Intermediate-stage transition metal ion exchange in a zeolite X

Abstract

The exchange behaviour of some divalent transition metal ions M²⁺ (Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Mn²⁺) in a zeolite NaX (SiO₂/Al₂O₃ 2.75) was studied at intermediate stages before equilibrium. The equivalent counter ion supply in the solution, given by the equivalent ratio of the two counter ions 2M²⁺/Na⁺, was found to be critical in determining the saturation level of exchange. The series of relative abilities of exchange was very similar to the well known selectivity series at equilibrium. It is suggested that water exchange of the metal ions in solution could be one of the factors controlling the relative ease of ion exchange.