Monovalent selective membrane for electrodialysis desalination of water for agriculture

Abstract

Abstract Agriculture is the world’s largest consumer of water accounting for about 70% of freshwater withdrawals. Faced with scarcity of pure water, it results in need in desalination to produce water for agricultural needs from brackish water, seawater or polluted sources. Widely used technologies reduce total salinity decreasing also the levels of calcium, magnesium, sulphates and phosphates required for normal growth of plants. Recently a layer-by-layer adsorption of charged polymers was proposed for creation of functional materials that would preferentially remove monovalent ions such as Na+ and Cl−. Our previous studies demonstrated the creation of cation selective membrane basing on affordable heterogeneous cation exchange membrane that specifically separated Na+ from Na+/Ca2+ mixed solution during electrodialysis. Further characterization showed that, in addition to the expected increase in specific selectivity with respect to singly charged counterions, there was an increase in the overall selectivity with respect to counterions. We provide data from measurements of electrical conductivity, diffusion permeability, and the results of calculating the transport numbers of counterions, demonstrating an increase in selectivity.