Reductions oxides, thiourea dioxide

Whiter fabrics are produced if an oxidative bleaching is followed by a reductive one this is often referred to as full bleaching. One such process involves a hydrogen peroxide oxidative bleaching, followed by addition of thiourea to the Hquor to generate thiourea dioxide for a reductive bleach in situ (115). 

Thiourea dioxide has a stronger reducing effect (-1100 mV) than hydrosulfite. Therefore, with sensitive dyes, a risk of over-reduction exists. In addition, the oxidation products of thiourea dioxide contribute to the nitrogen and sulfur contamination of wastewater. 

The reduction of diorgano tellurium dichlorides by thiourea dioxide in aqueous sodium hydroxide solution proceeds via diorgano tellurium oxides or dihydroxides as intermediates (see page 432). 

The two most popular chemicals used for reductive bleaching of wool are stabilized sodium dithionite and thiourea dioxide. Most reductive bleaching of wool is carried out using stabilized dithionite (2-5g/L) at pH 5.5-6 and 45-65°C for 1 h. Thiourea dioxide is more expensive than sodium dithionite, but is an effective bleach when applied (1-3 g/L) at 80°C and pH 7 for 1 h. Whiter fabrics are produced when oxidative bleaching is followed by a reductive process—this is often referred to as full bleaching. ... 

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