Removal and Recovery of Uranium from Groundwater Using Direct Electrochemical Reduction Method: Performance and Implications

Abstract

Removal of uranium from groundwater is of great significance as compared to in situ bioimmobilization technology. In this study, a novel direct electro-reductive method has been developed to efficiently remove and recover uranium from carbonate-containing groundwater, where U­(VI)­O2(CO3)3 4– and Ca2U­(VI)­O2(CO3)3 are the dominant U species. The transferred electron calculations and XPS, XRD analyses confirmed that U­(VI) was reduced to U­(IV)­O2 and accumulated on the surface of the Ti electrode (defined as Ti@U­(IV)­O2 electrode) with high current efficiencies (over 90.0%). Moreover, over 98.0% of the accumulated U­(IV)­O2 could be recovered by soaking the Ti@U­(IV)­O2 electrode in the dilute nitric acid. Results demonstrated that the accumulated U­(IV)­O2 on the surface of the Ti electrode played a key role in the removal of U­(VI), which can promote the electro-reduction of U­(VI). Therefore, the electrode could be used repeatedly and has a high removal capacity of U­(VI) due to the continuous accumulation of active U­(IV)­O2 on the surface of the electrode. Significantly, the uranium in both real and high salinity groundwater can be efficiently removed. This study implies that the proposed direct electro-reductive method has great potential for the removal and recovery of uranium from groundwater and uranium-containing wastewater.

Efficient and durable uranium extraction from uranium mine tailings seepage water via a photoelectrochemical method

“…Moreover, among various immobilized TiO 2 for photoelectrocatalysis purposes, TNA is considered to be a viable catalyst because of its large specific surface area, high stability, and unique charge carriers transport properties ( Wang et al., 2014 ). The Ti foil was used as the cathode, because its capability of serving as the U deposition site has been demonstrated in previous electrochemical uranium extraction studies ( Liu et al., 2019 ).…”

“…The bias potential might play two roles in PEC U extraction. One is driving direct EC U extraction on electrode surfaces ( Liu et al., 2019 ; Kim et al., 2015 ). However, the dark control experiments showed insignificant U extraction (≤7%) at all tested bias potentials ( Figures 2 C and S2 ), indicating a minor contribution of the direct EC U extraction.…”

Photoelectrochemical uranium extraction from uranium mine tailings seepage water

“…By comparing the U extraction efficiencies of the EC, PC, and PEC methods, obvious synergistic effects were observed in the PEC method: the synergy factor (calculated according to Supplementary Note 3 ) at 0.0 V, 0.5 V, and 1.0 V were 187%, 266% and 197%, respectively (Figure 2d). The bias potential might play two roles in PEC U extraction: (1) promoting the separation of charge carriers by triggering band bending within the photocatalyst 14 ; (2) driving direct EC U extraction on electrode surfaces 15 . The first role was evidenced by the increased 100 photocurrent with the increasing bias potential (Figure 2b).…”

“…was used as the anode, as TiO2 is the most developed and most commonly used model photocatalyst 51 , and its conduction band edge potential is suitable for U(VI) reduction 13 . A 3 cm × 3.5 cm Ti foil was used as the cathode, because its capability of serving as the U deposition site has been demonstrated in previous extraction studies 15 U concentration was measured by a well-established spectrophotometric method as described in the literature 26 . The extracted mass of the U was calculated by comparing the difference between the remaining and the initial U concentration in the reaction solution.…”

Graphene oxide modified H4L‐ion imprinting electrochemical sensor for the detection of uranyl ions

“…Although these schemes offer the advantages of high sensitivity and low detection limits, they require expensive equipment as well as higher operating costs. In contrast, electrochemical sensors prepared using chemically modified electrodes are effective detection techniques that require low cost equipment, rapid analysis, [15] ease of operation and high detection sensitivity [16] . Moreover, among the conventional methods for the detection of uranyl ions in solution, [17] adsorption solvation voltammetry (AdSV) [18] is one of the most commonly used methods.…”