Assessment of calcium polysulfide for the remediation of hexavalent chromium in chromite ore processing residue (COPR)

Mahmoud Wazne, Santhi Chandra Jagupilla, Deok Hyun Moon, Sarath Chandra Jagupilla, Christos Christodoulatos, Min Gyu Kim

Research output: Contribution to journalArticlepeer-review

101 Scopus citations

Abstract

Bench scale and pilot scale treatability studies were conducted to evaluate the remediation of hexavalent chromium [Cr(VI)] in chromite ore processing residue (COPR) using calcium polysulfide. The results from the bench scale study indicated that a calcium polysulfide dosage twice the molar stoichiometric requirement (2×) proved effective in meeting the New Jersey Department of Environmental Protection (NJDEP) total Cr(VI) and the Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Procedure (TCLP) regulatory standards. The treatment results were more effective at pH 12 than at pH 9.5. X-ray powder diffraction (XRPD) and X-ray absorption near edge structure (XANES) spectroscopy were also used to assess the treatment performance. Based on the bench scale results, an ex-situ pugmill pilot program was implemented to evaluate the applicability of the calcium polysulfide treatment on a larger scale (1000-lb batch test). The pugmill treatment results met Cr(VI) and TCLP regulatory standards over a period of 15 months. XANES analysis indicated that approximately 62% of Cr(VI) was reduced by calcium polysulfide at stoichiometric ratio of 2× after a curing period of 10 months.

Original languageEnglish
Pages (from-to)620-628
Number of pages9
JournalJournal of Hazardous Materials
Volume143
Issue number3
DOIs
StatePublished - 17 May 2007

Keywords

  • COPR
  • Chromite
  • Chromium
  • Polysulfide
  • Treatment

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