Calcium polysulfide remediation of hexavalent chromium contamination from chromite ore processing residue

• Published in: The Science of the total environment Vol. 364; no. 1; pp. 32 - 44
• Main Authors: Graham, Margaret C., Farmer, John G., Anderson, Peter, Paterson, Edward, Hillier, Stephen, Lumsdon, David G., Bewley, Richard J.F.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01.07.2006; Elsevier Science
• Subjects: Applied sciences; Calcium Compounds - chemistry; Calcium polysulfide; Carcinogens, Environmental - chemistry; Chromium - chemistry; COPR; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Groundwater; Groundwaters; Hexavalent chromium; Industrial Waste - analysis; Metallurgy; Natural water pollution; Pollution; Pollution, environment geology; Remediation; Scotland; Sulfides - chemistry; Thiosulfates - chemistry; Waste Disposal, Fluid - methods; Water Pollutants, Chemical - analysis; Water Supply - analysis; Water treatment and pollution; United Kingdom; Scotland; Great Britain; Europe; British Isles, Scotland, Glasgow; Hexavalent chromium; COPR; Remediation; Groundwater; Calcium polysulfide; Calcium Polysulfides; Reducing agent; Chromates; Heavy metal; Chemical reduction; Industrial waste; Decontamination; Solid waste; Water pollution; Mining industry; Chromium VI; Ground water
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2005.11.007

Past disposal of high-lime chromite ore processing residue (COPR) from a chemical works in S.E. Glasgow, UK, has led to continuing release of toxic and carcinogenic hexavalent chromium (Cr(VI)) to groundwaters which are highly contaminated with Cr(VI)O 4 2−. Traditional methods of remediating Cr(VI)-contaminated land, e.g. using ferrous sulfate and organic matter, have had limited success in converting Cr(VI) to less harmful and insoluble Cr(III). This paper describes the first application of calcium polysulfide (CaS x ) to the remediation of contaminated groundwater and high-lime COPR in a series of laboratory experiments, which have demonstrated the effectiveness of the treatment in quantitatively and rapidly reducing Cr(VI) to Cr(III) over the pH range (8–12.5) typically found at the sites. Cr(III)-organic complexes, present in groundwater at one location, were also effectively precipitated upon treatment with CaS x . The potential for large-scale use of CaS x in the remediation of Cr(VI) from COPR is also discussed.