**1. Introduction**

### **1.1 Water crisis**

Water is the source of life and regarded as the most essential resource of natural resources. In recent days, demand for water has increased due to tremendous growth in technology and industries. The ever increasing world population and rapidly advancing industrialization is causing more demand than ever for the dwindling supply of water, which makes it precious [1]. Many water pollutants are yet to be addressed, due to rapid industrialization there are new pollutants which are being discovered. New chemical compounds are continuously being developed and brought to the market and sooner or later they will be utilized in the aquatic systems. There may be adverse effects on human health and marine environments from emerging contaminants found in water. For human health, safe water that is free of harmful chemicals and pathogens is essential [2]. Water shortages will contribute to social and political unrest, water wars and diseases in the coming decades, and it will take a dramatic turn in the opposite direction unless new methods of providing clean water are found. Increased public awareness has led governments and

organizations worldwide to issue strict water pollution regulations. These days there is an increasing worldwide concern for the development of wastewater treatment technology [3]. The conversion of waste water into reusable water can be done by using scientific methods and that decreases the challenge towards the rising demand of water quality [4]. Comparing all industries, textile industries show a higher rate of consumption of water.

#### **1.2 Status of pollution due to textile industries**

Dyes can be characterized as substances that when applied to a substrate, provide color through a process that alters the crystal structure of the colored substances, at least temporarily. In the textile, pharmaceutical, food, cosmetics, plastics, photographic and paper industries, such substances with substantial coloring capability are commonly used. Dyes are categorized by application and chemical structure and consist of a group of atoms known as chromophores that are responsible for the color of the dye. The numerous functional groups, such as azo, anthraquinone, methine, nitro, carbonyl and others are used as chromophore-containing centers in dyes, in addition, electrons removing or donating substituents are called auxochromes in order to produce or enhance the color of the chromophores are also present in dyes. Over 10,000 different dyes and pigments are expected to be used industrially and over 7 x 105 tons of synthetic dyes are manufactured globally annually [5–7]. Using batch, continuous or semi-continuous processes, textile products can be dyed. The type of method used depends on many features, including the type of material such as fibre, yarn, fabric, construction of garments and clothes, as well as the generic type of fibre, the size of dye batches and the quality specifications of the dyed fabric. The batch process is the most common method of dyeing textile materials among these methods. In the textile industry, due to the inefficiency of the dyeing process, up to 200,000 tons of these dyes are lost to effluent every year during the dyeing and finishing operations. Unfortunately, as a result of their high stability to light, temperature, water, detergents, chemicals, soap and other parameters such as bleach and transpiration, most of these dyes avoid traditional wastewater treatment systems and remain in the setting. Furthermore, in the manufacture of textiles, anti-microbial agents resistant to biological degradation are frequently used, especially for natural fibres such as cotton. They are more recalcitrant to biodegradation by the synthetic origin and complex aromatic structure of these agents. A significant volume of water used mainly in the dyeing and finishing operations of the plants is used in the textile industry in its production methods. Both dry and wet processing include a textile unit. In an extended process series that produces a large amount of waste, the textile manufacturing process is distinguished by the high use of resources such as water, fuel and a broad variety of chemicals. A huge amount of solid and liquid waste is produced by textile processing units, some of which may be hazardous [8]. Considering the volume produced as well as the composition of the effluent, waste water from textile plants is listed as the most polluting of all industrial sectors. Moreover the increased demand for textile goods and the proportional increase in their production, along with the use of synthetic dyes, have led to make dye wastewater one of the key sources of serious pollution problems at the present time.

The nature of the waste produced depends on the range of fibres and chemical substances involved in the textile process, the processing methods and technologies that are being adopted. Usually the most important ecological problems associated with textile production are those associated with the degradation of the body of water caused by the discharge of raw waste [9]. Dyeing and finishing units are a key part of the produced waste water as they use a high volume of water in their

**189**

*Treatment of Textile Dyeing Waste Water Using TiO2/Zn Electrode by Spray Pyrolysis…*

operation, from fibre washing to bleaching, dyeing and washing of refined products [10]. On average, there is a sample mixture of compounds in around 200 L of water that could cause harm if strict precautions are not taken until they are released into the atmosphere. Wet process manufacturing utilizes color caustic soda, sulphuric acid, sodium peroxide, hydrochloric acid, dyes and chemicals. Moreover, other metals, which are carcinogenic in nature are reserved in the finished hosiery supplies

Dyes used by the textile industry are now mainly synthetic. They are predominantly extracted from two sources, coal tar and intermediates based on petroleum. Powders, pellets, gels or colloidal dispersions are the state of these dyes in the market. Usually the active ingredient concentrations in the dyes vary from 20 to 80 percent. These new dyes are regularly produced for meeting the demands of new technologies, new kinds of fabrics, detergents, developments in dyeing machineries, along with addressing the significant environmental problems faced

With the rapid shift in the textile industry's product profile, from high-cost cotton textiles to durable and flexible synthetic fibres, the pattern of consumption of these dyes is also shifting rapidly. Polyesters now account for a large portion of dye use. Dispersed dyes used in polyesters are therefore also expected to expand at a

To make it easier to understand, textile dyestuffs can be grouped into the following groups if we take general dye chemistry as one of the basis for grouping as azoic, acid sulfur, disperse, simple, reactive, mordant, oxidation vat solvent and

Green and Saunders developed one form of coloured azo compound in 1922, in which an amino group is attached to a solubilizing group e.g. methyl sulphate, -CH2-SO3H. In dye bath, they are slowly hydrolyzed and contain azo compound and formaldehyde bi sulphate. This free azo compound was able to color the fibres of cellulose acetate. The name of that dye was "ionamine." This ion amine, however, did not give satisfactory dyeing results. Baddiley and Ellis later developed sulpho ricinoleic acid (SRA) for the dyeing of acetate fibres in 1924. This SRA has been used as an agent for dispersion. SRA was later shown to be capable of dyeing nylon, polyester, acrylic, etc. This dye was called 'Disperse Dye' in 1953. As per the chemical structure disperse dyes are classified as nitro, amino ketone dyes, anthraquinonoid dyes, aono azo dyes, di- azo dyes. In this study we had used azo type of disperse dyes with the commercial names as Coralene Navy RDRLSR, Coralene Red

India is the second largest exporter of dyestuffs, after China. It is estimated that approximately 2% of the dyes produced are discharged directly in aqueous effluent, and 10% is subsequently lost during the coloration process [12]. The size of India's market is expected to touch \$250 billion in the next two years from \$150 billion. Although textile industries play an important role in Indian economy, the waste

Tiruppur, a textile hub, in Tamil Nadu, has emerged as the leading industrial cluster of cotton knitwear in South India for both the overseas and domestic markets primarily because of climate conditions which facilitate fast processing of yarn. Moreover the availability of raw materials and cheap labour has ensured that the activities of the textile industry here, have experienced rapid growth over the last two decades. Almost 80 percent of India's exports of cotton knitwear are from Tirupur today. There are 6,250 units involved here in different textile industry

*DOI: http://dx.doi.org/10.5772/intechopen.95325*

and let out as wastewater [11].

by some existing dyes.

faster rate.

fluorescent dyes.

3G, Rubru RD GLFI dye.

**1.3 Background and motivation of the present study**

water management is concerned predominant.

#### *Treatment of Textile Dyeing Waste Water Using TiO2/Zn Electrode by Spray Pyrolysis… DOI: http://dx.doi.org/10.5772/intechopen.95325*

operation, from fibre washing to bleaching, dyeing and washing of refined products [10]. On average, there is a sample mixture of compounds in around 200 L of water that could cause harm if strict precautions are not taken until they are released into the atmosphere. Wet process manufacturing utilizes color caustic soda, sulphuric acid, sodium peroxide, hydrochloric acid, dyes and chemicals. Moreover, other metals, which are carcinogenic in nature are reserved in the finished hosiery supplies and let out as wastewater [11].

Dyes used by the textile industry are now mainly synthetic. They are predominantly extracted from two sources, coal tar and intermediates based on petroleum. Powders, pellets, gels or colloidal dispersions are the state of these dyes in the market. Usually the active ingredient concentrations in the dyes vary from 20 to 80 percent. These new dyes are regularly produced for meeting the demands of new technologies, new kinds of fabrics, detergents, developments in dyeing machineries, along with addressing the significant environmental problems faced by some existing dyes.

With the rapid shift in the textile industry's product profile, from high-cost cotton textiles to durable and flexible synthetic fibres, the pattern of consumption of these dyes is also shifting rapidly. Polyesters now account for a large portion of dye use. Dispersed dyes used in polyesters are therefore also expected to expand at a faster rate.

To make it easier to understand, textile dyestuffs can be grouped into the following groups if we take general dye chemistry as one of the basis for grouping as azoic, acid sulfur, disperse, simple, reactive, mordant, oxidation vat solvent and fluorescent dyes.

Green and Saunders developed one form of coloured azo compound in 1922, in which an amino group is attached to a solubilizing group e.g. methyl sulphate, -CH2-SO3H. In dye bath, they are slowly hydrolyzed and contain azo compound and formaldehyde bi sulphate. This free azo compound was able to color the fibres of cellulose acetate. The name of that dye was "ionamine." This ion amine, however, did not give satisfactory dyeing results. Baddiley and Ellis later developed sulpho ricinoleic acid (SRA) for the dyeing of acetate fibres in 1924. This SRA has been used as an agent for dispersion. SRA was later shown to be capable of dyeing nylon, polyester, acrylic, etc. This dye was called 'Disperse Dye' in 1953. As per the chemical structure disperse dyes are classified as nitro, amino ketone dyes, anthraquinonoid dyes, aono azo dyes, di- azo dyes. In this study we had used azo type of disperse dyes with the commercial names as Coralene Navy RDRLSR, Coralene Red 3G, Rubru RD GLFI dye.

#### **1.3 Background and motivation of the present study**

India is the second largest exporter of dyestuffs, after China. It is estimated that approximately 2% of the dyes produced are discharged directly in aqueous effluent, and 10% is subsequently lost during the coloration process [12]. The size of India's market is expected to touch \$250 billion in the next two years from \$150 billion. Although textile industries play an important role in Indian economy, the waste water management is concerned predominant.

Tiruppur, a textile hub, in Tamil Nadu, has emerged as the leading industrial cluster of cotton knitwear in South India for both the overseas and domestic markets primarily because of climate conditions which facilitate fast processing of yarn. Moreover the availability of raw materials and cheap labour has ensured that the activities of the textile industry here, have experienced rapid growth over the last two decades. Almost 80 percent of India's exports of cotton knitwear are from Tirupur today. There are 6,250 units involved here in different textile industry

*Dyes and Pigments - Novel Applications and Waste Treatment*

**1.2 Status of pollution due to textile industries**

of consumption of water.

industrially and over 7 x 105

pollution problems at the present time.

organizations worldwide to issue strict water pollution regulations. These days there is an increasing worldwide concern for the development of wastewater treatment technology [3]. The conversion of waste water into reusable water can be done by using scientific methods and that decreases the challenge towards the rising demand of water quality [4]. Comparing all industries, textile industries show a higher rate

Dyes can be characterized as substances that when applied to a substrate, provide color through a process that alters the crystal structure of the colored substances, at least temporarily. In the textile, pharmaceutical, food, cosmetics, plastics, photographic and paper industries, such substances with substantial coloring capability are commonly used. Dyes are categorized by application and chemical structure and consist of a group of atoms known as chromophores that are responsible for the color of the dye. The numerous functional groups, such as azo, anthraquinone, methine, nitro, carbonyl and others are used as chromophore-containing centers in dyes, in addition, electrons removing or donating substituents are called auxochromes in order to produce or enhance the color of the chromophores are also present in dyes. Over 10,000 different dyes and pigments are expected to be used

ally [5–7]. Using batch, continuous or semi-continuous processes, textile products can be dyed. The type of method used depends on many features, including the type of material such as fibre, yarn, fabric, construction of garments and clothes, as well as the generic type of fibre, the size of dye batches and the quality specifications of the dyed fabric. The batch process is the most common method of dyeing textile materials among these methods. In the textile industry, due to the inefficiency of the dyeing process, up to 200,000 tons of these dyes are lost to effluent every year during the dyeing and finishing operations. Unfortunately, as a result of their high stability to light, temperature, water, detergents, chemicals, soap and other parameters such as bleach and transpiration, most of these dyes avoid traditional wastewater treatment systems and remain in the setting. Furthermore, in the manufacture of textiles, anti-microbial agents resistant to biological degradation are frequently used, especially for natural fibres such as cotton. They are more recalcitrant to biodegradation by the synthetic origin and complex aromatic structure of these agents. A significant volume of water used mainly in the dyeing and finishing operations of the plants is used in the textile industry in its production methods. Both dry and wet processing include a textile unit. In an extended process series that produces a large amount of waste, the textile manufacturing process is distinguished by the high use of resources such as water, fuel and a broad variety of chemicals. A huge amount of solid and liquid waste is produced by textile processing units, some of which may be hazardous [8]. Considering the volume produced as well as the composition of the effluent, waste water from textile plants is listed as the most polluting of all industrial sectors. Moreover the increased demand for textile goods and the proportional increase in their production, along with the use of synthetic dyes, have led to make dye wastewater one of the key sources of serious

The nature of the waste produced depends on the range of fibres and chemical substances involved in the textile process, the processing methods and technologies that are being adopted. Usually the most important ecological problems associated with textile production are those associated with the degradation of the body of water caused by the discharge of raw waste [9]. Dyeing and finishing units are a key part of the produced waste water as they use a high volume of water in their

tons of synthetic dyes are manufactured globally annu-

**188**

operations. It consists of 4900 knitting and sewing units, approximately 736 dyeing and bleaching units, 300 printing units, 100 embroidery units and 200 compacting, raising and calendar catering units. Buyers come regularly to visit Tirupur from about 35 countries. In addition to an income matching or exceeding the above amount to cater to the domestic market, this small town contributes around INR.11000 crores (Rs. 110 billion) in foreign exchange earnings annually to the government. In short, Tirupur's economic success depends heavily on this industry and most local people are active in the knitwear sector in one way or another. With a rough estimation of 7 × 105 –1 × 106 tons of fabrics produced per year, there are more than 100,000 commercial dyes. Though accurate statistics on the number of dyes released into the surroundings is not known, data shows that 10–15% of the used dyes are released into the environment as they are discharged as wastewater from textile industries causing severe pollution [13].

In Tirupur, the textile industry's water needs have been fulfilled by both surface water and ground water. About 28.8 billion litres of ground water are consumed annually by the units in Tirupur alone. This water is transported in tankers from the surrounding villages such as Avinashi, Palladam, Annur, Kangeyam, and from many parts of the nearby Erode district. Needless to mention, Tirupur faces extreme water shortages. Tankers supply about 80 percent of the total water requirement [14]. The textile units purchase water per tanker at a cost of Rs 250–450. The farmers sell the same thing at Rs 40–80 per tanker. Even at this rate, it is more profitable for farmers to sell water instead of carrying out agricultural activities.

## **1.4 Major challenges in the treatment of textile effluent**

Knowledge of environmental issues has increased dramatically over the past few decades and has become an important concern in textile trade due to different environmental and health regulations, and environmental policy is also increasingly dictated by market forces. Many chemicals used in the textile industry are causing problems with the ecosystem and health [15].

Textile processing is a water intensive process. The waste water generated by the industry is high in BOD, COD, pH, temperature, color, turbidity and toxic chemicals. These polluted effluents ought to be treated chemically to remove the hazardous material and chemicals so that the waste water will comply with the prescribed limits and can be discharged into the public sewer or into aquatic bodies [16]. The major challenges existing in the treatment of textile industrial effluents are recycling and reuse of wastewater, removal of color and reduction of Total Dissolved Solids (TDS) in the treated effluent, generation of huge amount of sludge, large units have invested in Individual Effluent Treatment Units (IETPs) and medium scale units have invested in Common ETPs. However, no techno-economically viable option is available for treating the effluent in small units.

#### **1.5 Existing conventional treatment methods and their limitations**

Removal of dye is possible by different or a combination of physical, chemical and biological methods. Adsorption, absorption, membrane filtration, and ultrasonic waves are physical methods; ion exchange, electrolysis, coagulation, traditional and advanced oxidation are chemical methods; and biological methods can be described using algae, fungi, and bacteria [17].

In chemical coagulation, electrostatic gravity between the dye solution and polymeric molecules with opposite loads generates coagulation. The disadvantages

**191**

*Treatment of Textile Dyeing Waste Water Using TiO2/Zn Electrode by Spray Pyrolysis…*

of this method are high sludge production and high dissolved solids in treated wastewaters and polymeric molecules with opposite loads generate coagulation. Chemical coagulation is efficient for sulfurous and disperse dyes. Acidic, direct, vat and reactive dyes coagulate with this method too, but do not settle, while cationic dyes do not even coagulate [18]. The conventional treatment methods such as activated sludge, coagulation and flocculation process, reverse osmosis and evaporation consume a lot of chemicals, high energy and are not sufficient to break down azo double bonds of reactive dyes. Also the secondary products or sludge produced becomes more difficult to be disposed. Huge amount of rejects from Reverse

A large number of well-established traditional decolourisation techniques involving physicochemical, chemical and biological processes, as well as some modern emerging techniques such as sonochemical or advanced oxidation processes, are shown in the available literature. In order to solve this problem, there is no single economically and technically feasible approach and typically two or three methods need to be combined to achieve an acceptable degree of colour

The main drawbacks of these physiochemical and biological treatment processes is that they generally lack the broad scope of treatment efficiency required to treat all diverse pollutants present in the textile waste water. The electrochemical technology that was developed can remove chemical components in an effective and

The electrochemical method is a safer, highly effective treatment method for the treatment of textile liquid waste containing a high concentration of dye. This technique has advantages for decolorization over others, such as the need for simple equipment, better accuracy, and shorter retention time to remove pollutants, less need for chemicals and simpler operation, and [22]. This challenge towards rising demand for quality water can be resolved by the application of certain sophisticated scientific techniques for the conversion of waste water into reusable water. The electrochemical methods for treatment of textile waste water include electro dialysis, electrical ion exchange, electro osmosis, electro oxidation etc. Though these methods have proven to be efficient it is not practically applicable because of

There exists a wide range of methods which can be employed to treat wastewater. With the recent technological development in electrochemical field, a new technique has been introduced in the industry, named as electro-coagulation. EC has been successfully used for decades in order to treat the wastewater of textile, food and protein, phosphate, tannery wastewater, restaurant wastewater and defluoridation. Electro-coagulation among them is cost effective and requires less maintenance. Hence electro-coagulation was applied in this study for the removal

This study focuses on the treatment of synthetic dyeing wastewater (obtained from Devi Threads, Pachapalayam) using EC method which addresses the need for techno-economically feasible option in treating the effluent from small scale clusters thereby solving the other above mentioned issues of dye removal, high

*DOI: http://dx.doi.org/10.5772/intechopen.95325*

Osmosis is another major problem [19].

**1.6 Electro chemical methods and their limitations**

its high cost and maintainability [23].

of dye from textile wastewater [24, 25].

sludge production and reuse of the effluent.

**1.7 Scope of the present study**

removal [20, 21].

economical way.

#### *Treatment of Textile Dyeing Waste Water Using TiO2/Zn Electrode by Spray Pyrolysis… DOI: http://dx.doi.org/10.5772/intechopen.95325*

of this method are high sludge production and high dissolved solids in treated wastewaters and polymeric molecules with opposite loads generate coagulation. Chemical coagulation is efficient for sulfurous and disperse dyes. Acidic, direct, vat and reactive dyes coagulate with this method too, but do not settle, while cationic dyes do not even coagulate [18]. The conventional treatment methods such as activated sludge, coagulation and flocculation process, reverse osmosis and evaporation consume a lot of chemicals, high energy and are not sufficient to break down azo double bonds of reactive dyes. Also the secondary products or sludge produced becomes more difficult to be disposed. Huge amount of rejects from Reverse Osmosis is another major problem [19].

A large number of well-established traditional decolourisation techniques involving physicochemical, chemical and biological processes, as well as some modern emerging techniques such as sonochemical or advanced oxidation processes, are shown in the available literature. In order to solve this problem, there is no single economically and technically feasible approach and typically two or three methods need to be combined to achieve an acceptable degree of colour removal [20, 21].

The main drawbacks of these physiochemical and biological treatment processes is that they generally lack the broad scope of treatment efficiency required to treat all diverse pollutants present in the textile waste water. The electrochemical technology that was developed can remove chemical components in an effective and economical way.

#### **1.6 Electro chemical methods and their limitations**

The electrochemical method is a safer, highly effective treatment method for the treatment of textile liquid waste containing a high concentration of dye. This technique has advantages for decolorization over others, such as the need for simple equipment, better accuracy, and shorter retention time to remove pollutants, less need for chemicals and simpler operation, and [22]. This challenge towards rising demand for quality water can be resolved by the application of certain sophisticated scientific techniques for the conversion of waste water into reusable water. The electrochemical methods for treatment of textile waste water include electro dialysis, electrical ion exchange, electro osmosis, electro oxidation etc. Though these methods have proven to be efficient it is not practically applicable because of its high cost and maintainability [23].

There exists a wide range of methods which can be employed to treat wastewater. With the recent technological development in electrochemical field, a new technique has been introduced in the industry, named as electro-coagulation. EC has been successfully used for decades in order to treat the wastewater of textile, food and protein, phosphate, tannery wastewater, restaurant wastewater and defluoridation. Electro-coagulation among them is cost effective and requires less maintenance. Hence electro-coagulation was applied in this study for the removal of dye from textile wastewater [24, 25].

#### **1.7 Scope of the present study**

This study focuses on the treatment of synthetic dyeing wastewater (obtained from Devi Threads, Pachapalayam) using EC method which addresses the need for techno-economically feasible option in treating the effluent from small scale clusters thereby solving the other above mentioned issues of dye removal, high sludge production and reuse of the effluent.

*Dyes and Pigments - Novel Applications and Waste Treatment*

–1 × 106

**1.4 Major challenges in the treatment of textile effluent**

problems with the ecosystem and health [15].

available for treating the effluent in small units.

described using algae, fungi, and bacteria [17].

**1.5 Existing conventional treatment methods and their limitations**

Removal of dye is possible by different or a combination of physical, chemical and biological methods. Adsorption, absorption, membrane filtration, and ultrasonic waves are physical methods; ion exchange, electrolysis, coagulation, traditional and advanced oxidation are chemical methods; and biological methods can be

In chemical coagulation, electrostatic gravity between the dye solution and polymeric molecules with opposite loads generates coagulation. The disadvantages

textile industries causing severe pollution [13].

rough estimation of 7 × 105

activities.

operations. It consists of 4900 knitting and sewing units, approximately 736 dyeing and bleaching units, 300 printing units, 100 embroidery units and 200 compacting, raising and calendar catering units. Buyers come regularly to visit Tirupur from about 35 countries. In addition to an income matching or exceeding the above amount to cater to the domestic market, this small town contributes around INR.11000 crores (Rs. 110 billion) in foreign exchange earnings annually to the government. In short, Tirupur's economic success depends heavily on this industry and most local people are active in the knitwear sector in one way or another. With a

than 100,000 commercial dyes. Though accurate statistics on the number of dyes released into the surroundings is not known, data shows that 10–15% of the used dyes are released into the environment as they are discharged as wastewater from

In Tirupur, the textile industry's water needs have been fulfilled by both surface water and ground water. About 28.8 billion litres of ground water are consumed annually by the units in Tirupur alone. This water is transported in tankers from the surrounding villages such as Avinashi, Palladam, Annur, Kangeyam, and from many parts of the nearby Erode district. Needless to mention, Tirupur faces extreme water shortages. Tankers supply about 80 percent of the total water requirement [14]. The textile units purchase water per tanker at a cost of Rs 250–450. The farmers sell the same thing at Rs 40–80 per tanker. Even at this rate, it is more profitable for farmers to sell water instead of carrying out agricultural

Knowledge of environmental issues has increased dramatically over the past few decades and has become an important concern in textile trade due to different environmental and health regulations, and environmental policy is also increasingly dictated by market forces. Many chemicals used in the textile industry are causing

Textile processing is a water intensive process. The waste water generated by the industry is high in BOD, COD, pH, temperature, color, turbidity and toxic chemicals. These polluted effluents ought to be treated chemically to remove the hazardous material and chemicals so that the waste water will comply with the prescribed limits and can be discharged into the public sewer or into aquatic bodies [16]. The major challenges existing in the treatment of textile industrial effluents are recycling and reuse of wastewater, removal of color and reduction of Total Dissolved Solids (TDS) in the treated effluent, generation of huge amount of sludge, large units have invested in Individual Effluent Treatment Units (IETPs) and medium scale units have invested in Common ETPs. However, no techno-economically viable option is

tons of fabrics produced per year, there are more

**190**
