Keywords: chromium (VI), chromium (III), ferrochrome slag, spinel, TCLP, redox chemistry, chromium release, solid waste management, SWM, submerged electric arc furnaces, ferrochrome alloys, leachate, hazardous waste, environmental pollution
Release behaviour of chromium from ferrochrome slag
Huge amount of ferrochrome slag, a solid waste is being generated from submerged electric arc furnace during manufacturing of ferrochrome alloy. The waste slag contains about 6–12% chromium as chromium oxide and it has the potentiality of releasing hazardous chromium compounds. Although chromium exists in the slag as highly immobile Cr (III) state, there is possibility of chromium release under different adverse conditions inter alia its conversion to highly leachable Cr (VI) state. While Cr (III) is an essential trace element in glucose synthesis, the Cr (VI) compounds are very toxic and highly leachable. This leaching characteristic may classify the slag as hazardous waste and restricts its use and disposal. Release of chromium from granulated slag was evaluated under laboratory batch studies with varying different experimental conditions. The results were analysed to find the conditions for maximum release of total chromium from the slag.