From Composition to Performance: Evaluating the Effect of Emulsion Liquid Membrane Components on Lead Removal from Water

Lead (Pb2+) is a toxic heavy metal commonly present in industrial wastewater. This study presents the development and optimization of an emulsion liquid membrane (ELM) system for rapid and efficient Pb2+ removal from aqueous solutions. The effects of solvent type, extractants, stripping agents, and surfactant amounts on lead removal efficiency were systematically evaluated. The optimized 22 mL membrane phase consisted of a mineral oil-toluene mixture (1:1, v/v) containing 3% sorbitan monooleate (SPAN80) and 5% di(2-ethylhexyl) phosphoric acid (D2EHPA), while the 18 mL internal phase contained 2.4 N sulfuric acid. The optimum emulsification speed and time were 10000 rpm and 1 min, and the reactor stirring speed for mixing the 40 mL emulsion phase with a 250 mL external aqueous phase containing approximately 1000 mg L-1 Pb2+ was 300 rpm. Under these conditions, the system achieved Pb2+ removal efficiencies exceeding 99% within 20 min, reducing the final concentrations to below 1 mg L-1 while maintaining high emulsion stability and reproducibility. The optimized parameters provide critical insight into the chemical and physical design of ELM systems, highlighting their potential for industrial-scale heavy metal removal. Additionally, considerations such as external phase pH reduction and potential membrane phase leakage are identified as important for scale-up and post-treatment processes. The findings demonstrate that the optimized ELM system offers a highly effective, rapid, and scalable strategy for lead removal or extraction from aqueous streams and effluents.