Membrane-based gas separation is a promising unit operation in a low-carbon economy due to its simplicity, ease of operation, reduced energy consumption and portability. A methodology is proposed to immobilise enzymes in stable water-in-oil (W/O) emulsions produced by direct membrane emulsification systems and thereafter impregnated them in the pores of a membrane producing emulsion-based supported liquid membranes. The selected case-study was for biogas (CO₂ and CH₄) purification. Upon initial CO₂ sorption studies, corn oil was chosen as a low-cost and non-toxic bulk phase (oil phase). The emulsions were prepared with Nadir^® UP150 P flat-sheet polymeric membranes. The optimised emulsions consisted of 2% Tween 80 (w/w) in corn oil as the continuous phase and 0.5 g.L⁻¹ carbonic anhydrase enzyme with 5% PEG 300 (w/w) in aqueous solution as the dispersed phase. These emulsions were impregnated onto a porous hydrophobic PVDF membrane to prepare a supported liquid membrane for gas separation. Lastly, gas permeability studies indicated that the permeability of CO₂ increased by ~15% and that of CH₄ decreased by ~60% when compared to the membrane without carbonic anhydrase. Thus, a proof-of-concept for enhancement of CO₂ capture using emulsion-based supported liquid membrane was established.

Membrane-based gas separation is an important unit operation in chemical industries due to its simplicity, ease of operation, reduced energy consumption, and compact structure. For gas separation, novel studies were carried out by synthesising enzyme-stabilised systems consisting of emulsion-based supported liquid membranes (E-SLMs) the pores of which pores were impregnated with water-in-oil (W/O) emulsions produced by direct membrane emulsification. This technique has gained attention, as it consumes low energy and is mild and suitable for sensitive enzymes. This case study involves the capture of CO₂ by the enzyme carbonic anhydrase (CA). The composition of the oil phase was optimised amongst various edible oils, aiming for the one with the highest CO₂ sorption capability. The water phase was optimised based on the stability of the CA enzyme in the aqueous phase in the presence of various surfactants and their concentrations. The optimised emulsions consisted of 2% Tween 80 (w/w) in corn oil as the continuous phase and 0.5 g L⁻¹ CA enzyme with 5% PEG300 (w/w) in aqueous solution as the dispersed phase. The emulsions were prepared with a Microdyn Nadir UP150 polymeric membrane. These emulsions were impregnated onto a hydrophobic PVDF membrane to prepare E-SLM. For comparative studies, liquid membranes were also prepared without the CA enzyme in the emulsions, and a supported liquid membrane (SLM) was prepared by impregnating corn oil onto the membrane. Lastly, the permeabilities of the main components of biogas, CO₂, and CH₄, through the SLM and E-SLMs, were evaluated. The permeability of CO₂ increased (~15%) and CH₄ decreased (~60%) through the E-SLM containing CA when compared to the SLM and E-SLM without CA. Subsequently, the selectivity of CO₂ increased in the presence of low concentration of CA. This work suggests the enhanced, synergetic effects of carbonic anhydrase within a bio-based emulsion system for CO₂ capture.