Electrode materials used for electrochemical oxidation of organic compounds in wastewater

Electrochemical oxidation (EO) of organic compounds is an outstanding technology capable of oxidizing organic pollutants to simple inorganic compounds such as H2O and CO2. Moreover, EO can be attributed to an energy-efficient process, since it requires only insignificant amount of energy in the form of an applied current or a potential to activate the electrodes. There is a vast variety of electrodes used in EO processes for organic compounds degradation. They are noble metal electrodes, such as Pt and Au, boron-doped diamond (BDD) electrodes, mixed metal oxide (MMO), graphite and carbon electrode, etc. In this regard, it becomes difficult to focus on existing electrode properties and characteristics and choose an anode material for a particular application. The aim of this study was to review information on existing anodes used in EO processes, their advantages and disadvantages, performance and application area. Thus far, MMO electrodes along with BDD electrodes are leading materials used in the processes of EO of dyes, pesticides, pharmaceuticals, industrial wastewaters, etc. This is due to their excellent catalytic properties and resistance to both corrosion and dissolution. The catalytic activity of MMO electrodes strongly depends not only on their composition but also on fabrication methods. Thus, a correlation was made between the methods of manufacturing, efficiency and cost in the MMO electrodes. Despite the wide variety of anodes, most of them are either relatively expensive to be used for large volumes of wastewater, or they consist of potentially toxic metals. Moreover, none of them are sufficiently efficient and stable. Therefore, cost-effective, efficient and green anodic materials are still under development.