A Review of Sulfonated Polymeric Nanofiltration Membranes and their Separation Performance after Sulfonation: Emphasizing on Dye Removal from Industrial Wastewaters

Replacing conventional separation processes with membrane processes saves energy. For this purpose, it is necessary to fabricate membranes with high mass transfer flux and long durability. Some synthetic polymers have considerable physicochemical properties and separation performance and are widely used in fabricating polymeric membranes. However, to improve the performance of polymer membranes, especially for use in water and wastewater treatment, there are various methods, among which sulfonation is one of the most important. In the sulfonation process, hydrophilicity increases by creating sulfonic groups in the polymer membrane structure. By introducing sulfonic groups on polymer chains, a wide range of membranes with different hydrophilic and hydrophobic properties can be prepared. This review focuses on sulfonation as an effective modification method to improve the performance of polymers used in the fabrication of nanofiltration membranes. The results show that the membrane behavior after sulfonation is improved from different aspects and the extent of this improvement is directly related to the degree of sulfonation, the nature of the polymer and the desired characteristics.