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 m2– 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.