Efficient degradation of high concentration azo-dye wastewater by heterogeneous Fenton process with iron-based metal-organic framework

A novel iron-based metal-organic framework, possessing high surface area and good catalytic activity, was proposed as a heterogeneous Fenton catalyst for degrading high concentration methylene blue (C-MB =500 ppm). The morphology and physicochemical properties of prepared catalysts were characterized by SEM, XRD, XPS, FT-IR, Raman spectra, etc. The obtained results showed that MOF-based catalysts MIL-100(Fe) and Fe-II@MIL-100(Fe) possess high surface area of 1646 and 1228 m(2) g(-1), respectively. The MB removal though adsorption by MIL-100(Fe) and Fe-II@MIL-100(Fe) is respectively 27 and 6% in 30 min, due to the electrostatic interaction between negative (or positive) adsorbent and positive pollutant. However, Fe-II@MIL-100(Fe) exhibited highest Fenton catalytic ability compared to MIL-100(Fe) and Fe2O3 catalysts. The catalytic activity of each active site, evaluated by the turn over frequency (TOF) value, varied in the order of Fe-II@MIL-100(Fe)> MIL-100(Fe) > Fe2O3. The main role of determining the decomposition efficiency, i.e., hydroxyl radical ((OH)-O-center dot) generation, surface redox properties and surface reaction, was greatly enhanced by the synergistic effect between Fe-II and Fe-III in Fe-II@MIL-100(Fe). Moreover, ironbased metal-organic framework retained the catalytic performance in a wide pH range of 3-8, and had a relative low iron leaching even in acidic condition. (C) 2015 Elsevier B.V. All rights reserved.