Joya Saha Barisal Textile Engineering College Email: joyasaha5966@gmail.com
Introduction
In recent years, there has been a growing awareness of the need for more sustainable and environment-friendly textile production methods. Eco-friendly textile dyeing and finishing refer to reducing water consumption, energy usage, and the release of harmful chemicals into the atmosphere, in conventional dyeing and finishing huge water pollution, energy consumption, and high water consumption.
Eco-Friendly Dyeing and Finishing Techniques
Use of natural dyes:
Natural dyes come from renewable resources such as plants, insects, animals, and minerals. Examples are indigo, madder, and cochineal. These dyes are biodegradable, non-toxic and making them a sustainable alternative to synthetic dyes. Natural dyes can be less consistent in color fastness and may require mordants which can sometimes be harmful.
Low-impact dyes:
Low-impact dyes are synthetic dyes that require less water, and less energy and produce less waste. These dyes are released from toxic chemicals and heavy metals. They achieve higher fixation rates, which mean more dye adheres to the fabric and less washes out into water. Examples are reactive dyes and acid dyes that bond directly with fibers at lower temperatures.
Ultrasonic waves:
The use of ultrasonic energy as a renewable source of power in textile dyeing has increased due to the increased pollution. On the other hand, for the health safety of textile garments as an alternative to harmful synthetic dyes, there is a growing natural dye, eco-friendly dyeing. Ultrasound is a sound wave that has a frequency above 20 kHz which frequency humans cannot hear humans. Ultrasonic waves can also be focused, reflected, and refracted but to reflect, refract, and focus they require a medium with elastic properties for their spread. Particles in the elastic medium oscillate and transfer energy through the medium in the direction of propagation when ultrasonic waves propagate. The waves can be distinguished as below.
In longitudinal waves, the particles vibrate in a direction parallel to the direction of propagation of the wave.
In transverse the particles vibrate in a direction perpendicular to the direction of wave propagation.
During each cycle of the wave, there is a compression or rarefaction. Rarefaction regions of low pressure can increase the formation of bubbles. These bubbles expand and finally, during the compression phase, bubbles violently collapse generating shock waves. The aspect of bubble formation and collapse is known as cavitation and cavitation is generally considered responsible for most of the physical and chemical effects in solid/liquid systems.
Advantages
Dyeing at lower temperatures saves energy
Reduced processing times.
Reduces the use of auxiliary chemicals.
Increasing of color shade.
Reduces costs.
Lower load to the effluent
Air dye technology:
Air dye technology operates the application of color to textiles without the use of water. Depending on the fabric, and type of dyeing, Air Dye uses up to 95% less water, and up to 86% less energy, contributing 84% less to global warming. According to an independent evaluation requested by the company. Air-dyed fabrics do not filter colors or fade as easily as vat-dyed fabrics because the dye is actually inside the fibers. The color application process does not pollute water. Using air instead of water to convey dye, no hazardous waste is emitted and no water is wasted.
Supercritical fluid:
Supercritical fluids are highly compressed gases that have properties of liquid and gas. Beyond a substance’s critical point by increasing temperature and pressure they are created.
Dyeing with supercritical CO2:
Supercritical fluid CO2 provides polyester to be dyed with modified dispersed dyes.
The supercritical fluid CO2 causes the polymer fiber to swell allowing the dispersed dye to easily diffuse within the polymer, penetrating the pore and capillary structure of the fibers.
The viscosity of the dye solution is smaller, it make the flow of the dye solutions easier and less energy-intensive. This deep penetration gives essential coloration to polymers. Dyeing and removing additional dye are done in the same vessel.
Rest dye is minimal and may be removed and recycled. Supercritical CO2 dyeing gives excellent results dye evenness, and shade improvement, and the physical properties of dyed yarns are equivalent to conventional methods.
Plasma technology:
Plasma is a relatively ionized gas consisting of positive ions. Plasma treatment has improved recently for textile processing due to its cost-saving, water-saving, and eco-friendliness. The preparatory process of fabrics, such as scouring, de-sizing, bleaching, dyeing/ printing, and finishing expend enormous amounts of water, produce pollution through discharge, and consume large amounts of energy. Plasma technology is carried out in a dry process, is energy efficient, requires a minimum amount of chemicals, and reduces pollution. For dyeing and finishing treatments to create suitable reactive surface require modification. For increasing some of the properties such as strength, hydrophobicity, hydrophilicity, antistatic properties, adhesion properties, dyeing, and printing ability of the fabrics used by plasma technology in the textile industry. To modify the surface, It is activated to textile fabrics which helps to increase the functional properties. Plasma technology minimizes the consumption of energy and other resources during the textile dyeing and finishing process.
The textile finishing sector uses different chemicals, which are harmful to the environment. Sometimes they may affect the textile material if not used properly. We can use enzymes instead of using such chemicals. When enzymes are used under the required conditions enzymes are very specific in action. In de-sizing, scouring, bleaching, washing, and degumming processes can be used enzymes.
Desizing is the process of removing sizing materials such as starch from fabric. The extensively used enzyme for the desizing process is a hydrolytic enzyme called amylase. It catalyzes the disruption of dietary starch to short-chain sugars, dextrin, and maltose which gives uniform wet processing. The advantage of these enzymes is that they are particular for starch, removing without damaging fabric. For desizing processes an amylase enzyme can be used at low-temperature (30- 60ºC) and maximum pH is 5.5-6.5.
Scouring means the removal of non-cellulosic material. Enzymes cellulase and pectinase are combined and used for bioscouring. The traditional scouring of cotton includes the use of dangerous chemicals that increase biological oxygen demand (BOD), chemical oxygen demand (COD) & total dissolved solids (TDS) in wastewater, and increasing overall cost & pollution of the environment. Enzymatic scouring gives a very comfortable handle compared to the harsh feel of the alkaline scouring process.
Cotton bleaching is done to remove natural pigments and give a pure white appearance to the fibers. Mainly flavonoids are accountable for the colour of cotton. H2O2 is used for bleaching to obtain the most adequate dyeing & to eliminate the complexity of treatment its residues must be removed. The traditional processing of cotton bleaching requires high amounts of alkaline chemicals and generates a huge amount of rinse water. The conventional bleaching agent uses an enzymatic bleaching system which would result in better result in product quality due to less fibre damage and savings on washing water needed for the elimination of hydrogen peroxide.
By the use of enzymes, dyeing can be done in the same bath resulting in less water consumption and less power to dye fabric. Lowering the amount of pollution produced.
Nanotechnology
Nanotechnology is used in textile fiber on a nanoscale for measuring diameters in the range of 1 to 100 nm. The use of nanotechnology has grown in textiles industry rapidly due to its unique and valuable properties. Nanoparticles have a large surface area-to-volume ratio and high surface energy. Thus contributing to a better affinity for fabrics and directing an increase in the durability of the function of finishes. Some nanoparticles used for imparting these textile finishes are:
Nanoparticles Properties
Silver Nanoparticles Anti-bacterial
Fe Nanoparticles Conductive magnetic properties
ZnO and TiO2 Nanoparticles UV protection, fiber protection, oxidative catalysis
TiO2 and MgO Nanoparticles Chemical and biological protective performance, self-sterilizing function.
SiO2 or Al2O3 Nanoparticles with PP or PE coating Super water repellent finishing, moth proofing
Indium-tin oxide Nanoparticles IR protective clothing
Ceramic Nanoparticles Resistance to abrasion
Carbon black Nanoparticles are resistant to abrasion, and chemicals and impart electrical conductivity.
Clay Nanoparticles have huge electrical, heat, and chemical resistance, anti-moth
Ultraviolet light radiation is absorbed from the sun by the ozone layer. Consequently damaging the earth’s protective ozone layer. The reduction of the ozone layer in the upper atmosphere has led to increased danger of exposure of skin to UV radiation as a result of increasing risk of skin cancer. So, the importance of UV protective finish has substantially extended. Protection of the skin against the action of solar radiation is a new objective of textile finishing since the textile does not always guarantee adequate protection. So specific protective functions of textiles against solar radiation. Ultraviolet radiation is short wavelength light between 290-400 nm. The ultraviolet radiation (UVR) band consists of three regions: UV-A (320 to 400 nm), UV-B (290 to 320 nm) and UV-C (100 to 290 nm). The most damaging type of UV radiation is short wavelength uv-c. UVA is the long wave UV wavelength (320–395nm) and UV makes about 95% of the UV radiation that reaches the Earth. Because of its possibility to penetrate the dermis layer of skin UVA is the main factor to causes skin aging, creese, and skin cancer. UVB is the mid-strength UV wavelength (280–320nm) most of which is absorbed by the atmosphere. While reaching the skin, it can only penetrate the epidermis layer and burns the superficial layers of skin. UVC is a short wavelength (200–280nm), is absorbed by the ozone layer, and does not come to the earth. To improve the UV blocking property of fabrics is to coat the surface with nanoparticles of inorganic is one of the method. Oxides such as TiO, ZnO, SiO, and Al₂O. Among these TiO and ZnO are commonly used as they absorb and scatter UV radiation than the conventional size and are better able to block UV. Nanoparticles have a larger surface area than conventional materials, leading to an increase in the effectiveness of blocking UV radiation.
Anti-static finsih:
In synthetic fibers such as polyester, polyamide static charge builds up because they have little moisture content. In cellulosic fibers, no static charges will gather because they have higher moisture content. Synthetic fibers have poor anti-static properties. Nanoparticles electrically conductive materials and waste the static charge that gathers on the fabric. TiO2, ZnO, and nano antimony-doped tin oxide (ATO) give anti-static effects because they are electrically conductive materials. Such materials effectively deplete the static charge which is gathered on the fabric.
Flame retardant finishes:
When a fabric is subjected to flame or heat source it does not burn. This means fabric resistance. A chemical applied in fabric to impart flame is called a flame retardant.
Fig: Flame retardant finishes
Conclusion
Eco-friendly textile dyeing and finishing have more advantages in developing the textile industry. In traditional dyeing and finishing water pollution, air pollution, and energy consumption. These problems are created. It has been found that the required scientific studies and systematic reports on the dyeing of textiles with eco-friendly natural dyes are still inadequate. There are lots of unharnessed natural products. As a result of the present excessive use of synthetic dyes, the production and application of synthetic dyes release vast amounts of waste and unfixed colorants causing serious health hazards and troubling the eco-balance of nature. Nowadays, there is increasing awareness among people towards the use of eco-friendly natural dyes as a result better biodegradability. They are non-toxic and nonallergic to the skin. Continuing research paving the way for eco-friendly textile dyeing and finishing.
References:
[1] Gunay, M. (2013). Eco-Friendly textile dyeing and finishing. BoD – Books on Demand.
[2] Buyle, G. (2009). Nanoscale finishing of textiles via plasma treatment. Materials Technology, 24(1), 46–51. https://doi.org/10.1179/175355509×417954
[3] Mohammad M. Hassan, Khaled Saifullah, Ultrasound-assisted sustainable and energy efficient pre-treatments, dyeing, and finishing of textiles – A comprehensive review, Sustainable Chemistry and Pharmacy, Volume 33, 2023, 101109, ISSN 2352-5541, https://doi.org/10.1016/j.scp.2023.101109.
[4] Liberato V. Haule, Lutamyo Nambela, Chapter 8 – Sustainable application of nanomaterial for finishing of textile material, Editor(s): Uma Shanker, Chaudhery Mustansar Hussain, Manviri Rani, In Micro and Nano Technologies, Green Nanomaterials for Industrial Applications, Elsevier, 2022, Pages 177-206, ISBN 9780128232965, https://doi.org/10.1016/B978-0-12-823296-5.00011-3.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
