Biocides, process chemicals

Glutaraldehyde (1,3-diformyl propane) is a powerful, cold disinfectant. It is used principally in aqueous solution as a biocide and chemical disinfectant. It has been widely used in the health services, e.g. in operating theatres, endoscopy units, dental units and X-ray film processing. 

Microorganisms such as bacteria, microscopic fungi and similar species can have mechanical, chemical and biological effects. Adverse effects of these kinds are referred to as biodegradation processes. Chemical compositions which provide protection from biodegradation processes are known as biocides or, in the case of fungi, fungicides. 

Removing suspended solids, decreasing cycles of concentration, and clarification all may be beneficial in reducing deposits. Biodispersants and biocides should be used in biofouled systems. Simple pH adjustment may lessen precipitation of certain chemical species. The judicious use of chemical corrosion inhibitors has reduced virtually all forms of aqueous corrosion, including underdeposit corrosion. Of course, the cleaner the metal surface, the more effective most chemical inhibition will be. Process leaks must be identified and eliminated. 

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. 

By 2000, the alpha olefin market had grown to more than 3. billion pounds. Technology had brought down the cost of producing them and simultaneously, a broad range of applications for all the alpha olefins expanded rapidly—surfactants, synthetic lubricants, plasticizer alcohols, fatty acids, mercaptans, comonomers, biocides, paper and textile sizing, oil field chemicals, lube oil., additives, plastic processing aids, and cosmetics. 

The Swedish Chemical Inspectorate (KEMI) has used substitution analysis to assess biocides with the goal of promoting sustainable agriculture. KEMI uses a seven-step process that evaluates not only the intrinsic... 

The basic idea of the CLH process is the transfer of responsibility for classification and labeling from industrial companies to authorities on a European Community level. In case of active substances in biocidal or plant protection products, all intrinsic properties including physicochemical properties, human health hazards, and environmental hazards are subject to the harmonization. By contrast, in the case of chemicals which are used in other application fields only some specific hazard classes are considered in the CLH procedure. According to Article 36 of the CLP Regulation, these are respiratory sensitization, carcinogenicity, germ cell mutagenicity, and reproductive toxicity. Consequently, these provisions have... 

Polyvinyl chloride is processed into a number of forms by including additives. Additives are used to vary the properties of PVC so that it can be made soft and flexible or hard and rigid. Additives are also used to inhibit decomposition as a result of exposure to sunlight, ozone, and chemicals. Plasticizers are the primary additive included in PVC materials. Di(2-ethylhexyl) phthalate (DEHP) and a host of other phthalates are the most common plasticizers. Plasticizers impart flexibility, thermal stability, strength, and resilience to PVC compounds. PVCs without plasticizers are classified as UPVC the letters stand for unplasticized polyvinyl chloride. UPVC is rigid and used for conduit, containers, gutters, and floor tiles. Other common PVC additives are biocides, lubricants, and pigments. 

Although the musk fragrances and biocides often are released to the aquatic environment, many of them may be transported to other media, including the atmosphere. As discussed above, the processes in the atmosphere are all chemical degradation processes and the ability for a chemical to reach the atmosphere will depend on the Henry s law constant (Hc). In addition, some of these products may be susceptible to chemical hydrolysis. Table 16.5 lists the musk fragrances and biocide compounds along with the Henry s law constant estimated by EPISuite... 

Waterside problems that lead to decreases in efficiency and material deterioration can be caused by a variety of mechanisms, such as electrochemical corrosion and deposition of foulants. These problems can be exacerbated by low flow, poor operational practice, process contamination, or specific stresses. It is also important to try to determine cause and effect relationships in order to provide a logical and practical water treatment solution. Such a solution will usually involve some form of cleaning, plus a combined engineering and chemical action plan. Inspection may be made easier by the use of a Boroscope or similar optical/video recording device. The color, texture, and quantity of all deposits should be noted, measurements of pits taken, and microbiological contaminants analyzed. It may be useful to conduct biocide efficiency tests on bacterial slimes. The period when a heat exchanger is open for inspection may be an opportune time for the permanent installation of ports for corrosion-monitoring probes. 

Until about ten years ago, protectant foliar fungicides (such as ethylene bis-dithiocarbamates and phthalimides) and soil sterilants (such as vapam or methylbromide) were the only chemical means of controlling diseases caused by Oomycetes. These compounds are nonspecific biocides affecting many vital cell processes of both the pathogen and the host plant. This means that they are non-selective,... 

Interest in (5,5)-fused ring systems developed in separate, albeit closely related, directions. In the first, chemists continue their quest for new compounds having unique biological, chemical and physical properties. In the second, emphasis is on the classification of aromaticity based upon molecular conformity with Hiickel s rule. An increasing understanding of the fundamental chemistry of heterocyclic ring systems has led to considerable advances in this field, as evidenced by the growing list of applications as biocides and in industrial processes. 

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