High-Purity Deionization.The process used for removal of all dissolved salts from water is referred to as deionization or demineralization. Deionizers (DI) remove both cations and anions, releasing hydrogen ions (H+) in exchange for the former, and hydroxyl ions (OH-) for the latter. The hydrogen and hydroxyl ions subsequently combine to form pure water. Mixed-bed deionizers produce water containing the lowest ionic concentrations. Dual-bed deionizers produce water of lesser quality, generally unacceptable for specialized medical purposes. Custom mixes of almost any kind as well as separate component are used for different applications. These combinations are most useful at the final polishing stage of the effluent.