Spontaneous electrochemical uranium extraction from wastewater with net electrical energy production

Extracting uranium from uranium-mine wastewater is highly important from both the environmental protection and the resource preservation perspectives. However, conventional adsorption methods and zero-valent-iron induced reductive precipitation methods have intrinsic limitations. Here we demonstrate a spontaneous electrochemical (SPEC) method that spatially decouples the uranium-adsorption-reduction reactions and the iron oxidation reaction, enabling stable and efficient uranium extraction with net electrical energy output. U(VI) species are firstly adsorbed on a carbonaceous electrode, and subsequently reduced by electrons derived from iron oxidation. In simulated wastewater, the SPEC method achieves a 12 times higher uranium extraction efficiency without saturation of the carbonaceous electrode, in comparison with the adsorption method. In real wastewater, the uranium extraction efficiency reaches 352 mg∙g-1 during 60 h operation with simultaneous net electrical energy production (0.65 Wh∙m-2), and the operation cost is only 3.46~5.99 USD∙kgU-1. This work potentially opens a new avenue for cost-effective uranium recovery from mine wastewater.