Title : Microbial biosurfactant stabilized emulsion liquid membrane for sequestration of dye from wastewater
Abstract:
Membrane technology is one of the emerging technologies for the recovery of toxic elements from wastewater. Liquid membrane is gaining more importance due to its various salient features such less expensive, more permeability, higher diffusivity coefficient, one step operation. Emulsion liquid membrane (ELM) techniques is successfully used for the extraction of heavy metals or precious metals, dyes,Organic acids and other compounds. ELM is made up of an internal phase inside the organic phase (also known as the membrane phase) that is stabilized by an emulsifier and distributed as minuscule, small droplets. ELM techniques have shown promise for dye removal, most studies have relied on synthetic surfactants. The potential of biosurfactants as environmentally friendly alternatives remains insufficiently explored. Instead of commercial chemical surfactants, the use of biologically synthesized emulsifiers becomes a productive alternative solution both in terms of economic and environmental point of view. This research aims to address these gaps by employing a microbial biosurfactant to stabilize ELM systems and evaluate their performance in separating dyes from wastewater. In the present study, a biosurfactant-stabilized emulsion liquid membrane (BS-ELM) was developed for the extraction of methylene blue (MB) dye from aqueous solution. Biosurfactant-producing microorganisms were isolated from soil and screened using CTAB (CetylTrimethylAmmonium Bromide) agar, HOA (Hydrocarbon Overlay Assay), drop collapse, and emulsification index tests. Among five isolates (BS1–BS5), strain BS4 exhibited superior emulsification ability and was identified as Stutzerimonas stutzeri (Accession No.: PV037561) through 16S rRNA sequencing. The biosurfactant produced by BS4 was characterized using 1H NMR (Proton Nuclear magnetic resonance spectroscopy), FTIR (Fourier transform infrared spectroscopy), and LC-HRMS (Liquid Chromatography-High Resolution Mass Spectrometry) analyses, revealing structural features similar to rhamnolipids. The BS-ELM formulation comprised waste cooking oil (WCO) as a green diluent, Aliquat 336 as a carrier, NaOH (0.8 M) as the internal phase, and biosurfactant-containing cell-free supernatant (CFS) as an emulsifier. Under optimized conditions (pH 9 of feed, stirring speed 400 rpm, treat ratio 2:1, 0.8M of internal phase concentration, 15% of v/v% of biosurfactant), the system achieved a maximum MB removal efficiency of < 94±1.3%. Zeta potential analysis of the BS-ELM yielded a value of +52 ± 2mV, confirming excellent emulsion stability. This study demonstrates the potential of BS-ELM as a sustainable and effective technique for dye removal, integrating microbial biosurfactants and waste-derived materials to enhance environmental compatibility. The dual focus on performance and waste valorisation offers valuable insights for green membrane design in wastewater treatment applications.
