In-situ grafting to improve polarity of polyacrylonitrile hollow fiber-supported polydimethylsiloxane membranes for CO2 separation.

Surface grafting modification was proposed to improve the surface polarity of polyacrylonitrile hollow fiber-supported polydimethylsiloxane (PDMS) membrane. The initiator 3-aminopropyltriethoxysilane containing one amine group was integrated into PDMS, and polyvinyl pyrrolidone (PVP) with strong polarity was connected to the surface by reacting with amine groups. Surface grafting modification was proven on X-ray photoelectron spectroscopy. The sharp decrease (from ∼98° to ∼28°) in water contact angle of the PDMS membrane indicated the significant improvement in surface polarity after the modification. The surface roughness of the PDMS membrane increased with the modification, and the PDMS surface immersed for 40s was almost covered with PVP. The membrane immersed in PVP solution for 10s improved CO2/H2, CO2/CH4, and CO2/N2 selectivities. While CO2 permeance slightly decreased from ∼2500 GPU to ∼2440 GPU. For the separation of CO2/CH4 and CO2/N2 mixed gases, all CO2/CH4 and CO2/N2 selectivities were improved after the modification. For the separation of CO2/H2 mixed gas, CO2/H2 selectivity was improved when the immersion time was below 30 s.