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 Fe3O4@SiO2/Bi2WO6-xF2x photocatalyst was successfully fabricated and used to photocatalytic Cr(VI) reduction, in which an inert protective layer (SiO2)-coated micro/nanostructured Fe3O4 particles can not only improve the chemical stability but also retain magnetic advantage of catalyst. The optimized 55% Fe3O4@SiO2/Bi2WO6-xF2x exhibited the highest catalytic activity in a reaction system of pH = 3, the apparent rate constant (k(app)/min(-1)) of 55% Fe3O4@SiO2/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 Bi2WO6 and Fe3O4@SiO2/Bi2WO6, respectively. After being illuminated for 90 min, nearly 100% percentage of Cr(VI) has been reduced to Cr(III) by using 55% Fe3O4@SiO2/Bi2WO6-xF2x as photocatalyst, which can be attributed to the synergistic effect of magnetic Fe3O4@SiO2 support - core, Bi2WO6- shell and the successful introduction of F- ions. A readily magnetic separation of Fe3O4@SiO2/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 Bi2WO6-based photocatalyst, but also presents a promising candidate for Cr(VI) reduction in the field of the industrial wastewater treatment.