Asymmetric composite PDMS membrane contactors for desorption of CO2 from monoethanolamine

Membrane gas solvent contactors have the potential to revolutionize carbon capture, because the technology combines the advantages of both membrane and solvent technologies. Here, an asymmetric composite poly dimethylsiloxane (PDMS) on porous polysulfone membrane contactor was studied for the desorption of CO2 from loaded 30 wt% monoethanolamine (MEA) solution. Importantly, this study investigated the performance of the contactor at temperatures where the MEA solution entered the contactor as a liquid and as a vapor. It was found that the PDMS contactor CO2 flux was comparable to other reported membrane contactors when the MEA solution was in the solvent phase, but when the feed was vaporized the CO2 flux increased by an order of magnitude. Similarly, the overall mass transfer coefficient had the same behavior, in that an order of magnitude increase was obtained when the MEA solution was above the boiling temperature. The CO2 permeability through the non-porous PDMS layer was calculated based on mass transfer correlations and the temperature trend was comparable to literature. This indicated that CO2 transport through the PDMS layer was the same for the range of temperature and phase conditions studied, and that the mechanism was based on CO2 transporting in the gas phase. Significantly high water fluxes were observed through the PDMS membrane, two orders of magnitude greater than CO2, which was comparable with other non-porous contactors. However, at 110 °C, the H2O/CO2 flux selectivity decreased to 14, indicative of the higher CO2 flux at that temperature because of the vapor feed.