Halogen biocides

Pittman, C. U. Jr. He, J. Yang, C. Tabaiei, M. Detoxification of PCBs, CFCs, CAHs and Halogenated Biocides in Soils, Sludges and Other Matrices Using Chemical Reductions, Am. Chem. Soc. Meet., Boston,... 

To reduce dust and increase stability, halogenated biocides or other products, such as Oxone, are often pressed into tablets (Fig. 6.3-16) of different sizes and shapes... 

Chemicals Chlorinated pyridinal Organophosphate pesticides o-Phthalaldehyde Triclosan Polychlorinated biphenyls Chlorofluorocarbons Chlorinated aromatics hydrocarbons Halogenated biocides Atrazine Petroleum hydrocarbons Amitraz Bifenthrin Other pesticides, herbicides, biocides, fumigants, germicides, etc. 

Detoxification and Destruction of PCBs, CAHs, CFCs, and Halogenated Biocides in Soils, Sludges, and Other Matrices Using Na/NHs... 

Halogenation of nitromethane is utilized to produce two economically important pesticides, chloropicrin [76-06-2J, a soil fumigant, and bronopol, a biocide useful for control of microbial growth in cosmetics and industrial appHcations. 

P. W. Austin. Unsaturated, halogenated thiocyanates, the preparation thereof and use as a biocide. Patent EP 316058,1989. 

Hendriks, A.J., H. Pieters, and J. de Boer. 1998. Accumulation of metals, polycyclic (halogenated) aromatic hydrocarbons, and biocides in zebra mussel and eel from the Rhine and Meuse Rivers. Environ. Toxicol. Chem. 17 1885-1898. 

Chlorinated micropoUutants are harmful for man and environment due to their toxicity, persistence, and bioaccumulation. Persistent compounds are very stable and difficult to get metabolized and mineralized by biological and chemical processes in the environment, and as a result, they have become ubiquitous in water, sediments, and the atmosphere bioaccumulation is the result of the lipophilicity of these compounds. Polychlorinated dibenzodioxins and -furans (PCDD/F) are not produced purposely like many of other chlorinated technical products, such as chlorinated biocides DDT, lindane, and toxaphene. The production and use of persistent organic pollutants (POPs), the dirty dozen has now been banned worldwide by the Stockholm protocol. It should be mentioned that about 3000 halogenated products have now been isolated as natural products in plants, microorganisms, and animals," but the total amount of these products is much smaller compared to xenobiotics. 

From the results presented in this work is should be evident that A -halamine biocidal polymer coatings are effective at inactivation of bacteria and the prevention of biofouling on surfaces. Once exhausted of halogen, the biocidal surface films can be regenerated by exposure to aqueous-free halogen. Thus, such coatings should have considerable commercial potential. 

In addition to providing new synthetic tools, it has been suggested that semiconducting powders may be of use in the natural decontamination of polluted waters. Solar irradiation of natural water supplies that have been treated with semiconducting powders could be used to oxidatively degrade pollutants. For example, the oxidation of cyanide to isocyanate, which decomposes into nitrogen and carbon dioxide, has been demonstrated. The oxidation of halides to atomic halogen and the oxidation of hydroxide to OH0 has also been observed. These species can be employed as biocides to provide potable water. 

If nitrogen compounds are present, the combined chlorine is in the form of chloramines, which are also volatile but exhibit minimal biocidal effect. Under circumstances of high nitrogen (ammonia) contamination in cooling systems, it may not be possible to regularly achieve breakpoint halogenation without a severe risk of corrosion to copper and other system components. 

In practice, the required ratio can be different from theoretical, as quite often additional bleach is required to provide HOC1 as an oxidant for algal slimes and other forms of chlorine demand. Also, it is necessary to have a permanent source of oxidant available to effect the promotion of HOBr. However, not all the available bromine generated is lost by biocidal reaction or by (limited) volatility. There is, in fact, some degree of recycling of the bromide ion (Br ) back into HOBr, so monitoring of bromine plus the combined free and total chlorine is necessary to strike the correct halogen balance. 

For some industrial cooling water applications, where process contamination is often an inherent problem, a high chlorine/low bromine ratio product may be preferable. This type of problem can happen, for example, where repeated hot/cold cycles are part of the process and some valve leakage and interchange of water between circuits may occur. Thus, the (lower cost) chlorine component is employed in satisfying the contaminant halogen demand and the bromine component (perhaps with some degree of Br recycle) subsequently acts as a biocide. 

The most recent enhancement of bromine biocide chemistry is the development of a stabilized single liquid bromine, under the brand Stabrex , from Nalco (now owned by Degremont/Suez Lyonnaise Des Eaux). The product is most likely a sodium hypochlorite/sodium bromide mix, stabilized with sulfamic acid. It contains 14% available halogen as Br (6% as Cl), and is stable for several months. Stabrex probably has some benefits over other bromine chemistries, but is also a premium priced product. 

Nanoscale metal oxides also exhibit biocidal properties due to their abrasive nature, alkaline surfaces, oxidizing power (when elemental halogens are preadsorbed), and the fact that their average particle charge (positive) attracts bacteria (which generally carry overall negative charge).11 In fact, nano-MgO is... 

Mechanisms of Direct Photolysis of Biocides Based on Halogenated Phenols... 

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