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General Princlpes
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Organohalide compounds have halogen-substituted hydrocarbon molecules. This means that each compound has fluorine, chloride, bromine, or iodine atoms in its structure. Alkyl halides in this group include dichlo-romethane (found in paint strippers), carbon tetrachloride (refrigerants), and 1,2-dibromoethane (an insecticide). The alkenyl or olefinic organohalides include: vinyl chloride (used to produce polyvinyl chloride, PVC), a known carcinogen, trichlorethylene (used for degreasing and as a drycleaning solvent), tetrachloroethylene, and hexachlorobutadiene (used as a hydraulic fluid). Aryl halides are used in chemical synthesis and as pesticides and solvents. They are derivatives of benzene and toluene. Polychlorinated bi-phenyls (PCBs), highly toxic materials, are an example of a halogenated biphenyl. Chlorofluorocarbons (CFCs), halons, and hydrogen-containing chlorofluorocarbons are of significant importance to the environment. CFCs, once used primarily as refrigerants and aerosol propellents, are believed to have caused the breakdown of the ozone layer and have been banned from production. Halogens used in fire extinguishers as halon have also been implicated in the depletion of the ozone layer and are being phased out. Hydrogen containing chlorofluorocarbons (HFCs) are being touted as the substitute for CFCs as refrigerants and plastic foam blowing agents. Chlorinated phenyls such as pentachlorophenol, are used to treat wood against fungi and insect infestation. The byproduct of that process causes hazardous waste, which has been known to cause liver damage and dermatitis.
Physical Properties of Individual Groundwater Chemicals
Published in John H. Montgomery, Thomas Roy Crompton, Environmental Chemicals Desk Reference, 2017
John H. Montgomery, Thomas Roy Crompton
An aqueous solution containing 300 ng/μL trichloroethylene and colloidal platinum catalyst was irradiated with UV light. After 12 h, 7.4 ng/μL trichloroethylene and 223.9 ng/μL ethane were detected. A duplicate experiment was performed but 1 g zinc was added to the system. After 5 h, 259.9 ng/μL ethane was formed and trichloroethylene was nondetectable (Wang and Tan, 1988). Major products identified from the pyrolysis of trichloroethylene between 300 and 800°C were carbon tetrachloride, tetrachloroethylene, hexachloroethane, hexachlorobutadiene, and hexachlorobenzene (Yasuhara and Morita, 1990).
Chemical Stabilization of Contaminated Soils
Published in David J. Wilson, Ann N. Clarke, Hazardous Waste Site Soil Remediation, 2017
Certain constituents appear to be more difficult than others to immobilize. These include: acetone, 1,2-dichloroethane, ethyl benzene, tetrachloroethylene, n-butanol, methanol, and pyridine. Other constituents were easily immobilized by all formulations: carbon disulfide, ethyl acetate, methylene chloride, 1,1,2-trichloro-1,1,2-trifluorethane, 1,2-dichlorobenzene, 1,4-dichlorobenzene, hexachlorobutadiene, and hexachloroethane. However, all constituents except pyridine could be treated to meet the TC requirements.
Volatile organic compound concentrations and their health risks in various workplace microenvironments
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Simge Çankaya, Hakan Pekey, Beyhan Pekey, Burcu Özerkan Aydın
Determination of the I/O ratios of VOC concentrations in each microenvironment is important so that the dominant environment can be determined. Therefore, the mean I/O ratios during each season were calculated (Table 6). The mean concentrations of 1,1,1-trichloroethane, 1,2-dichloropropane, toluene, styrene, sec-butylbenzene, and hexachlorobutadiene were higher indoors than outdoors in all microenvironments during both seasons. Generally, indoor concentrations of 24 VOCs were higher during winter than summer. The I/O ratios of VOCs detected in this study can be divided into three categories: primarily outdoor sources (I/O < 1.5), both indoor and outdoor sources (1.5 ≤I/O ≤ 10), and primarily indoor sources (I/O > 10) (USEPA 1999). The I/O ratios of trans-1,2-dichloroethylene ranged from 0.52 to 1.14, indicating that the source was primarily outdoors (Xu et al.2016). Additionally, bromochloromethane, CTC, dibromomethane, bromodichloromethane, and chlorobenzene detected at auto paint shops were primarily from outdoor sources because the I/O ratios were low (<1.5). Chlorobenzene and xylenes detected in restaurants also had primarily outdoor sources as did benzene detected at dry cleaners and photocopy centers. The I/O ratios of some VOCs were greater than 10 in some microenvironments. Examples at dry cleaners are isopropyl toluene, isopropyl benzene, sec-butylbenzene, and hexachlorobutadiene during both winter and summer and toluene in winter. This implies that these compounds had primarily indoor sources. Other VOCs had both indoor and outdoor sources.
Fluorinated Carbonates as New Diluents for Extraction and Separation of f-Block Elements
Published in Solvent Extraction and Ion Exchange, 2020
Petr Distler, Miriam Mindová, Jan John, Vasilij A. Babain, Mikhail Yu. Alyapyshev, Lyudmila I. Tkachenko, Ekaterina V. Kenf, Laurence M. Harwood, Ashfaq Afsar
As an alternative to saturated hydrocarbons, heavy halogenated diluents (ρdiluent > ρwater) were tested, mainly chlorinated short-chain hydrocarbons. The main advantage of these diluents was their higher density than water, because at high separated metal loadings the density of solvents based on diluents with low density can exceed the density of the aqueous phase which results in the reversal of the phases and severe complications of the separation processes. However, those chlorinated hydrocarbons such as hexachlorobutadiene, tetrachloroethylene or tetrachloromethane were found to suffer from different disadvantages such as corrosion problems, toxicity of the off-gasses, and volatility.[7,8] They were also found to be sensitive to ionizing radiation with some degradation products being miscible with or soluble in the aqueous phase.[9]
Identification of diluent degradation products in radiolyzed PUREX solvent
Published in Solvent Extraction and Ion Exchange, 2018
Satyabrata Mishra, Anil Kumar Soda, Madabhushi Sridhar, C Mallika, N. K Pandey, U. Kamachi Mudali
In literature, several reports [10–15] exist on the radiolytic degradation of TBP and TBP-diluent in the monophasic as well as biphasic systems and the effect of degradation on the extraction behavior for different metal ions. Tripathi et al. [8,16] evaluated the physiochemical changes due to gamma radiolytic degradation of 1.1 M TBP-DD system equilibrated with 1 M HNO3 by gas-liquid chromatographic (GLC) analysis. They observed an increase in the formation of degradation products with increase of irradiation time. Lloyd et al. [17] studied the alpha radiolysis of PUREX solvent as a function of temperature. This study mainly focused on the metal-induced hydrolysis of TBP. Tallent and Mailen [18] investigated the chemical degradation of NPH as well as TBP in NPH-nitric acid medium and concluded long-chain aliphatic acids to be the diluent degradation products in chemically degraded TBP/NPH system. The effect of gamma radiation on TBP in the presence of various diluents such as a mixture of n-paraffins, hexachlorobutadiene, and naphthenic hydrocarbon was evaluated by Egorov et al. [19] based on infrared spectroscopy as well as gas-liquid chromatography and reported the yield of nitration and oxidation products of diluents. They also found the yield of radiolysis products in the solution of TBP in naphthenic diluent to be more by a factor of 1.5 when compared to that produced for TBP in paraffinic diluents. Lesage et al. [20] detected the formation of TBP dimers during radiolysis using tandem mass spectrometry and isotopic labeling method. Formation of nitro organic compounds, organic nitrate/nitrites, and carbonyl compounds was reported by Sze et al. [21] when Isopar M was degraded with 3 M nitric acid. In 1995, Tahraoui and Morris [22] reviewed the literature data available on the decomposition of solvent extraction media during nuclear spent fuel reprocessing with respect to the mechanisms involved in the chemical and radiolytic degradation of TBP and diluents. Similarly, another review article by Mincher et al. [23], which mainly deals with effect of radiation on solvent extraction media and on TBP radiolysis, describes the plausible mechanism for the formation of primary and secondary degradation products. Lane [24] put forward a hypothesis on the possible degradation products of solvent as well as diluents.