Bio-Emulsion Liquid Membrane for Dual-Functional Water Treatment: Microplastic Removal and Antimicrobial Activity

Abstract

Microplastics are polymer particles smaller than 5 mm that originate from the degradation of larger plastic debris and persist in the environment. In the present study, polyethylene (PE) and polystyrene (PS) microplastics with particle sizes of 1–5 μm were used as model contaminants. It contaminates water sources, including drinking water, posing a significant risk to human health and the environment. In this study, a biosurfactant-based amphiphilic emulsifier was used in combination with Span 80 to develop a functional bioemulsion liquid membrane (Bio-ELM). The parameter optimization during Bio-ELM synthesis yielded the following optimized emulsification parameters: saponin (1% v/v), Span 80 (1.5% v/v), NaOH (0.2 M), MP: IP ratio (1:0.5), stirring speed 800 rpm, and emulsification time 5 min. The enhanced emulsion stability and membrane integrity are attributed to the interfacial activity of the biopolymer-derived saponin, which contains hydrophilic and hydrophobic functional moieties. They are responsible for improving ELM stability and facilitating selective transport. Emulsion stability was analyzed using the creaming index (CI) and microscopic images during parameter optimization. Two model microplastic samples, polyethylene (PE) and polystyrene (PS), were extracted using Bio-ELM, with extraction efficiencies of 95% and 89%, respectively. Bio-ELM demonstrated microbial growth inhibition, as evidenced by a zone of inhibition (ZOI). Bio-ELM components disrupt bacterial membranes and inhibit bacterial growth in contaminated water. Bio-ELM synthesis offers multifunctional properties, cost-effectiveness, environmental friendliness, enhanced emulsion stability, increased extraction efficiency, and antimicrobial activity. © 2026 American Chemical Society