Fabrication of self-doped sulfonated polyaniline membranes with enhanced antifouling ability and improved solvent resistance

The fabrication of self-doped sulfonated polyaniline S-PANI membranes is reported here for the first time and addresses key challenges of PANI membranes including fouling, solvent stability issues and acid leaching. Sulfonation of the PANI-powder was confirmed by FTIR, UV-VIS and SEM-EDX characterisation. The membranes were prepared via phase inversion approach in water from a solution of 23% w/v S-PANI and were chemically cross-linked with three different organic cross-linkers: α,α′-Dichloro-p-xylene (DCX), glutaraldehyde (GA) and terephtaloyl chloride (TCL). PANI, S-PANI, S-PANI DCX, S-PANI TCL and S-PANI-GA were evaluated for their hydrophilicity, morphology, chemical properties and filtration performance showing that the chemically cross-linked S-PANI membranes have superior stability and reusability in DMF when tested in dead-end cell at 5 bar. Filtration experiments in water showed that S-PANI-GA has an increase in PEG rejection of 2.3 times and a MWCO of 1800 Da in contrast with PANI and SPANI, which showed a MWCO above 5000 Da. Fouling performance using BSA, showed a significant improvement of flux recovery for S-PANI and S-PANI GA, with the membranes regaining 87% and 83% of their original flux after one cleaning-fouling cycle. Conversely, PANI had a flux recovery of only 40%. The low irreversible fouling of the membranes, 13% for S-PANI and 17% for S-PANI GA, against 65% for PANI after 3 cycles is an encouraging result for the reduction of costly and high environmentally impact chemical cleaning in membrane processes. Overall, this study provides a simple method to produce low fouling and long-term solvent resistant membranes to enhance the widespread use of membrane technology in industrial processes.