Oxidation with chlorine dioxide

Alternatives most frequently considered for taste and odor removal include breakpoint chlorination, aeration, ozonation, and oxidation with chlorine dioxide or potassium permanganate. None of these technologies have been found to approach the activated carbon adsorption process iri terms of effective treatment for this particular water quality problem. Another alternative is sorption onto other solids such as bleaching clays, synthetic resins or manganese dioxide. A brief summary of the advantages, disadvantages and cost factors associated with adsorption and alternative treatments for removal of tastes and odors... 

Nomnicrobial processes for destruction of cyanide wastes have been extensively investigated and are well known. Parga et al. (2003) have reported several oxidation methods for treating cyanide solutions. Such methods include (1) destruction of cyanide by oxidation with chlorine dioxide in a gas-sparged hydrocyclone reactor, (2) destruction by ozone in a stirred batch reactor, and... 

Oxidation of phenols with chlorine dioxide or chlorine produces chlorinated aromatic intermediates before ring rupture. Oxidation of phenols with either chlorine dioxide or ozone produces oxidized aromatic compounds as intermediates which undergo ring rupture upon treatment with more oxidant and/or longer reaction times. In many cases, the same nonchlorinated, ringruptured aliphatic products are produced using ozone or chlorine dioxide. 

Under drinking water plant treatment conditions, humic materials and/ or resorcinol do not produce trihalomethanes with chlorine dioxide even when a slight excess of chlorine (1 percent to 2 percent) is present. Also, saturated aliphatic compounds are not reactive with chlorine dioxide. Alcohols are oxidized to the corresponding acids. 

Hydrochloric acid in combination with chlorine dioxide can be used as a treatment fluid in water-injection wells that get impaired by the deposition of solid residues [332,333]. The treatment seems to be more effective than the conventional acidizing system when the plugging material contains iron sulfide and bacterial agents because of the strongly oxidative power of chlorine dioxide. Mixtures of chlorine dioxide, lactic acid, and other organic acids [1172,1173] also have been described. 

Although technically a chlorine oxide, chlorine perchlorate is of little importance. When ozone reacts with chlorine dioxide, the reaction produces Cl2Og dichlorine hexoxide. 

Oxidation of triazine herbicides with chlorine and chlorine dioxide has been widely studied [105-108]. In the case of sulfur-containing triazines, oxidation occurs mainly via cleavage of the weakened R-S-CH3 bond rather than by addition of chlorine. Reactions of S-triazines with chlorine are faster than with chlorine dioxide, and form sulfoxide, sulfone, and a sulfone hydrolysis product. Chlorination with chlorine dioxide only produced sulfoxide [108]. Lopez et al. identified the formation of sulfonate esters during the chlorination of ametryn and terbutryn [106, 107]. Triazine DBFs identified by Brix et al. exhibited higher toxicities than the parent compounds [105]. Similar to triazines, clethodim, a cyclohexanedione herbicide, is oxidized by hypochlorite and chloramines to clethodim sulfoxide and then to sulfone [109]. 

Spectrophotometry (or colorimetry) has been used to measure chlorine dioxide in water using indicators that change colors when oxidized by chlorine dioxide. Spectrophotometric analyzers determine the concentration of chlorine dioxide by measuring the optical absorbance of the indicator in the sample solution. The absorbance is proportional to the concentration of the chlorine dioxide in water. Indicators used for this technique include jV,jV-diethyl-p-phenylenediamine, chlorophenol red, and methylene blue (APHA 1998 Fletcher and Hemming 1985 Quentel et al. 1994 Sweetin et al. 1996). For example, chlorophenol red selectively reacts with chlorine dioxide at pH 7 with a detection limit of 0.12 mg/L. The interferences from chlorine may be reduced by the addition of oxalic acid, sodium cyclamate, or thioacetamide (Sweetin et al. 1996). 

Limoni B, Choshen E, Rav-Acha C. 1984. Determination of oxidants formed upon the disinfection of drinking water with chlorine dioxide. J Environ Sci Health Part A, A19(8) 943-957. 

The pyrimidine synthesis was therefore changed to the alkynyl ketone route as the appropriate precursors could be formed under much milder conditions. Thus, treatment of the chloro aldehyde 1002 with ethynyl Grignards or lithium species at low temperature, followed by mild oxidation with manganese dioxide, gave the desired chloro alkynyl ketones 1003, which could be successfully converted to the pyrimidine products 1004, by condensation with substituted guanidines, without displacement of the chlorine atom <2003X9001, 2005BMC5346>. 

Thionyl chloride is also formed by the oxidation with chlorine monoxide of sulphur in carbon disulphide or even of carbon disulphide itself,6 and in the interaction of carbonyl chloride with sulphur dioxide at temperatures above 200° C.,... 

Nitrosyl chloride has been prepared by passing nitrogen dioxide through moist potassium chloride,1 by the reaction of nitric oxide with chlorine,2 from nitrosylsulfuric acid and sodium chloride,3 and from nitrosylsulfuric acid and dry hydrogen chloride.4... 

Several operations may be employed to treat water prior to use. Aeration is used to drive off odorous gases, such as H2S, and to oxidize soluble Fe2+ and Mn2+ ions to insoluble forms. Lime is added to remove dissolved calcium (water hardness). A12(S04)3 forms a sticky precipitate of Al(OH)3, which causes very tine particles to settle. Various filtration and settling processes are employed to treat water. Chlorine, Cl2, is added to kill bacteria. Formation of undesirable byproducts of water chlorination may be avoided by disinfection with chlorine dioxide, C102, or ozone, 03. 

Although the free phenolic structures are oxidized faster, chlorine dioxide also destroys nonphenolic phenyl propane units and double bonds present in the pulp chromophores. After cleavage of the benzene ring various di-carboxylic acids are formed, such as oxalic, muconic, maleic, and fumaric acids in addition to products substituted with chlorine (Fig. 8-10). As a result of depolymerization and formation of carboxyl groups the modified lignin is dissolved during the chlorine dioxide treatment and in the sodium hydroxide extraction stage that usually follows. 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by inhalation. Moderately toxic by ingestion. A severe eye, skin, and mucous membrane irritant. Corrosive to body tissues. Flammable by chemical reaction. Explosive reaction with chlorine dioxide + chlorine, sodium, urea + heat. Reacts to form explosive products with carbamates, 3 -methyl-2-nitroben2anilide (product explodes on contact with air). Ignites on contact with fluorine. Reacts violently with moisture, CIO3, hydroxyl-amine, magnesium oxide, nitrobenzene, phosphorus(III) oxide, K. To fight fire, use CO2, dry chemical. Incompatible with aluminum, chlorine dioxide, chlorine. 

Apart from reactions of halides with inorganic (Chapter 3) and organic species (Section 4) and their oxidations by sundry anionic species, there remain oxidations by nonionic species and some substitution reactions not previously discussed. This section deals with oxidation by hydrogen peroxide and by oxygen, then with the oxidation by chlorine dioxide, and finally picks up some observations on phosphorus species. 

Mechanistic studies of the chemical oxidation of aliphatic amines have been reviewed extensively by Chow et al. [22]. Many studies of the mechanism of oxidation of amines have been performed with chlorine dioxide or ferricyanide as oxidants, because they have absorption bands with maxima at 357 and 420 nm, respectively. Changes in the absorbance at these wavelengths for the respective oxidants can be conveniently used to follow the kinetics of the reactions. On the basis of these studies, the electron-transfer mechanism shown in Scheme 1 has been proposed for amine oxidation. 

High-temperature oxidations with nitrogen dioxide or nitrogen dioxide and chlorine followed by treatment with water convert perfluoroalkyl hydrides and perfluoroalkyl iodides into perfluorocarboxylic acids. Perfluoroalkyl bromides and especially perfluoroalkyl chlorides do not react appreciably (equation 201) [455]. 

Of the chlorine oxides only chlorine dioxide has achieved industrial significance. It is a gas at room temperature. As a result of its explosive properties, it can only utilized in situ and even then has to be diluted with inert gases (nitrogen, carbon dioxide) to 10 to 15% (by volume). 

Brines contain between 30 and several hundred ppm of iodine (as iodide). The deposits in the USA are mainly in Michigan and Oklahoma. Extraction is similar to that of bromine. Brines are mixed with hydrochloric or sulfuric acid and oxidized with excess chlorine. The elemental iodine formed is blown out with air and absorbed in a sulfuric acid-hydroiodic acid-water mixture in an absorber. Reduction with sulfur dioxide converts the iodine into hydroiodic acid. Part of this is taken off and the hydroiodic acid oxidized with chlorine to iodine. The iodine is filtered off and dried and any organic impurities oxidized by melting under sulfuric acid. 

Cyanide may be detoxified to cyanate by oxidation with chlorine or hypochlorite (Chap. 15). Or the oxidation may be conducted by air in the presence of sulfur dioxide and copper ion at pH 9 or 10 [44]. Einally BOD reduction to 80-90% of the original values will be achieved via either biological waste treatment or alkaline chlorination methods before discharge. 

FIGURE 11.19 Reaction mechanism for oxidation of a phenolic lignin nnit with chlorine dioxide. 

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