Removal of Mercury and other Heavy Metals of Industrial and Contaminated Site Waste Waters by Organic Chelation, Coprecipitation and High Efficiency Particulate Removal

The effluents of many industrial processes, as well as surface water and groundwater from historically polluted sites, often contain unacceptably high levels of Hg and other toxic trace metals. Although inorganic Hg itself is not bioaccumulative, it is readily converted to methyl mercury in the ambient environment, and so should be removed before discharge. The U.S. EPA has identified mercury-contaminated groundwater and surface water as areas of particular concern, and has emphasized development of innovative, robust extraction technologies for the current round of SBIR funding. Frontier's SBIR technology involves co-precipitation of the trace metal with a thiol-containing organic complexing agent (MCX), which is soluble as an alkali salt but instantly forms extremely insoluble complexes with many transition metals, particularly Hg, Ag, Cu, Cd, Zn, Pb, Fe, As(III), Se(IV), Co, and Ni. Thus, the reagent can be added to the aqueous sample in soluble form, and the complexed trace metals can be quickly filtered or removed by flocculation and settling of the resulting precipitate. The mercury salt of MCX is so insoluble that Frontier has used it as an analytical "carrier" for the co-precipitation and extraction of other metals of analytical interest.Phase I results demonstrated that MCX not only exhaustively complexes and precipitates most dissolved toxic trace metals of concern, including Ag, Cd, Cu, Hg, Pb, Se(IV), As(III), Zn, and Tl, but in most cases it also has the ability to strip them from indigenous, competitive metal-binding ligands such as EDTA. The MCX/metal complex is insoluble in aqueous phase, and therefore precipitates efficiently in solution. MCX complexes Hg >99.9 percent over the entire range from pH 1 to 12, and >99.999 percent across the limited, but quite common, range of pH 3 to 6. Satisfactory complexation and precipitation of the target metals of interest occurred very rapidly, with >99 percent of metal removal occurring within the first minute.