Chemical and Biological Treatment of Dyes

Life of living or non-living being depends on water; in short, water is life. But these days, with the growing industrialization, it is spoiling a lot. Wastewater contains contaminants like acids, bases, toxic organic and inorganic dissolved solids, and colors. Out of them, the most undesirable are colors caused mainly by dyes. Color and other compounds present in water are always not desirable for domestic or industrial needs. The wastes of dyes are predominant amongst all the complex industrial wastewater. This water is dark in color and highly toxic, blocking the sunlight and affecting the ecosystem. Among all the dyes, azo dyes contribute to commercial dyes used widely in textile, plastic, leather, and paper industries as additives. The removal and degradation of azo dyes in aquatic environment is important because they are highly toxic to aquatic organisms. For every industry, clean technology has become an important concern. In this chapter, the authors discuss about existing processes as well as promising new technologies for textile wastewater decolorisation.

Removal of Dyes From Wastewater by Adsorption Onto Low-Cost Adsorbents

This chapter describes an up-to-date critique of the use of adsorption as a wastewater treatment technique for the removal of dyes. The topics range from the classification of dyes, their occurrence in water and toxicity, various treatment methods, and dye adsorption dynamics onto agricultural wastes and inorganic adsorbents such as clay and metal oxides and adsorption onto microbial biomass under varying operational conditions. It is demonstrated that the discussed materials form alternative adsorbents for dye adsorption from aqueous solutions with comparable or better removal efficiencies relative to the non-renewable coal-based granular activated carbons; they are cheap and abundant. The relative performance of the adsorbents under different environmental parameters for dye removal has also presented. The deductions made and alluded to from various kinetic and adsorption isotherm models are also discussed. The chapter presents the past, present, and suggestions for future considerations in search of non-conventional adsorbents for dye sequestration from aqueous solution.

Advanced Oxidation Processes for Dye Removal From Wastewater

Advanced oxidation processes (AOPs), namely the Fenton oxidation, ozonation, electrochemical oxidation, and photocatalysis, are potential alternative techniques for dye removal from textile effluents. Their inherent ability to completely mineralize pollutants including those recalcitrant to biodegradation and to be compatibly integrated in conventional technologies present grounds for consideration of AOPs as alternative wastewater treatment options. Advanced oxidation involves generation and subsequent reaction of various radicals and reacting species with the target compounds. This chapter discusses the fundamentals and chemistry and efficiencies of the Fenton process, ozonation, electrochemical oxidation, and photocatalysis processes for complete dye removal from wastewater. The reaction mechanisms, performance, and factors affecting efficiency are discussed.

Effect of Dyes on Water Chemistry, Soil Quality, and Biological Properties of Water

As the textile industries use aqueous method for dyeing processes, the color that is released in the environment is associated with the incomplete absorption of dyes on fibres. So, there is a strong need to reduce the amount of residual dye in textile effluent. Large amounts of liquid wastes are produced from textile industries that contain both organic and inorganic compounds. The degradation of azo dyes is difficult using the conventional processes. These complex azo dyes containing N=N bond have been found to show carcinogenic evidences on reductive cleavage. Azo dyes have capability to alter physical and chemical properties of soil, causing harm to the water bodies. Dyes are toxic in nature, which is lethal for microorganisms present in soil affecting agricultural productivity. The presence of azo dyes in water decreases its water transparency and water gas solubility. This reduces light penetration through water, decreases its photosynthesis activity, causing oxygen deficiency and de-regulating the biological cycles of aquatic system.

World of the Dye

The textile sector is 14% of total industrial production in India and contributes to about 4% of the gross domestic product and earns about 27% of India's total foreign exchange. Worldwide, up to 10,000 dyes are available and their annual production is above 7×105 metric tons, which are being used not only in textile sector but also applied in paper, food, and pharmaceutical industries. Textile industries in India have been consuming more than 100 L of water to process 1 kg of textiles and have contributed heavily in polluting surface and ground water resources in many regions of the country. The toxic and carcinogenic effect of untreated textile effluent is well understood. The decolorization and detoxification of industrial dye effluents is the most important aspect and is a major concern to meet environmental regulations. This chapter presents a review of literature on the significance of bioremediation technologies over other physicochemical methods for efficient removal of textile dyes from industrial waste effluents to improve the fragile ecosystems in different regions of the world.

Outdoor Pollution Management by Nanotechnology

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.

Impact of Textile Dyes on Human Health and Environment

The textile industry is one of the important industries that generates a large amount of industrial effluents. Color is the main attraction of any fabric. Manufacture and use of synthetic dyes for fabric dyeing has therefore become a massive industry. Synthetic dyes have provided a wide range of colorfast, bright hues. However, their toxic nature has become a cause of grave concern to environmentalists. Use of synthetic dyes has an adverse effect on all forms of life. Presence of sulphur, naphthol, vat dyes, nitrates, acetic acid, soaps, enzymes chromium compounds, and heavy metals like copper, arsenic, lead, cadmium, mercury, nickel, and cobalt and certain auxiliary chemicals all collectively make the textile effluent highly toxic. These organic materials react with many disinfectants, especially chlorine, and form byproducts (DBPs) that are often carcinogenic and therefore undesirable. This effluent, if allowed to flow in the fields, clogs the pores of the soil resulting in loss of soil productivity. This chapter gives an overview on the health and environmental impact of dyes.

Dyeing Processing Technology

Among the different substances containing organic compounds, dyes are considered the most important class, and they are now an essential requirement in the modern world, mostly in the textile industries. In addition to the textile colouring, they are used in automobile, leather, paints, paper industries, etc., but their importance in the textile industries is maximum. Because of huge demand of dye, the production of a variety of dyes with advanced properties has drastically increased. Since dyes are complex aromatic organic compounds containing conjugated double bonds, they are highly toxic to the biological community of the world. In this chapter, more emphasis is given for synthesis technologies of various kinds of dyes, different kinds of hazardous pollutants generated from the dyeing industries, and their environmental impact along with the implementation of the technology developed to reduce the pollutant and its effect to our sustainable environment. Hence, more focus has to be given for manufacturing and application of dyes from renewable natural resources.

Classification, Chemistry, and Applications of Chemical Substances That Are Harmful to the Environment

A detailed classification of dyes has been discussed along with their chemical class and chemistry. International, regional, and national classification and labeling systems are already established and tested in practice. These hazardous chemicals can be liquid, solid, gas, aerosol, mists, vapors, semisolid, etc. Hazardous chemicals have wide applications (e.g., dyes, which are used for coloring purpose; pesticides, which are used for pest control; fertilizers are an essential part of the agriculture system; plastic and plastic waste; and e-waste to name a few). In this chapter, the authors deal with the identity, classification, and application of these harmful chemicals, especially dyes, which are mandatory to use. More emphasis is given to the natural and synthesized dyes about their use along with their modrants, which are a necessary part of the dyes without which they can't exhibit colors. Dyes have wide variety of applications, which have also been discussed along with their various harmful effects on environment, mankind, and aquatic life.

Impact of Synthetic Dyes on Human Health and Environment

Colour is the most important part to make any fabric attractive, but its use for dying has become a major environmental hazard. Colloidal particles present with color increases the turbidity, gives bad appearance, foul odour, and obstructs the penetration of sunlight into water bodies required for the photosynthesis process, which interferes with the oxygen flow mechanism and hence marine life. So, it is essential to remove such pollutants from the waste water before its final disposal into water bodies. Photocatalysis is one of the advance oxidation processes, mainly carried out in the presence of light and suitable photocatalytic materials for the degradation of dyes. This chapter outlines the background of dye chemistry, the application areas, and the impact of dyeing effluents in the environment and on living beings.