LAUSR

Abstract Magnetic adsorbents in combination with magnetic separation techniques have received considerable attention in recent years due to their magnetically responsive nature for selective manipulation and rapid separation. Herein, we report a novel kind of magnetic hydrothermal carbon nanosheets loaded with magnesium ferrite as an efficient adsorbent for uranium uptake, in which the original hydrothermal carbon is used as matrix and precursor, and magnesium is treated as functional component. The as-prepared magnetic adsorbent possesses good acid resistance and excellent thermal stability and can work under practical acidic and hyperthermal conditions. Batch adsorption experiments indicate that the adsorbent can inspiringly overcome the ubiquitous negative influence of protonation and shows excellent adsorption performance for uranium with capacity up to 2208 mg g−1 in pure uranium solution, the highest value among all uranium adsorbents reported previously, and the distribution coefficients for uranium are all around 5 × 105 mL g−1 in multi-ion solution with the pH range of 2.5–4.5. Noteworthily, both adsorption capacity and removal rate of the magnetic adsorbent for uranium exhibit a rising trend with the increasing acidity, ionic strength and concentrations of competitive cations, which is unique among all the reported adsorbents to the best of our knowledge. The mechanism investigation reveals the ultrahigh capacity and the unique cation-synergistic adsorption property towards uranium is due to a thorough ion-exchange process containing multiple exchanges and rebalances. The final result of the exchanges is that a majority of adsorption sites are occupied by the highly-charged uranium. This study provides a general guidance for the design and construction of magnetic adsorbents with high capacity for uranium separation and recovery from nuclear industrial effluents and other uranium-containing systems.