Microwave-assisted synthesis of hydroxyapatite for the removal of lead(II) from aqueous solutions

Abstract

This study has the objective to evaluate the lead(II) removal capacity of hydroxyapatite powder synthesized by microwave as an alternative method to decrease production time and cost. Hydroxyapatite (HA) was synthesized by a microwave-assisted precipitation method using calcium nitrate and ammonium hydrogen phosphate as calcium and phosphorus sources, respectively. X-ray diffraction and Fourier transform infrared results clearly revealed that the resulting powder was HA with high purity and crystallinity. The obtained powder was used for the removal of lead(II) from aqueous solutions. The effects of pH, amount of adsorbent, initial lead(II) concentration, and contact time were studied in batch experiments. In the adsorption experiments, maximum lead(II) retention was obtained at pH6. Adsorption equilibrium was established after 40min. It was found that the adsorption of lead(II) on HA was correlated well (R (2) = 0.958) with the Freundlich equation for the concentration range studied. Both ion exchange and adsorption process were thought to exist in the removal process. This study indicates that easily and rapidly synthesized HA by microwave-assisted precipitation method could be used as an efficient adsorbent for removal of lead(II) from aqueous solutions.