The applicability of KNO3 synthesis by electrodialysis metathesis (ED-M) following: NaNO3 + K2SO4 --> KNO3 + Na2SO4 reaction scheme using Ralex PP membranes was examined. The effects of operating parameters: current density, feed concentration and composition on a current efficiency, solute and solvent transport were investigated. Current efficiencies observed were close to 100% and purity of the products exceeded 99%. It was found that electroosmosis contributed to water transport the most. At the same time, osmosis and solute back diffusion did not influence the process. (C) 2015 Elsevier B.V. All rights reserved.