Abstract
One of the most critical problems to be solved in membrane separation processes is the fouling of membranes. Fouling causes a reduction in current efficiency in processes using ion-exchange membranes. In this study, the mechanism of fouling on the anion exchange membrane, cation exchange membrane, and bipolar membranes caused by impurities such as CaCl2, MgCl2, Na2CO3, and NaHCO3 in the electrodialysis process of the feed solution containing NH4Cl and NaCl as the main components were investigated. The effects of initial impurity concentration on bipolar membrane electrodialysis stack resistance, demineralization, ion flux, acid and base conversion, and concentration of produced acid and base were investigated. SEM-EDX, XRD, FTIR, and TGA analyses were used for membrane characterization. Chemical cleaning was done to remove impurities in the membrane and spacer structure. The effects of chemical cleaning on cell performance were determined by comparing the process performances before and after cleaning. Experimental results showed that ions such as Ca2+ and Mg2+ in the feed solution cause precipitate on the cation exchange membrane and spacers in the base compartment. The results revealed that these precipitates do not cause structural damage to the membranes but affect their performance.
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