Superhydrophobic PVDF membrane induced by hydrophobic SiO2 nanoparticles and its use for CO2 absorption

In this study, we reported a simple and facile methodology to prepare superhydrophobic poly(vinylidene fluoride) (PVDF) membrane via nonsolvent induced phase inversion process. The addition of hydrophobic modified SiO2 nanoparticles (HMSNs) in ethanol bath resulted in PVDF precipitation dominantly by solid-liquid demixing, and the obtained membrane was uniformly skinless and composed of spherical microparticles. The deposition of HMSNs on the microspheres formed micro- and nanoscale structure, which was crucial for superhydrophobicity. When HMSNs concentration in bath was 2 g.L-1, the water contact angle of the modified PVDF membrane was higher than 160 and the surface free energy decreased to 0.9 mN.m(-1). Since the proposed modification allowed HMSNs migration into the membrane interior during the exchange between solvent and non-solvent, the hydrophobicity of internal surface of membrane pores and channels was also enhanced. This feature successfully inhibited the liquid intrusion into membrane pores, and promised a stable anti-wettability in long-term performance. The modified PVDF membrane was used in membrane contactor for CO2 absorption. The wetting problem was markedly alleviated in an intense 20-day test even with a 12 wt% 2-aminoethanol solution as absorption solution. Our results demonstrated that the incorporation of hydrophobic nanoparticles in coagulation bath is a promising approach to obtain superhydrophobic PVDF membrane for membrane gas absorption.