Designing High-Performance Nanofiltration Membranes for High-Salinity Separation of Sulfate and Chloride in the Chlor-Alkali Process

Enormous demand exists for separation of high-salinity solutions across various industries, especially in those high-pollution businesses which are urgently looking for high-throughput and precise-selective nanofiltration (NF) membranes stably operating at elevated concentrations and other harsh environments. This work develops a novel NF membrane (i.e., high-performance thin-film composite (H-TFC)) through straightforward structure design instead of complex post-treatment to achieve high performance during high-salinity separation of sulfate and chloride ions. Through manipulating dope composition and coagulation bath temperature, unique macro- and microstructures of the H-TFC membrane were designed: (1) The substrate possesses the best ratio of the spongy and fingerlike layers, which not only provides low resistance transport channels to improve the membrane permeability (13.0 L m(2-) h(-1) bar(-1)) but also ensures enough strength and minimum defects to treat high-salinity solutions. (2) The unique nominal pore size (0.364 nm) of the finely tuned selective layer can realize the separation of Cl- and SO42- at relatively high level (separation factor about 9000). The excellent long-term stability and resistance toward chlorine and heat grant the H-TFC membranes great potential for application in high-salinity solution separation of chlor-alkali and other industries.