Ultrasound Mechanism Of The Strengthening Process Of The Iron Electrode Electrolytic Preparation Of Sodium Ferrate

The mechanism of ultrasound affacting on the ferrate production reaction in concentrated alkaline solutions was investigated in this paper. Electrochemical characteristics of iron electrode in 14mol·L-1 NaOH solution with and without ultrasound were studied by using tafel plot method, cyclic voltammetry and alternative current impedance spectroscopy. Cyclic voltammetric curves of the saturated solution of FeO22- in 14mol·L-1 NaOH with and without ultrasound were also studied.1 The polarization curves of iron in 14mol·L-1 NaOH solution with and without ultrasound at 40℃were detected. An iron electrode served as the working electrode. A platinum electrode served as the counter electrode. An Hg/HgO electrode served as a reference electrode. At the active-passive transition potential and passive potential, the current densities with ultrasound were higher. At the same ultrasounic power, the increment of current densities at the potential from -0.45V to 0.50V (vs. Hg/HgO) decreased with increasing the ultrasonic frequency. At the same ultrasounic frequency, the increment of current densities at the potential region which mentioned above increased with increasing ultrasonic power.2 The effects of ultrasound on the cyclic voltammetric curves of iron in 14mol·L-1 NaOH solution at 40℃and 60℃were investigated. An iron electrode served as the working electrode. A platinum electrode served as the counter electrode. An Hg/HgO electrode served as a reference electrode. The existence of ultrasound increased the current densities of the plateau corresponding to the FeO42- production. At the same ultrasonic power, increasing ultrasonic frequency led to less increment of the current densities. At the same ultrasonic frequency, increasing ultrasonic power led to more increment of the current densities. Without ultrasound, at the scan reate of 20mV·s-1, the current density of the plateau corresponding to the FeO42- production was 2.35mA·cm-2. In the same condition (ultrasounic power=240W, scan rate=20mV·s-1), the current density of the plateau changed from 4.47mA·cm-2 to 3.58mA·cm-2 with the ultrasonic frequency changed from 26kHz to 76kHz. In the same condition (ultrasounic frequency=26kHz, scan rate=20mV·s-1), the current density of the plateau changed from 2.67mA·cm-2 to 4.47mA·cm-2 with ultrasonic power changed from 138W to 240W.3 Electrochemical impedance spectrum of iron in 14mol·L-1 NaOH solution with and without ultrasound at 40℃were investigated. An iron electrode served as the working electrode. A platinum electrode served as the counter electrode. And an Hg/HgO electrode served as a reference electrode. Ultrasound can decrease the charge transfer resistance of FeO42- production reaction. At the same ultrasounic power, the decrement of the charge transfer resistance decreased with increasing the ultrasonic frequency At the same ultrasounic frequency, the decrement of the charge transfer resistance increased with increasing the ultrasonic power The charge transfer resistance of FeO42- production reaction was 150.0? without ultrasound. In sonicated condition (ultrasounic power=240W), the charge transfer resistance changed from 98.1? to 130.0? when the ultrasonic frequency changed from 26kHz to 76kHz. In sonicated condition (ultrasounic frequency=26kHz), the charge transfer resistance changed from 105.0? to 98.1? when the ultrasonic power changed from 138W to 240W.4 Cyclic voltammetric curves of the saturated solution of FeO22- in 14mol·L-1 NaOH with and without ultrasound at 40℃were studied. Platinum electrodes served as the working electrode and the counter electrode. An Hg/HgO electrode served as a reference electrode. It was found that the current density of the plateau which was identified as the oxidation of FeO2- to FeO42- with ultrasound was higher than that without ultrasound. At the same ultrasonic power, the increment of current density of the plateau metioned above decreased with increasing ultrasonic frequency. At the same ultrasonic frequency, the increment increased with increasing of the ultrasonic power.