Highly Efficient and Selective Removal of Pb(II) ions by Sulfur-Containing Calcium Phosphate Nanoparticles

A facile one-step co-precipitation method was demonstrated to fabricate amorphous sulfur-containing calcium phosphate (SCP) nanoparticles, in which the sulfur group was in-situ introduced into calcium phosphate. The resulting SCP exhibited a noticeable enhanced performance for Pb(II) removal in comparison with hydroxyapatite (HAP), being capable of easily reducing 20 ppm of Pb(II) to below the acceptable standard for drinking water within less than 10 min. Remarkably, the saturated removal capacities of Pb(II) on SCP were as high as 1720.57 mg/g calculated by the Langmuir isotherm model, exceeding largely that of the previously reported absorbents. Significantly, SCP displayed highly selective removal ability toward Pb(II) ions in the presence of the competing metal ions (Ni(II), Co(II), Zn(II), and Cd(II)). Further investigations indicated that such ultra-high removal efficiency and preferable affinity of Pb(II) ions on SCP may be reasonably ascribed to the formation of rod-like hydroxypyromorphite cryst...