Electrodialysis process is a combination of electrochemical process and dialysis diffusion process. Driven by the external direct current electric field, using the selective permeability of the ion exchange membrane (that is, the cation can pass through the cation exchange membrane, the anion can pass through the anion exchange membrane), the negative and the cation move to the anode and the cathode, respectively. In the process of ion migration, if the fixed charge of the membrane is opposite to the charge of the ion, the ion can pass through; If they have the same charge, the ions are repelled, thus achieving the purpose of solution desalination, concentration, refining or purification.