Synthesis of isotype heterojunction by series calcination of multicomponent for high efficiency photocatalytic reduction of uranium

Abstract

Photocatalytic reduction of soluble U(VI) to insoluble U(IV) is considered to be one of the most effective strategies for uranium contaminant removal. Graphite carbon nitride (g-C3N4) was widely used in the photocatalytic reduction of uranium due to its adjustable band structure and excellent chemical stability. Herein, through supramolecular self-assembly method, using thiourea as precursors, a carbon nitride photocatalyst (sp-ICN) with an isotype heterojunction structure was prepared by multicomponent series calcination for photocatalytic reduction of U(VI). The effects of pH, photocatalyst dosage and initial uranium concentration were examined on the effectiveness of the sp–ICN–1.0 photocatalytic reduction of uranium. The optimal reaction rate of sp–ICN–1.0 was 0.088 min−1, being 2.8 and 2.6 times that for pristine TCN (0.031 min−1) and sp-MCN (0.034 min−1), respectively. After 5 recycling experiments, more than 90% of U(VI) can still be reduced, indicating that sp–ICN–1.0 has good stability and repeatability in photocatalytic reduction of uranium. The electrochemical characterization of sp–ICN–1.0 showed that the formation of carbon nitride isotype heterojunction could improve the efficiency of photogenerated carrier separation and transfer, also reduce the resistivity of electron migration. A potential mechanism for photocatalytic reduction in U(VI) has been proposed. The result provides an idea for the further development of a novel semiconductor carbon nitride photocatalyst for the photocatalytic reduction of uranium.