Catalyzed Air Oxidation of Thiosalts

Mill tailings waters containing thiosalts, when discharged into river systems constitute a severe environmental pollution problem. Complete oxidation of thiosalts to sulfuric acid by chemical means and neutralization of the acid prior to discharge of the effluent to receiving streams has long been considered a viable solution to the problem; subject to development of a simple and economic means of oxidation of thiosalts in large volumes of wastewater. In this context, the possibility of using catalyzed air oxidation of thiosalts to sulfate became the subject of active research and investigation ever since our finding of the ability of suitably complexed copper ions to catalyze the oxidation of thiosulfate by molecular oxygen. Extensive research has been carried out on the design and development of heterogeneous catalysts having this property. This work has involved the preparation of a number of polymer supported copper complexes for utilization in the air oxidation of polythionates. Recently, attention has been focused on the application of copper sulfide containing materials for this oxidation process. The results obtained in this comprehensive study are summarized and discussed.