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Industrial dye degradation


Synthetic dyes are found in a wide range of products such as clothes, leather accessories, and furniture. These dyes are commonly used every day. However, a side effect of their widespread use is that up to 12% of these dyes are wasted during the dying process and about 20% of this wastage enters the environment (mainly into water supply).

Dye degradation is a process in which the large dye molecules are broken down chemically into smaller molecules. The resulting products are water, carbon dioxide, and mineral byproducts that give the original dye its color. During the dyeing process, not all of the dye molecules are used. The water waste that the industry releases contains a percentage of these dye molecules. Dye molecules persist in the environment because many of them are not reactive towards light, acids, bases and oxygen. The color of the material becomes permanent.

Heterogeneous photocataylsis is a widely accepted technique of choice for environmental purification. The standard experimental set up for dye degradation photocatalysis is by using a UV lamp to provide energy for the creation of oxidizing radicals. is the addition of light to a semiconductor oxide/sulphide that results in electrons moving from the valence band to the conduction band. The electron-hole pairs formed will react with oxygen and water molecules to create superoxide anions and hydroxide radicals that have increased oxidizing and reducing abilities to be used on numerous industrial dye compounds.

Titanium dioxide (TiO2) is biologically stable, non-toxic, and cheap, which makes it a very common semiconductor for dye degradation. Due to its large band gap, some alterations can be made to improve its photocatalytic abilities such as the synthesis of 6,13-pentacenequinone/ TiO2. Titanium dioxide in conjunction with ultraviolet light can be utilized for the decolorization and detoxification of diluted colored water waste such as Alizarin, azo dyes, methyl red, methylene blue, etc. Reduced graphene oxide-TiO2 can act as photocatalyst for the degradation of methyl orange, azo-dye, and pharmaceutical water waste.

3-D structures of copper sulfide (CuS) is favored for methylene blue degradation because it is nontoxic, inexpensive, and stable under ambient conditions. It has efficient catalytic ability because of its high surface area to volume ratio allowing for better contact between the reactants and CuS.


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