Comparative study of uranium and thorium metal ion adsorption by gum ghatti grafted poly(acrylamide) copolymer composites.

Uranium and thorium ions were selectively removed from aqueous solution using synthesized gum ghatti grafted poly(acrylamide) gum--poly(AAm) composite. A gamma radiation induced free radical copolymerization technique was used to synthesize the copolymer composite of gum--poly(AAm). Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the graft copolymer gum--poly(AAm). The adsorption of uranium ions and thorium ions using the gum--poly(AAm) copolymer composites has been investigated in batch mode. The adsorptive characteristics were investigated by varying the pH, concentration and time for both ions. The adsorption method depends on the pH of each metal ion, and the highest adsorption percentage was achieved at pH 6.0. The adsorption statistics were justified by isotherm, kinetic and thermodynamic models. The Langmuir adsorption model was revealed to be the best fitted monolayer arrangement, with a maximum adsorption capacity of 367.65 mg g for the uranium ions and 125.95 mg g for the thorium ions. The adsorption of metal ions occurred by the ion exchange process, which was specified through the rate controlling step with a best-fitted pseudo-second order kinetic rate model. Thermodynamic analysis shows that the Δ and Δ values for the uranium ions and thorium ions were positive. The negative Δ values decreased with an increase in temperature, suggesting that the metal ion adsorption process was endothermic and spontaneous in behaviour.