Abstract
Sulfonated aromatic polymer (SAP) featuring hydrophilic nanochannels for water transport is a promising membrane material for desalination. SAPs with a high sulfonation degree favor water transport but suffer from reduced mechanical strength and membrane swelling. In this work, a hyperbranched polyester, H302, was introduced to crosslink a sulfonated styrene-ethylene/butylene-styrene (S-SEBS) copolymer membrane. The effects of crosslinking temperature and amount of H302 on the microstructure, and the pervaporation desalination performance of the membrane, were investigated. H302/S-SEBS copolymer membranes with different crosslinking conditions were characterized by various techniques including FTIR, DSC, EA, SEM, TEM and SAXS, and tensile strength, water sorption and contact angle measurements. The results indicate that the introduction of hyperbranched polyester enlarged the hydrophilic microdomain of the S-SEBS membrane. Crosslinking with hyperbranched polyester with heat treatment effectively enhanced the mechanical strength of the S-SEBS membrane, with the tensile strength being increased by 140–200% and the swelling ratio reduced by 45–70%, while reasonable water flux was maintained. When treating 5 wt% hypersaline water at 65 °C, the optimized crosslinked membrane containing 15 wt% H302 and heated at 100 °C reached a water flux of 9.3 kg·m−2·h−1 and a salt rejection of 99.9%. The results indicate that the hyperbranched-S-SEBS membrane is promising for use in PV desalination.
Highlights
Freshwater scarcity is considered the third global crisis after food and oil shortages, seriously threatening human lives and social development [1]
The results indicate that the hyperbranched-sulfonated styrene-ethylene/butylene-styrene (S-SEBS) membrane is promising for use in PV desalination
The results showed that the loose molecular structure of the hyperbranched polyester significantly enlarged the free volume, and the crosslinked network structure enhanced the mechanical properties of the membrane simultaneously
Summary
Freshwater scarcity is considered the third global crisis after food and oil shortages, seriously threatening human lives and social development [1]. Desalination by membrane technology plays a key role in solving worldwide freshwater scarcity. Among various membrane desalination technologies, pervaporation (PV) desalination has received increasing attention due to its unique advantages in handling high-salinity water; notably, its energy demands are independent of salt concentrations [2,3,4]. The membranes employed in the PV desalination process cover a wide range of materials including polymers, zeolites, amorphous silica and two-dimensional nanomaterials [2]. Due to their good film-forming ability and potential for scale-up and industrialization, Membranes 2020, 10, 277; doi:10.3390/membranes10100277 www.mdpi.com/journal/membranes
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