Organic radicals, degradation process

For some organic compounds, such as phenols, aromatic amines, electron-rich olefins and dienes, alkyl sulfides, and eneamines, chemical oxidation is an important degradation process under environmental conditions. Most of these reactions depend on reactions with free-radicals already in solution and are usually modeled by pseudo-first-order kinetics ... 

One of the most important fields of application of photocatalysis is the photodegeneration of organic compounds. These processes are used in particular for environmental decontamination, especially for wastewater treatment and air purification, because of the ability of semiconductors to totally degrade organics to C02, H 20, and inorganic anions under U V or visible light. This behavior is attributed to the photoinduced formation of radicals, such as OH, or to the adsorption and direct degradation of the pollutants. 

The optimal pH area for the mineralization of RB137 is foimd to be between 6-9, i.e. at neutral and weak basic conditions, with the highest TOC removal, 88.7 %, achieved after 60 minutes at pH 8. It can be seen that the mineralization proeess is mueh faster in first 30 minutes of treatment process than in next 30 minutes. That ean be attributed to the formation of large quantities of organic acids, including those resistant to OH radical degradation, in the last 30 minutes of treatment with significantly lower mineralization rate. The decrease in pH value after the treatment in comparison to initial value corresponds to the formation of acid by-products, mostly aliphatic [92]. 

New and up to-date materials have been developed in our laboratory to carry out Fenton photo-assisted processes efficient in the decoloration/degradation of organic pollutants that show stability against radical attack, do not allow the leaching of Fe-ions into the solution and intervene with suitable kinetics in the degradation processes. These new materials comprise Fe-ions supported on Nation membranes, Nafion-glass mats composites, alginate beads, amorphous polycrystalline fused copolymers and silica woven fabrics. 

PROBABLE FATE photolysis photooxidation definitely occurs, photooxidation half-life in water 3.2-160 days photooxidation half-life in air 1.19-11.9 hrs oxidation metal-catalyzed oxidation occurs in aerated surface waters, oxidation by peroxy radicals is important, photochemically produced hydroxyl radicals degrades compound in daylight hours, half-life 8 hrs hydrolysis not an important process volatilization not an important process sorption slight potential for adsorption onto organic materials, adsorption to sediment will be moderate biological processes biodegradation can occur other reactions/interactions chlorine present in water could chlorinate the eompound can be washed out by rain... 

PROBABLE FATE photolysis, based on data for 4-chlorophenol, intramolecular photolysis may be a very important fate, reaction with photochemically produced hydroxyl radicals has a half-life of 1.1 days, will degrade through photolysis if released to water oxidation can occur, but probably cannot compete with biodegradation hydrolysis not important volatilization not important sorption data inconclusive, but potential for adsorption by organics exists biological processes no data on bioaccumulation, biodegradation data not applicable to environment other reactions/interactions can be chlorinated further by chlorine present in HiO... 

More recently, longitudinal muon spin relaxation was used to measure rate constants for the reactions of organic radicals with molecular oxygen and with NO in the gas phase [32, 46]. The reactions are important in combustion processes and for the degradation of organic pollutants in the atmosphere. Accurate determinations by conventional techniques have often proved to be non-trivial, so that the muon technique appears to be a very valuable addition to the tool box of experimental methods. 

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