Abstract
Remediation of environmental pollution has become a hot issue in the world. Environmental pollution, mainly caused by toxic chemicals, includes air, water, and soil pollution. This pollution results not only in the destruction of biodiversity, but also the degradation of human health. Textile industrial effluent often contains the significant amount of synthetic and toxic dyes. Some dyes are water-soluble, dyes such as azo dyes, sulfonated azo dyes, etc. Hazardous effect of dyes results in the formation of tumor, cancer, liver or kidney damage, insomnia, diarrhea, nausea, vomiting, dermatitis, chronic asthma, coughing, headaches, and allergies in humans and also inhibit growth of bacteria, protozoan, plants, and different animals. A range of wastewater treatment technologies have been proposed that can efficiently reduce toxic dyes to less toxic forms such as nanotechnology. In this chapter, the authors give an overview of the various aspects of nanotechnology to remediate industrial textile dye effluents.
TopBackground To Dyes
Colorants are basically chemicals which is responsible for imparting color to the materials on which they are applied. Pigments and dyes are the types in which dyes are classified. Both are different from each other on the basis of their solubility. The crystalline or the particulate nature of the pigments is retained during the application. But dyes on the other hand became the integral part of the material because these are soluble and can be easily diffused into the material. Polymers, paints, and inks are the materials in which pigments are used. Dyes are considered as main source for contamination of water and it is considered as ionizing, aromatic, and colored materials. These compounds which originate from hydrocarbons such as anthracene, toluene, xylene, naphthalene, and benzene which are based on coal tar are used for coloring several materials such as greases, drugs, cosmetics, paper, food, waxes, fur, plastics, leather, textile materials, hair, and other products. Factors other than solubility are required for a coloured material to be considered as dyestuff.
The Physical Basis of Color
Dyes are colored due to adsorption of light in the visible region or in the 400-700 nm range. Color –possessing group i.e chromophore and conjugate systems i.e the system consisting of alternate single and multiple bonds must be possessed by dyes. Resonance of electrons is the force of stabilization in case of organic compounds which is exhibited by dye molecules. Presence of a chromophore which is the area of the molecule where the difference of the energy between the two separate molecular orbitals lies in the range of visible region is responsible for imparting colors to the dyes. π–π* and n–π* transitions occurs in chromophore and the solubility of dyes are effected by auxochromes which are present in most of the dyes. Transitions of n electrons occurred in auxochromes not the π–π* transitions. Carboxylic acid, amino, hydroxyl, sulfonic acid groups the the various auxochromes which is present in dyes and are responsible for color of the colorant. But these functional groups are not accountable for color production (Gupta et al., 2013, Janaki 2014, Mallakpour 2017, Mallakpour 2018, Saini et al., 2018).
Key Terms in this Chapter
Dye: Dye is a colored substance which provides color to another substrate through chemical bond with the substrate.
Effluent: Effluent is an outflowing of water or gas to a natural body of water, from a structure such as a wastewater treatment plant, sewer pipe, or industrial outfall, etc.