Polychlorinated biphenyls processes

The performance of SCWO for waste treatment has been demonstrated (15,16). In these studies, a broad number of refractory materials such as chlorinated solvents, polychlorinated biphenyls (PCBs), and pesticides were studied as a function of process parameters (17). The success of these early studies led to pilot studies which showed that chlorinated hydrocarbons, including 1,1,1-trichloroethane /7/-T5-6y,(9-chlorotoluene [95-49-8] and hexachlorocyclohexane, could be destroyed to greater than 99.99997, 99.998, and 99.9993%, respectively. In addition, no traces of organic material could be detected in the gaseous phase, which consisted of carbon dioxide and unreacted oxygen. The pilot unit had a capacity of 3 L/min of Hquid effluent and was operated for a maximum of 24 h. 

Unfortunately, processes are not always so simple. The members of groups such as polychlorinated biphenyls (PCBs) and PAHs, for example, do not all operate through the same principal mechanism of action. Also, some individual pollutants such as p,p -DDT or tributyl tin work through more than one mode of action. 

For polychlorinated biphenyls (PCBs), rate constants were highly dependent on the number of chlorine atoms, and calculated atmospheric lifetimes varied from 2 d for 3-chlorobiphenyl to 34 d for 236-25 pentachlorobiphenyl (Anderson and Hites 1996). It was estimated that loss by hydroxy-lation in the atmosphere was a primary process for the removal of PCBs from the environment. It was later shown that the products were chlorinated benzoic acids produced by initial reaction with a hydroxyl radical at the 1-position followed by transannular dioxygenation at the 2- and 5-positions followed by ring fission (Brubaker and Hites 1998). Reactions of hydroxyl radicals with polychlorinated dibenzo[l,4]dioxins and dibenzofurans also play an important role for their removal from the atmosphere (Brubaker and Hites 1997). The gas phase and the particulate phase are in equilibrium, and the results show that gas-phase reactions with hydroxyl radicals are important for the... 

Volatilization. Transfer of chemicals across the air/water interface can result in either a net gain or loss of chemical, although in many cases the bulk concentration in the air above a contaminated water body is low enough to be neglected (20). When the atmosphere is the primary source of the contaminant, as for example polychlorinated biphenyls in some parts of the Laurentian Great Lakes, atmospheric concentrations obviously cannot be neglected. The Whitman two-film or two-resistance approach (21) has been applied to a number of environmental situations (20, 22, 23). Transport across the air/water interface is viewed as a two-stage process, in which both phases of the interface can offer resistance to transport of the chemical. The rate of transfer depends on turbulence in the water body and in the atmosphere, the... 

CDP A process for destroying dioxins and polychlorinated biphenyls by treatment with a polyethylene glycol and sodium peroxide in a fixed catalyst bed. Developed by Sea Marconi Technologies, Turin, Italy. See also KPEG. 

Chloroff A process for removing chlorine from organic chlorides such as polychlorinated biphenyls by reaction with hydrogen under pressure, over a proprietary catalyst. Developed by Kinetics Technology International. See also Hi-ChlorofiF. 

Neostar A process for destroying waste organic chlorides (e.g., polychlorinated biphenyls) by heating with steam and hydrogen at over 1,000°C. The products are methane, ethane, other chlorine-free hydrocarbons, and hydrochloric acid. Developed by Cerchar, France. 

Relube A process for removing sulfur and chlorine compounds from waste oils, particularly those contaminated by polychlorinated biphenyls. Developed by Kinetics Technology International, The Netherlands, and operated first in Greece. 

Sydox [Sydney oxidation] A process for destroying polychlorinated biphenyls by oxidation. A catalyst containing ruthenium is used, and the temperature is kept below 100°C to prevent the formation of dioxins. Developed by J. Beattie at the University of Sydney in the 1980s by 1991 it had not been piloted. 

Terrence Collins is the Thomas Lord Professor of Chemistry at Carnegie Mellon University who contends that the dangers of chlorine chemistry are not adequately addressed by either academe or industry, and alternatives to chlorine and chlorine processors must be pursued. He notes, Many serious pollution episodes are attributable to chlorine products and processes. This information also belongs in chemistry courses to help avoid related mistakes. Examples include dioxin-contaminated 2,4,5-T, extensively used as a peacetime herbicide and as a component of the Vietnam War s agent orange chlorofluorocarbons (CFCs) polychlorinated biphenyls (PCBs the pesticides aldrin, chlordane, dieldrin, DDT, endrin, heptachlor, hexachlorobenzene, lindane, mirex, and toxaphene pentachlorophe-... 

The water insoluble, highly chemically and thermally stable PCBs used as insulating fluids for transformers and capacitors, in paints, copy paper, etc., are extremely toxic, persistent in the environment and bioaccumulating. PCBs are currently destroyed by incineration of concentrates at high temperatures or chemically with sodium metals or organosodium. Both processes are costly. The cathodic reduction/elimination of the chlorine from polychlorinated biphenyl... 

Highly halogenated organic compounds such as polychlorinated biphenyls and perchloroethylene appear to be too highly oxidised and low in energy content to serve as sources of electrons and energy for microbial metabolism. Bacteria are more likely to use them as electron acceptors in cell-membrane-based respiration processes [154]. The environmental fate of halogenated polymers such as polyvinylchloride or Teflon may depend on the question of whether it will be appropriate to sustain de-halorespiration processes. 

This book examines comprehensively the chlorine industry and its effects on the environment. It covers not only the history of chlorine production, but also looks at its products, their effects on the global environment and the international legislation which controls their use, release and disposal. Individual chapters are dedicated to subjects such as end use processes, water disinfection and metallurgy, environmental release of organic chlorine compounds, polychlorinated biphenyls, legal instruments and the future of the chlorine industry. 

The formation of polar metabolites from nonpolar materials may actually facilitate monitoring programs—in many cases the polar chemicals are highly concentrated in certain body fluids such as bile and urine. On the other hand, materials such as certain cyclodienes and polychlorinated biphenyls, which are very lipid soluble and resistant to metabolism, may accumulate and these chemicals may persist in the environment and may be transferred via the food chain to man. There is also interest in these biotransformation processes in lower organisms since the simplicity of these systems may lead to a better understanding of the phylogenetic development of xenobiotic metabolism. 

Polychlorinated biphenyls (PCBs) have been used in various industrial processes during the past 40 years but were not recognized as major environmental contaminants until 1966 (1). Fish as a major food source have attained the dubious honor of being the most frequently cited PCB contamination problem (2). In the following presentation disposition of PCBs in fish will be discussed from four points of view accumulation, metabolism, distribution and elimination. No attempt will be made to cover PCB residue levels found in fish in nature (3) or acute or chronic toxicity of PCBs in fish (4-20). 

The potential of modern chemical instrumentation to detect and measure the conposition of coirplex mixtures has made it necessary to consider the use of methods of multivariable data analysis in the overall evaluation of environmental measurements. In a number of instances, the category (chemical class) of the compound that has given rise to a series of signals may be known but the specific entity responsible for a given signal may not be. This is true, for example, for the polychlorinated biphenyls (PCB s) in which the clean-up procedure and use of specific detectors eliminates most possibilities except PCB s. Such hierarchical procedures simplify the problem somewhat but it is still advantageous to apply data reduction methods during the course of the interpretation process. 

XZ/N VI RON MENTAL APPLICATIONS OF CHEMOMETRics are of interest because of the concern about the effects of chemicals on humans. The symposium upon which this book is based served as an important milestone in a process we, the editors, initiated in 1982. As members of the Environmental Protection Agency s Office of Toxic Substances (OTS), we have responsibilities for the acquisition and analysis of human and environmental exposure data in support of the Toxic Substances Control Act. OTS exposure studies invariably are complex and range from evaluating human body burden data (polychlorinated biphenyls in adipose tissue, for example) to documenting airborne asbestos levels in schools. 

TechXtract is an extraction technology that has been used to remove a variety of contaminants from the surfaces of concrete, steel, brick, and other materials. Target contaminant types include organics, heavy metals, radionuclides, and polychlorinated biphenyls (PCBs). The technology uses proprietary chemical formulations in successive steps to remove these contaminants. The process employs as many as 25 different components in 3 separate chemical formulations that are applied to the contaminated surface and then removed in a multi-step, multicycle sequence. TechXtract is commercially available and has been used at multiple sites. 

---