Construction of high performance sulfonated aromatic block copolymer/ PTFE composite membrane for pervaporation desalination

Pervaporation (PV) has great prospect in desalination of hypersaline water and its application is still limited by lack of high performance membrane with high water flux and good sustainability. This study reported a method of constructing thin film composite (TFC) membrane consisting of sulfonated aromatic polymer (SAP) active layer and porous PTFE substrate for PV desalination. The TFC membrane was fabricated by hydrophilic modification of PTFE support, followed by coating polystyrene-grafted SEBS on the support and post-sulfonation. The modification of PTFE by a strong oxidant introduced oxygen-containing group and tuned its wettability for better adhesion with the active layer. Polystyrene-grafting on SEBS endowed more aromatic groups for sulfonation to attain highly hydrophilic S-SEBS-g-PSt active layer carrying rich sulfonic acid groups. At a higher sulfonation degree (SD) of 60%, the adhesion strength between the active layer and the support was increased to over 1 MPa, and meanwhile the microphase separation of S-SEBS-g-PSt was enhanced with enlarged and more continuous hydrophilic micro-domain and improved water permeation. An ultra-high water permeance of 109, 000-438, 400 GPU was achieved at 45-85 C. The outstanding performance of this membrane indicates the promising potential of the SAP composite membrane for practical application.