Adsorption of cadmium ion using a new composite cation-exchanger polyaniline Sn(IV) silicate: kinetics, thermodynamic and isotherm studies

A new organic-inorganic composite cation exchanger polyaniline Sn(IV) silicate has been synthesized. The physicochemical properties of this ion exchanger were determined using different analytical techniques including fourier transform infrared spectroscopy, simultaneous thermogravimetry-differential thermogravimetry analyses, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and elemental analysis studies. Ion exchange capacity and effect of heating temperature on ion exchange capacity were also carried out on this ion exchange material. Adsorption properties for different metal ions have been investigated and the results revealed that polyaniline Sn(IV) silicate had the highest adsorption capacity for Cd2+ ion. It's selectivity was tested by achieving some important binary separations. Dependence of adsorption on contact time, temperature, pH of the solution and exchanger dose had been studied to achieve the optimum conditions. Adsorption kinetic study showed that the adsorption process followed the first order kinetics. Adsorption data were fitted to linearly transformed Langmuir isotherm with R-2 (correlation coefficient) >0.99. The maximum removal of Cd2+ was found at pH 9. The adsorption was fast and the equilibrium established within 40 min. Thermodynamic parameters viz- entropy change, enthalpy change and Gibb's free energy change were also calculated.