High photocatalytic activity and stability of MnV2O6 and Mn2V2O7 synthesized by simple low temperature method for bromophenol blue degradation

Abstract

Developing an efficient catalyst for Bromophenol blue dye is of great importance for the degradation and mineralization of organic pollutants. Herein, in this study, a hydrothermal approach was used to prepare two different phases of manganese and vanadium mixed oxides, MnV2O6 and Mn2V2O7, and they were used as photocatalysts under visible light. To confirm the structural and morphological properties of MnV2O6 and Mn2V2O7 materials, XRD, SEM-EDS, ICP, BET, XPS, and UV–vis (DRS) were used. The linear fit plot for MnV2O6 and Mn2V2O7 indicates a band gap energy of 1.96 eV and 1.82 eV, respectively. The results revealed that Mn2V2O7 has better photocatalytic performance in bromophenol blue (BPB) degradation than MnV2O6: in 120 min, the BPB exhibits a degradation efficiency of 99.88% for Mn2V2O7 and 96.58% for MnV2O6, and COD was reduced from 41.2 mg/L to 1.37 mg/L for Mn2V2O7 and 4.21 mg/L for MnV2O6, confirming the substantial mineralization of BPB. The Mn2V2O7 preparation method improved its absorption in the visible region, which avoided the rapid charge recombination, and enhanced the electron transfer, resulting in the enhancement of its photocatalytic performance. Furthermore, free radical scavenging tests were carried out and showed that superoxide ions and hydroxyl radicals are responsible for the BPB dye conversion. Finally, this research illustrates a novel insight into designing two different phases of manganese and vanadium mixed oxides, with photocatalytic ability for wastewater treatment.