Efficient removal of heavy metal ions by diethylenetriaminepenta (methylene phosphonic) acid-doped hydroxyapatite.

Diethylenetriaminepenta (methylene phosphonic) acid (DTPMP) was first used as a dopant to modify hydroxyapatite and applied to remove Pb. The adsorption capacity of modified hydroxyapatite for Pb can reach 2185.92 mg/g, which was 10.4 times that of commercial nanohydroxyapatite. The characterizations after adsorption of Pb indicated the existence of chelation and the formation of the low bioavailability Pb(PO)(OH). Moreover, the interaction of different components containing DTPMP, HAP, and pollutant Pb was investigated by molecular dynamics (MD) simulation, which indicated that the organic-phosphonic group of DTPMP (POH) had a stronger complex effect with calcium ions or lead ions than that of the inorganic-phosphate group of HAP (PO) with the two metal ions, which affected the crystallinity of HAP, and greatly improved the removal effect of DTPMP doped HAP composites for Pb contaminants, the existence of amino groups can further enhance the affinity between DTPMP and HAP or lead ions. The chelation mechanism of DTPMP and Pb was probed in depth by combining basin analysis, topology analysis of atoms in molecules (AIM), electron localization function (ELF) analysis, bond order density (BOD) & natural adaptive orbital (NAdO)analysis and orbital component analysis.