Bimetal-organic framework MIL-53(Fe,Ni) stimulates peroxydisulfate to degrade rhodamine B: Properties and degradation mechanism

Metal-organic frameworks with high porosity have received much attention in environmental pollutant treatment. This study presented a simple single-pot solvent thermal method for the preparation of a bimetal-organic framework MIL-53(Fe,Ni), further used for activated peroxydisulfate to degrade rhodamine B (RhB). The morphology and structure of the sample were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, photoelectron spectroscopy, fourier transform infrared spectroscopy, and thermogravimetric analysis. The results showed that MIL-53(Fe,Ni) was successfully synthesized by the simple reaction, with high thermal stability and high specific surface area. The effects of pH value, co-existing ions, temperature, humic acid and different real water samples on RhB degradation were systematically investigated. Under optimized conditions, 93.9% of RhB was degraded within 180 min, together with excellent reusability. Quenching experiments and electron paramagnetic resonance showed that both free radicals (∙OH, SO4∙- and O2∙-) and non-free radicals (1O2 and direct charge transfer) were responsible for the RhB degradation. In addition, the identification of intermediates by high-resolution mass spectrometer and reaction site prediction calculations (electrostatic potential, Fukui function and molecular orbit analysis), proposing a possible degradation pathway of RhB. The work highlights the broad applications of bimetal-organic frameworks in advanced oxidation processes.