Investigation of adsorption of thorium from aqueous solutions using XAD-7 resin impregnated with a mixture of phosphate compounds in a batch system

In this study, thorium ions were adsorbed in a batch system by Amberlite XAD-7 ion exchange resin impregnated with phosphate compounds such as TOPO (tri-octylphosphine oxide) and T2EHP (tri-2-ethylhexyl phosphate). The effect of important parameters on the adsorption process such as pH, time, temperature and the presence of interfering ions, as well as the effect of appropriate detergent on desorption, was investigated and evaluated. Thermodynamic relationships and several isothermal adsorption models including Freundlich, Redlich-Peterson, Langmuir and Temkin were investigated to describe the adsorption equilibrium. The structure of the modified adsorbent was investigated by infrared (IR) spectroscopy and thermal gravimetric analysis (TGA) methods. Based on the results obtained from the tests of thorium adsorption on XAD-7 resins impregnated with phosphate compounds, it was concluded that the adsorption reaction is a spontaneous (negative Gibbs free energy changes) and an exothermic process (negative enthalpy changes). Among the isothermal adsorption models, the nonlinear Redlich-Peterson model had the best result at 35 °C.