Reduction of uranium (VI) in water with additive manufactured electrode

Abstract

Nuclear energy has a promising future, but conventional uranium resources are expected to be depleted within a century. Electrochemical extraction could overcome this roadblock by quantitatively recovering uranium dissolved in natural waters using high surface-area electrodes. In this paper, 3D-architected electrodes were manufactured and studied in an electrochemical cell for element extraction. First, untreated flat electrodes made by Laser Powder Bed Fusion (LPBF) and studied by Cyclic Voltammetry (CV) with a custom electrochemical flow cell in a solution of 1 mM Fe(III)(CN)₆³⁻, 0.1 M KCl have exhibited a shift in redox waves because of an oxidized surface. After electro-etching of the electrode surface with oxalic acid, CV exhibited wave positions closer to literature values with higher amplitudes. However, with a solution of 10⁻³ M uranium, 0.1 M NaCl with a pH of 2.3, no electrochemical signals were detected. In contrast, uranium electrochemically reacted with, and was quantitatively retained by an electrode coated with 10 nm of TiO₂ by Atomic Layer Deposition (ALD), and the electrode surface was able to retain uranium by chronoamperometry (CA) (about 0.5 mg for a surface of 3.0 cm²). To increase the reacting surface, 3D-architected electrodes were manufactured, electro-etched and TiO₂-coated. These electrodes showed a tenfold increase in uranium retention (up to 5.7 mg for a surface of 111.1 cm²) that could be partially re-dissolved in a new solution with a yield of 70 %. This work shows the interest of both surface functionalization and architected electrodes for elemental retention.