For the analysis of the feasibility of the proposed PEC U extraction method from the economic perspective, a cost-effective analysis is provided in Supplementary Note 11. We estimate that the cost for PEC U extraction from real U mine seepage water was $8.75/kgU and $15.63/kgU at 0.5 V and 1.0 V bias potential, respectively. In comparison, for the conventional terrestrial U resources, the acceptable exploitation cost is $260/kgU