Zinc extraction from a bioleaching solution by emulsion liquid membrane technique

Abstract Zinc separation from a bioleaching solution of a low-grade lead/zinc sulfide ore was performed by emulsion liquid membrane (ELM) technique. To study the extraction efficiency, the effect of key parameters including contact time, stirring speed, treat ratio, initial zinc concentration in the external phase, D2EHPA, Span80 and stripping agent concentration are studied and optimized. Maximum zinc extraction (≈71 %) was achieved at 20 min contact time, 150 rpm, 10 % (v/v) D2EHPA, 5 % (v/v) Span 80, 1.5 M sulfuric acid in the internal phase, and Vex/Vem = 5:1. The results showed that osmotic pressure gradient is responsible for water transport from the external phase into the internal phase and emulsion swelling in most cases. An excessive shear force, extra concentration of emulsion components and longer contact time trigger emulsion breakage and globule rupture.