Transport characteristics of ion-exchange membranes during electrodialytic concentration of electrolytes

Electrodialytic concentration was investigated in the instance of NaCl solution in the cell with compartments formed by ion-exchange membranes MK-40 and MA-41 but without brine circulation. The brine concentration and salt production rate of membrane pair were determined for different current densities. An approximate mathematical model of the process is discussed and used to calculate the transport parameters: the migrational current yield, the diffusional and osmotic permeability of the membrane pair, and the salt's hydration number. The contributions to electrodialytic concentration are estimated which are provided by each of the mechanisms of salt and water transport across the membranes. A method for determining the salt's hydration number is proposed.