Abstract: Hydroxyapatite-modified Ag⁺ (Ag-HAP) adsorbent was prepared by in-situ co-precipitation method. The effect of Ag⁺/Ca²⁺ molar ratio on defluorination and bacteriostasis was investigated. The infrared spectroscopy and XRD results show that Ag⁺ displaces Ca²⁺ into HAP lattice, forming a new Ag⁺-Ca²⁺ lattice.Both models including Langmuir and Freundlich can predict experimental data conducted. However, Langmuir model has better correlation coefficient than Freundlich model. The adsorptions of fluoride on Ag-HAP adsorbent are more agreeable with monolayer adsorption mode. The thermodynamic and kinetics parameters of adsorptions were obtained. The ΔG⁰＜0, ΔH⁰＞0 and ΔS⁰＞0 indicate that adsorption of fluoricle is a spontaneous and endothermic process with increased entropy, and an increase in temperature benefits adsorption. Activation energy of adsorption E_a=12.645 kJ/mol and migration energy E=7.331 kJ/mol indicate that adsorption is mainly physical adsorption. Kinetic adsorption data show that adsorption process follows the pseudo-second-order kinetic. The dynamic adsorption process of Ag-HAP adsorbent for defluorination and bacteriostatic inhibition was simulated by using a bibcock type water purifier. The bacteriostatic experiments show that the addition of Ag-HAP adsorbent greatly improves the bacteriostatic performance of drinking water.

Key words: hydroxyapatite, modified, defluorination, bacteriostasis, co-precipitation, kinetics