Magnetically recyclable Fe3O4@SiO2/Bi2WO6−xF2x photocatalyst with well-designed core-shell nanostructure for the reduction of Cr(VI)

Exploiting highly efficient and stable photocatalysts for treating Cr(VI)-containing wastewater is of great importance. Herein, a robust core-shell structurally magnetic Fe 3 O 4 @SiO 2 /Bi 2 WO 6−x F 2x photocatalyst was successfully fabricated and used to photocatalytic Cr(VI) reduction, in which an inert protective layer (SiO 2 )-coated micro/nanostructured Fe 3 O 4 particles can not only improve the chemical stability but also retain magnetic advantage of catalyst. The optimized 55% Fe 3 O 4 @SiO 2 /Bi 2 WO 6− x F 2 x exhibited the highest catalytic activity in a reaction system of pH = 3, the apparent rate constant (k app /min −1 ) of 55% Fe 3 O 4 @SiO 2 /Bi 2 WO 6−x F 2x for photocatalytic reduction of Cr(VI), as high as 0.027 min −1 , is approximately 5.4 and 2.6 times higher than that of Bi 2 WO 6 and Fe 3 O 4 @SiO 2 /Bi 2 WO 6 , respectively. After being illuminated for 90 min, nearly 100% percentage of Cr(VI) has been reduced to Cr(III) by using 55% Fe 3 O 4 @SiO 2 /Bi 2 WO 6−x F 2x as photocatalyst, which can be attributed to the synergistic effect of magnetic Fe 3 O 4 @SiO 2 support – “core”, Bi 2 WO 6 – “shell” and the successful introduction of F − ions. A readily magnetic separation of Fe 3 O 4 @SiO 2 /Bi 2 WO 6−x F 2x catalyst enabled it to reuse conveniently for practical industry application. Finally, the enhanced photocatalytic mechanism of catalyst was proposed for Cr(VI) reduction. The present study not only provides a new mean to solve the recovery of the Bi 2 WO 6 -based photocatalyst, but also presents a promising candidate for Cr(VI) reduction in the field of the industrial wastewater treatment.