Design and optimization of oleo gel membranes with tunable and enhanced VOCs/N2 separation performance

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A VOC-philic oil, Bis(2-ethylhexyl) adipate (DEHA), was impregnated into PEBA matrix to fabricate oleo gel membranes. DEHA, known for its effectiveness as a plasticizer and VOC absorbent, enhances membrane performance for VOC/N2 separation while providing environmental benefits. It serves as a viable alternative to bis(2-ethylhexyl) phthalate (DEHP), which is restricted due to its classification as a substance of very high concern (SVHC) and has been previously used in oleogel membrane fabrication. The membranes were tested with various representative VOCs selected from different solvent groups (including alkanes, alcohols, and aromatic compounds). As high as 75 wt% of DEHA content was incorporated into the membrane, resulting in a significant increase in VOC permeability (2–8 times depending on VOCs) without sacrificing the VOC/N2 selectivity. To elucidate the advantage of impregnating DEHA into the membrane, the mixing rule of permeabilities was applied to the oleo gel membranes with different oil contents, and the “intrinsic” permeabilities of the VOCs in DEHA were determined. The membrane performance was further investigated for the various VOCs at different feed VOC concentrations and temperatures, and the membrane stability was demonstrated over a 35-day test with permeation of different binary VOC/N2 mixtures. The PEBA/DEHA oleo gel membranes were about 50 % more permeable to the VOCs than the counterpart membranes incorporated with bis(2-ethylhexyl) phthalate (DEHP), indicating that the VOC-philic adipate was advantageous over phthalate for impregnation into the PEBA matrix to enhance the membrane performance.