Hydroxyapatite nanoparticles (HAP NPs) were synthesized by a one‐step hydrothermal method. The surface of HAP NPs was grafted —SH and —COOH chelating groups via in situ surface‐modification with iminodiacetic acid (IDA) and 3‐mercaptopropyl trimethoxysilane (MPS) to afford dual surface‐capped nano‐amendment HAP‐IDA/MPS. The structure of HAP‐IDA/MPS was characterized, and its adsorption performance for Hg²⁺, Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Cd²⁺ was evaluated. The total adsorption capacity of 0.10 g HAP‐IDA/MPS nano‐amendment for Hg²⁺, Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Cd²⁺ with an initial mass concentration of 20 mg·L^-1 reached 13.7 mg·g^-1, about 4.3 times as much as that of HAP. Notably, HAP‐IDA/MPS nano‐amendment displayed the highest immobilization rate for Hg²⁺, possibly because of its chemical reaction with —SH to form sulfide, possessing the lowest solubility product constant among a variety of metal sulfides.

Chitosan (CTS) was grafted onto the surface of amino-functionalized silver chloride silicon dioxide (AgCl@SiO₂-NH₂) cores to obtain AgCl@SiO₂/CTS hybrid nanoparticles. The as-obtained AgCl@SiO₂/CTS nanoparticles were chlorinated by NaClO solution to get AgCl@SiO₂/CTS-based chloramine nano-hybrid materials, denoted as AgCl@SiO₂/CTS-Cl. A transmission electron microscope was used to observe the morphology of the as-prepared samples AgCl@SiO₂/CTS and AgCl@SiO₂/CTS-Cl. At the same time, an X-ray diffractometer and an infrared spectroscope were utilized to characterize their crystal and chemical structures. Besides, ζ potentials were measured to elucidate the surface modification of AgCl nanoparticles by —NH₂, the antibacterial mechanism of AgCl@SiO₂/CTS-Cl was investigated by scanning electron microscopy, and Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as the to-be-tested strains to evaluate the antimicrobial activity of samples AgCl@SiO₂/CTS and AgCl@SiO₂/CTS-Cl. Findings demonstrate that sample AgCl@SiO₂/CTS exhibits a chain-like structure ascribed to the interaction between —NH₂, and each AgCl@SiO₂/CTS hybrid nanoparticle contains several AgCl cores. In the meantime, sample AgCl@SiO₂/CTS-Cl exhibits excellent antibacterial activity against E. coli and S. aureus, which is attributed to the synergistic antibacterial effect of Ag⁺ and Cl^-. Sample AgCl@SiO₂/CTS-Cl with a dosage of 640.00 μg·mL^-1 could completely kill the two kinds of tested bacteria in 12 h of incubation; it retains a high antibacterial efficiency even after 10 cycles of antibacterial tests.