Abstract: The presence of Cd²⁺ in water endangers human health, and the removal of Cd²⁺ pollution is a problem that needs to be solved. Wood vinegar modified hydroxyapatite (WV-HAP) was prepared by water bath stirring with hydroxyapatite (HAP) and low cost wood vinegar (WV), and it was used to remove Cd²⁺ from solution. WV-HAP was characterized by XRD, FT-IR, SEM and BET. The effects of initial pH, initial ion concentration, contact time and temperature on the adsorption characteristics of WV-HAP were investigated through adsorption experiments. The results show that the equilibrium adsorption capacity of WV-HAP is 46.43 mg/g under the conditions of adsorbent dosage of 2 g/L, temperature 298 K, initial concentration of Cd²⁺100 mg/L, pH=5 and adsorption time 4 h. The adsorption process of Cd²⁺ by WV-HAP conform to Langmuir isothermal adsorption model and quasi-second-order kinetic model. Thermodynamic study shows that the adsorption process is endothermic. Through the characterization of WV-HAP before and after Cd²⁺ adsorption, it is found that the adsorption mechanisms are mainly surface adsorption, pore adsorption and ion exchange. The adsorption capacity of WV-HAP to Cd²⁺ in solution is better than that of HAP, and WV-HAP is a potential Cd²⁺ adsorption material.

Key words: hydroxyapatite, wood vinegar, wood vinegar modified hydroxyapatite, adsorption, Cd²⁺ pollution, water treatment, ion exchange