Dyes used in textile industry, hazardous chemical contents and effects of treatment with ozonation on cod and color parameters

Discharging industrial wastes to the environment poses a greater threat than domestic wastes. Industrial wastewaters generally show great oscillations in terms of the composition of the chemicals they contain. The textile industry uses thousands of different dyes and pigments throughout the world. More than 50% of all dyes used in the industry are azo dyes. They generally contain at least one and at most four azo groups linked to two radicals which are at least one or both aromatic groups. Increased use of cotton has also led to significant increases in the use of reactive dyes. However, reactive azo dyes are potentially hazardous to the environment and highly important due to their cleavage into carcinogenic aromatic amines. In the current study, it was investigated that how the effect of samples selected from the types of dyestuffs used in the textile industry differ according to the known pollutant contents by measuring the COD values. Synthetic wastewater samples prepared from dyestuffs used in textile industry have been tried to be treated with ozonation method which is one of the advanced treatment techniques. Considering that there are many auxiliary chemicals used in dyeing processes, it is seen that only dyestuffs have a high effect on the pollution of textile wastewater alone. It has been observed that the ozone oxidation method breaks down the molecules of dyes and is therefore a very effective method for color removal. In the experiments carried out with the samples from the reactive, acid, disperse and optical birghtener dye groups, a very significant color removal was achieved in the alkaline environment that the color removal efficiencies reached up to 99%. Alkaline pH media is also effective in COD removal and yields twice as much as in acidic pH media.