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

Highly robust composite photocatalyst (WO3/MIL-53(Fe)) was synthesized and characterised. WO3/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 WO3. However, about 70% and 94% Cr(VI) reduction were achieved in the presence of MIL-53(Fe) and WO3/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. O2− 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.

本研究合成并表征了一种高稳定性的复合光催化剂（WO3/MIL-53(Fe)）。该催化剂对六价铬（Cr(VI)）的还原以及2,4-二氯苯氧乙酸（2,4-dichlorophenoxyacetic acid，2,4-D，一种有机氯除草剂）的氧化均表现出优异的光催化性能。在240分钟太阳光辐照后，仅以三氧化钨（WO3）为催化剂时，Cr(VI)的还原率仅约为30%；而分别以MIL-53(Fe)和复合光催化剂WO3/MIL-53(Fe)为催化剂时，Cr(VI)的还原率分别可达约70%和94%。在2,4-D与Cr(VI)的二元混合体系中，污染物的去除效率远高于单一组分体系，表明光氧化与光还原反应之间存在协同效应。超氧自由基（O2−）在Cr(VI)的还原过程中发挥关键作用，而空穴（h+）被证实是2,4-D降解过程中的主要活性物种。