Toxicity chlorination

Chlorine. Chlorine is a weU known disinfectant for water and wastewater treatment, however, it can react with organics to form toxic chlorinated compounds such as the tribalomethanes bromodichloromethane, dibromochloromethane, chloroform [67-66-3] and bromoform [75-25-2]. Chlorine dioxide [10049-04-4] may be used instead since it does not produce the troublesome chlorinated by-products as does chlorine. In addition, by-products formed by chlorine dioxide oxidation tend to be more readHy biodegradable than those of chlorine, however, chlorine dioxide is not suitable for waste streams containing cyanide. 

Dichloroethane is one of the more toxic chlorinated solvents by inhalation (49). The highest nontoxic vapor concentrations in chronic exposure studies with various animals range from 100 to 200 ppm (50,51). 1,2-Dichloroethane exhibits a low single-dose oral toxicity in rats LD q is 680 mg/kg (49). Repeated skin contact should be avoided since the solvent can cause defatting of the skin, severe irritation, and moderate edema. Eye contact may have slight to severe effects. 

Tetrachloroethane is one of the most toxic chlorinated hydrocarbons (127,128). The Hver is most affected. 

Hexachloroethane is considered to be one of the more toxic chlorinated hydrocarbons. The 1991 ACGIH recommended time-weighted average (TWA) for hexachloroethane was 1 ppm or 10 mg /m of air. Skin adsorption is a route of possible exposure ha2ard. The primary effect of hexachloroethane is depression of the central nervous system (147). Pentachloroethane and tetrachloroethylene are primary metaboHtes of hexachloroethane in sheep (148). 

The trichloroethylene is oxidized, the gaseous products are removed by the flowing air, and the ehlorine is eaptured by the solid soda and forms salt. The solid salt is removed by diseharging the used OXITOX at the bottom of the reaetor. This is a relatively slow reaetion and the central interest is in removing the last traees of toxic chlorinated compounds (for which TCE is only a model eompound), therefore a very simple model was used. Based on conservation prineiples, it was assumed that chloride removed from the gas phase ends up in the solid phase. This was proven in several material balanee ealeulations. No HCl or other ehlorinated compound was found in the gas phase. The eonsumption rate for TCE was expressed as ... 

Fire Hazards - Flash Point (deg. F) 82 OC 61 CC Flammable limits in Air (%) Data not available Fire Extinguishing Agents Water, dry chemical, carbon dioxide Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Toxic chlorine and phosgene gas may be formed in fires Behavior in Fire Not pertinent Ignition Temperature (deg. F) 932 Electrical Hazard Data not available Burning Rate No data. 

Caution All operations described in this procedure, should be performed in an efficient hood, because toxic chlorine and bromomethane are used in Steps A and B respectively, and hydrogen is evolved in Step C. 

Household ammonia should never be mixed with chlorine bleach, because a redox reaction occurs that generates toxic chlorine gas and hydrazine NH3 + OCl —> CI2 + N2 H4 (unbalanced) Balance this equation. 

The most industrially significant polymerizations involving the cationic chain growth mechanism are the various polymerizations and copolymerizations of isobutylene. In fact, about 500 million pounds of butyl rubber, a copolymer of isobutylene with small amounts of isoprene, are produced annually in the United States via cationic polymerization [126]. The necessity of using toxic chlorinated hydrocarbon solvents such as dichloromethane or methyl chloride as well as the need to conduct these polymerizations at very low temperatures constitute two major drawbacks to the current industrial method for polymerizing isobutylene which may be solved through the use of C02 as the continuous phase. 

The price of the oxidation equivalent varies with the reagent [288]. Oxygen in air is the cheapest, followed by chlorine, electricity, hydrogen peroxide and finally ozone. Oxydation with oxygen at low temperature is only feasible biologically. Chlorine often forms very stable, highly toxic chlorinated compounds, which often limits its use. 

The disposal and destruction of chlorinated compounds is a subject of great importance. In fact, in 1993, some environmental groups had proposed the need for a chlorine-free economy. The cost of complete elimination of chlorinated compounds is quite staggering with the latest estimate as high as 160 billion/year.46 The most common method to destroy chlorocarbons is by high-temperature thermal oxidation (incineration).47 The toxic chlorinated compounds seem to be completely destroyed at high temperatures however, there is concern about the formation of toxic by-products such as dioxins and furans.48... 

Oxidative catalysis over metal oxides yields mainly HC1 and C02. Catalysts such as V203 and Cr203 have been used with some success.49 50 In recent years, nanoscale MgO and CaO prepared by a modified aerogel/hypercritical drying procedure (abbreviated as AP-CaO) and AP-MgO, were found to be superior to conventionally prepared (henceforth denoted as CP) CP-CaO, CP-MgO, and commercial CaO/MgO catalysts for the dehydrochlorination of several toxic chlorinated substances.51 52 The interaction of 1-chlorobutane with nanocrystalline MgO at 200 to 350°C results in both stoichiometric and catalytic dehydrochlorination of 1-chlorobutane to isomers of butene and simultaneous topochemical conversion of MgO to MgCl2.53-55 The crystallite sizes in these nanoscale materials are of the order of nanometers ( 4 nm). These oxides are efficient due to the presence of high concentration of low coordinated sites, structural defects on their surface, and high-specific-surface area. 

Sources 1 BC Research, CPAR Report 245-1, Identification of the Toxic Constituents in Kraft Mill Bleach Plant Effluents . May 1974, p. 22. 2 BC Research, CPAR Report 245-2, Identification of the Toxic Constituents in Kraft Mill Bleach Plant Effluents . May 1975, p. 31. 3 R.H. Voss, J.T. Wearing and A. Wong. Effect of Hardwood Chlorination Conditions on the Formation of Toxic Chlorinated Compounds , Tappi, 1981, 64, 3, pp. 167-170. 4 R.H. Voss, J.T. Wearing and A. Wong, Effect of Softwood Chlorination Conditions on the Formation of Toxic Chlorinated Compounds , 1979 CPPA/TS Environmental Conference, Victoria BC, Canada, November 1979. 

Figure 6.25 Chemical stmctures of some toxic chlorinated organics.

Chemical/Physical. Readily reacts with moisture forming hydrates (Hollifield, 1979). Decomposes at 350 °C (Windholz et al, 1983), probably emitting toxic chlorine fumes. 

The experimental first-order decay rate for pentachlorobenzene in an aqueous solution containing a nonionic surfactant micelle (Brij 58, a polyoxyethylene cetyl ether) and illuminated by a photoreactor equipped with 253.7-nm monochromatic UV lamp is 1.47 x lO Vsec. The corresponding half-life is 47 sec. Photoproducts reported include all tetra-, tri-, and dichlorobenzenes, chlorobenzene, benzene, phenol, hydrogen, and chloride ions (Chu and Jafvert, 1994). Chemical/Physical. Emits toxic chlorinated acids and phosphene when incinerated (Sittig,... 

From time to time, railroad tank cars are involved in accidents that will leak liquid or gaseous chlorine that, when escaping into the air, forms toxic chlorine compounds. This is extremely dangerous, both as a fire hazard and for human health. When water is used to flush away the escaping chlorine, it may end up as hydrochloric acid, which can be hazardous to the water supply and to aquatic life. 

Development of Air Sampling and Analytical Methods for Toxic Chlorinated Organic Compounds—Research Report for Hexachlorocyclopentadiene", Southern Research Institute, Birmingham, AL, NIOSH Contract No. 210-78-0012, National Institute for Occupational Safety and Health, Cincinnati, OH, 1980. 

Development of Air Sampling and Analytical Methods for Toxic Chlorinated Organic Compounds—Research Report for... 

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