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IN SITU LEAD IMMOBILIZATION BY APATITE
Ma, Q. Y., S. J. Traina, T J. Logan, AND J A. Ryan*. IN SITU LEAD IMMOBILIZATION BY APATITE. D. J. Gentleman (ed.), ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 27(9):1803-1810, (1993).
The objectives were (1) to elucidate the mechanism of Pb immobilization by apatite and (2) to study the feasibility of using apatite to immobilize Pb from aqueous solution Pb, resin-exchangeable Pb, and Pb-contaminated soil materials.
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 0.18-19.7 µg L-1. Aqueous Pb in Pb-contaminated soil materials was reduced from 2273 to 36 µg 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.