Enhanced uranium capture by xanthan gum-polyacrylic acid bound porous g-C3N4 electrode via electrosorption, coordination and electrocatalytic reduction

Electrosorption holds extraordinary promise for uranium (U(VI)) capture but is still limited by the finite accessible active sites of electrode materials, poor surface wettability and its intrinsic co-ion repulsion effect. Here we originally designed KOH-etched porous graphitic carbon nitride (g-C3N4) as active material, and multi-functional crosslinked xanthan gum-polyacrylic acid (XG-PAA) as binder to fabricate g-C3N4-X electrode for U(VI) capture. The abundant in-plane nanopores on 2D g-C3N4 lamellar, rich O- and N-containing active sites, and 3D tough interconnected conductive architecture, endowed g-C3N4-X electrode with fast electron/ion transport channels, alleviated co-ions exclusion, superior electrochemical properties, and hydrophilicity. These unique structure characteristics enabled U(VI) ions to form micro electric-field attraction with negatively charged COO- groups in advance to alleviate co-ion repulsion, then to electro-migrate towards and coordinate with active sites, and eventually to be electrocatalytic reduced into U(IV) deposits. Consequently, the g-C3N4-X electrode exhibited a 1.87 times faster adsorption kinetics, a much higher removal ratio of 98.1% within 70 min than traditional PVDF-bound electrode. Meanwhile, the cumulative adsorption capacity of g-C3N4-X electrode after six cycles was up to 1459.1 mg g-1. This efficient, scalable, and cost-effective g-C3N4-X electrode represents a significant step forward toward the practical applications of U(VI) electrosorption.