Membrane fouling, chemical cleaning and separation performance assessment of ion-exchange membrane for diffusion dialysis in alkali recovery

Diffusion dialysis with ion exchange membranes (IEMs) has gained widespread industrial adoption. However, membrane fouling remains a persistent challenge, hindering their performance and escalating operational costs. This study specifically focuses on membrane fouling and cleaning in IEMs employed for waste alkali liquor recovery. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the characteristics of contaminants adhering to the membrane surface, revealing a complex mixture of I, O, Na, Mg, C and K as the primary contaminants. To mitigate membrane fouling, an enzyme-containing alkaline cleaning agent was employed. An orthogonal experimental design was adopted to optimize the critical cleaning parameters, including dilution ratio of cleaning agent, temperature, soaking time, and backwash time. The results of the orthogonal experiment indicated that the dilution ratio of cleaning agent played the most crucial role in enhancing membrane recovery, followed by soaking time, backwash time, and temperature. The optimal cleaning conditions were identified as a dilution ratio of 25, a soaking time of 40 min, a backwash time of 20 min, and a temperature of 35 degrees C. Under the optimized cleaning conditions, the membranes exhibited a remarkable recovery rate, achieving a maximum of 95.49 % restoration of their initial performance.