Bleaching with peracetic acid

The physical and chemical properties of peracetic acid is summerised in Table 6.5. The concentrated solution of peracetic acid is volatile and has a pungent smell 

The peroxide anion reacts with TAED to form DAED (diacetylethylenediamine) and peracetic acid anions. At pH 8-9 the peracetic acid anion is in equilibrium with the free peracetic acid. This equilibrium peracetic acid oxidises its own per anion to form active oxygen, which acts as a bleaching agent [88]. 

Though the use of peracetic acid has been suggested for bleaching of cotton but has never reached the commercial success like hypochlorite, chlorite and peroxide [89]. The mechanism of reaction is somewhat similar to that of hydrogen peroxide. 

Bleaching of 100% cotton in rope form in a J-Box with peracetic acid (1.5-2.5 g/1) at room temperature, followed by an alkaline hydrogen peroxide treatment at 90 C yield a good whiteness. 

Linen can be successfully bleached using a process consisting of scouring, alkaline hydrogen peroxide bleach and a peracetic acid bleaching stage. 

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Merits and demerits of bleaching with peracetic acid The advantages of peracetic acid as a bleaching agent are ... 

Oxidation/bleaching Treatment with peracetic acid and/or hydrogen peroxide, or sodium hypochlorite or sodium chlorite, or sulfur dioxide, or potassium permanganate or ammonium persulfate... 

Bleaching of cellulose acetate with peracetic acid... 

K Sakai and T Kondo. Delignification in peracid bleaching VI. Reaction of the P-aryl ether type model componnds with peracetic acid. Tappi 55 1702-1706, 1972. 

Synthetic Fibers. Most synthetic fibers are sufficientiy white and do not requite bleaching. For white fabrics, unbleached synthetic fibers with duorescent whitening agents are usually used. When needed, synthetic fibers and many of theit blends are bleached with sodium chlorite solutions at pH 2.5—4.5 for 30—90 min at concentrations and temperatures that depend on the type of fiber. Solutions of 0.1% peracetic acid are also used at pH 6—7 for 1 h at 80—85°C to bleach nylon. 

Iodoxybenzene has been prepared by the disproportionation of iodosobenzene,4Hi by oxidation of iodosobenzene with hypo-chlorous add or bleaching powder,7 and by oxidation of iodobenzene with hypochlorous acid or with sodium hydroxide and bromine.8 Other oxidizing agents used with iodobenzene include air,3 chlorine in pyridine,9 Caro s acid,19-11 concentrated chloric acid,15 and peracetic acid solution.13 Hypochlorite oxidation of iodobenzene dichloride has also been employed.14... 

The mechanism of activation is believed to be as follows. In an alkaline medium, hydrogen peroxide yields the perhydroxide anion (Scheme 10.22), which reacts with TAED (10.86) to form diacetylethylenediamine (10.87) and the peracetate anion (10.88) as in Scheme 10.30 [244]. At pH 8-9, the peracetate anion is in equilibrium with free peracetic acid, as in Scheme 10.31 [244]. The peracetic acid reacts with the peracetate anion to form nascent oxygen which is the active bleaching agent, as in Scheme 10.32 [244]. Further possible activators suggested by Kleber [244] include ... 

Bleaching is thought to take place through the perhydroxyl free radical (Scheme 10.40) [223]. Various attempts have been made over the last decade to elucidate the mechanism and demonstrate the potential of peracetic acid in bleaching. Temperature and pH are critical parameters with regard to the rate and degree of bleaching on the one hand and the... 

Acedox [Acetic oxidation] A pulp-bleaching process using peracetic acid as the oxidant. Developed by Eka Nobel in 1994 and first commercialized, in combination with Lignox, in Sweden in 1995. 

Bleached or oxidized starches are produeed by reaeting starch with a specified amount of reagent under eontrolled temperature and pH. The starehes treated with low levels of reagents, sueh as hydrogen peroxide, peracetic acid, ammonium persulfate and sodium hypoehlorite, in aqueous slurry are referred to as bleached starches. 

Laundry powders in Europe use sodium percarbonate and a bleach activator, tetraacetylethylenediamine ( ED), to form peracetic acid in the washing machine that then reacts with bleachable stains such as tea, red wine, coffee, and curry to remove /bleach them from cloth. Transition metal ions, in particular copper, cause first decomposition of peracetic add before it can bleach stains and second react with peroxide to form highly readive hydroxyl radicals that can cause dye and fabric damage [32]. Chelants bind with copper and other metals to prevent these unwanted side readions. 

Synthetic Fibers. Most synthetic fibers are sufficiently white and do not require bleaching, When needed, synthetic fibers and many of their blends ane bleached with sodium chlorite solutions. Solutions of 0.1% peracetic acid are also used,... 

Bleached starchd 1403 Hydrogen peroxide and/or peracetic acid with Carboxyl group increase <0.1%... 

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