Elimination of hexavalent chromium in leather using reducing agents

The presence of hexavalent chromium, Cr(VI) in leather and leather products has become a source of concern to the leather industry. Consequently research efforts are being made to identify the source of Cr(VI) and eliminate it in finished leathers. This paper deals with the study on the use of reducing agents based on sulfur and phosphonium compounds for elimination of hexavalent chromium in the leathers. Sodium bisulfite and tetrakis-hydroxymethylphosphonium sulfate were found to eliminate hexavalent chromium well below the detectable limit. The performance of these two compounds has also been studied by the external addition of dichromate in processing.