TY - JOUR
T1 - Long-term treatment issues with chromite ore processing residue (COPR)
T2 - Cr6+ reduction and heave
AU - Moon, Deok Hyun
AU - Wazne, Mahmoud
AU - Dermatas, Dimitris
AU - Christodoulatos, Christos
AU - Sanchez, Adriana M.
AU - Grubb, Dennis G.
AU - Chrysochoou, Maria
AU - Kim, Min Gyu
PY - 2007/5/17
Y1 - 2007/5/17
N2 - A pugmill treatability study was conducted to remediate chromite ore processing residue (COPR) using ferrous sulfate heptahydrate (FeSO4·7H2O) as a reductant. Two different types of COPR, with respect to particle size and mineralogy, were tested in this study. Two different stoichiometric ratios of FeSO4·7H2O to Cr6+ (5× and 8×) were applied to reduce Cr6+ to Cr3+. The effectiveness of FeSO4·7H2O treatment was assessed using the toxicity characteristic leaching procedure (TCLP) tests and X-ray absorption near edge structure (XANES) analyses. TCLP results obtained from the pugmill treatability study showed that TCLP Cr concentrations were less than the TCLP regulatory limit of 5 mg/L upon 8× FeSO4·7H2O treatment for up to 420 days but may fail to meet this regulatory limit in the long-term. XANES results obtained from samples cured for 300 days showed that all of the treated samples failed the New Jersey Department of Environmental Protection (NJDEP) clean up level for Cr6+ of 240 mg/kg. However, the Cr6+ concentration from the sample with the smaller particle size approached 240 mg/kg (338 mg/kg), suggesting that particle size reduction prior to the addition of reductant may improve the effectiveness of the treatment. COPR heaving was investigated with unconfined swell tests upon 5× and 8× FeSO4·7H2O treatment. The formation of ettringite, an expansive material, was investigated following the swell tests using X-ray powder diffraction (XRPD). Significant heaving (>50 vol%) was observed at curing times of 138 days for the 5× treatment and the ettringite formation was identified by XRPD analyses.
AB - A pugmill treatability study was conducted to remediate chromite ore processing residue (COPR) using ferrous sulfate heptahydrate (FeSO4·7H2O) as a reductant. Two different types of COPR, with respect to particle size and mineralogy, were tested in this study. Two different stoichiometric ratios of FeSO4·7H2O to Cr6+ (5× and 8×) were applied to reduce Cr6+ to Cr3+. The effectiveness of FeSO4·7H2O treatment was assessed using the toxicity characteristic leaching procedure (TCLP) tests and X-ray absorption near edge structure (XANES) analyses. TCLP results obtained from the pugmill treatability study showed that TCLP Cr concentrations were less than the TCLP regulatory limit of 5 mg/L upon 8× FeSO4·7H2O treatment for up to 420 days but may fail to meet this regulatory limit in the long-term. XANES results obtained from samples cured for 300 days showed that all of the treated samples failed the New Jersey Department of Environmental Protection (NJDEP) clean up level for Cr6+ of 240 mg/kg. However, the Cr6+ concentration from the sample with the smaller particle size approached 240 mg/kg (338 mg/kg), suggesting that particle size reduction prior to the addition of reductant may improve the effectiveness of the treatment. COPR heaving was investigated with unconfined swell tests upon 5× and 8× FeSO4·7H2O treatment. The formation of ettringite, an expansive material, was investigated following the swell tests using X-ray powder diffraction (XRPD). Significant heaving (>50 vol%) was observed at curing times of 138 days for the 5× treatment and the ettringite formation was identified by XRPD analyses.
KW - Chromite ore processing residue (COPR)
KW - Chromium (Cr)
KW - Ettringite
KW - Ferrous sulfate heptahydrate (FeSO·7HO)
KW - Heaving
KW - X-ray absorption near edge structure (XANES)
KW - X-ray powder diffraction (XRPD)
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U2 - 10.1016/j.jhazmat.2007.01.013
DO - 10.1016/j.jhazmat.2007.01.013
M3 - Article
C2 - 17275184
AN - SCOPUS:34247522399
SN - 0304-3894
VL - 143
SP - 629
EP - 635
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
IS - 3
ER -