Formation of low acetyl content cellulose acetate membrane for CO2/N2 separation

Abstract

The rising carbon dioxide (CO2) emissions over the decades is known to be a huge contributor to the greenhouse effect. CO2 capture and storage methods have been perceived as favourable solutions to prevent global warming and climate change rising from the greenhouse effect. One energy efficient technology for separating CO2 is the development of high-performing CO2 gas separating membranes. A variety of membrane-based gas separation technologies designed have shown promising results and are inexpensive. A high-performing membrane must have a defect-free, thin dense skin-layer with a porous sub-layer for support that permits great permeation rate and selectivity. Of all ranges of polymers used to make polymeric membranes for CO2/nitrogen (N2) separation, cellulose acetate (CA) polymer membranes are known for their high CO2 solubility. In this research, the effect of CA polymer concentrations at low acetyl group of 39.8% and casting thickness on the structure and morphologies of the membranes were studied. The CA polymer concentration was optimised from a range of 10 wt%, 15 wt% and 20 wt%, and the casting thickness was optimised from a range of 150 μm to 400 μm using wet-phase inversion technique. The results obtained exhibit a CA membrane with thin dense, selective skin-layer achieved at CA polymer concentration of 15 wt% and a casting thickness of 300 μm, with a CO2 permeance rate of 401.173 ± 0.579 (GPU), N2 permeance rate of 133.499 ± 0.148 (GPU) and selectivity of 3.009 ± 0.00656. This CA membrane is able to contribute to promising gas separation performances with enhanced physical and mechanical support by improvement of membrane permeance and selectivity towards CO2/N2 separation performance.