Experimental optimization of uranium (VI) extraction using emulsion liquid membrane: a response surface methodology approach

This study investigates the extraction of uranium (VI) from aqueous solutions using an emulsion liquid membrane (ELM) system. The ELM system consisted of kerosene as the organic diluent, di-(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant, and sorbitan monooleate (Span-80) as the surfactant. Sulfuric acid and potassium chloride were used as the stripping solution and tracer, respectively. Response Surface Methodology based on Central Composite Design was applied to examine the effects of process variables, including surfactant concentration in the membrane phase, sulfuric acid concentration in the stripping phase, initial pH of the feed phase, and mixing speed, as well as their interactions. Hydrodynamic parameters were optimized to maximize U(VI) extraction while maintaining high membrane stability. The optimization results revealed that the highest extraction efficiency was achieved by adjusting the Span 80 volume percentage to 1.93% (V/V), sulfuric acid concentration to 0.75 mol/l, feed phase pH to 3.03, and mixing speed to 180.56 rpm. The role of feed-phase pH was found to be significant in the ELM process for U(VI) pertraction. Under these conditions, an extraction efficiency of 99.94% was obtained, with optimized values for emulsion breakage, swelling, and stripping being 0.21%, 3.29%, and 99.69%, respectively.