Thermodynamics and ion exchange equilibria of Gd3+, Eu3+ and Ce3+ ions on H+ form of titanium(IV) antimonate

Titanium(IV) antimonate as a cation exchanger has been obtained in amorphous form by mixing titanium tetrachloride to antimony pentachloride in molar ratio of Ti/Sb in the starting solutions is unity. Ion-exchange equilibria of Gd3+, Eu3+ and Ce3+ ions with H+ form of titanium(IV) antimonate in MCl3–HCl media with a solution ionic strength of 0.1, in the reactionMn++R—H⇌R—M+nH+has been measured in both forward and reverse reactions at different reaction temperatures 25, 40 and 60 °C (±1 °C) by batch method. The thermodynamic selectivity sequence as a function of XM decrease in the order Gd3+>Eu3+>Ce3+ and this selectivity order is parallel to the equilibrium capacity of rare earth metal ions on H+ form of titanium(IV) antimonate. On the basis of exchange isotherms, thermodynamic equilibrium constants, and values of ΔG°, ΔH° and ΔS° for exchange of Gd3+/H+, Eu3+/H+ and Ce3+/H+ on titanium(IV) antimonate have been calculated. Negative values of entropy changes (ΔS°) have been reported for all exchange systems studied (M3+/H+) on the exchange materials of titanium(IV) antimonate.