Chlorite ion

Chlorite ion is oxidized rapidly to chlorine dioxide by ozone at pH 4, yielding one mol CIO2 per mol O3 when chlorite is in excess (k > lO" (39). The oxidation of bromite to bromate by ozone is too rapid to measure. Chlorine dioxide is oxidized rapidly to chlorate. Chlorate, bromate, and iodate ions do not react with ozone. 

Sodium Chlorite. The standard enthalpy, Gibbs free energy of formation, and standard entropy for aqueous chlorite ions ate AH° = —66.5 kJ/mol ( — 15.9 kcal/mol), AG = 17.2 kJ/mol (4.1 kcal/mol), and S° = 0.1883 kJ/(molK) (0.045 kcal/(molK)), respectively (107). The thermal decomposition products of NaClO, in the 175—200°C temperature range ate sodium chlorate and sodium chloride (102,109) ... 

Organic Reactions. The chlorite ion, CIO,, is mosdy a weak and slow oxidizer in alkaline aqueous solutions. Aldehydes (qv) can be readily oxidized to the corresponding carboxyhc acids in neutral or weakly acidic solutions. Mixing sohd sodium chlorite with combustible organic materials can result in explosions and fire on shock, exposure to heat, or dames. 

Sodium chlorite is not Hsted by the USEPA or any regulatory authority as a carcinogen. Studies conducted ia mice and rats did not show an increase in tumors in animals exposed to sodium chlorite in thek drinking water. Sodium chlorite has been found to have mutagenic activity in some in vitro test systems such as the Ames Salmonella reverse mutation assay without the presence of metaboHc activators. The significance of these test results in regard to human health is not clear because of the oxidizing effects of the chlorite ion (149). 

In many patent orHterature descriptions, a stabilized chlorine dioxide solution or component is used or described. These stabilized chlorine dioxide solutions are in actuaHty a near neutral pH solution of sodium chlorite that may contain buffer salts or additives to obtain chlorite stabiHty in the pH 6—10 range. The uv spectra of these solutions is identical to that of sodium chlorite. These pH adjusted chlorite solutions can produce the active chlorine dioxide disinfectant from a number of possible organic or inorganic chemical and microbiological reactions that react, acidify, or catalyze the chlorite ion. 

B. Slootmaekers, S. Tachiyashiki, D. Wood, and G. Gordon, "The Removal of Chlorite Ion and Chlorate Ion from Drinking Water," in Chlorine Dioxide Scientific, Tegulatory and Application Issues, American Water Works Association, International Sjmposium, Denver, Colo., Nov. 1—2,1989. 

R. M. Harrington, D. Gates, and R. R. Romano, "A Review of the Uses, Chemistry and Health Effects of Chlorine Dioxide and the Chlorite Ion, Chlorine Dioxide Panel of the Chemical Manufacturers Association, Washington, D.C., Api. 1989. 

A major disadvantage of this system is the limitation of the single-pass gas-chlorination phase. Unless increased pressure is used, this equipment is unable to achieve higher concentrations of chlorine as an aid to a more complete and controllable reaction with the chlorite ion. The French have developed a variation of this process using a multiple-pass enrichment loop on the chlorinator to achieve a much higher concentration of chlorine and thereby quickly attain the optimum pH for maximum conversion to chlorine dioxide. By using a multiple-pass recirculation system, the chlorine solution concentrates to a level of 5-6 g/1. At this concentration, the pH of the solution reduces to 3.0 and thereby provides the low pH level necessary for efficient chlorine dioxide production. A single pass results in a chlorine concentration in water of about 1 g/1, which produces a pH of 4 to 5. If sodium chlorite solution is added at this pH, only about 60 percent yield of chlorine dioxide is achieved. The remainder is unreacted chlorine (in solution) and... 

If the reagent that is added does not remain in the initial form in the reaction mixture, the investigator must carefully identify the actual species present. For example, the oxidation of iodide ions by chlorite ions in acidic solution has a rate given by... 

Write the 1 ewis structures of (a) water, H20 (b) methanal, H2CO and (c) the chlorite ion, CI02. Use the rules in Toolbox 2.1 note that we must add one electron for the negative charge of C102. ... 

Write the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet expansion), for (a) dihydrogen phosphate ion (b) chlorite ion (c) chlorate ion (d) nitrate ion. 

Chlorine dioxide, CIO2, reacts with hydroxide ions to produce a mixture of chlorate and chlorite ions. 

Determination of Chlorine Dioxide and Chlorite Ion in Drinking Water using Lissamine Green B and Horseradish... 

Chlorine dioxide is a yellow to reddish-yellow gas that can decompose rapidly in air. Because it is a hazardous gas, chlorine dioxide is always made at the place where it is used. Chlorine dioxide is used as a bleach at pulp mills, which make paper and paper products, and in public water treatment facilities, to make water safe to drink. In 2001, chlorine dioxide was used to decontaminate a number of public buildings following the release of anthrax spores in the United States. Chlorine dioxide is soluble in water and will rapidly react with other compounds. When it reacts in water, chlorine dioxide will form chlorite ion, which is also a very reactive compound. 

Because chlorine dioxide is a very reactive chemical, it is able to kill bacteria and microorganisms in water. About 5% of large water treatment facilities (serving more than 100,000 people) in the United States use chlorine dioxide to treat drinking water. It is estimated that about 12 million people may be exposed in this way to chlorine dioxide and chlorite ions. In communities that use chlorine dioxide to treat water for drinking uses, chlorine dioxide and its by-product, chlorite ions, may be present at low levels in tap water. 

In this profile, the term chlorite will be used to refer to chlorite ion, which is a water-soluble ion. Chlorite ion will combine with metal ions to form solid salts, (e.g., sodium chlorite). In water, sodium chlorite is soluble and will dissolve to form chlorite ions and sodium ions. More than 80% of all chlorite (as sodium chlorite) is used to make chlorine dioxide to disinfect drinking water. Sodium chlorite is also used as a disinfectant to kill germs. 

Chlorine dioxide is a very reactive compound and will not exist in the environment for long periods of time. In air, sunlight will quickly break apart chlorine dioxide into chlorine gas and oxygen. In water, chlorine dioxide will react quickly to form chlorite ions. In water treatment systems, chlorine dioxide will not form certain harmful compounds (e.g., trihalomethanes) when it reacts with dissolved organic compounds. Chlorine dioxide does form other disinfection byproducts, such as chlorite and chlorate ions. 

Like chlorine dioxide, chlorite is a very reactive compound. Since chlorite is an ion, it vrill not exist in air. In water, chlorite ions will be mobile and may move into groundwater. However, reaction with soils and sediments may reduce the concentration of chlorite ions capable of reaching groundwater. For additional information about what happens to chlorine dioxide and chlorite when they enter the environment, see Chapter 6. 

Chlorine dioxide is added to drinking water to protect people from harmful bacteria and other microorganisms. Most people will be exposed to chlorine dioxide and its disinfection by-product, chlorite ions, when they drink water that has been treated with chlorine dioxide. The EPA has set the maximum concentration of chlorine dioxide and chlorite ion in drinking water at 0.8 and 1.0 milligrams per liter (mg/L), respectively. However, the concentrations of chlorine dioxide and chlorite ion in your drinking water may be lower or higher than these levels. For additional information about how you might be exposed to chlorine dioxide and chlorite, see Chapter 6. 

Both chlorine dioxide and chlorite act quickly when they enter the body. Chlorine dioxide quickly changes to chlorite ions, which are broken down further into chloride ions. These ions are used by the body for many normal purposes. Some of these chloride ions leave the body within hours to days, mainly in the urine. Most of the chlorite that is not broken down also leaves the body in the urine within a few days following exposure to chlorine dioxide or chlorite. 

Families that drink water treated with chlorine dioxide may reduce the risk of exposure to chlorine dioxide and chlorite ions by drinking bottled water that has not been treated with chlorine dioxide or chlorite ions. 

EPA has set the maximum concentration of chlorine dioxide and chlorite ion for drinking waters at 0.8 and 1.0 mg/L, respectively. However, the concentrations of chlorine dioxide and chlorite ion in drinking water may be higher or lower than these levels. 

Chlorite ions and salts are strong oxidizers. Responsible care should be undertaken during disposal of chlorite ion solutions and salts. For example, solid sodium chlorite is unstable and can form explosive mixtures with oxidizable materials, such as organic compounds. Chlorite ion solutions should not be allowed to dry on textiles because this may result in a flammable combination (Kaczur and Cawlfield 1993 Vogt et al. 1986). No further information on the disposal of chlorite ions and chlorite salts were located. 

No other information was found in the literature about the releases of chlorine dioxide and chlorite (ions or salts) into air. 

Chlorate and chlorite ions are disinfection by-products (DBPs) from water treatment using chlorine dioxide. Table 6-2 contains data from four water treatment facilities in the United States that use chlorine dioxide as a disinfectant. Source water samples were also analyzed from each facility and no chlorite or chlorate ions were detected. In all water treatment plants, water taken from the distribution system (i.e., water sampled at water treatment plant) had measurable concentrations of both chlorite and chlorate ions. The ranges of concentrations were 15-740 and 21-330 pg/L for chlorite and chlorate, respectively (Bolyard et al. 1993). 

Chlorine dioxide is a very reactive compound and may exist in the environment for only short periods of time (see Section 6.3.2). Chlorine dioxide is readily soluble as a dissolved gas. However, chlorine dioxide can be easily driven out of aqueous solutions with a strong stream of air. The partition coefficient between water and C102(g) is about 21.5 at 35 °C and 70.0 at 0 °C (Aieta and Berg 1986 Kaczur and Cawlfield 1993 Stevens 1982). Transport and partition of chlorine dioxide in soils and sediments will not be significant. Chlorine dioxide is expected to be reduced to chlorite ions in aqueous systems (see Section 6.3.2.2). 

Like chlorine dioxide, the chlorite ion is a strong oxidizer (Rav-Acha 1998). Since chlorite is an ionic species, it is not expected to volatilize and will not exist in the atmosphere in the vapor phase. Thus, volatilization of chlorite ions from moist soil and water surfaces or dry soil surfaces will not occur. 

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