Spent pickling acidfrom the industrial galvanizing process currentlyrequires specialist disposal, yet there is the potential to recoverthe zinc as a valuable metal. In this work, we compare the extractionof zinc using tributyl phosphate from real galvanizing effluent andlaboratory prepared solutions. Both commercial and handmade hollowfiber membrane contactors are used for this purpose. While the zincis effectively extracted, care must be taken to prefilter the solutionupstream of the membrane contactor to minimize crud formation andinterfacial effects. The extraction of both zinc and HCl from theeffluent is satisfactorily described using mathematical models forboth the multicomponent equilibria and mass transfer balances. Indevelopment of the multicomponent equilibrium model, the thermodynamicequilibrium constants obtained from the ZnCl2–NaCl–HClaqueous system were found to be applicable to the ZnCl2–FeCl2–HCl system. [ABSTRACT FROM AUTHOR]