Comparative Investigation of Fe₂O₃ and Fe_1–<i>x</i>S Nanostructures for Uranium Decontamination

Abstract

Nowadays, more and more researchers pay close attention to the decontamination of radioactive uranium because of its high toxicity and long half-life in the environment. Although many strategies for the development of highly effective materials have been reported, their narrow pH operating range and high salinity seriously limit their widespread application in radioactive wastewater treatment. With the purpose of mitigating these drawbacks, herein we synthesized highly uniform iron sulfide (Fe1–xS) through the heating vulcanization of iron oxide (Fe2O3) microcubes. A comparative study of UVI removal on Fe1–xS and Fe2O3 was systemically investigated under a series of environmental conditions. Batch experiments illustrated that the UVI sorption activities on Fe2O3 and Fe1–xS nanostructures were different under various pH conditions, and UVI sorption on Fe1–xS exhibited strong tolerance to the ionic strength compared to that on the Fe2O3 sample. The sorption of UVI on Fe2O3 and Fe1–xS could reach equilibrium rapidly within a few minutes, which presented as a spontaneous endothermic process. The competitive Ca2+ ions presented in relatively high concentrations could strongly affect the distribution coefficients (Kd) of UVI on Fe2O3 and Fe1–xS due to the formation of ternary calcium–uranium carbonate complexes, whereas the Kd values were scarcely influenced by the Mg2+ concentrations. Furthermore, the application of Fe1–xS in different wastewater treatments presented a sorption performance superior to that of Fe2O3. Combining the Fourier transform infrared and X-ray photoelectron spectroscopy analysis, the enrichment of UVI on Fe1–xS was mainly attributed to the formation of UO22+···S2– bonding. Besides, we compared the sorption capacity of Fe1–xS with those of other systems. The studies further revealed that Fe1–xS could serve as a promising sulfide-based scavenger in the effective removal of UVI from various wastewater samples.