Experimental and modeling studies on simultaneous extraction of Pb2+, Cu2+, and Cd2+ from diluted acidic aqueous solutions by emulsion liquid membrane

Abstract

Lead, copper, and cadmium ions were simultaneously extracted from a diluted acidic aqueous solution using Bis-2-ethylhexyl phosphoric acid (D2EHPA) as a carrier, Sorbitan monooleate (Span 80) as a surfactant, Kerosene as a diluent, and H2SO4 as a reagent. The effect of the pH of the external phase, surfactant, and carrier concentrations, speed of the homogenizer, and the volume ratio (v/v %) of the external/membrane phases on the system performance were investigated. High extraction efficiencies of Pb2+, Cu2+, and Cd2+ ions were obtained; 100%, 100%, and 98%, respectively. A minimum breakage of 1.8% was also obtained at the best operating conditions. A modeling study of the system has shown no significant interaction effects of the three solutes (Pb2+, Cu2+, and Cd2+) on each other. Therefore, the three solutes permeate from the feed phase to the stripping phase due to their chemical potential. The competitive transport of the three ions at low initial concentrations has been found to be comparable. At low concentrations, the low diffusion rates of the three ions were compensated by the increase of their distribution coefficients. This has been reflected on the enhancement of the transport rates of the three solutes through the membrane to be comparable.