A self-driven solar coupling system with activated carbon felt cathode for resourcefully purifying uranium and organic contaminated water

Abstract

With the continuous development of nuclear energy, it becomes increasingly important to recover uranium from the radioactive wastewater, in which various organics may combine with uranyl ions (UO22+) to form refractory complexes. Developing highly active cathode materials for uranium reduction is essential to improve the performance of self-driven solar coupling system (SSCS) in treating complex radioactive wastewater. In this study, an activated carbon felt (ACF) cathode is prepared by anodizing carbon felt (CF) in NaOH solution to adjust the surface morphology and functional groups. The ACF is then used in a SSCS combined with a TiO2 nanorods array (TNA) photoanode for the efficient recovery of uranium and the rapid degradation of organic pollutants with simultaneous electricity generation. Compared to CF, the functionalized ACF with oxygen-containing functional groups, provides sufficient sites for UO22+ adsorption and facilitates the charge separation. The SSCS with the ACF cathode exhibits removal ratios of approximately 99.9 % for tetracycline hydrochloride (TCH) and UO22+, with removal rates of ∼ 0.025 and ∼ 0.154 min−1, respectively. In contrast, the SSCS with the CF cathode achieves removal rates of ∼ 0.006 and ∼ 0.026 min−1. Additionally, a maximum power density of 0.94 mW·cm−2 with a fill factor of 23.36 % is achieved. After 20 cycles, the system maintains removal ratios of 99.1 % for TCH and 98.2 % and UO22+. Intensive investigation also reveals that the system functions robustly in treating complex wastewater with a complicated condition of pH, co-exited ions, and various pollutant concentrations. Furthermore, efficient removal of organics and uranium is also achieved from polluted seawater or under real sunlight illumination. This paper presents a simple method to prepare low-cost, highly active and stable cathodes for uranium reduction in an easy-to-operated, energy-saving and economical solar-driven system.