ION-EXCHANGE KINETICS IN ULTRA PURE WATER-SYSTEMS

The continuous production of ultra pure water on an industrial scale uses ion exchange mixed beds as a major method of reducing ionic impurities to sub-mu-g dm-3 concentrations. Under such demanding operating conditions, particularly the high flow rate and high volume requirements of condensate purification in the power generation industry, it is the kinetics rather than the equilibria of the exchange processes that becomes the main controlling factor. The interactions between anion and cation exchange rates have been studied, particularly with respect to changes in the aqueous phase pH within a bed of exchange resins. The cause and effects of cation exchange resin fouling, both in laboratory tests and in practical applications, have been investigated. The most suitable choice of ion exchange system for ultra pure water production, whether mixed or separate beds, is discussed.