V bias voltage and 100.0% at 1.5 V, respectively. Therefore, the PEC extracted U species on the Ti electrode could be fully recovered by applying a dilute acid and a low bias voltage. The U extraction performance of the proposed PEC method in real U-mine seepage water was also evaluated, and the results are present in Figure . The U extraction capacity of the PC method was only 0.04 gU m -3 •h -1 , and decreased dramatically to 0.02 gU m -3 •h -1 after only 2 cycles. For comparison, the PEC method extracted 5.54 mg U from 0.78 L seepage water after 13 cycles without noticeable efficiency decrease, revealing its exceptional stability and high efficiency with U-mine seepage water compared with the PC method. The U extraction capacity is calculated to be 0.48 gU m -3 •h -1 and 0.67 gU m -3 •h -1 at applied bias potentials of 0.5 V and 1.0 V, respectively, which are 12 -17 times higher than the PC method. Moreover, the bias potential applied here served only as a driving force to separate the charge carriers (Figure ).