Treatment/Bioremmediation of Electroplating and Leather Tanning Effluents Containing Chromium

Abstract

Chromium salts used in chrome plating and tanning industries are the cause of environmental pollution and loss of metal values exerting pressure on primary reso-urces because of effluent discharge and related solid sludge/waste disposal. In order to recover chromium from such effluents/waste, processes based on solvent extrac-tion, ion exchange and biosorption were developed. From electroplating effluent -93% chromium was recovered by solvent extraction with tributyl phosphate. The raffinate contained only 3.5 ppm chromium which can further be reduced by increasing the O/A ratio and be discharged in the stream. Amberlite IRA 400 and IRA 900 resins were used to study the extraction of chromium from electroplating effluent by ion exchange process. Both the resins were used to study the extraction of chromium from electrop-lating effluent by ion exchange process. Both the resins showed comparable extraction efficiency for chromium(VI) and the raffinate contained only very minute amount of chromium meeting the environmental regulatory norms for discharge in the stream. From the tannery effluent triva-lent chromium was also recovered by ion exchange with Amberlite IRA 120(Na+) and biosorption with Aspergillus niger. By electrodialysis, NaCI from the Cr(III) solution of tannery was removed to recycle the chrome solution in the hides. Thus by solvent extraction, ion exchange, biosorption and electrodialysis technique chromium can be recovered from electroplating and tannery effluent meeting environmental regulatory norms and making these suitable for discharge into the stream.