Visible-light induced electron-transfer in MoO3 QDs/g-C3N4 nanosheets for efficient photocatalytic reduction of U(VI)

Visible light-driven photocatalytic technology has become an effective method to remove U(VI) from wastewater. Herein, MoO3 quantum dots (MQDs) were prepared by a one-step oxidation method using molybdenum disulfide as the precursor. The MQDs were used to modify g-C3N4 nanosheet photocatalysts (MQDn-C3N4, where n represents the mass percentage of MQDs) to enhance the photocatalytic performance of g-C3N4 nanosheets. The morphology, chemical composition and optical properties of the MQDn-C3N4 composites were investigated by a series of characterization methods. The MQD3-C3N4 could remove 96.4% of U(VI) after 150 min of illumination, which was about 1.9 times that of g-C3N4. The MQD3-C3N4 samples had excellent stability and recyclability after five cycles. The possible mechanism of the photocatalytic process was proposed through radical trapping experiments and electron spin-resonance, in which the reduction of U(VI) is facilitated by photogenerated e– and •O2– radicals. The MQDn-C3N4 photocatalyst is expected to provide new concepts for the treatment of wastewater containing radionuclides. •MQDs were successfully combined with g-C3N4 nanosheets by calcination.•The MQDn-C3N4 composites exhibited highly efficient and stable photocatalytic activity.•The efficient and stable activity is attributed to the role of MQDs to transport electrons.•The mechanism of photocatalytic reduction of U(VI) by MQDn-C3N4 composites was elucidated.