NH2-Fe-MILs for effective adsorption and Fenton-like degradation of imidacloprid: Removal performance and mechanism investigation

This investigation enables amino-functionalized metal-organic frameworks (MOFs) materials for the removal of imidacloprid (IMC). Two Fe-based MOF materials of NH2-MIL-88B(Fe) and NH2-MIL-101(Fe) both exhibited high adsorption capacity and Fenton-like degradation ability for IMC which were utilized to remove IMC from aqueous solution. Although the adsorption capacity of NH2-MIL-101(Fe) was higher than that of NH2-MIL-88(Fe), the degradation abilities of both MOF materials were similar. The removal efficiencies were evaluated through several basic studies, including concentrations of catalyst (0.12-0.3 g/L) and IMC (20-100 mg/L), pH of solution (3-11), and amounts of 30% H2O2 (0-2.0 mu L/mL). By optimizing the above factors, the total removal ratio of IMC by NH2-MIL-88B(Fe) was as high as 93%, whereas the removal ratio of NH2-MIL-101(Fe) was 97%. Moreover, these MOF materials were proven to be stable and recydable. The free radical quenching experiment and density functional theory calculation were applied to research the removal mechanism, and the hydroxyl radicals (center dot OH) was found to be the key active intermediate. The high catalytic efficiency can be attributed to the synergy of the Fe3+/Fe2+ redox cycle.