TY - GEN
T1 - Reductive treatment of Chromite Ore Processing Residue (COPR)
T2 - GeoCongress 2008: Geotechnics of Waste Management and Remediation
AU - Chrysochoou, Maria
AU - Dermatas, Dimitris
AU - Moon, Deok Hyun
AU - Christodoulatos, Christos
PY - 2008
Y1 - 2008
N2 - 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.
AB - 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.
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U2 - 10.1061/40970(309)94
DO - 10.1061/40970(309)94
M3 - Conference contribution
AN - SCOPUS:66449128275
SN - 9780784409701
T3 - Geotechnical Special Publication
SP - 748
EP - 755
BT - Proceedings of Sessions of GeoCongress 2008 - GeoCongress 2008
Y2 - 9 March 2008 through 12 March 2008
ER -