Hydrogel membranes generally possess weak mechanical properties , and the membrane surface is susceptible to abrasion, which results in the loss of superwetting properties and oil/water separation ability. Therefore, we prepared a flexible freestanding membrane using a dual-cross-linking approach. A mixed solution of sodium alginate (SA) and polyvinyl alcohol (PVA) was covalently and ionically cross-linked with borax and calcium chloride (CaCl 2 ) to form a hydrogel, and sodium carbonate (Na 2 CO 3 ) solution was then added to synthesize calcium carbonate (CaCO 3 ) in situ. The combination of covalent and ionic cross-linking improves the tensile strength . The prepared SA/PVA/borax/CaCO 3 (SPBC) membrane maintained excellent superwetting properties and oil/water separation ability, even after abrasion. The SPBC membranes have broad application prospects in the oily wastewater purification owing to their numerous advantages, such as cost effectiveness, high separation efficiency, and improved mechanical strength .
Fengxiang Liu,Shuang Wang,Jinsheng Li,Xiaodong Wang,Zhipeng Yong,Yinghe Cui,Dan Liang,Zhe Wang
Novel double cross-linked composite membranes are fabricated based on diazoniabicyclo-type poly (ionic liquid) with trimethoxysilane groups ([TSPDO]BrCl) and norbornene-type polybenzimidazole (NbPBI). During membrane fabrication, in-situ free radical polymerizations and in-situ sol-gel reactions are completed to form the poly (ionic liquid)-NbPBI cross-linked networks and the Si-O-Si networks, respectively. An obvious advantage of this strategy is that the trimethoxysilane groups are fixed by the first cross-linked networks before hydrolysis reaction . Such method can avoid structural defects caused by SiO 2 particle aggregation in the membranes. Compared to the pristine NbPBI cross-linked membrane, the NbPBI-TSPDO cross-linked membranes exhibit enhanced thermal stability, mechanical properties, and proton conductivity . Considering the comprehensive performance, the NbPBI-TSPDO 30 membrane has the highest proton conductivity of 0.061 S cm −1 at 170 °C under anhydrous conditions. Moreover, NbPBI-TSPDO membranes display an improved PA retention rate of up to 81% and 64% at 160 °C for 400 h and 80 °C/40% RH for 96 h, respectively.
危险品化学品经营许可证（带存储）