Molecular design of chlorine-resistant polymer for pervaporation desalination

Pervaporation (PV) desalination membranes have good anti-fouling properties due to its hydrophilic dense surface structure. However, organic fouling is inevitable in long-term operation. Sodium hypochlorite (NaClO) is commonly used for cleaning organic pollutant, but it may damage polymeric membrane. Thus, designing membrane material with good chlorine resistance is crucial for expanding its lifespan. In this study, polyvinyl alcohol (PVA) was selected to prepare PV membrane in concern of its hydrophilicity and good film forming property. Its chlorine resistance was improved by removing the more active 1,2-diols of PVA by reacting with sodium periodate, grafting with poly (styrene-co-maleic anhydride) to decrease its crystallinity, and crosslinking using a fluorocarbon surfactant (FS). The resulting PV membrane exhibited the highest reported chlorine resistance of 768000 ppm·h among PV and RO membranes with a high-water flux of 44.5 ± 1.5 kg/m2·h and salt rejection of 99.93%. A long-term fouling and cleaning cycle experiment was carried out using 10000 ppm humic acid to mimic organic foulants. The flux was recovered 100% after the NaClO cleaning. Hence, the chlorine-resistant PV membrane had the ability for sustainable desalination application.