Highly efficient electro-sorption and enrichment of U(VI) from real seawater using modified 3D flexible carbon felt via a flow-through operation

The efficient uptake of U(VI) ions from the real seawater as the nuclear energy source was of paramount importance. Here, the three-dimensional (3D) flexible carbon felts (FCFs) with N dopants and oxygen-containing groups (o-NFCF) were prepared via the solvothermal method. The obtained FCFs were used as the adsorbents for the uptake and enrich of U(VI) by a flow-through electro-sorption operation in the laboratory-designed device. The pristine FCF (pFCF) displayed a 5.0 mg/g capacity under the initial conditions of 10 mg/L U(VI), which was improved with the presence of an electric field (7.2 mg/g, 0.6 V). The o-NFCFs with 2.58 at.% N dopant and 11.09 at.% oxygen functionalities on the surface would lead to the enhanced performance (11.8 mg/g). This was facilitated by the aid of an electric field (18.8 mg/g, 0.6 V) with a Q max of 44.6 mg/g as well. The decreased activity was observed in the simulated seawater (16.4 mg/g) and real seawater (10.6 mg/g), respectively, probably ascribed to the coexistence of organisms and complex ions. The uptake stability of U(VI) from the real seawater was then observed, ascribed to the desorption capability of U(VI) from the surface of o-NFCF. In this process, o-NFCF could be in-situ regenerated simultaneously. By doing so, the enrichment of U(VI) to 5.85 mg/L concentration from a real seawater was obtained. Mechanistic studies and DFT simulations indicated that the electrochemical properties of 3D-NFCF materials dominated the electro adsorption of U(VI).