Hydrogen peroxide is one of the cleanest, most versatile chemicals available. It is used:

• in the paper industry as a bleaching agent and for de-inking in wastepaper recycling
• in the textile industry as a bleaching agent, oxidizer and desizing agent
• in environmental protection for the detoxification and color removal of wastewater
• for off-gas treatment and for bioremediation of contaminated soil
• in the pharmaceutical and cosmetic industry as a disinfectant and bleaching agent
• in the detergent and cleanser industry
• in the packaging and food industry as a disinfectant for aseptic packaging and bacteria control
• in the chemical industry for epoxidation, hydroxylation and other oxidation reactions
• in electronics for pickling of metal surfaces
• in electronics for cleaning of silicon discs in the production of printed circuit boards as a bleaching agent for oils, waxes, fibers and other natural products

In the bleaching of kraft pulp, hydrogen peroxide is one of the chemicals applied in multi-stage processes. Alkaline conditions are required to generate the active bleaching species from H₂O₂, the per-hydroxyl anion. Consequently, extraction stages can be used for peroxide addition to boost the effects on extraction and brightness.

The application of H₂O₂ allows:

• top brightness levels with improved brightness stability
• optimized economy through savings in the total chemicals required
• low residual of halogenated compounds, both in pulp (OX) and in effluent (AOX)
• low effluent color

Hydrogen peroxide is applied as the exclusive bleaching agent in sulfite pulp brightening. In single or two-stage processes it allows bleaching to full brightness.

Descon offers technical assistance to customers for the evaluation and the optimization of existing processes, as well as the evaluation of alternatives for the bleaching procedure. Information and assistance in setting up storage tanks and dosing units from our Engineering Services is available.

Mechanical pulp, generated by the conventional ground-wood process or modern refining technology, that is TMP or CTMP and APMP processes, is bleached with hydrogen peroxide to very high brightness levels. Yield and fiber properties are kept on a very high level. The conventional approach is the application of H²O² together with caustic soda as alkali source, sodium silicate for stabilization and buffering, and a chelant for the sequestering of metal traces in the wood pulp.

Hydrogen peroxide gives

• high brightness and high brightness stability against aging and yellowing
• moderate effluent load and good biodegradability

In paper recycling the removal of printing ink is the most important objective in case the fibers should be reused in the manufacture of printing papers or tissue grades. Brightening and color removal are secondary targets. Fiber brightening is achieved mainly with H²O².

The alkaline conditions of re-pulping of wastepaper are ideally suited for a simultaneous application of hydrogen peroxide. Small amounts of hydrogen peroxide are sufficient to

• Improve brightness and
• Prevent alkaline yellowing

In post bleaching steps, e.g. in a disperser, the brightness is further improved.

Hydrogen peroxide is undoubtedly the most versatile bleaching agent available to the textile industry. It offers many advantages namely:

 

§  Ease of application

§  Potential for reducing process times

§  Minimization of effluent problems

§  Preservation of the quality of pure and blended textile fibers

§  A high and extremely stable degree of whiteness

 

 

Textile Animal Fibers

 

Wool and silk are bleached easily with hydrogen peroxide. After scouring, wool may be bleached by immersion or ad and dry techniques, using alkaline or acid solutions.

Prior to bleaching, silk is usually degummed. Hydrogen peroxide addition assists this process and it is universally used as the bleaching agent for natural silk, usually in an alkaline solution.

 

Textile Artificial Fibers or Regenerated Cellulose

 

Rayon and spun rayon produced from regenerated cellulose do not contain as many impurities as natural cellulosic fibers and therefore bleaching with hydrogen peroxide can be carried out under milder conditions.

 

 

Textiles-Dye Oxidation 

Certain textile dyes may be "fixed" by hydrogen peroxide. The use of hydrogen peroxide directly, or in the form of its derivatives sodium perborate and sodium carbonate peroxyhydrate, facilitates the oxidation of vat and some sulphur dyes after their application to textiles.

 

 

Textiles-Synthetic Fibers

 

Bleaching of 100% synthetic fibers is not normally required however blends of synthetic with natural fibers are often bleached using hydrogen peroxide. When used alone, synthetic fibers do not normally require bleaching. However, blends of synthetic fibers with natural or regenerated fibers, e.g. cotton -polyester are frequently bleached. The most popular bleaching agent is hydrogen peroxide and it is used in both batch and continuous processes.

 

Hydrogen peroxide is used to bleach a wide range of different products. The standard approach is the application of H²O² under alkaline conditions. The concentration and the pH value can differ in a wide range in order to take care of the specific sensitivity of the products to be bleached. Wood veneer, wooden products, straw and grasses are examples for these products. Hair and bristle need specially buffered bleaching conditions to maintain the raw materials quality. Other products are bleached under weak to strong acidic conditions, e.g. sulfuric acid, vegetable oils or animal products like fish oil.