Bleaches such as hydrogen peroxide and chlorine play a crucial role in the processing of fibers into paper or textiles. These bleaches are commonly used to remove impurities, enhance whiteness, and improve the overall quality of the final product.
In the papermaking industry, hydrogen peroxide and chlorine are employed during the pulping process. Pulping involves breaking down the raw fibers into a pulp that can be utilized for paper production. Chlorine is often used in the first stage of pulping, known as "chlorination," where it reacts with lignin and helps to separate it from the cellulose fibers. By removing lignin, the chlorine bleach reduces the yellow-brown coloration, resulting in a brighter and whiter pulp.
However, the use of chlorine in pulping processes has raised environmental concerns due to the production of harmful byproducts, such as organic chlorinated compounds. To address this, many pulp mills have transitioned to more environmentally friendly alternatives, like oxygen delignification and the use of hydrogen peroxide.
Hydrogen peroxide is widely used in the bleaching stage following chlorination, referred to as "delignification." It acts as an oxidizing agent, effectively breaking down any remaining lignin and improving the brightness and purity of the pulp. Hydrogen peroxide offers the advantage of being more environmentally benign, as its only byproducts are water and oxygen.
In the textile industry, bleaching processes are applied to remove natural color pigments, stains, or unwanted impurities from fibers. Chlorine bleaching has been commonly used, mainly for cellulosic fibers like cotton. It involves immersing the fibers in a chlorine bleach solution, where the chlorine oxidizes and breaks down the impurities.
However, similar to paper production, the environmental impact of chlorine bleach has led to the adoption of alternative bleaching methods in textile manufacturing. Hydrogen peroxide is again a popular choice due to its ability to whiten fibers effectively without compromising the environment. It can be used in combination with other agents or under controlled conditions, such as alkaline or acidic pH, to achieve desired results.
In conclusion, both hydrogen peroxide and chlorine play vital roles in the processing of fibers into paper or textiles. While chlorine bleach has traditionally been applied to remove impurities, the concerns over its environmental impact have led to increased usage of hydrogen peroxide. Hydrogen peroxide offers an effective and environmentally friendly alternative, improving the brightness, whiteness, and overall quality of fibers in paper and textile production.
Chemistry
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- How are bleaches such as hydrogen peroxide and chlorine used when fibres are processed into paper or textiles?
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