Electrodialysis Electrodialysis units recover plating chemicals differently from the recovery units discussed thus far. The membranes are thin sheets of plastic material with either anionic and cationic characteristics. Electrodialysis units are constructed using a plate and frame technique similar to filter presses. Alternating sheets of anionic and cationic membranes are placed between two electrodes. Hydrogen and oxygen evolves.
Positive ions travel to the negative terminal and negative ions travel to the positive terminal.
The electrolyte also provides overall electrical conductivity to the cell. In some units, the current is periodically reversed to protect the membrane from fouling. Electrodialysis is compatible with most plating baths, and the design size of a unit is dependent upon the rinse water flow rate and concentration. Electrodialysis has advantages and disadvantages. For instance, the process requires very little energy and can recover highly concentrated solutions.