Reductive treatment of Chromite Ore Processing Residue (COPR): Lessons from a field study

Maria Chrysochoou, Dimitris Dermatas, Deok Hyun Moon, Christos Christodoulatos

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

2 Scopus citations

Abstract

A bench- and pilot-scale treatability study conducted on Chromite Ore Processing Residue (COPR) from a deposition site in New Jersey showed that regulatory compliance to 20 (current) or 240 (up to 2006) mg/kg Cr(VI) was not possible using several common reductants (zero valent iron, pyrite, ferrous sulfate) due to the slow release of Cr(VI) from the binding minerals and the competing oxidation of iron and ferrous by oxygen. Initial success as evidenced by alkaline digestion was an artifact of the method, which facilitated Cr(VI) reduction during the test itself. X-ray Absorption Near-Edge Structure (XANES) analyses showed that the actual Cr(VI) concentrations in the solid were significantly higher (>1,000 mg/kg) in both ferrous sulfate and calcium polysulfide treated samples. Calcium polysulfide decreased Cr(VI) to non-detectable values (<2 mg/kg) for long monitoring times (up to 11/2 years), as measured by alkaline digestion. The apparent success of calcium polysulfide is attributed to its slow oxidation, so that sulfide is available during analysis to reduce Cr(VI) that slowly diffuses out of the COPR matrix. The comparison of the in situ sulfide oxidation and Cr(VI) release rates can facilitate the design of a successful reductive treatment. Copyright ASCE 2008.

Original languageEnglish
Title of host publicationProceedings of Sessions of GeoCongress 2008 - GeoCongress 2008
Subtitle of host publicationGeotechnics of Waste Management and Remediation, GSP 177
Pages748-755
Number of pages8
Edition177
DOIs
StatePublished - 2008
EventGeoCongress 2008: Geotechnics of Waste Management and Remediation - New Orleans, LA, United States
Duration: 9 Mar 200812 Mar 2008

Publication series

NameGeotechnical Special Publication
Number177
ISSN (Print)0895-0563

Conference

ConferenceGeoCongress 2008: Geotechnics of Waste Management and Remediation
Country/TerritoryUnited States
CityNew Orleans, LA
Period9/03/0812/03/08

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