Miscellaneous inorganic ion exchangers:

Exchangers like apatites and sulphides are included in this class. The anionic and cationic components of the apatite structure, M₁₀ (XO₄) Y, are exchangeable, where M = Ca, Sr, Ba, Cd and Pb; X= P, As, V, Cr, Mn, Si, Ge and Y= F₂, Br₂ (OH)₂, O and CO₃^2-. The structure, physicochemical properties, thermal stability and ion exchange properties of these materials have been reported. The ion exchange properties of a wide range of sulphides e.g., Ag₂S, FeS, CuS, ZnS, PbS, CdS, NiS, As₂S₃ and Sb₂S₃ have been studied. The sulphides are selective towards cations forming insoluble sulphides. The metal of the sulphide is displaced by the appropriate ion in solution.