Studies of cation-exchange thermodynamics for alkaline earths and transition metal ions on a new crystalline cation-exchanger aluminium tungstate: Effect of the surfactant's concentration on distribution coefficients of metal ions

A new crystalline cation-exchanger aluminium tungstate was synthesized by mixing solutions of 0.1 M aluminium nitrate and 0.1 M sodium tungstate at pH 1.2. The ion-exchange capacity of the material was found 1.17 meq g−1 (for Na+). The Kd values for some alkaline and transition metal ions were performed in 0.1 M HNO3 and TritonX-100 (non ionic surfactant) solvent systems by batch process. Some important and analytically difficult quantitative and selective separations were achieved by using the packed column of this cation-exchange material column. Ion-exchange equilibria of alkaline and transition metal ions and thermodynamic parameters viz. equilibrium constant (Ka), values of standard Gibbs free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were determined on this ion-exchange material. The effect of temperature on ion-exchange isotherm of alkaline earth metal ions (Mg2+, Ca2+, Sr2+, Ba2+)/H+ systems and transition metal ions (Fe2+, Co2+, Ni2+, Cu2+)/H+ systems were studied at different temperatures 30, 40, 50, and 60 °C. The selectivity coefficients at constant ionic strength (0.03 mol/kg) for alkaline and transition metal ions were also evaluated.