Fouling deposition as an effective approach for preparing monovalent selective membranes

Membrane fouling is always thought to be a disadvantage aspect for their performance during electro-membrane processes. The irreversible fouling is hard to clean and steadily adheres on the membrane surface and generally induces the degradation of membranes. Considering structural similarity between irreversible surface fouling layer and functional layer of the perm-selective membranes, we proposed here a novel technique called “fouling-deposition” for the modification of ion exchange membranes. Taking an anion exchange membrane (AEM) as an example, surface of Neosepta AMX membrane was modified by fouling deposition of sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) through electrodialysis process for studying monovalent selectivity for chloride ions (Cl−). The fouling compound was characterized via compositional and chemical analysis by infrared spectroscopy whereas scanning electron microscopic micrographs revealed a successful fouling of SPPO on the substrate membrane. The excellent perm-selectivity (PSO42−Cl−) between Cl− and SO42− was obtained during electrodialysis performance evaluation. Compared to the traditional membrane modification methods, the fouling deposition method has several salient features such as easy tuning of functional layer thickness and density by varying applied current, fluid velocity and operating time, superior perm-selectivity, lower area resistance and higher ions flux. It also provides an alternative procedure for the membrane surface modification which could be a great contribution in the scientific researches.