Brackish water desalination using electrodialysis with monovalent selective membranes

Abstract

Electrodialysis with selective membranes is used to desalinate surface waters while preserving the polycharged ions. Layer-by-layer adsorption of alternating positively charged and negatively charged polyelectrolytes at the surface of the substrate membrane is known as a simple and cheap method for the production of selective membranes. In this article we investigate model membranes surficially coated from one side with two types of anion exchange modifiers and conclude that for both types of created samples a high limiting current of salt ions is observed but the intensity of a side process, a shift in the pH of the treated solution, increases after the modification. We propose that it is more reasonable to modify membranes by this method with polymeric quaternary ammonium substances, which are less catalytically active in water dissociation reaction. This will reduce the energy demand of the process and will improve the quality of treated waters.