Highly-efficient and easy separation of γ-FeO selectively adsorbs U(Ⅵ) in waters.

The migration and transformation of uranyl [U (Ⅵ)] ions in the environment are quite dependent on the geological condition in particular with the site enriched in Fe. In this study, the interfacial interaction of U (Ⅵ) ions with maghemite (γ-FeO) particles was studied and the interaction mechanism was explored as well. Batch experiments confirm that γ-FeO can effectively remove U (Ⅵ) from an aqueous solution within a relatively short reaction time (R% > 92.01% within 3 min) and has a considerable capacity for U (Ⅵ) uptake (q: 87.35 mg/g). γ-FeO displays an excellent selectivity for U (Ⅵ) elimination. Results on the effects of natural organic matter such as humic acid (HA) indicated that HA could promote the interfacial interaction between γ-FeO and U (Ⅵ) under acidic conditions. Compared with other radionuclides (e.g., Sr(Ⅱ) and Cs(Ⅰ)), U (Ⅵ) was more effectively removed by γ-FeO. The U (Ⅵ) removal by γ-FeO is primarily due to electrostatic interactions and precipitation that result in the long-term retardation of uranium. γ-FeO not only can fast and selectively adsorb U (Ⅵ) but also can be magnetically recycled, demonstrating that γ-FeO is a cost-effective and promising material for the clean-up of uranyl ions from radioactive wastewater.