Efficient photoelectrocatalytic separation of uranium from complex wastewater using a flour-derived Cu single-atom/carbon nitride composite electrode

The treatment of uranium-containing wastewater faces major challenges, including complex compositions, strong interference from coexisting ions, poor selectivity of conventional methods, and rapid blockage of electrode active sites. Here, we utilize expired flour as a low-cost biomass carbon/nitrogen source and copper oxalate as a copper precursor to prepare a biomass-derived carbon-supported copper single-atom catalyst (Cu-SAs/BC). This catalyst is then composited with g-C 3 N 4 at an optimal mass ratio of 2:3 and loaded onto carbon felt to construct a Cu-SAs/BC-g-C 3 N 4 photoelectrocatalytic electrode. The electrode achieves a uranium removal efficiency of 99.4% within 5 min under optimal conditions (total loading 13 mg, pH 4–6), and exhibits rapid removal across a wide initial concentration range of 5–100 mg/L. The distribution coefficient for U(VI) reaches 6.5 × 10 4  mL/g, significantly surpassing those of coexisting interfering ions (Al, Zn, Fe, Mn, Ca). Complete uranium removal from actual uranium mining seepage water is achieved within 20 min. Mechanistic studies confirm that phosphate groups on the electrode surface specifically chelate and coordinate with UO 2 2+ enabling rapid and targeted enrichment of uranyl ions. The UO 2 2+ ions then migrate to Cu-N x active sites, accept electrons, and undergo reduction to form U(Ⅳ), producing UO 2 precipitates that automatically detach under square-wave potential for efficient separation. This study provides a low-cost, sustainable biomass-derived single-atom catalytic material and a technological pathway for uranium recovery from complex radioactive wastewater.