Photoelectrochemical Degradation of Azo Dyes in Aqueous Solutions: A Review

Literature data on the oxidative degradation of azo dyes are summarized. Processes of photoelectrochemical oxidation with various approaches to the removal of azo dyes from wastewater are considered. Recent advances in photoelectrochemical techniques designed to enhance degradation efficiency are discussed, including photoelectrochemical oxidation (PEO), photoelectro-Fenton (PEF), and solar photoelectro-Fenton (SPEF). The key problems are discussed such as the use of semiconductor materials as electrodes, the effect of operational parameters on dye degradation in wastewater, the design of reactors, and the combined photoelectrochemical oxidation systems including those with integrated fuel cells. A comparative analysis of electrochemical anodic oxidation (AO) versus PEO processes for azo dye treatment is provided. The data on identification of azo dye degradation products and their toxicity are presented.