Selective separation of copper and zinc from spent chloride brass pickle liquors using solvent extraction and metal recovery by precipitation-stripping

Copper and zinc were recovered from spent chloride brass pickle liquor using solvent extraction and precipitation-stripping. Speciation diagrams reveal that bivalent copper and zinc and their monovalent chlorocomplexes were present in the liquor. Copper was extracted by hydroxyoxime LIX84IC in kerosene while zinc was extracted using D2EHPA. 98.8% copper was extracted at an equilibrium pH of 2.5 using 30% v/v LIX 84IC whereas 98.3% zinc was extracted at an equilibrium pH of 2 using 15% v/v D2EHPA. Precipitation-stripping of loaded organic phase using oxalic acid resulted in recovery of copper and zinc as water insoluble oxalates. Solubility plots developed on theoretical considerations for copper-oxalic acid and zinc-oxalic acid system predicted the yield of precipitates in close agreement with experimental values. 97.3% of both copper and zinc present in the pickle liquor were recovered as their oxalates. The organic phase could be used for multiple cycles. Calcinations of the oxalates to their oxides did not induce any change in the ordered structure observed in oxalates. Morphology of the precipitates revealed highly agglomerated particles. Copper oxide 100% pure and zinc oxide with 99.1% purity were obtained as value added products. A process flow diagram of the proposed scheme is presented that could be implemented to generate wealth from waste.