Sustainable chemical processing of flowing wastewater through microwave energy

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 α-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 α-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.