Uptake of various cations by imperfectly ordered KAlSiO₄ prepared by solid-state reaction of kaolinite with K₂CO₃

The uptake of various cations by imperfectly ordered KAlSiO₄ was investigated. The KAlSiO₄ was prepared by solid-state reaction of kaolinite with K₂CO₃ at 550°C for 24 h. Uptake experiments were performed at 60°C using 0.5 g of the KAlSiO₄ and 50 ml of solution containing 10^-3-10^-1 M of each cation, with and without 0.5 M NaCl buffer. The cations were alkali (Li⁺ and Na⁺), alkaline earth (Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺) and transition metal cations (Ni²⁺, Co²⁺, Cu²⁺ and Zn²⁺). From the comparison of uptakes of various cations by KAlSiO₄ and zeolite Na-A, it was found that the ratio of uptake by both exchange materials increased with decreasing ionic radius of the exchanging cations, the KAlSiO₄ showing higher uptake of Ni²⁺ than zeolite Na-A. This trend became more distinct for the uptake of Ni²⁺ in simulated acid waste solution and ground-water because of the suppressinz effects by co-existing alkali and alkaline earth cations especially for zeolite Na-A.