Abstract
Water pollution by the textile industry is an emerging issue. Textile industry is the major industrial sector which contributes to water pollution. Textile industry releases a huge amount of unfixed dyes in wastewater effluents. About 20% of the dye production all over the world is discharged as waste in industrial effluents by textile industry. These dyes are highly stable and colored substances which disturb the aqueous ecosystem significantly. Therefore, there is a need for methods to remove organic dyes from textile industrial effluents. Photo catalysis and catalytic wet oxidation are best practices for degradation of dyes in wastewater. In photo catalysis, the dye molecules can be completely degraded into inorganic non-toxic compounds by irradiation of the dye solution under visible or ultraviolet light in the presence of semiconductor metal-oxide photo catalysts. In catalytic wet oxidation, various metal-based catalysts in supported or unsupported form can be used as heterogeneous catalysts for degradation of dyes in the presence of oxygen or hydrogen peroxide. These processes have several preferences like easy separation of the catalyst from reaction mixture and recycling of the catalyst.
Highlights
A large amount of water is being used in the textile industry for preparing fabric and dyeing process
Azo dyes consisting of a diazotized amine coupled to an amine or a phenol and contain one or more azo (–N = N–) linkage comprise about half of all textile dyes used in the present textile industry
The heterogeneous photo catalysis, which can be used for degradation of organic pollutants by initiation of redox transformations, has been proved as an efficient tool for degradation of aqueous as well as atmospheric organic pollutants
Summary
Water is an important resource in our society. In our planet, Earth, less than a 0.7% of the total of water is fresh water and only 0.01% is available to be used. Azo dyes consisting of a diazotized amine coupled to an amine or a phenol and contain one or more azo (–N = N–) linkage comprise about half of all textile dyes used in the present textile industry The concentrations of these dyes in textile wastewater are significantly high, as about 20% of dye residues are released into effluents [4]. The dye discharge into the environment poses serious threat to sustainability of ecosystems because they are highly resistant to natural degradation These dyes have been declared as carcinogenic and tumorigenic material by the International Agency for Research on Cancer (IARC) and National Institute for Occupational Safety and Health; these dyes are still in use in textile dyeing processes. The textile effluents should be effectively treated before final disposal [5–7]
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