Adsorption of Cu (II) ions from industrial wastewater on natural hydroxyapatite extracted from bone ash

Wastewaters that contain heavy metals like Cu are dangerous for environment and they can be removed by natural hydroxyapatite (HAP). Natural HAP (N-HAP), extracted from bovine cortical bone ash, is a good choice for substitution of commercial HAP because it is cheaper than commercial HAP and simpler to prepare, too. Several experiments were done to investigate the sorption capacity of Cu (II) to N-HAP in various particle sizes, temperatures, initial concentrations, pH and reaction times. In this study, the sorption of copper ions from a Cu solution onto HAP particles with sizes of 1323.2 and 82.3 nm at three initial pH values of 4.50, 6.00 and 7.50 was studied. The results showed that better performance was obtained through an 82.3 nm particle size and higher pH values. The experimental data were analyzed using Langmuir, Freundlich and Arrhenius equations for equilibrium, kinetic and thermodynamic studies. The analysis showed a maximum adsorption capacity of N-HAP as being 1.631 mmol/g at a pH of 7.5 and small particle size. Kinetically, the prepared N-HAP is a feasible sorbent that retains Cu (II) ions through a favorable and spontaneous sorption process.