Jiawen Fu,Haowei Pan,Mingzhe An,Zihao Li,Hong Wang,Xinping He,Chunhai Yi
Polyvinyl alcohol (PVA) is a promising membrane material for pervaporation (PV) desalination. However, the adjustment and control of the cross-linking structure is still a challenge for PVA membrane. In this study, a novel pH-resistant PVA-based composite membrane for efficient pervaporation desalination was developed by precisely adjusting the cross-linking behavior. Vinyl alcohol-vinylamine copolymer (VA-co-VAm) containing both hydroxyl and amino groups was synthesized. Cross-linking reaction was carried out based on the Schiff base reaction between amino groups (in VAm moiety) and glutaraldehyde (GA) under alkaline conditions. Cross-linking degree of PVA selective layer was carefully controlled by adjusting the amino group content in copolymer. Results showed that membrane prepared with VA-co-VAm that containing 5 wt% N-vinylformamide (NVF) displayed superior hydrophilicity and the largest free volume fraction. Pervaporation test indicated that the modified cross-linking membrane showed good stability under extreme pH conditions. Specifically, under strong acid conditions (pH ~ 1) and alkaline conditions (pH ~ 14), the membrane showed excellent desalination performance with water flux over 12 kg/(m 2 h), and the salt rejection higher than 99.95%. Based on the above results, the prepared membrane offers a promising platform for desalination under extreme pH conditions, which shows great potential in industrial wastewater treatment.
In this study, a highly hydrophilic membrane was developed by an interfacial reaction using two aqueous monomers for pervaporation (PV) desalination. Two water-soluble monomers, procyanidin (PC) and vinyl alcohol-vinylamine copolymer (VA-co-VAm), were applied to prepare membranes on hydrophobic polyvinylidene difluoride (PVDF) membranes through interfacial reactions. Catechol groups of PC were oxidized to quinone groups under weakly alkaline conditions, which could react with amino groups of VA-co-VAm to form a cross-linked network. The PVDF membrane was first dipped into a PC aqueous solution to form a thin PC liquid layer on the surface. Accompanied by the PC liquid layer, the PVDF membrane was then dipped into the VA-co-VAm solution to induce the interfacial reaction. The composition and structure of membranes were observed, and the effects of different factors on the desalination performance were investigated. By applying two aqueous monomers in the interfacial reaction process, the obtained thin membrane showed good hydrophilicity with a water contact angle of less than 42°. A water flux of 42.16 kg/(m2·h) at 60 °C was obtained by treating a feed solution (3.5 wt % NaCl). At all testing procedures, the salt rejection remained higher than 99.99%. Besides, the membrane displayed superior stability over 48 h of testing. According to the above results, the prepared membranes showed great potential in the process of PV desalination. This work provides a new approach for highly permeable PV membrane preparation through an interfacial reaction using two water-soluble materials.
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