Effective electrochemical synthesis of ferrate(<scp>vi</scp>) utilizing a porous iron foam anode and its application in the removal of azo dye reactive red 24

Anode passivation is a significant challenge in the electrochemical synthesis of ferrate(vi), resulting in diminished Fe(vi) production efficiency. In this study, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and <i>E</i>-<i>t</i> polarization curves were used to evaluate the electrochemical properties and the formation of passivation layers on two anode materials, namely, pure iron (PI) and porous iron foam (PIF). Results revealed that PIF had favorable characteristics for ferrate(vi) generation, such as improved electron transfer capability and mitigated anode passivation compared with PI. Experiments also confirmed that PIF significantly outperformed PI in ferrate(vi) synthesis, achieving a synthesis efficiency of up to 63% in 14 M NaOH solution. The synthesized ferrate(vi) was subsequently applied to the treatment of the dye reactive red 24 (RR24), yielding a high removal efficiency of up to 98% at a ferrate/RR24 mass ratio of 2 g g^-1.