Development and characterization of an aloe vera-based bio-emulsifier for sustainable bio-emulsion liquid membrane systems for wastewater treatment

Emulsion instability poses a challenge in the development of emulsion liquid membrane (ELM) systems, as coalescence and phase separation hinder their effectiveness in wastewater treatment. This study presents a bio-emulsion liquid membrane (Bio-ELM) system that uses Aloe vera leaf (AVL) extract as a natural bio-emulsifier. AVL extract was characterized using HPLC and GC-MS, confirming the presence of amphiphilic bioactive compounds that reduce interfacial tension and form uniform nanoscale droplets. The critical micelle concentration (CMC) of the bio-emulsifier was 2% v/v, which corresponded to a surface tension of 18 mN/m. Bio-ELM exhibited droplet sizes of 50-200 nm, shear-thinning behavior verified by rheological analysis, and FTIR evidence indicating bio-emulsifier incorporation into the membrane phase. Optimization studies identified the optimal conditions as a bio-emulsifier concentration of 2.5% v/v, stirring speed of 800 rpm, internal phase concentration of 0.25 M, pH 8, and membrane-to-internal phase ratio of 1:1.5. Under these conditions, Bio-ELM achieved a 98% extraction efficiency for methylene blue dye from a synthetic aqueous solution. Dimensionless numbers (Capillary, Bond, and Marangoni numbers) provide insights into the balance of viscous, interfacial, and elastic forces governing emulsion stability. Stability assessments showed that the Bio-ELM maintained structural integrity and performance for up to 15 days. This study demonstrates the potential of an Aloe vera-derived bio-emulsifier to address emulsion instability, offering a sustainable alternative for environmental remediation using Bio-ELM technology.