On the Mechanism of Electrochemical Transpassive Dissolution of Fe-Based Anodes in Binary Hydroxide Media

Abstract

Ferrates(VI) are potentially an environmental friendly cleaner for both waste water and drinking water treatment. Therefore, effective synthesis of ferrate becomes a challenging task for several research groups all over the world. Electrochemical methods for preparation of Fe(VI) can be considered as “green” because no harmful and expensive chemicals to oxidize Fe to the 6+ oxidation state are used. Knowledge of the reaction mechanism can help to improve conditions for large scale electrochemical preparation of ferrates in low-temperature molten media. The influence of parameters such as the composition of molten hydroxide, temperature and anode composition on the mechanism of the formation of ferrates during electrochemical dissolution of iron-based electrodes transpassive is addressed. Cyclic voltammetry and electrochemical impedance spectroscopy were chosen to characterize this process. The number of exchanged electrons during transpassive iron dissolution was determined and a reaction mechanism was proposed. Different mechanisms of transpassive iron dissolution were found for both different anode materials and molten media used.