Mechanistic insights into efficient catechol removal using saponin-based emulsion liquid membrane

Catechol, a toxic organic pollutant commonly discharged from industrial effluents, poses serious threats to aquatic ecosystems and human health. In this study, saponin-based Emulsion Liquid Membranes (ELM) were developed as a green and sustainable alternative for catechol removal from wastewater. Saponin, a natural emulsifier, was used to formulate oil-based ELM, and the membrane phase was characterized using interfacial, rheological, and dynamic light scattering techniques. Process optimization through the Box-Behnken Design achieved an extraction efficiency of 88.9% with only 2% membrane breakage under optimal conditions of 3 v/v% saponin concentration, 2 v/v% span 80 concentration, 0.15 M internal phase concentration, and 30 min contact time. Kinetic studies revealed that the pseudo-second-order model best described the extraction process, with a rate constant of 0.0576 min^-1, confirming efficient mass transfer. These results highlight the potential of saponin-based ELM as an eco-friendly and effective separation technology. However, challenges remain regarding long-term membrane stability, selectivity in complex wastewater matrices, and large-scale implementation. Overall, this work demonstrates the feasibility of bio-based ELMs for industrial wastewater treatment and value-added compound removal, while emphasizing the need for further research to address scale-up and operational stability.