Transport of impurities and water during potassium nitrate synthesis by electrodialysis metathesis

• KNO3 obtained by electrodialysis metathesis: NaNO3 + K2SO4 → KNO3 + Na2SO4.
• Both products current efficiency close to 100%, purity >99%.
• Negligible osmosis and back diffusion.
• Electroosmosis prevents products concentration.
• Complex mechanism of contaminants transport.

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.