IN-SITU LEAD IMMOBILIZATION BY APATITE

Lead contamination is of environmental concern due to its effect on human health. The purpose of this study was to develop a technology to immobilize Pb in situ in contaminated soils and wastes using apatite. Hydroxyapatite [Ca10(PO4)6(OH)2] was reacted with aqueous Pb, resin-exchangeable Pb, and Pb-contaminated soil material. The effectiveness of natural apatite to attenuate Pb was also tested. Hydroxyapatite reduced initial Pb concentrations of 5-500 mg L-1 to 0.18019.7 mug L-1. Aqueous Pb in Pb-contaminated soil materials was reduced from 2273 to 36 mug L-1 after reaction with hydroxyapatite. We hypothesize that Pb was immobilized by dissolution of hydroxyapatite and precipitation of hydroxypyromorphite [Pb10(PO4)6(OH)2]. The effective removal of Pb from aqueous solution, exchange resin, and Pb-contaminated soil material suggests that apatite has the potential to immobilize Pb in situ in Pb-contaminated soils and wastes.