Chlorine dioxide hypochlorous acid

Lactic acid, alkyl fatty acids (salicylic acid, glycolic add, benzoic add Chlorhexidine gluconate/acetate Fatty alkyl 1,3-diaminopropane A-Fatty alkyl 3-aminopropionate, A-hydroxyethyl-A-carboxymethyl fatty acid sodium salt of amidoethylamine Ethyl alcohol, propyl alcohol, benzyl alcohol, pine oil Sodium hypochlorite (liquid chlorine bleach), chlorine dioxide, hypochlorous acid, trichloro- and dichloroisocyanuric acids and their salts, sodium perborate and activator, peroxy acid (per acid), magnesium salt of peroxy phthalic acid, oxygen bleach generated from ozone... 

The conditions for chlorate formation are high pH, low reactant concentrations, and the presence of excess chlorine or hypochlorous acid. Thus, the addition of free chlorine or hypochlorite to chlorine dioxide treated water, which contains chlorite as a by-product of the chlorine dioxide treatment, predominandy forms chlorate in the pH 5—8 range typically used in water treatment (140). 

J. A. WojTowicz, Dichlorine monoxide, hypochlorous acid and hypochlorites. Kirk-Othmer Encyclopedia of Chemical Technology, 4th edn., Wiley, New York, 1993, Vol. 5, pp. 932-68. J. J. Kaczur and D. W. Cawlfield, Chlorine dioxide, chlorous acid and chlorites, ibid., pp. 968-91. 

The oxidation pathways of chlorine dioxide under actual conditions are complex because a number of species including chlorine, hypochlorous, chlorous, and chloric acids are formed as intermediates. A rapid conversion of chlorine dioxide to chloride and chlorite (chlorous acid, pK 2.0) may first take place, followed then by a slow phase during which mainly the chlorite reacts with the pulp components. However, continuous generation of chlorine dioxide during bleaching takes place, for example, by the reaction between chlorite and chlorine (or hypochlorous acid) ... 

Typical biocides include hypochlorous acid, chlorine dioxide, hypobromus acid, hydrogen peroxide, ozone, ultraviolet-light treatment, phenolics, aldehydes, and quaternary ammonium compounds (Ref 73, 80). A brief description of each follows (Ref 73, 80). Hypochlorous acid is probably the most commonly used biocide and also one of the most powerful oxidizing agents. The sources of hypochlorous acid are chlorine gas and sodium hypochlorite. In aque-... 

In addition to the concentration of hydrogen ion and chloride ion, the relative amounts of reactants, chlorine(III), and chlorine (or hypochlorous acid), also affect the stoichiometry. For the chlorine(III)-hypochlorous acid reaction, Emmenegger and Gordon (48) noted that with chlorine(III) in excess there was a marked improvement in the production of chlorine dioxide. Actually, the theoretical amount preducted by Eq. 22 is exceeded, but chlorine or hypochlorous acid catalysis of the disproportionation of chlorous acid might explain this discrepsuicy. Whereas eui increase in the chlorine(III) concentration increases the amount of chlorine dioxide produced (40, 48, 162), an increase in the hypochlorous acid concentration favors the formation of chlorate ion (40, 99, 226). White and co-workers (226) suggest that this is consistent with the inclusion of the reaction... 

For water treatment purposes, only small amounts of chlorine dioxide are necessary, so the reaction products chlorite and chlorate are also present only at low concentrations. If chlorination is carried out with chlorine gas, hypochlorous acid is rapidly formed, which acts as a biozide. 

In solutions, the concentration of available chlorine in the form of hypochlorite or hypochlorous acid is called free-available chlorine. The available chlorine in the form of undissociated A/-chloro compounds is called combined-available chlorine. Several analytical methods can be used to distinguish between free- and combined-available chlorine (8). Bleaches that do not form hypochlorite in solution like chlorine dioxide and nonchlorine bleaches can be characterized by thek equivalent available chlorine content. This can be calculated from equation 5 by substituting the number of electrons accepted divided by two for the number of active chlorine atoms. It can also be measured by iodomettic titration. 

Hypochlorous acid can also be used, but the reaction is slower. Chlorine dioxide is also made by adding acid to sodium chlorite solutions by the overall reaction in equation 11 ... 

Dichlorine monoxide, hypochlorous acid, and hypochlorites. Chlorous acid, chlorites, and chlorine dioxide. 

Hypochlorous Acid—Sodium Chlorite System. In this method, chlorine gas is educted into water forming a hypochlorous acid solution which then reacts with aqueous sodium chlorite to produce chlorine dioxide (114—116). Hypochlorous acid, formed from the disproportionation of chlorine gas in water ... 

Demonstrated chlorine dioxide yields from chlorite are 95% or higher in properly operated systems. Excess hypochlorous acid is commonly used to achieve a high conversion. 

The reaction chemistry changes when the initial reactant concentrations are low or there is excess hypochlorous acid present. The [CI2O2] intermediate disproportionation route to chlorine dioxide becomes less important (eq. 48), and the route to chlorite formation by hydrolysis predominates as does the reaction with any available excess HOCl to form chlorate and chlorine ... 

PPG [Pittsburgh Plate Glass Company] A process for making calcium hypochlorite. Hypochlorous acid and chlorine monoxide, generated by reacting chlorine and carbon dioxide with sodium carbonate monohydrate, are passed into lime slury. Invented in 1938 by I. E. Muskatt and G. H. Cady at the Pittsburgh Plate Glass Company. 

When the reaction temperature of step one increases, the total oxidant concentration in the off-gas is >6 mg m-3, but this depends on capacity and hypochlorite concentration. Careful analysis with infrared methods demonstrated that this total oxidant concentration was derived from chlorine dioxide. Measurements of the concentrations between steps one and two showed that concentrations were higher than in the off-gas and that hypochlorous acid (HOC1) was also found, which was totally absent in the off-gas. 

The effects of the steady-state situation and the effect of the peak load can be described using a model. When the caustic concentration is low, either through initial concentration effects or by mass transfer limitations, the reaction of chlorine with chlorite can occur and chlorine dioxide (Equations 25.3 and 25.8) is formed near the gas-liquid interface. The concentration of chlorite seems quite important and is influenced by temperature (decomposition) and the hypochlorite concentration. A higher chlorite concentration will give, according to the reactions of Equations 25.3 and 25.8, a higher chlorine dioxide content in the presence of chlorine and/or hypochlorous acid. 

Cbemical/Physical. The aqueous chlorination of indole by hypochlorite/hypochlorous acid, chlorine dioxide, and chloramines produced oxindole, isatin, and possibly 3-chloroindole (Lin and Carlson, 1984). 

Wet oxidation of phenol at elevated pressure and temperature gave the following products acetone, acetaldehyde, formic, acetic, maleic, oxalic, and succinic acids (Keen and Baillod, 1985). Chlorine dioxide reacted with phenol in an aqueous solution forming p-benzoquinone and hypochlorous acid (Wajon et al., 1982). 

Chemical/Physical. Under atmospheric conditions, the gas-phase reaction with OH radicals and nitrogen oxides resulted in the formation of p-tolualdehyde (Atkinson, 1990). Kanno et al. (1982) studied the aqueous reaction of p-xylene and other aromatic hydrocarbons (benzene, toluene, o-and /n-xylene, and naphthalene) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. The amount of cyanogen chloride formed increased at lower pHs (Kanno et al, 1982). Products identified from the OH radical-initiated reaction of p-xylene in the presence of nitrogen dioxide were 3-hexene-2,5-dione, p-tolualdehyde, and 2,5-dimethylphenol (Bethel et al., 2000). 

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