Hexavalent chromium in the recovery of ferrochromium from slag

A successful jigging process has been developed to recover ferrochromium metal from waste dumps. The potential for generating Cr(VI) during this operation has been investigated. The tests conducted indicate that there is no evidence for the continual release of Cr(VI) during the jigging operation. For instance, where Cr(VI) was detected it more likely occurs from the slag than from the metal and could arise either from the partially altered chromite or baghouse dust found on the dump. The removal of Cr(VI) from a synthetic solution containing 40 mg l(-1) Cr(VI) was investigated. Reduction with ferrous sulphate followed by filtration or coagulation with lime were effective in removing Cr(VI) from this solution to achieve levels < 0.1 mg l(-1), conforming to those stipulated by the World Health Organisation for discharge into lakes and rivers. If necessary, this could be applied to remove Cr(VI) from the jigging-plant effluent. The removal of Cr(VI) by adsorption on coke was also investigated. This is only effective under acidic conditions and does not apply to alkaline jigging-plant effluent. Published by Elsevier Science Ltd. All rights reserved.