Nature identification and morphology characterization of cation-exchange membrane fouling during conventional electrodialysis.

The aim of this work was to study the effect of a concentrate solution pH value and of the composition in calcium, carbonate, and protein of a diluate solution to be treated by conventional electrodialysis on the fouling of cation-exchange membranes (CEM). It appeared that after demineralization of solutions containing CaCl(2) and CaCl(2)+Na(2)CO(3) using a concentrate solution maintained at a pH of 12, mineral fouling appeared on both sides of the CEM. The nature of the deposits was identified as calcium hydroxide and/or carbonate on both surfaces. The mineral fouling presented an aggregation-like crystal following a carnation-like pattern of aggregates of small rhombohedral crystals with CaCl(2) added alone, while CaCl(2)+Na(2)CO(3) yielded a smoother spherical crystal. Protein fouling was detected only on the CEM surface in contact with the diluate after demineralization of a solution containing CaCl(2)+Na(2)CO(3) using a concentrate pH value of 2.