Magnetic MIL(Fe)-type MOF-derived N-doped nano-ZVI@C rods as heterogeneous catalyst for the electro-Fenton degradation of gemfibrozil in a complex aqueous matrix

Abstract

The application of metal-organic frameworks (MOFs) as suspended heterogeneous catalysts in electro-Fenton (EF) process for water treatment is almost inexistent. Fe-MOFs synthesized from phthalic acid-based linkers were spindle-shaped MIL(Fe)-88B and NH2-MIL(Fe)-88B crystals, whereas their calcination yielded nano-ZVI@C and nano-ZVI@C-N. The lipid regulator gemfibrozil was spiked into 0.050 M Na2SO4 solutions or urban wastewater and treated in electrolytic cells with an air-diffusion cathode to generate H2O2. The nano-ZVI@C-N catalyst obtained at 800 ºC showed the highest activity, with high stability as deduced from the low iron leaching and high recyclability. Almost total drug removal and significant mineralization was feasible in both matrices at near-neutral pH. The presence of core-shell nano-ZVI and Fe3O4 nanoparticles encapsulated in N-doped fusiform porous carbon rods was revealed, ensuring the Fe(III) conversion to Fe(II). Carbon doping with N contributed to the enhanced catalytic activity, and the strong magnetism facilitated the post-treatment catalyst recovery.