Synthesis of hydroxyapatite and hydroxyapatite/Fe3O4 nanocomposite for removal of heavy metals

Abstract

In the present study, hydroxyapatite (HAp) and magnetic nanocomposite of HAp were used to recover and remove lead ions from an aqueous solution. For this purpose, chicken thighbone was used as the starting material. Lead ion adsorption was performed discontinuously within the temperature range 25–55℃, contact time 5–120 min, adsorbent dose 0.25–5 g/L, and pH 2–9. Under optimum conditions, the maximum lead ion adsorption efficiency was determined to be 93.75% and 96.11% by HAp and HAp/Fe3O4, respectively. FTIR, SEM, and EDS analyses were applied to characterize the adsorbents. Equilibrium data were studied using Langmuir, Freundlich, and D-R isotherm models. From the Freundlich constant and the determined isolation factor, it can be concluded that the adsorption process using both mentioned adsorbents is desirable and physical. Maximum lead adsorption capacity using HAp and HAp/Fe3O4 adsorbents was determined to be 105.26 mg/g and 109.89 mg/g, respectively, suggesting that these adsorbents have a satisfactory potential to adsorb lead ions. Thermodynamic investigation showed that the lead ion adsorption process is exothermic and spontaneous in both adsorbents, the degree of spontaneous adsorption process in the magnetic composite of HAp/Fe3O4 is higher, and the energy required for the adsorption process is less than that of HAp.