Polydimethylsiloxane nanofilm-enhanced membrane contactors for CO₂ capture

Gas-liquid membrane contactors are attractive for CO₂ capture from flue gas due to process intensification; however, conventional porous membranes can be gradually wetted by the liquid solvent, resulting in a dramatic decrease in CO₂ flux. Herein, we demonstrate a facile method for coating hydrophobic polydimethylsiloxane (PDMS) nanofilms on porous hollow fiber membranes (HFMs) using solutions containing 0.4–5 mass% PDMS. The PDMS nanofilm covers the nanopores on the membrane surface and increases hydrophobicity, preventing pore infiltration by the liquid solvent and increasing CO₂ flux. For example, coating the HFMs with a 5 % PDMS solution enhances CO₂ mass transfer coefficient by more than 10 times, from 0.0020 to 0.028 cm s⁻¹, and CO₂ permeance from 24 to 330 GPU, higher than commercial silicone membrane modules (PermSelect) and most leading membrane contactors reported in the literature. CO₂ capture performance is also thoroughly investigated as a function of gas composition, gas flow rate, liquid flow rate, and transmembrane pressure, providing helpful guidance in designing next-generation membrane contactors for various gas separations.