants. The information can aid in our understanding of removal properties of STPs on various pollutants and evaluating the ecological/health risks of STPs as point pollutant sources.
This study evaluated the removal of multiple pollutants, i.e., polybrominated diphenyl ethers (PBDEs), novel halogenated flame retardants (HFRs), sulfonamide antibiotics (SAs), and heavy metals (HMs), by a full-scale reversed A2/O process in a sewage treatment plant (STP) in Guangzhou, China. The reversed A2/O process demonstrated high removal efficiencies (REs) for total PBDEs (60.5%±4.3%), novel HFRs (98.4%±2.8%) and HMs (70.1%±1.2%), and a relatively low RE for SAs (25.0%±2.3%). BDE 209, the dominant PBDE congener, showed a high residual concentration (13.41±5.18 ng/L) in the suspended particulate matter (SPM) of treated effluents. Some novel HFRs, dechlorane plus (DP) and decabromodiphenyl ethane (DBDPE), were detected in the SPM of the raw sewage (7.50±4.14 ng/L and 11.52±11.65 ng/L, respectively). The removal of SAs was mainly through biodegradation in the activated sludge bioreactors(ASBs).Of the HMs, Mn and Ni exhibited the lowest REs (47.5%±2.2% and 35.0%±2.6%, respectively), while Cr and Cu showed the highest removal (REs > 80%). In terms of treatment units in the reversed A2/O process, ASBs showed the highest RE (27.8%) for the multiple pollutants. The information can aid in our understanding of removal properties of STPs on various pollutants and evaluating the ecological/health risks of STPs as point pollutant sources.
2020, 31(10): 2831-2834
doi: 10.1016/j.cclet.2020.08.006
Abstract:
This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac (DCF), as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanoparticles (nZVI), respectively. Further observations on the evolution of O2 activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase (started by nZVI/Cu2+). Interesting breakpoints were observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH, as the original nZVI just consumed up to Fe(Ⅱ) and Cu(Ⅱ) appeared again. It suggested that the four-electrons reaction of O2 and Cu-deposited nZVI would occur to generate water prior to the breakpoints, while Cu(0) and Fe(Ⅱ) would play most important role in activation of O2 afterwards. Through the electron spin resonance (ESR) analysis and quenching experiments, ·OH was identified as the responsible reactive species. Further time-dependent quantifications in the cases of Cu(0)/Fe(Ⅱ) systems were carried out. It was found that the ·OH accumulation was positively and linearly correlated with nCu dose, Fe(Ⅱ) consumption, and Fe(Ⅱ) dose, respectively. Since either Cu(0) or Fe(Ⅱ) would be inefficient in activating oxygen to produce ·OH, a stage-evolution mechanism of O2 activated by nano Fe/Cu bimetals was proposed involving: (a) Rapid consumption of Fe(0) and release of Fe(Ⅱ) based on the Cu-Fe galvanic corrosion, (b) adsorption and transformation of O2 to O22- at the nCu surface, and (c) Fe(Ⅱ)-catalyzed activation of the adsorbed O22- to ·OH.
This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac (DCF), as compared to much slow removal of DCF by Cu(Ⅱ) or zero valent iron nanoparticles (nZVI), respectively. Further observations on the evolution of O2 activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase (started by nZVI/Cu2+). Interesting breakpoints were observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH, as the original nZVI just consumed up to Fe(Ⅱ) and Cu(Ⅱ) appeared again. It suggested that the four-electrons reaction of O2 and Cu-deposited nZVI would occur to generate water prior to the breakpoints, while Cu(0) and Fe(Ⅱ) would play most important role in activation of O2 afterwards. Through the electron spin resonance (ESR) analysis and quenching experiments, ·OH was identified as the responsible reactive species. Further time-dependent quantifications in the cases of Cu(0)/Fe(Ⅱ) systems were carried out. It was found that the ·OH accumulation was positively and linearly correlated with nCu dose, Fe(Ⅱ) consumption, and Fe(Ⅱ) dose, respectively. Since either Cu(0) or Fe(Ⅱ) would be inefficient in activating oxygen to produce ·OH, a stage-evolution mechanism of O2 activated by nano Fe/Cu bimetals was proposed involving: (a) Rapid consumption of Fe(0) and release of Fe(Ⅱ) based on the Cu-Fe galvanic corrosion, (b) adsorption and transformation of O2 to O22- at the nCu surface, and (c) Fe(Ⅱ)-catalyzed activation of the adsorbed O22- to ·OH.
2020, 31(10): 2835-2838
doi: 10.1016/j.cclet.2020.03.035
Abstract:
In this paper, a novel mesoporous silica gel evenly doped by Prussian blue nanoparticles (PBMSG) was successfully synthesized by using N, N-dimethylamide as template with a large Barrett-Emmett-Teller (BET) surface area of 505 m2/g and an average pore size of 2.9 nm. The static adsorption experiments showed that the equilibration time of PBMSG for Cs+ was about 30 min. The adsorption isotherm of PBMSG for Cs+ accorded with Langmuir model and the theoretical maximum adsorption capacity was 80.0±2.9 mg/g. When the initial concentration of Cs+ was 1.00 mg/L, the adsorption partition coefficient Kd could reach 3.5×104 mL/g After adsorption, Cs+ could be eluted by dilute hydrochloric acid (pH 2) with an efficiency of 89.8%, while no K+, Fe3+, Fe2+ was eluted. PBMSG exhibited good selectivity toward Cs+ and Rb+. In the presence of high concentration of K+, the selective adsorption of PBMSG could change the mass ratio of K+, Rb+ and Cs+ from 96.63:0.83:1.00–1.12:0.73:1.00. The separation of Cs+ and Rb+ from K+ with similar concentration (100 mg/g) was realized by column experiment. This indicated that PBMSG was suitable for rapid recovery of low concentration of rubidium and cesium from complex matrixes, such as wastewater and salt lake brine, etc.
In this paper, a novel mesoporous silica gel evenly doped by Prussian blue nanoparticles (PBMSG) was successfully synthesized by using N, N-dimethylamide as template with a large Barrett-Emmett-Teller (BET) surface area of 505 m2/g and an average pore size of 2.9 nm. The static adsorption experiments showed that the equilibration time of PBMSG for Cs+ was about 30 min. The adsorption isotherm of PBMSG for Cs+ accorded with Langmuir model and the theoretical maximum adsorption capacity was 80.0±2.9 mg/g. When the initial concentration of Cs+ was 1.00 mg/L, the adsorption partition coefficient Kd could reach 3.5×104 mL/g After adsorption, Cs+ could be eluted by dilute hydrochloric acid (pH 2) with an efficiency of 89.8%, while no K+, Fe3+, Fe2+ was eluted. PBMSG exhibited good selectivity toward Cs+ and Rb+. In the presence of high concentration of K+, the selective adsorption of PBMSG could change the mass ratio of K+, Rb+ and Cs+ from 96.63:0.83:1.00–1.12:0.73:1.00. The separation of Cs+ and Rb+ from K+ with similar concentration (100 mg/g) was realized by column experiment. This indicated that PBMSG was suitable for rapid recovery of low concentration of rubidium and cesium from complex matrixes, such as wastewater and salt lake brine, etc.
2020, 31(10): 2839-2842
doi: 10.1016/j.cclet.2020.08.021
Abstract:
Electrochemical detection is an efficient method for the detection of Bisphenol A (BPA). Herein, a sensitive photo-electrochemical sensor based on two-dimensional (2D) TiO2 (001) nanosheets was fabricated and then used for BPA electrochemical detection. Upon light irradiation, the 2D TiO2 (001) nanosheets electrode provided a lower detection limit of BPA detection compared with an ambient electrochemical determination. The low detection limit is ~5.37 nmol/L (S/N=3). Furthermore, profiting from the photoelectric characteristics, the 2D TiO2 (001) nanosheets electrode exhibits a nice regeneration property. After 45 min of light irradiation, the electrochemical signal was regenerated from 14.7% to 82.9% of the original signal at the 6th cycle. This is attributed to the non-selective ·OH mediation produced by the 2D TiO2 (001) nanosheets mineralizing anodic polymeric products and resuming surface reactive sites. This investigation indicates that photo-assistance is an efficient method to improve the electrochemical sensor for detecting BPA in water environments.
Electrochemical detection is an efficient method for the detection of Bisphenol A (BPA). Herein, a sensitive photo-electrochemical sensor based on two-dimensional (2D) TiO2 (001) nanosheets was fabricated and then used for BPA electrochemical detection. Upon light irradiation, the 2D TiO2 (001) nanosheets electrode provided a lower detection limit of BPA detection compared with an ambient electrochemical determination. The low detection limit is ~5.37 nmol/L (S/N=3). Furthermore, profiting from the photoelectric characteristics, the 2D TiO2 (001) nanosheets electrode exhibits a nice regeneration property. After 45 min of light irradiation, the electrochemical signal was regenerated from 14.7% to 82.9% of the original signal at the 6th cycle. This is attributed to the non-selective ·OH mediation produced by the 2D TiO2 (001) nanosheets mineralizing anodic polymeric products and resuming surface reactive sites. This investigation indicates that photo-assistance is an efficient method to improve the electrochemical sensor for detecting BPA in water environments.
2020, 31(10): 2843-2848
doi: 10.1016/j.cclet.2020.08.015
Abstract:
There is a growing need to eliminate antibiotic resistance genes (ARGs) in the environment and mitigate widespread antibiotic resistance. Graphitic carbon nitride (g-C3N4) was successfully synthesized via facile thermal polymerization approach and its potential for adsorption treatment of ARGs in water was examined. Batch adsorption experimental results revealed that g-C3N4 powders had robust adsorption activity for the gene ampC and ermB. Adsorption kinetics and isotherms were systematically investigated to explain the adsorption mechanism. The apparent adsorption equilibrium could be reached within 180 min. The adsorption process effectively removed ARGs (ampC and ermB) from water with 3.2 log and 4.2 log reductions, respectively. In addition, experimental data were analyzed by several models and simulated well with Langmuir isotherm and pseudo-second-order model. It indicated that adsorption process might be dominated by the chemical rate-limiting step. Moreover, the effects of temperature and pH on the removal of ARGs were conducted and the isoelectric point (IEP) was obtained. Finally, we have demonstrated that the g-C3N4 is a novel adsorbent and can be used as column packing to remove ARGs by filtration.
There is a growing need to eliminate antibiotic resistance genes (ARGs) in the environment and mitigate widespread antibiotic resistance. Graphitic carbon nitride (g-C3N4) was successfully synthesized via facile thermal polymerization approach and its potential for adsorption treatment of ARGs in water was examined. Batch adsorption experimental results revealed that g-C3N4 powders had robust adsorption activity for the gene ampC and ermB. Adsorption kinetics and isotherms were systematically investigated to explain the adsorption mechanism. The apparent adsorption equilibrium could be reached within 180 min. The adsorption process effectively removed ARGs (ampC and ermB) from water with 3.2 log and 4.2 log reductions, respectively. In addition, experimental data were analyzed by several models and simulated well with Langmuir isotherm and pseudo-second-order model. It indicated that adsorption process might be dominated by the chemical rate-limiting step. Moreover, the effects of temperature and pH on the removal of ARGs were conducted and the isoelectric point (IEP) was obtained. Finally, we have demonstrated that the g-C3N4 is a novel adsorbent and can be used as column packing to remove ARGs by filtration.
2020, 31(10): 2849-2853
doi: 10.1016/j.cclet.2020.08.017
Abstract:
A magnetic mesoporous expanded perlite-based (EPd-APTES@Fe3O4) composite was designed and synthesized as a novel adsorbent for enrichment of rare earth ions in aqueous solution. Effect of various factors including the pH of solution, contact time and adsorbent dosage on the adsorption behaviors of yttrium(Ⅲ) by the EPd-APTES@Fe3O4 nano-material composites from aqueous solution was investigated. The maximum adsorption capacity of the as-prepared materials for yttrium(Ⅲ) ions was 383.2 mg/g. Among the various isotherm models, the Freundlich isotherm model could well described for the adsorption of the rare earth ions at pH 5.5 and 298.15 K. The kinetic analysis indicated that the adsorption process followed the pseudo-second order kinetics model, and the rate-determining step might be chemical adsorption. Thermodynamic parameters declared that the adsorption process was endothermic. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the quantum chemical calculation indicated that the yttrium(Ⅲ) ions were captured on the EPd-APTES@Fe3O4 surface mainly by coordination with functional group of -NH2. More importantly, the adsorption-desorption studies indicated that the EPd-APTES@Fe3O4 nano-material composites had a high stability and good recyclability.
A magnetic mesoporous expanded perlite-based (EPd-APTES@Fe3O4) composite was designed and synthesized as a novel adsorbent for enrichment of rare earth ions in aqueous solution. Effect of various factors including the pH of solution, contact time and adsorbent dosage on the adsorption behaviors of yttrium(Ⅲ) by the EPd-APTES@Fe3O4 nano-material composites from aqueous solution was investigated. The maximum adsorption capacity of the as-prepared materials for yttrium(Ⅲ) ions was 383.2 mg/g. Among the various isotherm models, the Freundlich isotherm model could well described for the adsorption of the rare earth ions at pH 5.5 and 298.15 K. The kinetic analysis indicated that the adsorption process followed the pseudo-second order kinetics model, and the rate-determining step might be chemical adsorption. Thermodynamic parameters declared that the adsorption process was endothermic. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the quantum chemical calculation indicated that the yttrium(Ⅲ) ions were captured on the EPd-APTES@Fe3O4 surface mainly by coordination with functional group of -NH2. More importantly, the adsorption-desorption studies indicated that the EPd-APTES@Fe3O4 nano-material composites had a high stability and good recyclability.
2020, 31(10): 2854-2858
doi: 10.1016/j.cclet.2020.06.020
Abstract:
In recent years, oil spills caused by human activities have occurred frequently, and the resultant oil pollution has received extensive attention worldwide. In this paper, a total of 50 water samples were collected from the northeastern part of the South China Sea, and total petroleum hydrocarbons (TPHs) and n-alkane content in the samples were analyzed by gas chromatography-flame ionization detector (GC-FID) technology. The petroleum hydrocarbon characteristic indices, such as carbon predominance index (CPI) and terrigenous/aquatic ratio (TAR), were calculated to trace the source of petroleum hydrocarbons. The measured value of TPHs ranged from 121.31–603.02 μg/L. For surface waters, the TPHs in the northern coastal waters and the central waters were higher than that in the far shore. For vertical waters, the TPHs sharply decreased at first, and then increased slowly and finally reached a steady state. The n-alkanes in the water samples were concentrated in C10-C38, and they were mainly from terrestrial higher plant. The waters in the near shore, mid-layer and deep sea showed a strong reducing terrestrial characteristic, while the surface waters in the open sea showed an obvious oxidizing endogenous characteristic.
In recent years, oil spills caused by human activities have occurred frequently, and the resultant oil pollution has received extensive attention worldwide. In this paper, a total of 50 water samples were collected from the northeastern part of the South China Sea, and total petroleum hydrocarbons (TPHs) and n-alkane content in the samples were analyzed by gas chromatography-flame ionization detector (GC-FID) technology. The petroleum hydrocarbon characteristic indices, such as carbon predominance index (CPI) and terrigenous/aquatic ratio (TAR), were calculated to trace the source of petroleum hydrocarbons. The measured value of TPHs ranged from 121.31–603.02 μg/L. For surface waters, the TPHs in the northern coastal waters and the central waters were higher than that in the far shore. For vertical waters, the TPHs sharply decreased at first, and then increased slowly and finally reached a steady state. The n-alkanes in the water samples were concentrated in C10-C38, and they were mainly from terrestrial higher plant. The waters in the near shore, mid-layer and deep sea showed a strong reducing terrestrial characteristic, while the surface waters in the open sea showed an obvious oxidizing endogenous characteristic.
2020, 31(10): 2859-2863
doi: 10.1016/j.cclet.2020.08.040
Abstract:
The occurrence of biologically active pharmaceuticals in aquatic environments raised the potential risks to aquatic species. Among these marketed biological active pharmaceuticals, it has been estimated that 40% of them target G-protein-coupled receptors (GPCRs). We have illustrated pharmaceutical activities of GPCR targeted pharmaceuticals in English and Japanese wastewater by the in vitro transforming growth factor-α (TGFα) shedding assay. However, as the most important producer and consumer of pharmaceuticals, the occurrence of GPCR targeted pharmaceuticals in China had remained unclear. In this study, we investigated the pharmaceutical activities of GPCR targeted pharmaceuticals in secondary effluents of Chinese wastewater treatment plants. We discovered antagonistic activities against angiotensin (AT1) receptor at up to 7.2×102 ng-valsartan-equivalent quantity/L in Chinese wastewater for the first time as well as agonistic activities against dopamine (D2) receptor. Furthermore, in parallel with the assay, we determined concentrations of GPCR targeted pharmaceuticals in target wastewater by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS). Through the comparison of predicted antagonistic activities calculated by concentrations and potency values from the assay, we found that the measured antagonistic activities against AT1 receptor from the assay were higher than the predicted AT1 activities from valsartan, irbesartan, and losartan, indicating the potential existence of other unknown AT1 antagonists in wastewater.
The occurrence of biologically active pharmaceuticals in aquatic environments raised the potential risks to aquatic species. Among these marketed biological active pharmaceuticals, it has been estimated that 40% of them target G-protein-coupled receptors (GPCRs). We have illustrated pharmaceutical activities of GPCR targeted pharmaceuticals in English and Japanese wastewater by the in vitro transforming growth factor-α (TGFα) shedding assay. However, as the most important producer and consumer of pharmaceuticals, the occurrence of GPCR targeted pharmaceuticals in China had remained unclear. In this study, we investigated the pharmaceutical activities of GPCR targeted pharmaceuticals in secondary effluents of Chinese wastewater treatment plants. We discovered antagonistic activities against angiotensin (AT1) receptor at up to 7.2×102 ng-valsartan-equivalent quantity/L in Chinese wastewater for the first time as well as agonistic activities against dopamine (D2) receptor. Furthermore, in parallel with the assay, we determined concentrations of GPCR targeted pharmaceuticals in target wastewater by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS). Through the comparison of predicted antagonistic activities calculated by concentrations and potency values from the assay, we found that the measured antagonistic activities against AT1 receptor from the assay were higher than the predicted AT1 activities from valsartan, irbesartan, and losartan, indicating the potential existence of other unknown AT1 antagonists in wastewater.
2020, 31(10): 2864-2870
doi: 10.1016/j.cclet.2020.03.051
Abstract:
In this study, various conditions for the removal of polyvinyl alcohol (PVA) by electrocoagulation (EC) coupled catalytic oxidation are systematically studied. The direct oxidation of the anode, the reduction of the cathode, the oxidation of ·OH and ·Cl, and the synergistic effect of flocculation on the degradation of polyvinyl alcohol are investigated. It is observed that the optimum experimental conditions obtained are as follows: Cell voltage 9 V, natural pH 7, NaCl concentration 0.02 mol/L, and interelectrode distance 3.0 cm. The evolution of iron ions is also discussed in the EC process. By contrast, EC had made an outstanding contribution to the removal of PVA, which removes 71.29% of PVA. Free radicals, especially ·OH and ·Cl, are equivalent to the contribution of the electrodes in the degradation of PVA. And the contribution of PVA degradation by anode oxidation and cathode reduction are 12.76% and 8.02%, respectively. Characterization of solution and floc, such as Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), GC–MS and molecular weight, showed that PVA is effectively removed by the EC process, and a possible degradation pathway is proposed.
In this study, various conditions for the removal of polyvinyl alcohol (PVA) by electrocoagulation (EC) coupled catalytic oxidation are systematically studied. The direct oxidation of the anode, the reduction of the cathode, the oxidation of ·OH and ·Cl, and the synergistic effect of flocculation on the degradation of polyvinyl alcohol are investigated. It is observed that the optimum experimental conditions obtained are as follows: Cell voltage 9 V, natural pH 7, NaCl concentration 0.02 mol/L, and interelectrode distance 3.0 cm. The evolution of iron ions is also discussed in the EC process. By contrast, EC had made an outstanding contribution to the removal of PVA, which removes 71.29% of PVA. Free radicals, especially ·OH and ·Cl, are equivalent to the contribution of the electrodes in the degradation of PVA. And the contribution of PVA degradation by anode oxidation and cathode reduction are 12.76% and 8.02%, respectively. Characterization of solution and floc, such as Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), GC–MS and molecular weight, showed that PVA is effectively removed by the EC process, and a possible degradation pathway is proposed.
2020, 31(10): 2871-2875
doi: 10.1016/j.cclet.2020.06.002
Abstract:
Metal nanoclusters have shown great potential in photocatalysis, while simultaneous removal of both inorganic and organic contaminants by metal nanoclusters under visible light is less explored. Here, we synthesized Agm(SR)n (SR represents 3-mercaptopropyltriethoxysilane ligand) nanoclusters (~1 nm) via a reduction of silver triphenylphosphine under ambient conditions in the presence of 3-mercaptopropyltriethoxysilane. The nanocluster was characterized by UV–vis spectroscopy, high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectrum (FTIR), and X-ray photoelectron spectroscopy (XPS). Under 5 W blue LED, the Agm(SR)n/P25 exhibits enhanced catalytic activity for simultaneous methyl orange (MO) oxidation and Cr(Ⅵ) reduction, and also for synchronous 4-chlorophenol oxidation and Cr(Ⅵ) reduction. Mechanism studies by electrochemical impedance spectroscopy (EIS), photoluminescence (PL), electron spin resonance (ESR) etc. and control experiments reveal that the unique structure of silver nanoclusters with thiolate ligands is vital to the high catalytic performance, and both the photo-generated holes and superoxide radicals are responsible for the decomposition of MO.
Metal nanoclusters have shown great potential in photocatalysis, while simultaneous removal of both inorganic and organic contaminants by metal nanoclusters under visible light is less explored. Here, we synthesized Agm(SR)n (SR represents 3-mercaptopropyltriethoxysilane ligand) nanoclusters (~1 nm) via a reduction of silver triphenylphosphine under ambient conditions in the presence of 3-mercaptopropyltriethoxysilane. The nanocluster was characterized by UV–vis spectroscopy, high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectrum (FTIR), and X-ray photoelectron spectroscopy (XPS). Under 5 W blue LED, the Agm(SR)n/P25 exhibits enhanced catalytic activity for simultaneous methyl orange (MO) oxidation and Cr(Ⅵ) reduction, and also for synchronous 4-chlorophenol oxidation and Cr(Ⅵ) reduction. Mechanism studies by electrochemical impedance spectroscopy (EIS), photoluminescence (PL), electron spin resonance (ESR) etc. and control experiments reveal that the unique structure of silver nanoclusters with thiolate ligands is vital to the high catalytic performance, and both the photo-generated holes and superoxide radicals are responsible for the decomposition of MO.
