Color has an important role to play in textile, food, printing, pharmaceutical and cosmetic industries. Azo dye is extensively used as coloring agent in most of the industrial processes. However, it has become a matter of debate regarding the toxic and carcinogenic components it contains. It has also posed a challenge for the textile industries for its removal from the industrial waste water.
The azo dyes are synthetic dyes formed by azo group which consists of two nitrogen atoms linked with each other. In the primeval times, azotes in French meant nitrogen and that is how the word 'azo' originated. Azo dyes are also known as azoic or nepthol dyes. The azo dyes are chiefly of red, brown and yellow colors. The chemicals from which these dyes are manufactured are called fragrant amines.
These dyes are not directly applied on the fabrics but, they are constructed within the fibres. To achieve this, the fibres are soaked in one element of the dye and then another component of the dye is infused in the fibre. In this way the azo dye is produced. As the dye is inbuilt in the fibre, the color is very fast and hence, this dye is widely used for coloring fabrics in the textile industry.
Dyes used in the food and textile industry consist of 60-70% of azo dyes. They are synthetic colors and most of them contain only one azo group. However, there are some azo dyes that contain more than one azo group. In opposition to the belief, azo dyes are not made from coal or tar. The specialty of this dye is that it can provide almost all colors.
The aromatic compounds in the azo dyes are the reason that they produce strong and variety of colors. Manufacturing azo dyes is pretty easy and cheap as the components of the dyes are cheap and easily available. In addition, while producing it; different levels can be set, and adjusted easily according to the requirement. Furthermore, the energy required for the process is also less, as the composition of chemical structure happens at or below the room temperature.
In fact all the chemical processes of azo dye are done using water. And it is easy, and cheap to avail water, even cleaning and disposing off is simple. Due to all these reasons azo dyes are cheap, easily produced and widely used. Azo dyes are consistent compared to other natural food dyes. They are steady and firm, when compared to the pH series of food. They do not fade when exposed to light and oxygen, and are also heat resistant.