Removal of thallium from aqueous solutions using Fe-Mn binary oxides

Highlights: • Fe-Mn binary oxides were efficient in adsorption of Tl at salt background as high as 0.5 M NaNO₃. • Tl removal was due to the combined surface complexation, oxidation, precipitation and adsorption. • The adsorption kinetics well followed the pseudo-second-order model. • The adsorption isotherms well followed the Langmuir model. - Abstract: In this study, Fe-Mn binary oxides, which harbor the strong oxidative power of manganese dioxide and the high adsorption capacity of iron oxides, were synthesized for Tl(I) removal using a concurrent chemical oxidation and precipitation method. The adsorption of Tl onto the Fe-Mn adsorbent was fast, effective, and selective, with equilibrium sorption reaching over 95% under a broad operating pH (3–12), and high ionic strength (0.1–0.5 mol/L). The adsorption can be well fitted with both Langmuir and Freundlich isotherms, and the kinetics can be well described by the pseudo-second-order model. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra suggest that surface complexation, oxidation and precipitation were the main mechanisms for the removal of Tl. This study shows that the Fe–Mn binary oxides could be a promising adsorbent for Tl removal.