This book discusses various examples on the use of ion exchange in chemical processing, mainly in aqueous systems but also in non-aqueous systems and in gas streams. The theory behind these examples is briefly discussed in order to make the subjects better understood. The focus is on ion exchange rather than on chemical processing, it is therefore addressed to all those working in chemical processing industries or in parallel industries for whom ion exchange is not their primary field of experience. Dr Emmanuel (Manos) Zaganiaris joined the European Laboratories of Rohm and Haas France in 1975, where he was in charge of the technical support to customers, sales and marketing, for the applications of ion exchange resins. He retired in 2006 to become consultant. In 2012 he received the Ion Exchange Award of the Society of Chemical Industry.