Ozone: Revolutionizing Textile Processing for a Greener Future
Welcome to our blog post on “Ozone: Revolutionizing Textile Processing for a Greener Future.” In a world where the demand for food and clothing is growing alongside the population, finding sustainable solutions for the textile industry is crucial. Enter ozone, a powerful tri-atomic form of oxygen that offers remarkable oxidation capacity. By utilizing ozone, textile manufacturers can reduce water and energy consumption, minimize chemical usage and waste production, and achieve a more environmentally friendly approach. In this article, we will explore the advantages of ozone, its specific applications in denim processing, and its role in cotton pretreatment, dyeing, and finishing processes. Join us as we uncover how ozone is revolutionizing textile processing for a greener and more sustainable future.
Introduction
Apart from the human race, animal & plants kingdoms too consume earth’s resources in sustaining and trying to keep their existence. The world population will grow additionally around 35% by 2050. The increasing population will need to cater with food and clothing. The economic upward move is believed to create an increase in the requirement of fabrics as a basic necessity. More consumption means more production, which means more utilization of input raw materials. Water is also an important raw material that is required as part of chemicals/dyes & auxiliaries plus additional processes used in textiles. The same discarded & used contaminated water as effluent need to be treated in environment friendly way to recycle to preserve the natural resources intact.
The textile sector utilizes huge amounts of electricity, fuel, and water with corresponding greenhouse gas emissions (GHGs). Textile manufacturing, especially wet processes, uses a large quantity of water and produces a significant volume of contaminated effluents. Saving water and minimizing water pollution has become a key strategy to move the textile industry toward more environmentally friendly processes.
Sustainability is usually divided into three categories:
- Social,
- Economic,
- Environmental.
Compliance with all three categories is essential for the full implementation of sustainability.
Ozonation is a sustainable process that saves water and energy. At the same time, the ozonation process does not require chemicals or uses less chemicals at low temperatures does not produce waste, and reuses water.
Ozone is a tri-atomic form of oxygen (o3) with a remarkable oxidation capacity. ozone is produced through generators; the ozone generation system produces ozone onsite using oxygen from the PSA oxygen generator as the feed gas. This O2 gas is subjected to a high voltage, an electric corona (similar to lightning) in the ozonator module, where the molecular oxygen breaks down to atomic oxygen.
Ozone must be produced in situ because it cannot be stored and transported and is very reactive. There are two basic methods for generating ozone artificially:
- Corona discharge
- Ultraviolet radiation
All ozone-generating methods depend on the applied energy. The bonds holding the oxygen atoms in a molecular form break with the energy, which allows them to dissociate and then reform as ozone.
Oxidative agents are used in de-sizing, bleaching, dyeing, clearing, surface modification, and wastewater treatments for applications in the textile sector. The main oxidative agent used in the textile sector is hydrogen peroxide.
The use of an activator, generally caustic soda, and high temperatures are required for hydrogen peroxide bleaching.
On the other hand, ozone is usually applied at room temperature because of its decreasing solubility at high temperatures, and ozone is active in the whole pH range compensating the requirement of pH adjustment chemicals.
Of course, the pH of the aqueous solution affects the reactions of ozone, but ozone is capable of giving oxidation reactions in neutral, acidic, or alkaline solutions. In the textile industry, ozone is utilized in various processes such as:
Ozone
Ozone, composed of three atoms of oxygen, can be utilized to oxidize many organic and inorganic impurities. It is an irritating pale blue gas, is reactive, is heavier than air, and cannot be stored or transported. For this reason, it has to be generated “in situ.” The German chemist C. F. Schönbein discovered ozone and named it so based on the Greek word “ozein” (to smell).
The first large-scale ozone application was for water purification. It is known that ozone is thermodynamically unstable and spontaneously reverts to oxygen; the structure of the ozone molecule.
Ozone is not a stable substance and breaks down into oxygen, with different half-lives basically depending on the temperature. Owing to its relatively short half-life, ozone should be generated onsite and it could not be stored like other chemicals
Ozone is highly competitive and is typically 1.2–1.5 times less costly than chlorine dioxide from an economic point of view. Ozone has a higher oxidation potential than many known chemicals.
Advantages of Ozone
- Ozone is a very strong oxidant and is used as an important disinfectant in the treatment of water and air.
- It does not leave any organic waste after water treatment.
- Ozonation can be carried out in any media and does not involve any other Chemicals.
- Ozone eliminates different inorganic, organic, and microbiological problems.
Denim Applications by Ozone
Denim finds its usage as a timeless, ageless, and sexless product in our life. The subsequent different washing types or finishing stages have constituted into a major industry itself. It is chiefly designed to bring a specific, unique, and aesthetic finish to the final garment.
In order to give the desired effect on the denim, a number of mechanical and chemical processes are applied to the fabrics. Bleaching denim with sodium hypochlorite causes a huge problem of AOX (adsorbable halogenated organic compounds).
Approximately 70 L of water is used for one denim. Stone washing methods are harmful to the environment and human health.
Ozone is capable of breaking down the dyestuffs, including indigo, into smaller and colorless fragments. This oxidizing capacity of ozone is utilized for fading denim garments to substitute the use of enzymes, pumice stones, or hypochlorite bleaching processes.
PET is not faded by ozone; however, ozone can be used to fade dyed cotton or other cellulosic yarns. Ozone is successfully used to recover the back staining of indigo garments.
Other oxidizing agents such as potassium permanganate and benzoyl peroxide are available for denim garment processing; however, the most important advantage of ozone is its ecofriendly nature, and it is a good alternative to other techniques.
Isatin and anthranilic acid may form during the oxidation of indigo and these products may cause yellowing. When the fading process is applied much more, it needs to be rinsed with water to remove yellowing.
Studies have shown that ultrasound and nano-bubble methods, which when combined with ozone, increase the effectiveness of ozone.
Ultrasonic cavitations improve the penetration of ozone into the fabric and then ozone decomposes indigo; therefore, ozone is much more effective when used along with ultrasonic energy.
One of the innovative processes that use ozone gas in the denim sector is nano-bubble technology. Ozone gas can be injected into the system instead of air to obtain nano-bubbles.
By means of nano-bubble, the efficiency of ozone gas in the liquid surplus will be increased and the washing effects desired to be shown to customers in a shorter, more efficient, and environmentally friendly way will be obtained.
One of the chief troubles in denim production is indigo back staining. Backstaining decreases the white–blue contrast and results in an evenly distributed bluish color all over the garment comprising local abraded areas, pockets, and labels.
Cotton Pretreatment, Dyeing, and Finishing by Ozone
Cotton is the most preferred fiber in the textile industry due to its being comfortable, healthy, and easily accessible. For this reason, all new technologies are generally applied to cotton products. But cotton needs pretreatment processes before dyeing and finishing process due to its natural structure (oils, wax, mote).
In particular, ozone can be used alone or in combination with other processes such as ultrasound, UV, and plasma. Ozonation can be used in textile companies for washing and treating denim fabrics, bleaching cotton fabrics, after-clearing of polyester, decolorization, and clearing wastewater. Recently, ozone technology has also been used for surface modifications in composite applications. There is no doubt that ozone will play a more important part in the near future both in the textile industry.
