Removal of U(VI) from aqueous solution via photocatalytic reduction over WO3/g-C3N4 composite under visible light

Abstract In the present research, WO3/g-C3N4 composites were prepared and used for the photocatalytic reduction of U(VI). The coupling of WO3 and g-C3N4 leads to the formation of the Z-scheme type-heterojunction structure of WO3/g-C3N4, enhancing the visible-light absorption, the separation efficiency of photo-generated carriers, and subsequently the photocatalytic activity. Compared with WO3 and g-C3N4, the as-prepared WO3/g-C3N4 composites displayed a high photocatalytic performance for U(VI) removal under pH 5.0–6.0. The maximum U(VI) removal efficiency was obtained on WO3/g-C3N4(1:6), which was 1.83- and 4.58-times fold than g-C3N4 and WO3, respectively. The maximum amount of U(VI) removed by WO3/g-C3N4 composite reached 2250 mg/g. The TEM images, XPS spectrum, and XRD spectra confirmed that the U(VI) was photo-reduced to U(IV) in the form of UO2. ESR spin trapping and scavenging tests showed that O2− was the dominating active component for U(VI) reduction, while OH displayed a minor effect on U(VI) reduction.