Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
584600 | Journal of Hazardous Materials | 2007 | 7 Pages |
Abstract
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+ (5à and 8Ã) 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 8à 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 5à and 8à 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 5à treatment and the ettringite formation was identified by XRPD analyses.
Keywords
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Health and Safety
Authors
Deok Hyun Moon, Mahmoud Wazne, Dimitris Dermatas, Christos Christodoulatos, Adriana M. Sanchez, Dennis G. Grubb, Maria Chrysochoou, Min Gyu Kim,