Physicochemical Study of the Formation and Decomposition of Organohalogen Compounds

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The purpose of this study is to qualify and establish the physicochemical properties of organohalogen compounds such as PCDD/Fs and PBDD/Fs. The formation and decomposition behaviors of the organohalogen compounds can be estimated using their physicochemical properties.1.Determinations of vapor pressure of PCDD/Fs, OBDD, Kanechlor 300 and BFRs using Knudsen effusion methods. A new apparatus with a very small Knudsen cell was especially designed for the vapor pressure measurements of dioxin congeners and other POPs. The apparatus was calibrated by reference compounds, and the vapor pressure results were compared with the available reference data. The adsorption experiments were also carried out by mean of Knudsen cell. The apparent vapor pressures of OCDD with calcium hydroxide, hematite, graphite and activated carbon were measured. The adsorbing abilities of these compounds were estimated from the apparent vapor pressures of OCDD.2.Heat capacities of solid phase, melting points and enthalpies of fusion for DD, DF, OCDD and OCDF were measured by a modulated differential scanning calorimeter. Thermodynamic functions of gas phase such as heat capacity, entropy and standard enthalpy of formation for PCDD/Fs were calculated by the molecular orbital method with density functional theory. The temperature dependences of enthalpies of formation for DD, DF, OCDD and OCDF were estimated in the range from the solid phase to the gas phase using the data obtained in this study and reference data.3.Thermodynamic properties (heat capacity, entropy, enthalpy and Gibbs energy of formation) of PBDD/Fs were calculated by Density function theory and statistical thermodynamics theory. The employed methods were evaluated using brominated arenes compounds with experimental thermodynamic data.