![]() 2014 Seifollahi & Rahbar-Kelishami 2019). Response surface methodology (RSM) is a popular technique which helps identify the optimal conditions through a constructive set of desired experiments ( Benyahia et al. Design of experiments, a methodical approach for studying the effect of operating variables, is a key requirement for effective statistical analysis and development of a new approach. Emulsion stability is reported as one of the key factors contributing to extraction efficiency ( Liu et al. ELM, proposed as an advanced membrane process, operates through creation of a three phase system and enhanced mass transfer areas achieved by the water–oil emulsion globules. Emulsion liquid membrane (ELM) is identified as a suitable recovery method for metals found in wastewater and other organic and inorganic components ( Kislik 2010 Jusoh & Othman 2017). Many of these methods are considered to be inefficient in terms of low recovery rates at low metal concentrations, excessive chemical usage leading to secondary pollution, lack of eco-friendliness and disposal difficulties ( Ma et al. Treatment of metal contaminated water has been investigated using several physico-chemical methods like adsorption, coagulation, precipitation and ion exchange. Also, presence of zinc in water causes heath disorders like bone disorders, pancreatic dysfunctional, vertigo and other neurological damage when present in high concentrations ( Hafshejani et al. Due to the toxic nature of zinc, the disposal of untreated wastewater contaminated with zinc is unacceptable and leads to bioaccumulation of the metal in the ecosystem ( Wang et al. Zinc emanated from electroplating industries contributes a huge amount in the wastewater and is required to be treated or recovered. Zinc, a metal used extensively galvanization applications, is a potential candidate used in corrosion protection through plating techniques. Use of metals has increased due to their increased use in automobile, infrastructure, insulation manufacturing and other specialty industries. Pollution of water bodies due to metal contamination has gained significant attention recently due to the volume of the contaminated wastewater generated and recalcitrant nature of the metals. The perturbation plot shows that the extraction of zinc was affected by variables in the following order of effect: zinc concentration > surfactant concentration > carrier concentration > external pH > external phase to emulsion volume ratio > internal phase concentration. At the optimized conditions experiment was carried out and the maximum extraction was found to be 97.4%. The response surface methodology (RSM) analysis identified that the optimal variable values for the maximum extraction of zinc were: external pH – 3.8, surfactant concentration 4% (vol.), internal phase concentration – 1.61N, zinc concentration – 742 mg/L, external phase to emulsion volume ratio – 0.94 and carrier concentration – 8.9%. ![]() The extraction percentage of zinc increased with the increase in concentration of surfactant. The liquid membrane was prepared by using waste cooking oil along with the surfactant, SPAN 80 and the internal phase, sulfuric acid. In this research study, removal of zinc ions from the industrial wastewater was investigated using green emulsion liquid membrane technology.
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