Biomass-based 0D/3D N-CQD/MIL-53(Fe) photocatalyst for the simultaneous remediation of multiple hazardous pollutants in sewage

Abstract

The useful implementation of MIL-53(Fe)-based materials in the area of photocatalytic wastewater remediation has been limited for a long time. In this study, we used biomass materials to construct a zero-dimensional/three-dimensional (0D/3D) N-CQD/MIL-53(Fe) photocatalyst via an in situ synthesis, and then used it to realize the simultaneous remediation of sewage containing hexavalent chromium (Cr(VI)) and methylene blue (MB). The photocatalytic efficiencies for Cr(VI) and MB reached 90.13% and 69.31%, with constant values up to 0.04323 and 0.01101, respectively. The reduction rate of Cr(VI) was 8 times that of pristine MIL-53(Fe), while avoiding the need for strong acid conditions. Theoretically, MB is regarded as a hole scavenger while being oxidized, thereby realizing the effective detachment of photoexcited charges. Meanwhile, the compounding with nitrogen-doped carbon quantum dots (N-CQDs) modulated the electronic and the band gap structure of MIL-53(Fe) favorably, and widened the absorption range of visible light operation. Moreover, the introduction of 0D materials also increased the surface area of the 3D skeleton, which was more conducive to establishing more active sites on MIL-53(Fe). Ultimately, we propose a feasible mechanism for the photocatalytic reaction. This work expands a sustainable path for increasing the photocatalytic performance of MIL-53(Fe), and proposes a new direction for the high-value conversion of biomass resources.