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Environmental impact of fashion |
Green textiles are fabrics or fibres produced to replace environmentally harmful textiles and minimise the ecological impact. Green textiles (or eco-textiles) are part of the sustainable fashion and eco-friendly trends, providing alternatives to the otherwise pollution-heavy products of conventional textile industry, which is deemed the most ecologically damaging industry.
Green textiles may also refer to clothing or accessories designed to use organic or recycled materials, less packaging and more energy-efficient manufacturing.
Silk is a traditional textile material made up of silk fibroin and sericin. [1] The two materials in silk typically require prior separation before the silk can be further processed for clothing. Traditional textile methods involve soap, alkali, or both to degum textile silk. Ultrasonic degumming is a greener degumming process that is being researched. It includes degumming via sonification, which controls the rapid sol-gel transition of silk fibroin to form a hydrogel, regulating the protein structure to obtain protein-based materials.
Hemp (Cannabis sativa) is a material used to produce fabrics at a lower cost than synthesis polymers. Hemp fibers are composed of cellulose, hemicellulose, pectin, lignin, and ester wax. The presence of cellulose allows hemp to have good water absorbency, comfort, and stability during textile processing. Ongoing research is being done on the incorporation of natural pomegranate extract into hemp fabrics to improve their dyeability and antibacterial properties. [2]
Lyocell is a light cellulose fiber that is created by dissolving wood pulp. There are three general approaches to creating lyocell: physical blending, chemical reaction, and post-treatment. [3] Lyocell is being favoured, rather than its predecessor, viscose fibre, because lyocell's manufacturing process does not involve volatile and odiferous carbon disulfide. Lyocell is 50% more absorbent than traditional cotton and requires less energy and water to produce, i.e. the chemicals used to produce the fibers are managed in a closed-loop system. [4]
Green textiles are treated with green-synthesized nanoparticles. Nanoparticles are considered to be easy to synthesize, eco-friendly, and biocompatible in nature. Since textiles are host materials for the development of microbial infection, there is a need for antimicrobial clothing. Coating textile surfaces using nanoparticles or in-situ synthesis of nanoparticles with fabrics is an emerging tactic in yielding highly-finished green textiles.
Types of Nanoparticles
1. Silver Nanoparticles
Silver nanoparticles, also known as Nano Silver, are commonly used in biomedical fields due to their outstanding antimicrobial nature. [5] They are also applicable in textiles, cosmetics, electronics, paints, the food industry, and medicinal fields. Nano Silver is synthesized by polysaccharides extracted from different marine macroalgae (Colpomenia sinuosa, Jania rubins, 'Pterocladia capillacae, and Ulva fasciata). Clusters of silver-poly(acrylates) can be synthesized via the reduction of Silver nitrate. [6] Nano Silver is the most common nanoparticle used in green textiles. It is a natural antimicrobial agent that acts as a catalyst for deactivating fungi, viruses, and bacteria required for oxygen intake. It also does not harm the human body's chemistry.
2. Gold Nanoparticles
Gold particles, called Collodial gold when dispersed in water, are used in the textile industry. Particle diameter varies from 1 to 100 nm. Textile functionalization using gold nanoparticles has improved in the recent years. Green synthesis of gold nanoparticles is performed on cotton fabrics by in-situ synthesis for functionalization, popularized for cellulose material. [7] It is treated by washing cotton fabric with HAuCl4 aqueous solutions in various concentrations. Gold particles were revealed with effective reduction of 4-nitrophenol by using Sodium borohydride. Cotton fabrics treated by gold nanoparticles resulted in improved antibacterial activity, UV-blocking ability of the fabric, and improved Raman signs of dyes on fabric.
Laccase is a multi-copper oxidase that catalyzes the oxidation of one electron of a wide range of phenolic and non-phenolic compounds to radical forms. The enzyme requires a molecule of oxygen as a co-substrate for catalysis and yields water as the sole by-product. Laccase-catalyzed synthesis of dye molecules represents a greener choice to reduce the environmental footprint of conventional synthesis processes. Laccase is considered to meet the textile industry's needs in terms of productivity, as it has proven to efficiently color nylon and wool fibers. Laccase has also proven to be difficult in keeping a low purity and homogeneity of the produced dyes.
Wet processing is the treatment of textile substrates with colorants and chemicals. [9] In conventional wet processing of textiles, excessive amounts of toxic and hazardous chemicals are utilized, and extremely large amounts of water are consumed.
Introduction of new bi- and multi-functional reactive dyes have significantly reduced energy and water consumption by at least half. This is caused by its enhanced properties in dye exhaustion, allowing for lower temperature conditions to be used. [10]
Discovery of biodegradable dyes with improved fixation qualities. Alternative dye options such as pre-reduced sulfur and water-insoluble dyes that do not require reducing agents have made dyeing processes much more eco-friendly. Green reducing agents such as sugar-based reducing agents are commonly used to replace non-eco-friendly reducing agents like sodium sulfate. [11]
Ionic liquids have been used as green solvents in making wet processing more sustainable. Research established that non-aqueous solvents could potentially replace water consumption in wet processing. [12] This results in saving energy through indirect decrease in the usage of water. Ionic liquids possess high dissolving properties, are non-volatile, and have low vapor pressure which labelling them as recoverable green solvents that produces no emissions and are eco-toxic. [13]
Via Neutralization
Neutralization is the primary treatment where the suspended solids are eliminated via the technique of sedimentation, flotation, flocculation, and coagulation techniques.
Anaerobic Bacteria
The secondary treatment process is to utilize anaerobic bacteria, and microorganisms, on the surface of sewage waters. The role of this bacteria is to reduce the amount of sludge and the ability to produce methane gas. This in turn can be used as an alternative energy source. An additional advantage to this treatment is that phosphorus can be removed as well. [14]
Oxidation
The tertiary treatment for water pollution is through the use of redox reactions. Using redox reactions, chemical oxidation can be used to remove the color and odor, organic and inorganic compounds from wastewater. This is treated using specific ranges of pH to precipitate. [15] Carbon oxidation can also be utilized. By using activated carbons from a range of commercial carbon-based porous-material, organic micropollutants can be removed from wastewater. The benefit is that it does not generate oxidation byproducts, thus different from a usual oxidation process.
A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and may require a mordant to improve the fastness of the dye on the fiber.
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the only manufacturing method, and many other methods were later developed to form textile structures based on their intended use. Knitting and non-woven are other popular types of fabric manufacturing. In the contemporary world, textiles satisfy the material needs for versatile applications, from simple daily clothing to bulletproof jackets, spacesuits, and doctor's gowns.
Fiber or fibre is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.
Rayon, also called viscose and commercialised in some countries as sabra silk or cactus silk, is a semi-synthetic fiber, made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecular structure as cellulose. Many types and grades of viscose fibers and films exist. Some imitate the feel and texture of natural fibers such as silk, wool, cotton, and linen. The types that resemble silk are often called artificial silk.
Dry cleaning is any cleaning process for clothing and textiles using a solvent other than water.
In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and as a frame material for eyeglasses; it is also used as a synthetic fiber in the manufacture of cigarette filters and playing cards. In photographic film, cellulose acetate film replaced nitrate film in the 1950s, being far less flammable and cheaper to produce.
Lyocell is a semi-synthetic fiber used to make textiles for clothing and other purposes. It is a form of regenerated cellulose made by dissolving pulp and dry jet-wet spinning. Unlike rayon made by some of the more common viscose processes, Lyocell production does not use carbon disulfide, which is toxic to workers and the environment. Lyocell was originally trademarked as Tencel in 1982.
Dyeing is the application of dyes or pigments on textile materials such as fibers, yarns, and fabrics with the goal of achieving color with desired color fastness. Dyeing is normally done in a special solution containing dyes and particular chemical material. Dye molecules are fixed to the fiber by absorption, diffusion, or bonding with temperature and time being key controlling factors. The bond between dye molecule and fiber may be strong or weak, depending on the dye used. Dyeing and printing are different applications; in printing, color is applied to a localized area with desired patterns. In dyeing, it is applied to the entire textile.
N-Methylmorpholine N-oxide (more correctly 4-methylmorpholine 4-oxide), NMO or NMMO is an organic compound. This heterocyclic amine oxide and morpholine derivative is used in organic chemistry as a co-oxidant and sacrificial catalyst in oxidation reactions for instance in osmium tetroxide oxidations and the Sharpless asymmetric dihydroxylation or oxidations with TPAP. NMO is commercially supplied both as a monohydrate C5H11NO2·H2O and as the anhydrous compound. The monohydrate is used as a solvent for cellulose in the lyocell process to produce cellulose fibers.
Nanofabrics are textiles engineered with small particles that give ordinary materials advantageous properties such as superhydrophobicity, odor and moisture elimination, increased elasticity and strength, and bacterial resistance. Depending on the desired property, a nanofabric is either constructed from nanoscopic fibers called nanofibers, or is formed by applying a solution containing nanoparticles to a regular fabric. Nanofabrics research is an interdisciplinary effort involving bioengineering, molecular chemistry, physics, electrical engineering, computer science, and systems engineering. Applications of nanofabrics have the potential to revolutionize textile manufacturing and areas of medicine such as drug delivery and tissue engineering.
In biochemistry, a cross-linked enzyme aggregate is an immobilized enzyme prepared via cross-linking of the physical enzyme aggregates with a difunctional cross-linker. They can be used as stereoselective industrial biocatalysts.
Janus particles are special types of nanoparticles or microparticles whose surfaces have two or more distinct physical properties. This unique surface of Janus particles allows two different types of chemistry to occur on the same particle. The simplest case of a Janus particle is achieved by dividing the particle into two distinct parts, each of them either made of a different material, or bearing different functional groups. For example, a Janus particle may have one-half of its surface composed of hydrophilic groups and the other half hydrophobic groups, the particles might have two surfaces of different color, fluorescence, or magnetic properties. This gives these particles unique properties related to their asymmetric structure and/or functionalization.
Bamboo textile is any cloth, yarn or clothing made from bamboo fibres. While historically used only for structural elements, such as bustles and the ribs of corsets, in recent years different technologies have been developed that allow bamboo fibre to be used for a wide range of textile and fashion applications.
In textile manufacturing, finishing refers to the processes that convert the woven or knitted cloth into a usable material and more specifically to any process performed after dyeing the yarn or fabric to improve the look, performance, or "hand" (feel) of the finish textile or clothing. The precise meaning depends on context.
Silver nanoparticles are nanoparticles of silver of between 1 nm and 100 nm in size. While frequently described as being 'silver' some are composed of a large percentage of silver oxide due to their large ratio of surface to bulk silver atoms. Numerous shapes of nanoparticles can be constructed depending on the application at hand. Commonly used silver nanoparticles are spherical, but diamond, octagonal, and thin sheets are also common.
Cotton recycling is the process of converting cotton fabric into fibers that can be reused into other textile products.
Wet Processing Engineering is one of the major streams in Textile Engineering or Textile manufacturing which refers to the engineering of textile chemical processes and associated applied science. The other three streams in textile engineering are yarn engineering, fabric engineering, and apparel engineering. The processes of this stream are involved or carried out in an aqueous stage. Hence, it is called a wet process which usually covers pre-treatment, dyeing, printing, and finishing.
A copper nanoparticle is a copper based particle 1 to 100 nm in size. Like many other forms of nanoparticles, a copper nanoparticle can be prepared by natural processes or through chemical synthesis. These nanoparticles are of particular interest due to their historical application as coloring agents and the biomedical as well as the antimicrobial ones.
Scouring is a preparatory treatment of certain textile materials. Scouring removes soluble and insoluble impurities found in textiles as natural, added and adventitious impurities, for example, oils, waxes, fats, vegetable matter, as well as dirt. Removing these contaminants through scouring prepares the textiles for subsequent processes such as bleaching and dyeing. Though a general term, "scouring" is most often used for wool. In cotton, it is synonymously called "boiling out," and in silk, and "boiling off."
Cold pad batch (CPB) is a method of dyeing textiles, typically cellulosic fibers such as cotton, in which the textile is impregnated with dye in a cold state, rather than being heated. High dye fixation and no thermal energy are the advantages of the CPB process. CPB-dyed fabrics are less expensive, have a softer hand feel, and have a cleaner surface than exhaust dyed materials. The process may take up to 12 hours in the batching process, depending on the depth of the shade. The disadvantage is that batching is a time-consuming and lengthy process. The process was developed in 1960.