Removal of Mercury and Other Heavy Metals of Industrial and Contaminated Site Waste Waters by Organic Chelation, Coprecipitation and High-Efficiency Particulate RemovalEPA Contract Number: 68D01062
Title: Removal of Mercury and Other Heavy Metals of Industrial and Contaminated Site Waste Waters by Organic Chelation, Coprecipitation and High-Efficiency Particulate Removal
Investigators: Bloom, Nicolas S.
Current Investigators: Hensman, Carl E.
Small Business: Frontier Geosciences Inc.
EPA Contact: Richards, April
Project Period: September 1, 2001 through September 1, 2003
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2001) Recipients Lists
Research Category: Watersheds , SBIR - Water and Wastewater , Small Business Innovation Research (SBIR)
Description: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.
The Phase II primary research objective is to translate the process from Phase I bench-top studies to pilot-scale treatment, and to account for industrial concerns such as environmental toxicity of the treatment reagent, large-scale solid/liquid separation, and long-term storage and disposal of the treatment sludge. The Phase II research will involve Unocal Thailand, Ltd., as a co-sponsor, allowing swift application of pilot technology to the field, and so strengthening the development of the commercial technology.