Synthesis of an iron-graphene based particle electrode for pesticide removal in three-dimensional heterogeneous electro-Fenton water treatment system

Herein, a novel nitrogen-doped graphene-iron based electrocatalyst was synthesized by a simple one-step high-temperature annealing of dehydrated Prussian blue (Na₄Fe(CN)₆·10H₂O) as a cost-effective precursor. The synthesized nitrogen-doped catalytic particle electrodes (NCPEs) were then used as heterogeneous electro-Fenton (EF) catalyst in a three-dimensional (3D) system. A high degree of graphitization and rich nitrogen doping content were observed after characterization of synthesized Fe₃C@nitrogen doped-graphene-iron oxide (Fe₃C@N-GE-Fe₃O₄) that both are beneficial for promoting oxygen reduction reaction (ORR) as a critical step in electrochemical oxidation of pollutants. The promotional effect of combining 3D and EF systems was evaluated by comparing the performance of different electrochemical processes including homogeneous EF process for the removal of p-nitrosodimethylaniline (RNO) as a model pollutant. The effect of operational parameters such as voltage, pH, NCPEs loading, and reusability on RNO decolorization was also investigated to achieve optimum conditions for pesticide removal from water as the final step of this study. RNO decolorization efficiency was found to be the best in 3D-NCPEs system comparing to other processes including 3D system with granular activated carbon (GAC) as particle electrode. Synthesized particle electrode demonstrated an excellent RNO degradation ability even in its saturated state (~91% of RNO decolorization) with low concentration of iron leaching. Moreover, in the reusability experiments of NCPEs for over 1500 min and after the fifth test, RNO decolorization efficiency remained up to 87%. Finally, the synthesized catalyst was capable of removing up to 93% of targeted pesticides from the water under optimal conditions obtained from the previous step.