1 Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad, 45650, Pakistan.
2 Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, H3G 1M8, Canada.
3 Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK. Electronic address: sergio.gonzalez-cortes@chem.ox.ac.uk.
4 School of Engineering, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA, UK.
5 Materials Division, King Abdulaziz City for Science and Technology, Riyadh, 11442, Kingdom of Saudi Arabia.
6 Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK. Electronic address: xiao.tiancun@chem.ox.ac.uk.
7 Department of Physics and Applied Mathematics, Pakistan Institute of Engineeri

Iron oxide nanostructured catalysts have emerged as potential candidates for efficient energy conversion and electrochemical energy storage devices. However, synthesis and design of nanomaterial plays a key role in its performance and efficiency. Herein, we describe a one-pot solution combustion synthesis (SCS) of a-Fe₂O₃ with glycine as a fuel, and a subsequent reduction step to produce iron-containing catalysts (i.e., Fe₃O₄, Fe-Fe₃O₄, and Fe⁰). The synthesized iron-based nanoparticles were investigated for methyl orange (MO) degradation through Microwave (MW) energy under continuous flow conditions. Fe-Fe₃O₄ showed higher MO degradation efficiency than a-Fe₂O₃, Fe₃O₄ and Fe⁰ at low absorbed MW power (i.e. 5-80 W). The enhanced degradation efficiency is associated to the combination of higher availability of electron density and higher heating effect under MW energy. Investigation of dielectric properties showed relative dielectric loss of Fe₃O₄, Fe-Fe₃O₄, and Fe⁰ as 3847, 2010, and 1952, respectively. The calculated average local temperature by the comparative analysis of MW treatment with conventional thermal (CT) treatment showed a marked thermal effect of MW-initiated MO degradation. This work highlights the potential of microwave-driven water depollution under continuous-flow processing conditions and demonstrates the positive impact that earth-abundant Fe catalyst synthesized by green SCS method can have over the treatment of wastewater.