Dynamic Electrochemical Study Of Ultrasound To Iron Electrochemical Oxidation Process Of The Preparation Of Ferrate

The reaction mechanism and the effects of ultrasound on the reaction processes were investigated during the anodic oxidation of iron to produce sodium ferrate in concentrated alkaline solutions by electrochemical methods, such as linear potential sweep, cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical experiments were carried in a three–electrode cell with platinum as a counter electrode and Hg/HgO as a reference electrode with and without ultrasound respectively. The bulk electrolysis method was performed to investigate the reaction rate affected by ultrasound in the production of sodium ferrate too. The experimental results show:1. The rate of sodium ferrate formation is the highest when using a cast iron anode. It was lower when pure iron electrode was used. Steel anode can't be used to produce ferrate. The reaction rate increases with increasing temperature and NaOH concentration.2. There are three reaction procedures during the anodic oxidation of iron to produce sodium ferrate in concentrated alkaline solutions which are the active dissolution of iron, the transition from active dissolution to passive state and the formation of FeO₄^2- in the transpassive regime, where the oxygen evolution starts. In the active dissolution potential regime(-0.95V～-0.40V vs Hg/HgO, the same in all potentials mentioned in this paper), Fe dissolves mainly via a two-electron transfer reaction to a soluble bi-valent iron species of HFeO₂^- ion; At the active-passive transition potential(-0.40V～0V), two products are involved: HFeO₂^- and FeO₂^-. A passive Fe₃O₄ film was formed by the oxidation of an intermediate Fe(OH)₂ surface species in the active dissolution reaction; Then a Fe₂O₃ film formed by succeeding oxidation of Fe₃O₄ film which leads the electrode to a passive state(0V～0.55V). In the transpassive regime (higher than 0.55V), oxygen starts to evolve...