Technology Of Dyeing By V A Shenai Pdf Download

Citation: Mia R, Selim M, Shamim AM, et al. Review on various types of pollution problem in textile dyeing & printing industries of Bangladesh and recommandation for mitigation. J Textile Eng Fashion Technol. 2019;5(4):220-226. DOI: 10.15406/jteft.2019.05.00205

This work is aimed at giving emphasis on the present pollution condition in dyeing & printing industries of Bangladesh due to different textile pollutant. Though the economy of our country is increasing day by day due to medium and small-scale industrial activities, the toxic waste discharge is contributing severe pollution to the environment by this dyeing & printing industry. The liquid & solid effluents from different industries are causing a major destruction to the environment, ecology, agriculture, aquaculture and public health since the development of textile industries in the country. So, it is high time to give a break to the pollution and time it out gradually to save the river system. It had become a prerequisite to take required steps to mitigate the pollution problems in each industrial establishment, particularly at dyeing and printing industries that are discharging massive amount of liquid effluent to the rivers every day. Here various types of pollution which is created by the textile dyeing & printing industries are discussed and some suggestions including raw materials purchasing, Eco-friendly dyeing etc. are point out for mitigation.

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Pollution is the mixture of contaminants in the natural environment that creates adverse effect in environment. Pollution can be formed from chemical substances or misuse of energy such as; noise heat and light Pollutants are the components of pollution. Nowadays different pollutions are creating many hazards to our environment and lives. The pollutants from dyeing, printing and finishing industries have become an alarming issue. Though color is the main attraction of any textile material, it may cause hazards to environment and living beings. We use different dyes for getting required color. In ancient time, natural dye was the main substance for dyeing textile materials. But because of insufficiency of natural dyes and increasing demand of dyed and printed textiles, only natural dyes are unable to fulfill the required demand of dyed and printed textile. So, nowadays a synthetic dye has taken the market of natural dyes. People have started using synthetic dye in every sector of textile dyeing and printing. But the problem is synthetic dye is very toxic and hazardous to our environment. The presence of different dyes like Sulphur, Azoic, indigoids, nitrates, acidic acid, soap, enzymes, complex compounds, heavy metals and certain auxiliary chemicals all are make the textile effluent highly toxic. Thus, the effluent from dyeing and printing industries carry many dyes and other additives which are added during the coloring process. These are to be delivered easily through lakes and rivers especially because they have high water solubility. They may also degrade to form products which are highly toxic and carcinogenic. Thus, these dyes are harmful for living organism. It is most important to save the environment from this effluents.1

Though the pollutants of these synthetic dyes are highly toxic, we cannot avoid using these during dyeing considering a very high demand of dyed and printed textiles and it is a major problem. For solving this problem, some mitigation processes must be taken through which we can prevent the surface of normal water by highly toxic dye water.2 To solve this problem, firstly it is essential to identify and quantify the chemicals in the waste waters. In Bangladesh, there has a lot of dyeing and printing industries where synthetic dyes are used in a wide range. Several schemes have been proposed in different countries to control the harm of these toxic dyes and chemicals to create better environment and protect the ecosystem from further degradation. So, a developing country like Bangladesh needs to apply their designed policies from the beginning. In our project, we will discuss about these pollution problems which cause harm to our environment and the mitigation processes regarding to the problems.

Dyeing industry: Till the midst of 19th century all the dyes used for textile products were produced naturally, until the invention of mauvine in1856.3 When the synthetic dyes have invented , after that people started using it in a wide range because these dyes are reasonably price, available in a lot of various colors and they have good color fastness. The textile industry is now producing & using 1.3 million tons of dyes and pigments per year, where most of them are synthetic as well as toxic. 10-25% textile dyes are wastage during the dyeing process and 2-20% is discharged as aqueous effluent. The discharge of dye containing effluent into the water is harmful because of their chemical nature and toxicity.4

Air pollution: Most processes performed in the wet processing industries produce gaseous emissions. The gaseous air has been identified as the 2nd greatest pollution problem for dyeing and printing industries. Air pollution occurs by the emission of different types of gases such as CO2, NO2, SO2 etc.6

Water pollution: The dyeing and printing industries use a huge amount of water in their manufacturing processes. The waste water from the dyeing and printing industries is identified as the most polluted water considering the volume generate as well as the effluent composition.7 In textile industry 2000000REF tons of dyes are turned to effluent every year during dyeing, finishing and printing operations, due to the inefficiency of dyeing process.

The increased demand of dyed product which is dyed by synthetic dyes produce wastewater after dyeing. This waste water is the main source of pollution problem in recent time. Because most of the industry use conventional waste water treatment plant. The dyes from different sources are stay in the long time in the environment because of their high thermal & photo stability.8

Water pollution: Water is consumed many more by textile industry. The percentage of water consumption is 3.2% for various processes such as Desizing, Bio-Polishing, scouring, bleaching, mercerizing, dyeing, printing and other finishing process in total water consumption. After using the water in different processes, it mixed with various dyes, chemicals or other auxiliaries, which are then contaminated & creates water pollution. In recent times, the use of synthetic dyes, synthetic fibers, and synthetic finishes are increased rapidly in textile industry (Figure 2).

Sources of air pollution: Different sources of air pollution mainly generated in weaving & spinning industry. Dust particles are available in yarn & fabric manufacturing unit. Though air pollution is little bit in wet processing industry, but it creates harmful effect on environment. The main source of air pollution in dyeing & printing industries is steam generation by coal and water. When the steam is generated, it produces carbon, carbon dioxide, carbon monoxide and Sulphur, which again cause air pollution.

Maintaining low-liquor ratio dyeing: The amount of chemical used depends on bath ratio. When the dyeing industry use less bath ratio, then less amount of chemicals is required in the dye bath. For that reason, environment is less polluted.

Salt management: Although salt is cheap, effective and has very low toxicity, it has to be used with optimum dosage for each individual for each dyeing. For this reason, the dyes which exhaust minimum salt in dyeing is recommended, e.g. Cibachrome LS dye.

Minimizing machine cleaning: In dyeing operations, start-ups, stop offs, and colour changes cause intensive cleanings and pollution in effluents. For minimizing effluents generation, the same color is repeatedly run in the same machine or group colours (red, yellow, blue) and then run the dyes within one colour family from lighter to darker values and from brighter to duller chromes.

Our ideas on pollution prevention: By assessing the literature, we see that the largest waste stream from most textile mills involved in washing, bleaching, and dyeing is wastewater. Textile mill wastewater is often contaminated with process chemicals (dye, salt, bleach, detergent, etc.), oil, and energy from hot water discharges. As a result, wastewater discharge permit limits, such as BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), aquatic toxicity, and metals content, are often difficult to meet. According to a research in Thailand, water usage in a typical mill can easily top 40,000 gallons per day costing more than $30,000 annually in water and sewer fees.

Another area where waste can be reduced is in chemical mixing. Adding excessive chemicals to recipes will increase cost and may cause quality problems. For complete exhaustion, Different dye mixtures have required different amounts of salt. There are many opportunities to reuse wastewater in a textile mill. For example, final rinse water from dyeing can be used as make-up water for the dye bath. Final rinses from scouring and bleaching may be used for makeup water in desizing. Wastewater from many sources may be suitable for washing process equipment and floors (after sweeping or another dry clean-up). As an example, we may add, in Viyellatex Group they do not discharge the treated effluent into the sewerage or local pond or river rather than they use that water as flash water in the toilet.18 This type of little steps can help to reduce the wastage of water where the process is very easy but the only lacking is a noble intention. Some mills have reduced operating costs substantially by installing water reuse systems.

The coloration of jute fiber is mainly carried out with basic dye in slightly acidic medium. As acid degraded the cellulose [5], there is a possibility to decrease the strength of jute fiber. Moreover, the dyeing process of jute with basic dye is complicated and many of the basic dyes are not fast to acids, alkalis, washing and particularly to light [6]. Again, the achievable color ranging with basic dye is not as wide as the reactive dye which is popular dyestuff for cellulose dyeing. Reactive dye is the worldwide acceptable dye for the coloration of cotton goods due to their ease of applicability, cost, brilliancy of color and high wet fastness properties [7]. However, in spite of being a cellulosic fiber, jute is normally not dyed with reactive dye. Reactive dyeing of jute is not economical for its high crystallinity and high degree of orientation [8] which is the hindrance of high color yield. Again the dye exhaustion is low due to presence of comparatively less amount of cellulose (58% - 63%) [1] than cotton (94%) [9]. It is not possible to increase the amount of cellulose in the fiber. However, increasing the percentage of dyesite in the fiber is a logical principle to improve the dye exhaustion of jute fiber. According to Bashar and Khan [10], the introduction of cationic sites within the cellulose is an effective way to increase the dye adsorption. Cationic sites can be introduced either by aminization or cationization [11]. Treatment of jute with chitosan is an aminization technique to introduce cationic site within the fiber polymer (Figure 1) structure and 17dc91bb1f