Synthetic phosphates as binding agent of Pb, Zn, Cu and Cd in the environment

The sorption of Pb, Zn, Cu and Cd from aqueous multiple-species solutions by synthetic hydroxyapatite (HAP) was investigated. HAP was reacted with solutions containing different heavy metals concentrations (10, 100 and 500 mg/L) for four times (2, 4, 24 and 48h). The results showed that HAP was very effective in removal heavy metals from aqueous solutions. Approximately 95-99% of the Pb applied was removed from solutions, with the best sorption capacity of 497 mg of Pb/g of HAP, while 92-99% of Zn, 93-99% of Cu and 88-99% of Cd added were attenuated, with best removal capacity of 498, 485 and 477 mg/g, respectively. Sorption mechanisms other than dissolution/precipitation of crystalline phases could be involved in attenuating heavy metals concentrations such as ion exchange, coprecipitation, surface complexation and formation of amorphous phases. The study results confirm HAP provides a cost effective method for the decontamination of solutions polluted by heavy metals.