Published Online: 15 DEC 2006
Copyright © 2002 by Wiley-VCH Verlag GmbH & Co. KGaA
Ullmann's Encyclopedia of Industrial Chemistry
How to Cite
Süss, H. U. 2006. Bleaching. Ullmann's Encyclopedia of Industrial Chemistry. .
- Published Online: 15 DEC 2006
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Bleaching is the removal of color from various materials. It is predominantly achieved by an oxidative or reductive treatment, which destroys chromophores. In principle all oxidizing or reducing chemicals can act as bleaching agents, but on an industrial scale only a few compounds are used in bleaching processes. Chlorine dioxide, hydrogen peroxide, and sodium dithionite are predominantly applied. The alternative to a chemical reaction is the adsorption of colored impurities on pigment surfaces, like active carbon or bleaching clays. This method is applied mainly in purification or bleaching of liquids.
A bleaching process removes impurities; thus, in parallel the bleached good is cleaned. The “art of bleaching” is to reach a desired decrease in color with the least negative impact on quality and properties of the bleached material. Chemicals and processes are selected on the basis of their ability to achieve brightness and quality targets with a small amount of byproducts or residuals and low impact on the environment.
Bleaching of fibers for paper production is the most important industrial application. Highest effectiveness is guaranteed by a combination of several process steps in a bleach plant. Textile fabric bleaching is the second most important application. Modern bleaching technology aims for the most moderate use of resources, the lowest consumption of water, and best biodegradability of the compounds dissolved during the bleaching process.