Selective Separation of Zinc and Iron from Spent Pickling Solutions by Membrane‐Based Solvent Extraction: Process Viability

This work reports the viability of the selective separation of zinc from spent pickling solutions by means of membrane‐based solvent extraction to get a high concentrated zinc solution with a negligible content of iron and other metals that could be used in a electrolytic process to recover zinc in a metallic form. By working with waste effluents as feed solutions that contained these main components, Zn 78 g/L av., Fe 90 g/L av., and HCl 237 g/L av., Tributyl phosphate (TBP) and water were selected as the extractant and back‐extraction agent that allowed maximum zinc separation and recovery. With the kinetic results obtained in a bench‐scale set‐up containing two hollow fiber (HF) modules the selectivity of zinc over iron recovery, αZn/Fe, was calculated. The parameter αZn/Fe depended on the initial metallic concentration in the feed solutions and reached a maximum value of αZn/Fe = 146 (g Zn/g Fe).