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Bleaching

  1. Hans Ulrich Süss

Published Online: 15 DEC 2006

DOI: 10.1002/14356007.a04_191.pub2

Ullmann's Encyclopedia of Industrial Chemistry

Ullmann's Encyclopedia of Industrial Chemistry

How to Cite

Süss, H. U. 2006. Bleaching. Ullmann's Encyclopedia of Industrial Chemistry. .

Author Information

  1. Degussa AG, Hanau-Wolfgang, Germany

Publication History

  1. Published Online: 15 DEC 2006

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Abstract

The article contains sections titled:

1.Introduction
2.Bleaching Agents
2.1.Pretreatment
2.2.Oxidizing Agents
2.2.1.Oxygen
2.2.2.Chlorine Dioxide and Sodium Chlorite
2.2.3.Hydrogen Peroxide and Other Peroxo Compounds
2.2.4.Ozone
2.2.5.Chlorine and Hypochlorites
2.3.Reducing Agents
2.3.1.Sodium Dithionite
2.3.2.Sulfur Dioxide
2.3.3.Sulfinic Acid Derivatives
3.Enzymes
4.Bleaching Processes
4.1.Pulp
4.1.1.Chemical Pulp
4.1.2.Mechanical Pulp
4.1.3.Paper Recycling (Deinking)
4.1.4.Environmental Aspects of Pulp Bleaching
4.2.Textile Fibers
4.3.Other Products

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.