Structural and physicochemical investigation of ageing of ion-exchange membranes in electrodialysis for food industry

• Published in: Separation and purification technology 2014-02, Vol.123, p.229-234
• Main Authors: Ghalloussi, R., Chaabane, L., Larchet, C., Dammak, L., Grande, D.
• Format: Article
• Language: English
• Subjects: Ageing; Conductivity; EDX; Electrodialysis; Ion-exchange membranes; SEM
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2013.12.020

•Ageing mechanism of 2 IEMs used for 2years in ED for food industry was investigated.•Used IEMs lost some ion-exchange sites, and their conductivity decreases sharply.•CEM became denser and more hydrophobic; AEM became thicker and more hydrophilic.•Significant degradation in the polymer matrix of both membrane types was found.•Microheterogeneous model was applied to explain the IEMs ageing mechanism. The ageing mechanism of ion-exchange membranes (IEMs) used in electrodialysis for food industry was investigated through the use of several analytical techniques. Structural and physicochemical properties of two different IEMs, i.e. a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM) were studied. The comparison of conductivity, thickness, water uptake, ion-exchange capacity and contact angle values as well as SEM micrographs and energy dispersive X-ray (EDX) spectra between new and used samples showed a significant degradation of membranes after 2years of use in an electrodialysis module. The CEM became denser and more hydrophobic, while the thickness of the AEM increased and the membrane became more hydrophilic. A significant degradation in the polymer matrix of both membrane types was found. The used membranes lost a part of their ion-exchange sites, and their specific electrical conductivity significantly decreases. To explain the important variations of equilibrium properties, we have applied the microheterogeneous model.