Recovery of sulfuric acid from copper tank house electrolyte bleeds

Many hydrometallurgical processes produce large amounts of acid waste. For example, copper SX/EW process plants typically bleed a concentrated sulphuric acid stream (electrolyte) from their tank house in order to limit the build up of impurities in the electrowinning stage. A process based on solvent extraction, to selectively recover up to 90% of the sulphuric acid from electrolyte bleed streams, has been developed. This is recovered as a pure aqueous acid stream at a concentration of up to 130 g/L that can be recycled back into the tank house circuit thus reducing both neutralisation and acid make up costs. The acid concentration of the electrolyte is reduced from 180 g/L to as low as 18 g/L. The extraction system involves the use of a branched long chain aliphatic tertiary amine tris(2-ethylhexyl)amine (TEHA) as the extractant, Shellsol 2046 as the diluent and octanol as a modifier. The equilibrium data and simulation results were also compared with an alternative extractant, CYANEX 923.