Ageing of ion-exchange membranes used in an electrodialysis for food industry: SEM, EDX, and limiting current investigations

摘要

Ion-exchange membranes, used in some food industrial electrodialysis (ED) applications, were investigated by measuring their physicochemical and structural parameters, in order to evaluate their evolution during this application. Two used membranes (one cationic and one anionic) were analyzed at the end of their useful life (twoyears of ED operation) and compared with their respective fresh new samples to assess the evolution of their structural and physicochemical characteristics, and explore their deterioration. The limiting current density, ion-exchange capacity, water content, and contact angle values were determined for each new and used membrane. Scanning electron microscopy and energy dispersive X-ray were also performed. The used cation-exchange membranes (CEMs) suffered from significant degradation; nonetheless, it was generally more robust and resistant than the anion-exchange counterpart, which was more unstable. A significant degradation in the polymer matrix of both membrane types was found. Both used CEMs and anion-exchange membranes (AEMs) lost a part of ion-exchange sites, and the different parameters show a fouling of the AEM and a loss of functional sites of the CEM.