Comparative performance assessment of solvents for the extraction of H2SO4 from spent electrolytic bleed stream of copper industry

Abstract

Direct disposal of any waste into soil/water/air is a matter of great concern due to their hazardous effects on the living beings and environment Stringent environmental rules imposed on every manufacturer has forced them to reuse-recover-recycle their industrial waste before its final disposal, leading to the emergence of the concept of zero waste technology. Thus all the waste and the discarded by-products are considered as a secondary resource for some new value added product. Copper industry is one such waste effluent producer. In the process of electro-refining of blister copper, the optimum concentration and composition of the electrolyte in the tank is maintained by a periodical purging out of the electrolyte loaded with unwanted species of arsenic, antimony, iron, nickel etc. This represents a considerable amount of copper and sulphuric acid loss in large plants (although only about 1% of this stream is purged out). The purged electrolyte is subjected to electro-winning to recover copper and the copper depleted waste stream enriched with H2SO4 and other impurities originally present is discarded as spent electrolyte. In this endeavor, a hydrometallurgical process has been developed to treat a real life stream discarded from a copper electro winning tank to recover acid values instead of adopting the alkaline treatment and disposal of hydroxide waste. The acid depleted solution may further be used to recover metal values. An extensive study has been carried out on the extraction and stripping of the acid in a pure form using various organic solvents. The extraction and stripping efficiencies of the three solvents used in this study have been compared and are in the order of TEHA > alamine 336 > cyanex 923 and cyanex 923 > TEHA = alamine 336 respectively. (C) 2016 Elsevier B.V. All rights reserved.