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 HI form of titanium(IV) antimonate in MCl3-HCl media with a solution ionic strength of 0.1, in the reaction Mn+ + R-H reversible arrow R-M + nH(+) has been measured in both forward and reverse reactions at different reaction temperatures 25, 40 and 60 degreesC (+/-1 degreesC) by batch method. The thermodynamic selectivity sequence as a function of X, 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 DeltaGdegrees, DeltaHdegrees and DeltaSdegrees for exchange of Gd3+/H+, Eu3+/H+ and Ce3+/H+ on titanium(IV) antimonate have been calculated. Negative values of entropy changes (AS') have been reported for all exchange systems studied (M3+/H+) on the exchange materials of titanium(IV) antimonate. (C) 2002 Elsevier Science B.V. All rights reserved.