Characterization of an anion-exchange membrane subjected to phosphate and sulfate separation by electrodialysis at overlimiting current density condition

The structural degradation of an anion-exchange membrane used on the separation of phosphate from sulfate ions at overlimiting current density conditions was investigated. To this, the chemical structure changes, apparent counterion transport number, limiting current density, the apparent fraction of surface conductive regions, degree of hydrophobicity, membrane resistance and conductivity, morphology and thermal degradation profile were studied for the original and used samples of the anion-exchange membrane. The results showed that the degradation of the membrane fixed ion groups and structural polymer backbone affected the ionic transport conditions, reducing its apparent permselectivity and fraction of conductive regions. Also, the increase in the hydrophobicity degree together with the formation of cavities observed in the membrane surface may be responsible for the alteration of membrane conductivity, leading to a higher limiting current density value and a decrease in the plateau length. [Display omitted] •Anion-exchange membrane was investigated before and after the separation process.•Degradation of the membrane functional groups and polymer backbone was reported.•The degraded membrane exhibited a lower counterion transport number.•The plateau length was shortened by surface hydrophobization and cavities formation.•The involvement of co-ions may cause an increase in water content in used membrane.