Synergistic Effect of the Sulfur Vacancy and Schottky Heterojunction on Photocatalytic Uranium Immobilization: The Thermodynamics and Kinetics

Not only a critical matter in the nuclear fuel cycle but uranium is also a global contaminant with both radioactive and chemical toxicity. Reducing soluble hexavalent uranium [U(VI)] to relatively nonimmigrated tetravalent uranium [U(IV)] by photocatalytic technologies is recognized as a highly promising strategy for avoiding environmental pollution and re-extracting uranium resources from nuclear wastewater. Herein, we have designed a heterojunction photocatalyst constructed from the carbon aerogels (CA) and the CdS nanoflowers with an S-vacancy (CA@CdS-SV). With the S-vacancy and heterojunction being synergized, the U(VI) removal rate exceeded 97% in 40 min without the addition of any sacrificial agents. As impacted by the synergistic effects of the S-vacancy and heterojunction, thermodynamics and kinetics revealed that photogenerated electrons were first captured via shallow traps generated by vacancies on CdS-SV and then transferred to the CA surfaces through the heterojunction to realize the spatial separation of carriers, thereby achieving a satisfactory performance. This work is considered to underpin the improvement of U(VI) immobilization by exploiting the synergistic effect of vacancy engineering and the Schottky heterojunction from the perspective of thermodynamics and kinetics.

Automated summary

In this study, a heterojunction photocatalyst composed of carbon aerogels and CdS nanoflowers with an S-vacancy was designed for efficient removal of uranium contaminants from nuclear wastewater. The synergistic effects of the S-vacancy and heterojunction enabled spatial separation of carriers, resulting in satisfactory performance.