Electrochemical ion exchange

Electrochemical ion exchange (EIX) is a novel separation process, which has been developed at Harwell over a number of years. Absorption of ions into an EIX electrode is controlled by an externally applied potential. Elution is achieved by simple polarity reversal - no eluant chemicals are required. This enables multiple use of ion exchange capacity. EIX has been demonstrated to absorb cations of IA, IIA, transition and post-transition metals as well as anions. To date, EIX has mainly been applied to nuclear waste streams. For example, using an inorganic ion exchanger, caesium and cobalt have been selectively removed from sodium- and lithium-bearing feeds respectively. With appropriate ion exchangers, anions such as nitrate, borate, chloride, and sulphate can also be removed by EIX. Other potential applications include removal of heavy metals (e.g. Hg and Cd) from industrial effluents and conventional water softening. This paper gives a summary of the scientific principles involved, as well as details of operating experience. (author)