Specific Bleaching Agents

Thermal decomposition of hydroxyalkyl hydroperoxyalkyl peroxides produces mixtures of starting carbonyl compounds, mono- and dicarboxyHc acids, cycHc diperoxides, carbon dioxide, and water. One specific hydroxyalkyl hydroperoxyalkyl peroxide from cyclohexanone (2, X = OH, Y = OOH) is a soHd that is produced commercially as a free-radical initiator and bleaching agent (see Table 5). On controlled decomposition, it forms 1,12-dodecanedioic acid (150). 

All proteolytic enzymes described are fairly non-specific serine endoproteases, cleaving peptide chains preferentially at the carboxyl side of hydrophobic amino acid residues. The enzymes convert their substrates into small, readily soluble fragments which can be removed easily from fabrics. Only serine protease can be used in detergent formulations, as thiol proteases such as papain would be oxidized by the bleaching agents, acidic proteases are not active at common laundry conditions, and metalloproteases such as thermolysin would lose their metal cofactors because of complexation with the water-softening agents or hydroxyl ions. 

The first step in the restoration process is dry cleaning with soft erasers. Old mounts or supports, usually highly acidic, are removed. Immersion in water is prescribed for removal of discoloration in the more stable forms of art on paper etchings, prints, engravings, and some drawings. For specific stains that cannot be removed with water or other solvents, bleaching agents are applied locally. Deacidification by total immersion is preferred a spray is used when this is not possible. 

NaOCl kg 0-50 Depending on fibre specifications and end uses, resp. the use of alternative bleaching agents... 

Uses The importance of CIO2 is steadily rising, replacing elemental chlorine as a bleaching agent in the pulp and paper and the textile industry and as a specific... 

Surfactants, builders, and bleaches are quantitatively the major components of modern detergents the auxiliary agents discussed in this section are introduced only in small amounts, each to accomplish its own specific purpose. Their absence from current detergent formulations is difficult to imagine. 

Agents for chemical bleaching rely on different types of peroxides. Potentiometric or amperometric biosensors that detect the highly specific and sensitive reaction of enzymes like katalases with their corresponding substrates can be used for on-line measurement [84]. The sensors can be manufactured with simple technologies at moderate cost, but their stability is not sufficient for integration in household appliances. 

A transient optical absorption study of charge recombination dynamics was recently reported on CD CdS with a crystal size of 5 nm (no details of the deposition were provided) [35]. Three different time constants for the decay of the transient absorption bleaching were measured (0.8 psec, 17 psec, and 800 psec) and were attributed to three groups of nanocrystals with specific defects. Tri-octylphosphine oxide (TOPO), a well-known passivating agent for CdSe nanocrystals that acts by binding to Cd, was found to increase the relative contribution of the 800-psec recombination, which was therefore attributed to volume recombination, since the TOPO is expected to reduce the relative contribution of surface recombination (represented by the two shorter time constants). 

The silver dye bleach reaction is very slow (65MI11401), and an additional agent is needed to promote the reaction between the immobile silver image and the immobile dye. 1,4-Diazines have been used as catalysts for this reaction, 2,3-dimethylquinoxaline (65), 2,3-diphenylpyrazine (66) and 2-hydroxy-3-aminophenazine (67) being specific examples. 

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