Chlorite process

The basic experiment that demonstrated the effects of molecular ordering is a rather simple one. Southern pine chips were delignified using the acid chlorite process at 60°C, then extracted with caustic solutions to remove the hemicelluloses. The pulp was then divided into two batches. One was used as a control the other was immersed in distilled water inside stainless steel vessels and heated through the temperature cycle of a typical kraft cook. During this cycle, the pulp was held at 170°C for approximately 2 h. The two batches of pulp were then used to make handsheets, and their papermaking properties were compared. 

The reaction involving chlorite and iodide ions in the presence of malonic acid, the CIMA reaction, is another that supports oscillatory behaviour in a batch system (the chlorite-iodide reaction being a classic clock system the CIMA system also shows reaction-diffusion wave behaviour similar to the BZ reaction, see section A3.14.4). The initial reactants, chlorite and iodide are rapidly consumed, producing CIO2 and I2 which subsequently play the role of reactants . If the system is assembled from these species initially, we have the CDIMA reaction. The chemistry of this oscillator is driven by the following overall processes, with the empirical rate laws as given ... 

HCIO4, one of the strongest of the mineral acids. The perchlorates are more stable than the other chlorine oxyanions, ie, chlorates, CIO chlorites, CIO or hypochlorites, OCf (3) (see Chlorine oxygen acids and salts). Essentially, all of the commercial perchlorate compounds are prepared either direcdy or indirectly by electrochemical oxidation of chlorine compounds (4—8) (see Alkali and chlorine products Electrochemical processing). 

Component, wt % Wood Process Chlorite holoceUulose Kraft... 

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

After World War I, other chlohne-based bleaches were developed. In 1921 the use of chlorine dioxide for bleaching fibers was reported followed by the development of the commercial process for large-scale production of sodium chlorite. In 1928 the first dry calcium hypochlorite containing 70% available chlorine was produced in the United States. This material largely replaced bleaching powder as a commercial bleaching agent. 

Other Cellulosics. Rayon is bleached similarly to cotton but under milder conditions since the fibers are more easily damaged and since there is less colored material to bleach. Cellulose acetate and triacetate are not usually bleached. They can be bleached like rayon, except a slightly lower pH is used to prevent hydrolysis. The above fibers are most commonly bleached with hydrogen peroxide. Linen, dax, and jute requite more bleaching and mil der conditions than cotton, so multiple steps are usually used. Commonly an acidic or neutral hypochlorite solution is followed by alkaline hypochlorite, peroxide, chlorite, or permanganate, or a chlorite step is done between two peroxide steps. A one-step process with sodium chlorite and hydrogen peroxide is also used. 

In solution, chlorine dioxide decomposes very slowly at ambient temperatures in the dark. The primary decomposition process is hydrolysis of chlorine dioxide into chlorite and chlorate ions. The hydrolysis rate is a function of the concentration of hydroxyl ions and temperature, proceeding rapidly at solution pH values above 10 ... 

Chlorine dioxide produced from the methanol reductant processes contains carbon dioxide and small amounts of formic acid. For this reason, sulfur dioxide and chloride-based chlorine dioxide processes are stih used for sodium chlorite production. This problem has been addressed by recycling a portion of the vapor from methanol-based generators so that formic acid further reacts to carbon dioxide ... 

Other Uses. As a biocide, chlorine dioxide is more effective than chlorine over a wider pH range. Chlorine dioxide is also less corrosive and more compatible with some materials of constmction. Chlorine dioxide has a wide variety of small appHcations in drinking water, food processing (qv), cooling towers, and oil recovery. In these areas, chlorite is the preferred source of chlorine dioxide. 

Industrial Processes. The use of sodium chlorite as an oxidizer in NO and SO combustion flue gas scmbber systems has been described... 

Oil Field and Petroleum Processing. Sodium chlorite is finding increasing use as the choice precursor for generating chlorine dioxide for biocidal control in the production of cmde oil (see Petroleum). The use of water in the oil field pumping and processing systems presents significant... 

Chlorine dioxide, discovered in 1811 by Davy, was prepared from the reaction of potassium chlorate with hydrochloric acid. Early experimentation showed that chlorine dioxide exhibited strong oxidizing and bleaching properties. In the 1930s, the Mathieson Alkali Works developed the first commercial process for preparing chlorine dioxide from sodium chlorate. By 1939, sodium chlorite was established as a commercial product for the generation of chlorine dioxide. 

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... 

FBA may be applied by exhaustion from the same bath. If the polyester portion of the blend is to be bleached with sodium chlorite, the cotton is usually brightened in a second step since most FBAs for cotton are destroyed by sodium chlorite. Both types of FBA are normally compatible with a hydrogen peroxide bleaching process. 

The Diox Process, Newark, N. J., Wallace and Tieman, 1949 Intimate mixtures of the solid chlorite with finely divided or fibrous organic matter may be explosive and very sensitive to heat, impact or friction. 

The primary function of the mammalian red blood cell is to maintain aerobic metabolism while the iron atom of the heme molecule is in the ferrous (Fe+2) oxidation state however, copper is necessary for this process to occur (USEPA 1980). Excess copper within the cell oxidizes the ferrous iron to the ferric (Fe+3) state. This molecule, known as methemoglobin, is unable to bind oxygen or carbon dioxide and is not dissociable (Langlois and Calabrese 1992). Simultaneous exposure of sheep to mixtures of cupric acetate, sodium chlorite, and sodium nitrite produced a dose-dependent increase in methemoglobin formation (Calabrese et al. 1992 Langlois and Calabrese 1992). 

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