Factors affecting sorption of organic pollutants by natural sorbents (soils, sediments, clays, humic materials, and dissolved organic matters) and sorption coefficients for selected pollutants are reviewed on the basis of the literature results and interpretations; with 681 references examined. The most significant aspects of the sorption process are discussed: sorption isotherms and sorption kinetics; effects of sorbent physico-chemical characteristics (pH, cation exchange capacity, ionic strength, surface area, etc.); effect of the temperature; sorption of volatile compounds; effect of the presence of a cosolvent; association with dissolved organic matter; effect of the sorbent concentration; “hysteresis” or nonsingularity in the sorption–desorption process, and its implications in the transport of these contaminants through soil columns. The experimental and prediction methods adopted for the determination and estimation of the sorption coefficients are also described. Literature sorption coefficients for selected hydrophobic, polar, and ionizable compounds are collected. The compounds taken into consideration belong to the following classes: monoaromatic hydrocarbons, polycyclic aromatic hydrocarbons, chlorinated alkyl and aryl compounds, phenol and chlorinated phenols, polychlorobiphenyls, dioxins, and pesticides. The respective sorption coefficients (log Kd) and organic carbon-referenced sorption coefficients (log Koc) are tabulated together with the most relevant characteristics of the respective sorbent, the measurement temperature, and the experimental methods. The log Koc values are averaged and compared with other experimental and estimated literature data. Differences of sorption coefficients on soils and sediments and effect of pH on sorption coefficients for ionizable compounds are evidentiated.
The experimental techniques and the prediction procedures for the determination or evaluation of the vapor pressure of environmentally relevant organic compounds are described; with 259 references examined. For each of them the characteristics of precision and accuracy are given, when available from the literature. The experimental methods are classified as "direct" and "indirect." The first class includes all those which can measure directly the vapor pressure, while the second concerns those which need "known" vapor pressures of reference compounds for the calibration. Prediction methods are based on the application of the Clapeyron-Clausius equation or on the quantitative structure-property relationships. Also correlation methods require a suitable calibration. The vapor pressures at ambient temperature for several polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and furans, selected pesticides, and some reference compounds are tabulated together with the vapor pressure equations and the enthalpy values in the temperature range of measurement. A critical comparison, based on a statistical analysis of the data obtained with different methods and derived from 152 references, is also carried out.
The main products of the oxidation of tetrafluoroethylene induced by heat, ultraviolet light, and ionizing radiation are carbonyl fluoride, tetrafluoroethylene oxide, hexafluorocyclopropane, and a liquid polymeric peroxide. The reactions were carried out by a static method in the gas phase.IN an earlier Note,l it was shown that tetrafluoroethylene reacts with oxygen under y-or X-irradiation." The present Paper gives further results on the oxidation induced by ionizing radiation together with those obtained by subjecting tetrafluoroethylene and oxygen mixtures to thermal treatment or ultraviolet irradiation. The oxidation leads in all cases to carbonyl fluoride, tetrafluoroethylene oxide, hexafluorocyclopropane, and a polymericperoxidic liquid (C,F,O,),.For all the irradiations, at room temperature, the products account for more than 90% of the gaseous mixture. On the other hand, a proportionately large yield of hexafluorocyclopropane is obtained in the thermal reaction. These results are summarized in Table 1.
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