Visible-Light-Driven Zr-MOF/BiOBr Heterojunction for the Efficient Synchronous Removal of Hexavalent Chromium and Rhodamine B from Wastewater.

Abstract

With the rapid industrial development, the coexistence of multiple pollutants in wastewater has become a common phenomenon. Thus, developing highly efficient decontamination methods is imperative. In this work, a string of UiO-66-NH2/BiOBr heterojunctions with varying ratios of BiOBr were prepared and applied to remove hexavalent chromium Cr(VI) and rhodamine B (RhB). The possible growth process of BiOBr nanosheets on UiO-66-NH2, removal activity of contaminants, and photocatalysis mechanism were investigated. When the mass ratio of UiO-66-NH2 to BiOBr reaches 1:0.75, the heterojunction (NB-75) shows optimal photocatalytic activity. After 30 min of adsorption, the total removal rates of Cr(VI) (50 mg/L) and RhB (10 mg/L) over NB-75 (0.25 g/L) reaches 96.7% within 120 min of illumination and 98.9% within 80 min of illumination, respectively. For the removal process, there are two factors. The first is the high adsorption capacity for RhB and Cr(VI) owing to the high porosity of UiO-66-NH2 and interlayer surface positive charge of BiOBr. The second is the improved visible-light photocatalytic performance of the UiO-66-NH2/BiOBr heterojunction via rapid separation of photoinduced carriers. In addition, the active species capture study reveals that the electrons (e–) and the superoxide radicals (•O2–) play key roles in Cr(VI) reduction, while the holes (h+) are major reactive groups participating in the degradation of RhB. This work demonstrated a kind of promising MOF-based photocatalysis material for eliminating Cr(VI) and RhB simultaneously.