Ozone bleaching

Oxidation. Oxidation is one of the main chemical methods to treat and decompose dyes in wastewater. The oxidation agents used ate chlorine, bleach, ozone, hydrogen peroxide, Fenton s reagent, and potassium permanganate. 

Ozone bleaching (Z) - Because oxygen dehgnification is limited, additional de-Hgnifying agents must be used before final bleaching. Ozone is a possibility, but... 

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

Chlorine Dioxide. Like ozone, chlorine dioxide [10049-04-4] is a powerflil oxidant. It is usually generated as used. It has been used for disinfecting drinking water and bleaching paper pulp. Its effectiveness in killing microorganisms is well documented (305,306), and it has received recent study as a gas to sterilize medical devices. It requites 50% rh or higher to be effective. Bacterial cells had a D-value of 2.6 min and spores of 24 min (307). 

Ozone Flecking, stippling, bleached spotting, pigmentation conifer needle tips become brown and necrotic Oldest leaves most sensitive youngest least sensitive Palisade or spongy parenchyma in leaves with no palisade 0.03 59 4 hr... 

Bleaching between veins, tip and margin burn, leaf abscission marking often similar to that of ozone... 

Technical, economic, and environmental advantages exist for ozone bleaching of pulp in the paper industry as an alternate to hypochlorite or chlorine bleaching which yields deleterious compounds to the environment. 

A typical ozone system consists of 100 g/hr at a concentration of 1.0 percent to 1.5 percent in air fed to the bottom of bleach collection tanks through ceramic spargers (pore size of approximately 100 t). The system contains air compression and drying equipment, automatic control features, and a flat-plate, air-cooled ozone generator. Regeneration of bleach wastes totaling about 10,000 gallons a year, and recovery of other chemicals can also be cost effective. 

A student warned his friends not to swim in a river close to an electric plant. He claimed that the ozone produced by foe plant turned foe river water to hydrogen peroxide, which would bleach hair The reaction is... 

Figure 5. Union Camp Corporation s high consistency ozone bleaching paddle conveyor reactor. (From White et al., 1993.)...

Hurst, M. M., Effects of Pulp Consistency and Mixing Intensity on Ozone Bleaching, Tappi J, 76(4) 156 (1993)... 

Kappel, J., Brauer, P., and Kittel, F. P., Fligh-Consistency Ozone Bleaching... 

EnZone [Enzyme ozone] A pulp bleaching process using the enzyme xylanase in combination with oxygen, ozone, and hydrogen peroxide. Invented by K.-E. L. Eriksson at the University of Georgia and piloted in 1998. 

Proposed as a source of ozone for removing NO-, and S02 from flue-gas, and for pulp-bleaching. 

Ozone is a powerful though relatively unselective oxidant which is being considered in several pulp mills as a replacement for chlorine in bleaching chemical pulp. The first installation of ozone bleaching equipment was in 1992. The ozone required for a large pulp mill is about 10 ton/day 03 for a 1000 t/day pulp [129]. The phase volume ratio (gas/pulp) of about 8 wt% ozone by corona... 

Electrosynthesis gives a good concentration for pulp bleaching but the scale-up of electrosynthesis reactors to the range of 1 ton/day of ozone is problematic. The capital and operating costs probably make electrosynthesis uncompetitive with the corona discharge process [129],... 

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