Enhanced oxidative and adsorptive removal of thallium(I) using Fe3O4@TiO2 decorated RGO nanosheets as persulfate activator and adsorbent

In this study, Fe3O4@TiO2 decorated reduced graphene oxide (RGO) nanosheets were synthesized by loading iron oxide on the surface of RGO nanosheets and subsequently coating by titanium oxide, which can be employed as the persulfate (PS) activator and high-performance adsorbent toward thallium (Tl). PS could be effectively activated by the Fe3O4@TiO2 decorated RGO nanosheets due to the presence of RGO and Fe(II), resulting in the rapid oxidation of Tl(I) to Tl(III). The removal of Tl(I) was found to be pH-dependent, with the removal efficiency of more than 88.5% in the pH range of 8.0–12.0 at the optimal PS dosage of 10 mM and material dosage of 0.2 g/L. The surface precipitation of Tl2O3 and enhanced adsorption affinity toward Tl were deduced to be main mechanisms for the extremely efficient removal of Tl(I) ions during the oxidation and adsorption hybrid process. The maximum removal capacity of the material at pH 8.0 was estimated as 673.2 mg/g based on the fitting result from the Langmuir model. Approximately 94.7% of ultimate removal capacity could be accomplished within the first 10 min at the initial Tl concentration of 8.5 mg/L. The PS catalytic oxidation coupled with the adsorption technique using the prepared Fe3O4@TiO2 decorated RGO nanosheets were proven to be a promising approach for Tl(I) removal from water.