Efficient electrosorption of uranyl ions by a homemade amidoxime-modified carbon paper-based electrode in acidic aqueous condition

BACKGROUND: Electrosorption efficiency for uranyl ion (UO₂²⁺) capture is low in acid solution due to the adverse effect caused by protons. This requires novel electrodes effective at acid conditions for UO₂²⁺ electrosorption in highly acidic industrial effluents such as spent nuclear fuel treatment. RESULTS: In the current study, UO₂²⁺ electrosorption was conducted using an amidoxime-modified carbon paper (CP-AO) electrode. The effects of voltage and frequency, pH, UO₂²⁺ initial concentration, and competing ions on UO₂²⁺ electrosorption were investigated. The reusability and electrochemical properties of the CP-AO electrode were studied. The experimental results showed that the current CP-AO electrode worked well in acidic conditiona (pH = 3) with a square wave periodic voltage (SWPV, −4 V, 1000 Hz), and outperformed a previously used carbon felt-based electrode. The CP-AO electrode showed considerable selectivity toward UO₂²⁺ in the presence of competitive ions. After seven rounds of continuous electrosorption–desorption, the CP-AO electrode still showed good UO₂²⁺ uptake efficiency. The electrosorption mechanisms were studied in-depth based on experimental and characterization results. The electrosorption of UO₂²⁺ by the CP-AO electrode was due mainly to the electric field force moving UO₂²⁺ to the surface of the electrode, leading to electrodeposition of uranium compounds and the formation of electrically neutral substances. CONCLUSIONS: The results indicated that based on SWPV electrosorption the CP-AO could be a desirable treatment approach for acidic uranium-containing wastewater with promising practical applications.