An Overview of Applications of the Electro-Fenton (e–/H2O2/Fe2+) Oxidation Processes: Degradation of Acid and Basic Dyes in the Industrial Wastewaters

Abstract: As a result of the rapid development of industry and technology, a great increase has been observed in the use of chemicals and toxic substances harmful to the environment, especially in the last 20 yr. The harmful effects of industrial wastewater, which are formed as a result of the use of chemical and toxic substances as raw substances and by products in many technology branches, adversely affect the environment. Traditional treatment methods are quite inadequate in the treatment of industrial wastewater. Water pollution is one of the most important environmental problems of today. Since water is the most basic need of living things and the source of great economic activities, it is an indispensable resource for the continuation of living and non-living life. Acid dyes, one or more in the molecule contain a sulfonic acid group or a carboxylic acid group. Acid dyes are chemically classified as anionic dyes. Direct metal-complex and reactive dyestuffs containing sulfonic acid groups are also anionic. Basic dyes are in the form of hydrochlorides of organic bases and are found in the colored part of the cationic group dye. Basic dyes, contain N or S atoms as positive charge carriers. Different chemical, physical and biological processes such as chlorination, ozonation, adsorption and microfiltration are widely used in cleaning the environments where industrial wastes are present. However, in all of these methods organic substance can be removal by transferring it from one phase to another. However, due to increasing environmental pollution, the treatment process has changed to develop new methods that can decompose organic substances into CO2 and H2O instead of transferring them from one phase to another. Hybrid systems in which different oxidation processes are applied simultaneously in the same electrochemical cell, are widely used today in order to increase the efficiency of the electrochemical methods.