Valorization of desalination brine: Uranium recovery via square wave-enhanced electrophoto-catalysis with a rGO/CuSA-CN cathode

Square-wave voltage enables rapid, efficient uranium removal, outperforming constant-voltage methods. • The rGO/CuSA-CN electrode achieves 3.34 mg/g/h uranium extraction in brine—the highest reported value. • Chlorella-pretreated biofouling quadruples uranium extraction rate, electrode maintaining 100% efficiency over 24 cycles. • Bridges desalination brine valorization with strategic uranium recovery, advancing nuclear energy circular economy. Uranium extraction from seawater is widely regarded as the most promising approach for uranium resource acquisition. However, the extremely low uranium concentration in seawater (3.3 μg/L) presents significant technical challenges. This work develops a novel rGO/CuSA-CN electrophoto-catalytic composite electrode, achieving remarkable breakthroughs in uranium recovery from desalination concentrated brine—a typical desalination brine valorization practice that converts an environmental waste stream into a strategic resource supply. Remarkably, under natural seawater pH (pH 8), the application of square wave voltage enables 98.0% uranium removal from a 10 mg/L solution within 5 min, a performance far outperforming constant voltage methods; square wave voltage enables rapid uranium deposition and sustained electrode activity by periodically reversing the potential, which inhibits passivation, promotes U(V) re-oxidation and prevents active site blockage. Furthermore, by simulating biofouling conditions with Chlorella pretreatment, we discovered an unexpected synergy that quadrupled the uranium extraction rate, reaching 3.34 mg/g/h from the pretreated brine—a rate significantly higher than most reported values for direct seawater extraction and suggesting practical viability for high-throughput processing. This finding offers a new perspective for adapting extraction technologies to real-world desalination plant conditions. In selectivity experiments, the electrode exhibited exceptional performance, with a uranium-to‑magnesium distribution coefficient ratio (K d (U)/K d (Mg)) reaching 72.6 even against the strongest interference. This work establishes a new paradigm for desalination brine valorization, transforming a problematic waste stream into a strategic resource and advancing the circular economy of nuclear energy materials. Download: Download high-res image (115KB) Download: Download full-size image