Sorption mechanism of copper ions on synthetic and natural dentine hydroxyapatites

Abstract

Removal of copper ions from aqueous solutions on synthetic and dentine waste hydroxyapatites (HAP) was investigated in batch sorption experiments. Kinetics of sorption followed a pseudo-first order model. Steady-state data show agreement with the Sips isotherm compared with Freundlich and Langmuir models. The higher surface area and carbonated nature of synthetic hydroxyapatite were not sufficient to reach higher sorption capacity than natural one. Ion-exchange and precipitation contributed on removal of Copper despite level ionization of hydroxyapatites. Proton and metal exchanges with copper ions contributed to process of sorption with prevalence of proton-exchange at low copper ion concentrations. High temperatures promoted the removal efficiency of Cu(II) onto the natural and synthesised hydroxyapatites. The thermodynamic parameters showed that sorption process was spontaneous, endothermic and associated entropy at the solid/solution interface increased at high temperatures.

Keywords

• copper
• sorption
• hydroxylapatite
• dentine waste, isotherm