MIL-53 (Fe)-based photo-sensitive composite for degradation of organochlorinated herbicide and enhanced reduction of Cr(VI).

• High-performance WO 3 /MIL-53(Fe) bifunctional composite photocatalyst was fabricated and characterised. • Efficient degradation of toxic organochlorinated herbicide from low concentration acidic solutions achieved. • Enhanced catalytic efficiency and elimination rate of WO 3 /MIL-53(Fe) were recorded for 2,4-D–Cr(VI) multicomponent system. • The positive charged surface of WO3/MIL-53(Fe) at pH <pH pzc was beneficial to adsorb Cr 2 O 7 2− species. • The WO 3 /MIL-53(Fe) possesses high photostability and exhibits good catalytic reusability. Highly robust composite photocatalyst (WO 3 /MIL-53(Fe)) was synthesized and characterised. WO 3 /MIL-53(Fe) exhibits remarkable photocatalytic efficiency for reduction of Cr(VI) and oxidation of 2,4-dichlorophenoxyacetic acid (2,4-D) organochlorinated herbicide. After 240 min sunlight irradiation, only ∼30% reduction ratio of Cr(VI) was recorded in the presence of WO 3. However, about 70% and 94% Cr(VI) reduction were achieved in the presence of MIL-53(Fe) and WO 3 /MIL-53(Fe), respectively. The removal efficiency proceeds more rapidly in the binary mixture of 2,4-D and Cr(VI) than in the single component system, indicating synergetic effect between the photooxidation and reduction reactions. O 2 − played a key role in the reduction of Cr (VI) and h+ is confirmed to be the dominant active species in the degradation of 2,4-D. [ABSTRACT FROM AUTHOR]