Ion-exchange equilibria of synthetic 13X zeolite with Ni2+, Co2+, Zn2+ and Cd2+ ions

Samples of Linde 13X zeolite with 97.5 % of their sodium ions replaced by Cd2+, 76.5 % by Zn2+, 75.4 % by Co2+ and 71.7 % by Ni2+ were studied by chemical analysis, differential thermal analysis, thermogravimetric analysis and X-ray analysis to determine their unit cell composition and thermal stability. Ion-exchange isotherms at 5, 25 and 45°C for the M2+–Na+ exchange are reported and the thermodynamic quantities ΔG°, ΔH° and ΔS° calculated. The results are discussed with respect to hydration of cations, the possible sites they occupy in the zeolite and chemical reactions in the liquid phase.