Self-reinforcing extraction of uranium(VI) from wastewater via uranium-incorporated hematite photoelectrochemical system

The development of photoelectrochemical (PEC) systems to convert soluble uranium into valuable precipitates offers an attractive approach for wastewater treatment. However, their scalability is hindered by costly synthetic electrode and energy-intensive operations. Herein, we investigated the credibility of hematite, a naturally abundant photosensitizer, for uranium extraction from mine wastewater, with a particular focus on the influence of structural uranium on the PEC performance. Interestingly, uranium incorporation largely tunes the electronic structure and photoelectric response of hematite, enhancing carrier transfer for realizing efficient U(VI) extraction. Density functional theory calculations verified the band gap reduction after uranium incorporation, which retards charge recombination and enhances light response. The optimized mineral photoanode delivered a high photocurrent of 51.21 mA·cm⁻² at 1.2 V_SCE, yielding extraction efficiency close to 100 % from mine wastewater. Over diurnal cycles, the system extracted 9.34 mg of U from real wastewater. Soluble U(VI) was precipitated as (UO₂)O₂·2 H₂O and Na[(UO₂)O(OH)]·H₂O on carbon felt, ensuring its easy recovery. This work emphasizes previously overlooked role of uranium in optimizing the photochemical reactivity of mineral resources. Given the abundance of uranium-bearing ferric oxides in mining areas, this approach based on the application of local materials provides a self-sustaining route for pollutant decontamination and resource utilization.