Removal of Hg and Other Toxic Trace Metals in Industrial Waste Waters

ISSN： 1938-6478

Source： Proceedings of the Water Environment Federation, Vol.2001, Iss.5, 2001-01, pp. : 194-212

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Abstract

The effluents of many industrial processes, as well as surface and groundwater from historically polluted sites, often contain unacceptably high levels of mercury and other toxic trace metals. In these situations, most toxic trace metals exist initially in cationic form. Significant portions of the metals remain in the wastewater, due to complexation with dissolved or colloidal ligands. What is required is a treatment that will strip the metals from the ambient ligand/metal complexes, and supply a removal vehicle.During the completion of a US EPA Small business Innovative Research Program (SBIR) Phase I, Frontier Geosciences identified a thiol-based chelating agent 1- pyrrolidinedithiocarbamate, ammonium salt (APDC). APDC not only exhaustively complexes most dissolved toxic trace metals of concern, including Ag, Cd, Cu, Hg, Pb, Se, As, Zn and Tl, but in most cases, it has the ability to strip them from ambient, competitive metal-binding ligands, such as EDTA. The APDC/metal complex is insoluble in aqueous phase, and so precipitates efficiently in solution. APDC complexes Hg >99.9% from pH 1 to 12, and >99.999% from pH 3 to 6. Complexation of >99.99% of Hg occurs in under one minute.The use of a co-precipitant or carrier metal is demonstrated to beneficial if the target toxic metals are below 10 ppb in the wastewater and preliminary findings concerning competitive binding are discussed.