Adsorption of Zn2+ from aqueous solutions by si-substituted carbonated hydroxylapatite: Equilibrium, kinetics, and mechanisms

A kind of low-cost silicon-substituted carbonate hydroxyapatite (Si-CHAP) powder was successfully fabricated by using eggshell powder, H3PO4, Ca(OH)(2), Na2SiO3, and Na2CO3 under sonochemistry coprecipitation condition. Si-CHAP could serve as an ideal adsorbent to remove zinc ion (Zn2+) from aqueous solution. Under the optimized conditions, the removal efficiency of Zn2+ in solution by Si-CHAP could reach to 96.2%. The adsorption mechanism was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Notably, the adsorption process followed the Langmuir isotherm and pseudo-second-order model, and the saturation adsorption capacities were calculated to be 102.0, 103.1, and 105.3 mg g(-1) at 293, 303, and 313 K, respectively. Thermodynamic studies indicated that the adsorption of Zn2+ by Si-CHAP is endothermic. Mechanism studies revealed that the dominate mechanism was chemical adsorption. These results showed that Si-CHAP is an effective adsorbent for the removal of Zn2+ from aqueous solution, and thus providing a good method to treat Zn2+ in the waste water. (c) 2018 American Institute of Chemical Engineers Environ Prog, 37: 1901-1907, 2018