Effects of particle size and acid addition on the remediation of chromite ore processing residue using ferrous sulfate.
A bench-scale treatability study was conducted to assess the effects of particle size and acid addition on the remediation of chromite ore processing residue (COPR) using ferrous sulfate. The remediation scheme entailed the chemical reduction of hexavalent chromium [Cr(VI)] and the mitigation of swell potential. Leaching tests and the EQ3/6 geochemical model were used to estimate the acid dosage required to destabilize Cr(VI)-bearing and swell-causing minerals. The model predicted greater acid dosage than that estimated from the batch leaching tests. This indicated that mass transfer limitation may be playing a significant role in impeding the dissolution of COPR minerals following acid addition and hence hindering the remediation of COPR. Cr(VI) concentrations determined by alkaline digestion for the treated samples were less than the current NJDEP standard. However, Cr(VI) concentrations measured by X-ray absorption near edge structure (XANES) were greater than those measured by alkaline digestion. Greater Cr(VI) percentages were reduced for acid pretreated and also for smaller particle size COPR samples. Upon treatment, brownmillerite content was greatly reduced for the acid pretreated samples. Conversely, ettringite, a swell-causing mineral, was not observed in the treated COPR.
Jagupilla
Santhi Chandra
SC
WM Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
Moon
Deok Hyun
DH
Wazne
Mahmoud
M
Christodoulatos
Christos
C
Kim
Min Gyu
MG
D000143:Acids; D002857:Chromium / Q000032:analysis / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005296:Ferrous Compounds; D007220:Industrial Waste; D008669:Metallurgy; D008903:Minerals / Q000032:analysis; D009532:Nickel / Q000032:analysis; D010316:Particle Size; D010865:Pilot Projects
D000143:Acids; D005296:Ferrous Compounds; D007220:Industrial Waste; D008903:Minerals; C501337:ettringite; D002857:Chromium; C074702:chromium hexavalent ion; C020748:ferrous sulfate; D009532:Nickel; C017558:nickel sulfide