A study on equilibrium and kinetics of ion exchange of alkaline earth metals using an inorganic cation exchanger – zirconium titanium phosphate

An advanced inorganic cation exchange material of the class of tetravalent metal acid (TMA) salt, zirconium titanium phosphate (ZTP), has been synthesized by a modified sol–gel technique. ZTP has been characterized by elemental analysis (ICP-AES), thermal analysis (TGA), FTIR and X-ray diffraction studies. The Nernst–Planck equation has been used to study the forward and reverse ion exchange kinetics of Mg (II), Ca (II), Sr (II) and Ba (II) with H (I) at four different temperatures. The mechanism of exchange is particle diffusion, as confirmed by the linear tdimensionless time parameter) vs t (time) plots. The exchange process is thus controlled by the diffusion within the exchanger particles for the systems studied herein. Further, various kinetic parameters like self-diffusion coefficient (D0), energy of activation (Ea) and entropy of activation (S*) have been evaluated under conditions favouring a particle diffusion-controlled mechanism.