Fi bres and dissolving dyes this water is released in

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fi bres and dissolving dyes. This water is released in large amounts and causes most of the water pollution. The water released carries with it most of the toxic chemicals and therefore needs to be treated. The wastewater treatment is usually done through primary, secondary and tertiary stages. However, these treatment processes do not remove many of toxic materials such as dissolved solids and trace metals. This calls for advanced treat- ment technologies for the treatment of wastewater ef fl uent from textile industries. Currently, studies are conducted to explore the possibilities of using nanomaterials for treating wastewater from textile industries. Some of the techniques include the use of nanochemicals for photocatalysis, nanosorbents for adsorption and zeolites for pollutants removal. Also, several treatment technologies are combined together to form the zero liquid discharge process to purify and recycle virtually all of the wastewater produced. Fig. 1 Percentage of textile industries distributed by state. Source: Ibid 62 P. Senthil Kumar et al.
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2 An Overview of the Textile Industry The textile industry can be subdivided into different sectors based on the raw material being processed: the cotton industry, woollen industries, synthetic fabric industries, etc. These industries consist of a string of elaborate processes to produce the fi nal product as shown in Fig. 2 . The major process among them is the textile printing and dyeing process. Some of the steps involved in these two processes are pre-treatment, the dyeing and printing processes, fi nishing. Pre-treatment is carried out by washing, desizing, scouring and other processes. These processes require large amounts of water. Dyeing is done to transfer the desired colour to the required fabric and produce the coloured fabric. For this purpose, the dye is dissolved in water. Printing on the other hand is a kind of dyeing Fig. 2 Textile industry fl ow chart (Babu et al. 2007 ) Nanochemicals and Ef fl uent Treatment in Textile Industries 63
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which is concentrated on a single portion of the fabric that makes up the design. In dyeing, the colour is applied using a solution of the dye, where the dye is suspended in water. Printing on the other hand employs the dye in the form of a thick paste. After the dyeing or printing processes, it is important for the fabric to undergo the fi nishing processes. The fi nishing processes are necessary to impart speci fi c prop- erties to the fabric such as strength, softness and durability. The fi nishing process is carried out using several fi nishing agents for softening, creating cross-links within the fabric and waterproo fi ng. All these processes require some amount of water and therefore can lead to release of harmful chemicals and toxins into the ef fl uent stream, essentially requiring effective water treatment. In some cases, mercerization, base reduction processes are carried out before dyeing and printing.
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  • Fall '19
  • N. Gokarneshan

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