Bleaching agents

Bleaching agents are the materials, which are used for the lightening, decolorizing or whitening of a substrate by the chemical reactions.  The color producing materials are generally organic in nature, containing “chromophores” (Chromophore is that portion of molecule that absorbs light photons).

The bleaching action is normally based on the oxidation or reduction processes that degrade the color systems. Chemical bleaches works in one of two ways:

Oxidizing bleach breaks the chemical bonds that make up the chromophores. Thus the molecule either does not contain the chromophore, or the chromophore does not absorb visible light.

Reducing bleach converts double bonds of the chromophoric carbonyl groups into textiles or pulp.

The bleaching agents are mostly used for the following purposes:

Textile bleaching: In textile process industries, these agents are used to remove the remaining unwanted materials (e.g. soil, colored compounds, etc) before dying and finishing. In textile process industries, the bleaching of the fabrics is generally named as “Scouring”, in which the washing of the fabric is carried out in hot alkali solutions. 

Pulp bleaching: bleaching agents are used to decrease the color of the pulp. The main use of this pulp bleaching is to make white paper from the pulp.

Laundering purposes: normally alkaline aqueous solution of sodium hypochlorite is used for this purpose. This bleach is highly effective for fabrics whitening and germicidal activity, however not suitable for all fabrics.

Cleaning purpose: Bleaching agents have extensive uses as hard surface cleaners, to remove strains, and also for the disinfection of the surfaces (industrial use). Sodium hypochlorite, hydrogen peroxides or many other alkaline solutions along with surfactants and auxiliaries are used for the purpose.

Bleaching agents are also used for the bleaching of pulp and paper, hair, fur, foodstuff and oils.

Bleaching agents are not considered as the environment damaging substances, as most of them are organic substances, however bleaching of the chemical substances or conventional bleaching using elemental chlorine produces large amount of chlorinated organic compounds such as chlorinated dioxins etc. Chlorinated dioxins are highly toxic, and have bad influence on human health.

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