Environmental considerations chlorination

Various industrial pilot plants and full-scale operations, using radiation-chemical processing have been reported, with production rates -50 to -1000 tons per year (Spinks and Woods, 1990 Chutny and Kucera, 1974). Production rates less than -50 tons per year are not considered viable. These operations are or have been conducted in countries such as the United States, the former U.S.S.R., Japan, and France. However, some operations have also been reported in the former Czechoslovakia and Romania, especially in connection with petroleum industry. In the United States, chlorination of benzene to gammexane (hexachlorocyclohexane) was hotly pursued at one time by radiation or photoinitiation. Since the early seventies the activity has dwindled, presumably due to lack of demand and environmental considerations. 

Environmental concerns. See also Environmental considerations Environmental factors Environmental impacts Environmental issues ascorbic acid, 25 758-759 chlorine, 25 679 dyes and dye intermediates,... 

N205 in organic solvents Chlorinated solvents encompass a much wider range of nitrations and permit synthesis of polynitrated species directly without the formation of acidic by-products (an important environmental consideration). It is also suitable for the nitration of strained-ring heterocyclic skeletons. 

Prior to the discovery of a-sulfonation of anthraquinone, nitration was the only useful method for preparing a-substituted anthraquinones. The nitro group of a-nitroanthraquinones can be replaced in a manner similar to the sulfonic acid moiety, e.g., by chlorine atoms and amino, hydroxy, alkoxy, or mercapto groups. Reduction readily yields aminoanthraquinones. Nitration of anthraquinone has gained increasing importance because of environmental considerations, this method offering an economical alternative to a-sulfonation... 

A considerably increased choice of suitable solvents (toluene, EtOAc, various ketones), not limited to environmentally unfriendly chlorinated ones (e.g., CH2C12). 

A second group of important POP s is represented by chlorinated pesticides. Major attention was attributed to the environmental occurrence and fate of DDT and its numerous metabolites. As a result a comprehensive knowledge about the major properties with respect to environmental considerations (environmental stability, toxicological effects, transport processes including its global distribution etc.) exists. For instance the information on the degradation pathway under aerobic as well as under anaerobic conditions is nearly complete as illustrated in Fig. 3. 

In addition to water, oxygenated hydrocarbon solvents are generally preferred whenever the formulation allows them. This is also due to environmental considerations. Types of solvents used include alcohols, esters, ketones, and the alcohol ethers associated with inks. Some paints still use hydrocarbon solvents such as turpentine and kerosene, and there a few instances of chlorinated hydrocarbon solvents, such as trichloroethylene, being used. Finally, there are solventless delivery systems such as electrodeposition used in some applications such as automotive coatings. 

Chlorine dioxide has been evaluated as a replacement for chlorine [1630]. Gaseous chlorine as a biocide for industrial applications is declining because of safety and environmental and community impact considerations. Various alternatives have been explored, for example, bromo-chorodimethyl hydan-toin (BCDMH), nonoxidizing biocides, ozone, and chlorine dioxide. Chlorine dioxide offers some unique advantages because of its selectivity, effectiveness over a wide pH range, and speed of kill. Safety and cost considerations have restricted its use as a viable replacement. 

Although chlorination with sodium dichloroisocyanurate is still by far the most commonly used method of shrink-resist finishing, there is considerable concern over the environmental influence of its AOX contribution. For this reason, its usefulness could decline in future and there has been considerable investigation of alternatives to this attractively cost-effective treatment. 

Westing, A.H. 1978. Ecological considerations regarding massive environmental contamination with 2,3,7,8-tetrachlorodibenzo-jpara-dioxin. Pages 285-294 in C. Ramel (ed.). Chlorinated Phenoxy Acids and Their Dioxins. Ecol. Bull. (Stockholm) 27. 

---