Insight into the enhanced visible-light photoreduction of aqueous Cr(VI) by assembled Fe3O4/LDO/BiOBr composites

Abstract

We synthesized Fe3O4/LDO/BiOBr composites (Fe3O4/ZnAl-layered double oxide/bismuth oxybromide) by hydrothermal self-assembly and calcination treatment. The UV–visible diffuse reflectance spectra showed that Fe3O4/LDO/BiOBr had a significant redshift and enhanced visible-light absorption ability. Fe3O4/LDO/BiOBr demonstrated excellent photoreduction activity in response to Cr(VI), and the photocatalytic efficiency for 50 mg/L Cr(VI) was 98% within 30 min by Fe3O4/LDO/BiOBr-1.5. The improved behavior of Fe3O4/LDO/BiOBr for Cr(VI) was attributed to the construction of electron transfer path and efficient separation of photogenerated carriers. Fe3O4 acted as the electron-bridge between LDO and BiOBr, which accelerated the carrier transfer speed and reduced the interface resistance. The transient photocurrent response and electron transfer rate of Fe3O4/LDO/BiOBr-1.5 were 5.3 and 2.2 times greater than those of BiOBr, respectively. Fe3O4/LDO/BiOBr-1.5 also exhibited favorable durability and reusability, potential application in real Cr(VI) wastewater, and easy recovery ability from solutions under an external magnetic field. This study provided a ternary assembled Fe3O4/LDO/BiOBr for efficient photoreduction of high concentrations of Cr(VI) by effective solar light harvesting, which expanded the application of LDO-based catalysts in future wastewater treatment devices.