Chemical oxidative degradation ozone

Polyisobutylene has the chemical properties of a saturated hydrocarbon. The unsaturated end groups undergo reactions typical of a hindered olefin and are used, particularly in the case of low mol wt materials, as a route to modification eg, the introduction of amine groups to produce dispersants for lubricating oils. The in-chain unsaturation in butyl mbber is attacked by atmospheric ozone, and unless protected can lead to cracking of strained vulcanizates. Oxidative degradation, which leads to chain cleavage, is slow, and the polymers are protected by antioxidants (75). 

The double bond present in the diene part of the elastomer is generally more susceptible to thermal and oxidative degradation. The selective hydrogenation of olefmic unsaturation in NBR imparts significant improvements in resistance to degradation and other properties, such as permeability, resistance to ozone and chemicals, and property retention at high temperature. 

ChemicaPPhysical Hwang et al. (2003) studied the chemical oxidation of mancozeb (100 ppm) in aqueous solution using ozone (continuously supplied at a concentration of 3 ppm) and chlorine dioxide (20 ppm). Ozonation of the solution for 60 min yielded several degradation compounds including ethylene thiourea as the major product. Degradation of mancozeb by chlorine dioxide also yielded ethylene thiourea. After 60 min of treatment, mancozeb was still detected suggesting that chlorine dioxide was less effective as an oxidant than ozone. However, the investigators... 

These factors have led researchers to examine novel methods for tire degradation of these contaminants, including liquid-phase photocatalytic oxidation. The treatment of wastewaters contaminated with agents like chlorinated aromatics has also prompted research into the optimum methods of integrating chemical oxidation techniques with existing water treatment methods, particularly biological treatment and ozonation techniques [37],... 

UV radiation is also the basis of several chemical oxidation technologies where the action of radiation and free radicals generated in the process allow for a high degree of micropollutant degradation and/or disinfection. Similar to ozonation or hydrogen peroxide oxidation, UV radiation may act on the matter present in water in two dilferent ways direct photolysis or indirect photolysis (e.g., free radical oxidation). 

The main constituents of NOM in natural water are humic substances consisting of humic and fulvic acids. Humic substances are the precursors of THMs. These must be degraded before chlorine disinfection because once THMs are formed they cannot be removed by chemical oxidation. Ozonation can degrade humic substances into low molecular weight compounds that are less reactive toward chlorine, and hence can minimize the formation of... 

PAHs in water can be chemically oxidized by chlorination and ozonation. A high efficiency of PAH degradation from chlorination has been reported by Harrison et al. (1976a, 1976b) for both laboratory and waste-water treatment plant conditions. Pyrene was the most rapidly degraded PAH. Benz[a]anthracene, benzo[a]pyrene, and perylene were also highly degraded. 

Methods to remove trace organic compounds of all types from aqueous solution (J5, 16, 17) have been studied extensively. One was to deal with pesticide pollution of water supplies by using an oxidant for chemical degradation. Among the many chemical oxidants available, certain ones have shown that they reduce the concentration of organic contaminants—e.g., ozone, chlorine dioxide, chlorine, the peroxides, and potassium permanganate (iS, 19, 20, 21). 

Chemical degradation with oxidizing agents (ozone, nitric acid, or wet oxidation with atmospheric oxygen at high pressure and high temperature with or without a catalyst). 

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