Efficient U(VI) capture co-driven by multiple synergistic mechanisms in an advanced asymmetrical photoelectrocatalytic system

Electro/photo/photoelectro-catalytic technologies have shown huge potential for U(VI) capture. However, current researches mainly focus on designing various electrode materials, but rarely on the significance of structure match and cooperative working mechanism of anode and cathode for U(VI) removal. Here, a multi-mechanism co-driven (MMCD) photoelectrochemical method, involving electrosorption, micro electric-field attraction, coordination and photoelectrocatalytic reduction, was originally proposed. Through purposeful design of an advanced asymmetrical photoelectrocatalytic system, consisting of 1D/2D TiO2/graphene (GTR) photoanode and xanthan gum-polyacrylic acid bound graphene (RGX) cathode, the MMCD system exhibited enhanced photoelectrocatalytic activity, fast electron transfer ability, and abundant binding active groups, which drove U (VI) ions to fast electro-migrate towards the surface of RGX cathode, then form micro electric-field attraction and coordination with electronegative O-containing groups, and finally be catalytically reduced into electroneutral sediments with the aid of photoelectrons from GTR anode. Ultimately, the MMCD system displayed a high removal rate of 90.5 % at 1.0 V, 1.7 times and 4.5 times that of electrochemical and photocatalytic methods. Its kinetic rate was also 71 % and 296 % faster than that of the latter two methods. Meanwhile, this system also exhibited an improved reduction efficiency of U(VI) to U(IV), high selectivity as well as good reusability.