Sorption of some radionuclides from nuclear waste effluents by polyaniline/SiO composite: Characterization, thermal stability, and gamma irradiation studies.

Polyaniline/SiO composite was successfully prepared via in situ polymerization using polyvinyl alcohol as a surfactant. The prepared PAn/SiO composite was used for the removal of Zr(IV), U(VI), and Mo(VI) ions from their liquid solutions. PAn/SiO composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized composite was irradiated with γ-radiation from a Co-60 radioactive source with absorbed dose 50, 100, and 150 kGy and the corresponding changes in structural properties of the composites were studied. The thermal and radiation stabilities of PAn/SiO composite in terms of saturation capacities were studied. PAn/SiO composite has a good thermal stability as it retained about 78.83% of its saturation capacity upon heating at 400±1 °C, while the saturation capacity of PAn/SiO composite was increased from 191.28 to 319.16 mg/g for Zr(IV) with varying the irradiated doses from 0 to 150 kGy. The sorption studies for several metal ions revealed marked selectivity of PAn/SiO composite towards Zr(IV), U(VI), and Mo(VI) ions with selectivity order; Zr(IV) > U(VI) > Mo(VI). The results indicated that PAn/SiO composite removed 95.33, 75.97, and 52.87% from Zr(IV), U(VI), and Mo(VI) ions, respectively at pH 3.26. Hence, analytical utility of PAn/SiO composite was accomplished by performing some quantitative separation such as separation of U(VI) ions from monazite leachate and separation of Zr(IV), U(VI), and Mo(VI) ions from simulated liquid waste. Thermodynamic parameter studies concluded that the adsorption of Zr(IV), U(VI), and Mo(VI) ions was spontaneous and endothermic in nature.