Treatment of Cr(VI)-containing wastes in the South African ferrochrome industry–a review of currently applied methods

South Africa holds approximately threequarters of the world’s viable chromite ore resources1,2,3 and dominates the global production of ferrochrome(FeCr)4. FeCr is a relatively crude alloy of predominantly iron and chromium, used mainly in the production of stainless steel. There are currently fourteen separate FeCr smelters in South Africa, with a combined production capacity5 in excess of 4.7 Mt/a. Table I provides an overview of the production capacities of these facilities and also indicates recent capacity increases. Although the current electricity shortage in South Africa and the rising cost of power have partially stunted growth in this electricityintensive industry, it is foreseen that South Africa will remain the leading producer of FeCr in the foreseeable future. Hexavalent chromium, Cr(VI), is formed in small quantities as an unintended by-produc during ferrochrome production6. Certain Cr(VI) species are regarded as carcinogenic, with specifically airborne exposure to these Cr(VI) species being associated with cancer of the respiratory system7,8. In a recent paper, the generation of Cr(VI) in the various production processes utilized by the South African FeCr industry was reviewed and possible mitigating steps were discussed6. In the present paper, Cr(VI) treatment strategies currently employed by the South African FeCr producers in dealing with waste products, possibly containing Cr(VI), are reviewed.