Efficient removal of Se-79 from highly acidic solution using SiO2 particles functionalised with iron hydroxide

Due to its high solubility, radioactivity and toxicity, the separation of selenium from spent fuel reprocessing waste and industrial wastewater has attracted much attention. In this study, a novel adsorbent FeOOH@SiO2 with particle size of ~100 mu m was successfully prepared by loading FeOOH on micron-sized silica with emulsion methods. FeOOH@SiO2 with good acid resistance, gamma-irradiation and thermal stability exhibits excellent adsorption abilities for Se(IV) and Se(VI) including fast adsorption kinetics, great adsorption capacities (11.0 mg/ g for Se(IV) and 6.04 mg/g for Se(VI)) and preferable adsorption selectivity. It is worth noting that FeOOH@SiO2 can still remove nearly 90 % of Se(IV) and 80 % of Se(VI) even in 3 mol/L HNO3 system. Combined with the observations from X-ray photoelectron spectroscopic characterization and surface potential measurement, the adsorption mechanism caused with electrostatic attraction and the formation of inner complexes for Se(IV), and reduction reaction and partial formation of outer complexes for Se(VI) can be deduced. After 4 adsorption-desorption cycles, FeOOH@SiO2 still exhibits satisfactory reusability. Dynamic column experiments also demonstrated that FeOOH@SiO2 exhibited excellent removal capabilities towards Se(IV) and Se(VI) from real water samples. The present work demonstrates that FeOOH@SiO2 has great potential application for 79Se removal in highly acidic nuclear waste.