Electrocatalytic Removal of Low-Concentration Uranium Using TiO₂ Nanotube Arrays/Ti Mesh Electrodes

Groundwater containing naturally occurring uranium is a conventional drinking water source in many countries. Removal of low concentrations of uranium complexes in groundwater is a challenging task. Here, we demonstrated that the TiO₂ nanotube arrays/Ti (TNTAs/Ti) mesh electrode could break through the concentration limit and efficiently remove low concentrations of uranium complexes from both simulated and real groundwater. U(VI) complexes in groundwater were electro-reduced to UO₂ and deposited on the TNTAs/Ti mesh electrode surface. The adsorption rate and electron transfer rate of the anatase TNTAs/Ti mesh electrode were twice that of the rutile TNTAs/Ti mesh electrode. Therefore, the anatase TNTAs/Ti mesh electrode exhibited excellent electrocatalytic activity toward the electrochemical removal of U(VI), which could work at a higher potential and significantly reduce the energy consumption of U(VI) removal. The U(VI) adsorption capacity on the anatase TNTAs/Ti mesh electrode was limited due to the low U(VI) concentration. However, the anatase TNTAs/Ti mesh electrode displayed a huge U(VI) removal capacity using the electroreduction method, where adsorption and reduction of U(VI) were mutually promoted and induced continuous accumulation of UO₂ on the electrode. The accumulated UO₂ can be easily recovered in dilute HNO₃, and the electrode can be used repeatedly.