This book discusses the interaction of strongly basic anion exchangers with some metal cations. These polymers are a high tonnage production of the chemical industry, and are widely used in various chemical and technical operations, particularly in the treatment of water at thermal and atomic power stations. Their interaction with metal cations, especially with iron, an unpredictable and uncontrollable process, leads to their intoxication and rapid exhaustion. However, if the interaction of these polymers with cations is controlled, then in the polymer phase, ultra-fine particles of the compounds are formed, which radically change their physical and chemical properties. These composites become selective sorbents and catalysts with good hydro and aerodynamic properties to carry out processes in flow, an important factor in technology. This is demonstrated by patents on water purification from chromates, nitrate/nitrite, sulphides and air purification from iodine and hydrogen sulfide. The book also shows, for the first time, that cations Fe3+, Cr3+, Al3+, Ga3+, In3+, lanthanide (III) in the phase of strongly basic anion exchangers form compounds of the jarosite mineral type.