Thin-film nanofiltration membrane with monomers of 1,2,4,5-benzene tetracarbonyl chloride and ethylene diamine on electrospun support: preparation, morphology and chlorine resistance properties

Novel polyimide nanofiltration membranes were prepared by interfacial polymerization using 1,2,4,5-benzene tetracarbonyl chloride (BTC) and trimesoyl chloride solution in n-hexane and aqueous solution of ethylene diamine on electrospun PVDF support followed by thermal treatment. The BTC was synthesized by the reactions of 1,2,4,5-benzene tetracarboxylic acid with thionyl chloride using triethylamine as a catalyst. The polyimide layer prepared by optimized conditions such as temperature, heating time and interfacial polymerization method found to be good for performance of selective layer. Optimized conditions are confirmed from scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis–differential thermal analysis and differential scanning calorimetry studies. The NF membrane containing polyimide selective layer exhibited 7 ‘gallon/ft² day’ water flux and ‘94.8%’ salt rejection. Although the salt rejection values of these polyimide membranes were close to the commercial NF polyamide membranes, these membranes exhibited high chlorine resistance. After chlorination for 100 h in a 200 ppm NaClO solution, polyimide membrane showed 1.4% increased flux and about 2.2% decline in salt rejection.