ECO-FRIENDLY CHEMICAL PROCESSING ON TEXTILE
The textile industry is currently facing a challenging environment with regards to quality and productivity due to the globalization of the world market. The highly competitive atmosphere, combined with the increasing need for ecological parameters, makes it imperative for textile processors to be mindful of both quality and ecology. Pollution control boards’ guidelines for the textile processing industries further exacerbate concerns about the environment-friendliness of the processes. As a result, the textile industry must innovate and change their processes to meet these challenges, and this is where biotechnology comes in.
Biotechnology is one field that is revolutionizing conventional processing into eco-friendly processing of textiles. To achieve eco-friendly processes, enzymes are used in wet processing of textiles. Enzyme formulations are used in different processes such as bio-bleaching, dyeing, rove scouring, finishing, neps removal, printing, wash-off treatment, dye synthesis, and effluent treatment. With increased environmental awareness, government legislations, and global competition, innovations for pollution reduction have become a necessity.
Green technology, which refers to eco-friendly technology, is achieved by using enzymes in enzymatic processing. Enzymatic processing involves the application of biological organisms, systems, or processes to manufacturing industries. Enzymatic processing firms will rely mainly on inexpensive substrates for biosynthesis, processes that will function at low temperatures, and will consume little energy.
Enzymes are protein substances made up of more than 250 amino acids. They are classified based on their specificity, and the concept of treating fabrics with enzymes to improve their surface properties was first developed in Japan in 1989. Enzymatic treatment has become more important due to present concerns for a clean and eco-friendly environment.
Enzymatic processing offers several advantages over conventional chemical processing, including lower energy and water consumption, reduced waste generation, and improved product quality. Enzymatic processes are also milder, resulting in less damage to the fabric and reduced processing times. The use of enzymes in textile processing offers a more sustainable and eco-friendly alternative to conventional chemical processing.
Enzymes play a significant role in the textile industry, and their application is classified into six categories. The first is Oxido Reductases, which facilitate oxidation-reduction reactions by transferring atoms or electrons. The second group is Transferases, which transfer groups containing C, N, P, or S from one substrate to another. The third category is Hydrolases, which catalyze cleavage reactions by hydrolysis. The fourth category, Lyases, removes groups from substrates without hydrolysis or oxidation. Isomerases, the fifth category, catalyze intermolecular rearrangements to form an isomer, while Ligases split C-C, C-O, C-N, C-S, or C-halogen bonds without hydrolysis or oxidation.
The use of enzymes in the textile industry has numerous benefits, including being highly specific with minimal side effects, low energy requirements, safe handling, and non-corrosive applications. They also reduce the loads on Effluent Treatment Plant (ETP) plants due to the reduced use of chemicals, and enzymes are easily biodegradable. However, enzymes are highly sensitive to pH, heavy metal contamination, and temperature, and caution is necessary in their application. Live steam should never be injected into a bath containing enzymes, and compatibility with ionic surfactants is limited and must be checked before use.
One of the most commonly used enzymes in textile processing is Amylases, which are employed as desizing agents to remove starch from fabrics after weaving. Starch is a polysaccharide composed of glucose units primarily linked by a (1–4) glucosidic bond with a (1–6) linked side chain. Amylopectin, which accounts for around 70-80% of starch, contains branches at about every 20-24th glucose residue, while amylose is a more linear polymer. Amylases, including α-amylases, β-amylases, and glucoamylase, are hydrolase enzymes that hydrolyze 1-4 α glucosidic linkage of amylase and amylopectin of starch to convert them into soluble dextrins. Various commercially available amylases find applications in textiles.
Enzymes are biological catalysts that can speed up chemical reactions. They are widely used in various industries, including textiles. In textiles, enzymes are used to modify fibers and fabrics to improve their properties. There are different types of enzymes used in the textile industry, including amylases, cellulases, pectinases, proteases, peroxidases, catalases, and laccases.
Amylases are enzymes that catalyze the hydrolysis of starch. There are three types of amylases used in the textile industry: thermostable amylases, conventional amylases, and low-temperature amylases. Thermostable amylases can work at high temperatures, between 70-110°C, and at a pH range of 6.0-6.8. Conventional amylases work at lower temperatures, between 50-70°C, and at the same pH range. Low-temperature amylases, which are mostly fungal amylases, work at temperatures between 30-70°C.
Cellulases are enzymes that cleave the β-glucosidic linkage of cellobiose chains or cellulose. Commercially available cellulases are a mixture of three types of enzymes: endoglucanases, exoglucanases, and cellobiases. Endoglucanases randomly attack cellulose enzymes and hydrolyze the β-glucosidic linkage of cellobiose chains. Exoglucanases of cello-biohydrolases hydrolyze the β-glucosidic linkage of cellulose to release cellobiose from the cellulose chain. Cellobiases hydrolyze cellobiose into soluble glucose units. All three enzymes work together synergistically to hydrolyze cellulose. Acid cellulases and neutral cellulases are two types of cellulases that find major applications in textiles.
Pectinases are a mixture of enzymes that are widely used in the fruit juice industry. Polygalacturonases, pectin methyl esterase, and pectin lyases are the three types of enzymes found in this group. These enzymes act on pectins, which are large polysaccharide molecules made up of chains of galacturonic acid residues, found in the primary cell walls of cotton and jute.
Proteases are enzymes that hydrolyze peptide bonds formed by specific amino acids. Commercial proteases are available that can work in different ranges of pH and temperature. Trypsin (pancreatic), papain-based, and alkaline proteases are three types of proteases that find industrial applications in textiles.
Peroxidases or catalases are oxidoreductase class of enzymes that effectively degrade hydrogen peroxide to water and molecular oxygen. Catalases are hem-containing enzymes containing a non-protein part that is a derivative of heme, including the metal iron. These enzymes can degrade hydrogen peroxide at different pH ranges and temperatures.
Laccases are oxidoreductase class of enzymes belonging to blue oxidase-copper metalloenzymes. They find applications in various industries, including textiles, due to their ability to oxidize phenolic compounds.
Enzymes are essential biological catalysts that accelerate the rate of chemical reactions in living systems without undergoing any permanent chemical changes themselves. They work by forming a specific complex with the substrate, known as the “lock and key” model, or through the “induced-fit” theory proposed by Koshland Jr. Enzymes can catalyze chemical reactions under mild aqueous conditions, eliminating the need for high temperatures, extreme pH values, or chemical solvents. This makes enzymes highly desirable for chemists. For example, thermostable amylases catalyze starch hydrolysis in the temperature range of 70-110oC and at pH 6.0-6.8, while neutral cellulases work in the pH range of 6.0-7.0 and at a temperature range of 40-55oC. Enzymes such as peroxidases and laccases, which are oxidoreductase class of enzymes, have specific applications in textile industries. The peroxidase enzyme decomposes hydrogen peroxide into water and molecular oxygen, while laccases are active at pH 3-5 and in the optimal temperature range of 30-50oC, and oxidize using molecular oxygen as an electron acceptor from the substrate.
Enzymes are being utilized in the textile industry for eco-friendly wet processing techniques. One such technique is bio-singeing, which is a method of achieving clearer pile on terry towel goods without burning protruding fibers. This method involves treating the fabric with a powerful cellulose composition enzyme, which also improves the absorbency and softness of the fabric.
Desizing cotton with amylases is another technique that has been in use for almost a century. Enzymes, mainly of bacterial origin such as Bacillus subtilis, are used to remove starch and its derivatives from woven fabrics. Today, a range of amylases is available that act at different temperatures, from 20°C up to 115°C. The optimal pH for the treatment ranges between 5 and 7, depending on the enzyme used. Enzymatic desizing is the preferred method in wet processing prior to dyeing, especially when high levels of dye fastness are required. Incomplete removal of starch might cause friction fastness problems.
Desizing enzymes come in different forms and can act at various temperatures, from room temperature in batch form to high temperatures for continuous desizing. One method of enzymatic desizing involves padding the fabric with an enzyme solution at pH 6-7 and batch processing for 20-24 hours at room temperature. The fabric is then washed in a jigger. Another method involves desizing using a jigger or jet with an enzyme concentration of 5%, wetting agent of 1%, and pH 6-7%.
textiles. Therefore, bleaching is often required to achieve the desired whiteness or brightness of the fabric. Traditionally, bleaching is done using harsh chemicals like chlorine, which is harmful to the environment. However, enzymatic bleaching with laccases has emerged as an eco-friendly alternative.
Laccases are oxidoreductase enzymes that catalyze the oxidation of phenolic compounds with the concomitant reduction of molecular oxygen to water. They are capable of decolorizing and degrading a wide range of substrates, including lignin, dyes, and textile auxiliaries.
Enzymatic bleaching with laccases offers several advantages over conventional bleaching methods. It is a mild and selective process that does not damage the fibers, resulting in improved fabric quality and longer lifespan. It also reduces the need for harsh chemicals, which decreases the environmental impact and improves the sustainability of the textile industry.
Enzymatic bleaching with laccases is carried out at a pH range of 4-7 and a temperature range of 20-50°C. The process can be optimized by adjusting the enzyme concentration, reaction time, and temperature. Laccases can also be used in combination with other enzymes or chemical agents to achieve better results.
In conclusion, enzymatic wet processing using various enzymes such as amylases, lipases, pectinases, and laccases has emerged as a promising eco-friendly alternative to conventional textile processing methods. It offers several advantages such as milder processes, reduced environmental impact, improved fabric quality, and longer lifespan. With further research and development, enzymatic wet processing has the potential to revolutionize the textile industry towards a more sustainable future.
dye molecules present in the fabric to reveal the underlying fabric color, creating a white or lighter-colored pattern on a colored background. This is achieved by using a chemical agent that destroys the dye and leaves the fabric underneath untouched. The most commonly used discharge agent is sodium bisulfite, which is applied to the fabric through the screen after the printing paste has been applied. The fabric is then steamed to fix the print, and washed to remove any excess chemicals and to achieve the desired hand feel.
Advantages of discharge printing:
- Allows for intricate and detailed designs
- Can create a soft hand feel on the fabric
- Can be used on a variety of fabric types, including cotton, silk, and rayon
- Results in a unique and distinctive look
Disadvantages of discharge printing:
- Can be difficult to control the discharge agent and achieve consistent results
- Can be harmful to the environment if proper precautions are not taken
- Requires additional processing steps and chemicals
- May not be suitable for all dye types or fabric colors.
scouring process and showed effective removal of undyable neps without any adverse effect on the dyeability or strength properties of the cotton fabric. Laccases are copper-containing oxidase enzymes that can break down lignin and other phenolic compounds. The laccase treatment can be combined with conventional scouring and bleaching processes or used as a standalone treatment.
Another enzyme, endo-1,4-beta-glucanase, has also been studied for its potential to remove neps from cotton fabric. This enzyme can selectively hydrolyze the cellulose chains in neps without affecting the surrounding cotton fibers. Endo-1,4-beta-glucanase has shown to be effective in reducing neps while maintaining the strength properties of the cotton fabric.
In conclusion, enzymes play an important role in cotton finishing processes by providing sustainable and efficient solutions for various fabric properties. From softening to dyeing, enzymes can reduce the environmental impact of cotton finishing while improving the quality and performance of cotton fabrics. Ongoing research on new enzyme formulations and applications continues to expand the possibilities for cotton finishing.
well as the reaction conditions play a crucial role in the laccase-catalyzed decolourisation of textile dyes. Overall, the use of laccase for the decolourisation of textile effluent offers a promising alternative to traditional methods that often involve harsh chemicals and can be detrimental to the environment.
In summary, laccase is an enzyme that has shown promise in various applications in the textile industry, such as bioscouring, rove scouring, anti-shrink treatment for wool, and decolourisation of textile effluent. Its ability to work under mild reaction conditions and its environmentally friendly nature make it an attractive alternative to traditional methods. However, further research is needed to optimize the use of laccase in these applications and to explore its potential in other areas of textile processing.
and eco-friendliness. Therefore, research is ongoing to identify more suitable and efficient mediators.
ii) Enzyme immobilization is a promising technique in the development of biocatalysts for textile wastewater treatment. However, further research is required to optimize the immobilization process, increase the stability of the immobilized enzymes, and reduce the cost of immobilization.
iii) Nanotechnology can be utilized to enhance the catalytic activity of enzymes and improve their stability under harsh conditions. Nanoparticles can be used to encapsulate the enzymes, protect them from denaturation, and improve their reusability.
iv) Bioinformatics can be used to identify novel enzymes with enhanced catalytic activity and specificity for textile dye degradation. In silico screening of microbial genomes can accelerate the discovery of new enzymes and reduce the time and cost of enzyme development.
v) Integration of enzymatic treatment with other advanced oxidation processes (AOPs) such as photocatalysis, ozonation, and electrochemical oxidation can enhance the efficiency and effectiveness of textile wastewater treatment.
In conclusion, enzymatic treatment of textile wastewater is a promising technology that can provide a sustainable and eco-friendly alternative to conventional chemical treatments. However, further research is required to optimize the enzyme systems, enhance their stability and reusability, and reduce the cost of enzyme production and immobilization.
In conclusion, the use of enzymes in textile processing shows great potential in reducing the environmental impact of the industry. Enzymatic treatments can reduce the use of hazardous chemicals and reduce energy, water, and chemical consumption. However, there are still some challenges to be addressed, such as the high initial cost of enzymatic processing and the need to identify suitable mediators for efficient and non-toxic enzymatic treatments. Further research and development are needed to enhance the activity of enzymes, reduce production costs, and create more versatile and rugged multifunctional enzymes. Ultimately, the continued progress in biotechnology will pave the way for the total replacement of hazardous chemicals with eco-friendly enzyme-based treatments, leading to a cleaner and more sustainable textile industry.
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