Advanced Oxidation Processes for the Removal of Food Dyes in Wastewater

Many synthetic food dyes and their by-products, such as aromatic amines and phenolic compounds, occurring in industrial wastewater, are toxic to aquatic environment and, because of their carcinogenic and mutagenic nature, they result in a risk for the environment and human health when wastewater is reused or released into environment. Therefore, an effective wastewater treatment is required before effluent possible reuse or disposal. In the last years, advanced oxidation processes (AOPs) have been successfully investigated in the removal of a wide range of organic and inorganic contaminants from water and wastewater because of their capacity to promote the formation of highly reactive radicals (especially hydroxyl radicals). However, most of the studies available in scientific literature have been focused on the application of AOPs in the degradation of organic dyes from textile industries rather than food dyes. Therefore, while the literature about dye treatment by AOPs in textile wastewater is consolidated, less information is available for food dyes. Accordingly, this manuscript summarizes the main results related to the removal of food dyes by AOPs. In particular, conventional methods (biological and adsorption processes) are shortly introduced before to focus this mini-review on consolidated (namely, ozonation and homogeneous Fenton/photo-Fenton) and new (namely heterogeneous photocatalytic processes) AOPs.