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|a Emulsion liquid membrane (ELM) process has received significant attention due to its simple operation and high selectivity to the target solute. One of the potential applications of ELM is in the separation and purification of succinic acid from fermentation process. The most important aspects for a successful ELM process are liquid membrane formulation and emulsion stability. In this study, the formulation of ELM was investigated to find a suitable carrier, diluent and stripping agent. The stability of water-in-oil (W/O) emulsion was studied by investigating the ratio of organic to internal phase, homogenizer speed, emulsifying time, and surfactant concentration. The stability of water-in-oil-in-water (W/O/W) was investigated by varying sorbitan monooleate (Span 80) and polyoxyethylenesorbitan monooleate (Tween 80) concentrations, agitation speed, and agitation time. Experiments on the effect of stripping agent concentration, treat ratio, carrier concentration, pH of external phase, modifier concentration, extraction time, and agitation speed were carried out in batch process to find the most influencing parameters for succinic acid extraction. The optimum recovery of succinic acid was studied using response surface methodology (RSM). The favourable conditions for ELM application in the succinic acid recovery was determined by varying the external feed concentration and potential of liquid membrane recycling. The results show that palm oil as a diluent, Amberlite LA2 as a carrier, and sodium carbonate (Na2CO3) as a stripping agent were selected in liquid membrane formulation. The most stable condition of W/O emulsion was obtained at 3:1 organic to internal phase ratio, 7000 rpm of homogenizer speed, 5 minutes of emulsification time, and 3% (w/v) of Span 80 concentration. The most stable W/O/W emulsion was obtained at 5% (w/v) Span 80, 1% (w/v) Tween 80, 300 rpm agitation speed, and 3 minutes agitation time. At the best condition of 0.01M Na2CO3, 1:3 treat ratio, 0.7M Amberlite LA2, 10% modifier, pH 2, and 3 minutes of extraction time, the extraction of succinic acid was up to 70%. The most significant parameters of stripping agent and carrier concentrations, and treat ratio were selected for RSM optimization study and the results show that 38.9% and 36.3% of succinic acid was recovered from aqueous solution and fermentation broth respectively. The ELM purification of succinic acid showed that at favourable condition, 84% of succinic acid was recovered with almost 100% purity and the liquid membrane is good up to the second cycle. The findings of this study show that ELM process is a promising technology to extract and recover succinic acid from bio-based production.
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