Reclamation of Chromium from Wastes

TLDR: In this paper, the application of ion exchange for chromium reclamation from effluents is reviewed, and the main type of chromium waste is sludges from plating plants containing up to 20% Cr2O3.

Abstract: With industrial development comes increasing amounts of hazardous wastes and a simultaneous depletion of raw materials. The storage of hazardous solid and liquid wastes at dump sites presents a serious health and safety risk to the community, and other disposal methods are required. It seems prudent to consider wastes as a resource, which can be detoxified and converted to usable products. One such waste from industrial effluents is chromium. The application of ion exchange for chromium reclamation from effluents is reviewed. However, the main type of chromium waste is sludges from plating plants containing up to 20% Cr2O3. There are thousands of tons of this sludge in storage throughout the world. The methods of detoxification of the sludge are reviewed. The most effective method is probably the oxidation of Cr(III) followed by washing-out of chromic acid or sodium chromate. The solution obtained in the washing operation can be directly re-used in a plating plant. The most important step of the process is oxidation of Cr(III) to Cr(VI). The are few wet reactions which are practical for the conversion of Cr(III) to Cr(VI). The most promising method is oxidation by air at 850–900°C.