Abstract Bipolar membranes have conventionally been used for the production of acids and bases from their salts. A new class of applications has been identified and developed recently, based on the recognition that these membranes can act as highly selective cation or anion membranes in a conventional electrodialysis type operation. This high degree of selectivity can be used to purify various acid/base streams that arise from industrial operations such as ion exchange, battery production and minerals processing. The AQUATECH acid/base purification process achieves product purities and concentrations that are not achievable via conventional electrodialysis, diffusion dialysis or ion retardation techniques. Details of the process are presented and discussed.