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首页> 外文期刊>Environmental toxicology and chemistry >GIBBS FREE ENERGIES OF FORMATION OF PCDDS: EVALUATION OF ESTIMATION METHODS AND APPLICATION FOR PREDICTING DEHALOGENATION PATHWAYS
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GIBBS FREE ENERGIES OF FORMATION OF PCDDS: EVALUATION OF ESTIMATION METHODS AND APPLICATION FOR PREDICTING DEHALOGENATION PATHWAYS

机译:PCDDS形成的吉布斯自由能:估计方法的评估和预测除盐途径的应用

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摘要

Gibbs free energies of formation for the ideal gas, liquid phase, and species in solution were estimated for 75 polychlorinated dibenzo-p-dioxins (PCDDs) at 298.15 K and 100,000 Pa. These values were used to calculate standard redox potentials, with H_2 as the electron donor. Owing to the lack of experimental thermodynamic data for the involved chemical species, the standard-state ideal gas enthalpies of formation were evaluated by several semiempirical methods including the Modified Neglect of Diatomic Differential Overlap (MNDO), Austin Model 1 (AM1), and MNDO-Parametric Method 3 (PM3). Three different implementations of Benson's group additivity method for estimation of ideal gas enthalpies of formation were also evaluated. As a result of the evaluation, the CHETAH program based on Benson's group additive method was chosen for ideal gas enthalpy of formation calculations. Entropies, vapor pressure, and aqueous solubility were calculated by existing methods in order to complete the thermodynamic cycle. Calculated redox potentials indicate that chlorodioxins, including 2,3,7,8-tetrachlorodioxin, can serve as electron acceptors in anaerobic environments, at least from a thermodynamic perspective.
机译:估算了在298.15 K和100,000 Pa下对75种多氯二苯并二恶英(PCDDs)的理想气相,液相和溶液中的物种形成的吉布斯自由能。这些值用于计算标准氧化还原电势,H_2为电子给体。由于缺乏所涉及化学物种的实验热力学数据,因此通过几种半经验方法(包括改良的双原子微分重叠忽略(MNDO),奥斯丁模型1(AM1)和MNDO)对标准状态下理想的形成气体焓进行了评估。 -参数方法3(PM3)。还评估了Benson基团可加性方法的三种不同实现方式,用于估算理想的地层气体焓。评估的结果是,选择了基于Benson基团加成法的CHETAH程序来计算理想的地层气体焓。通过现有方法计算熵,蒸气压和水溶性,以完成热力学循环。计算出的氧化还原电势表明,至少从热力学角度来看,包括2,3,7,8-四氯二恶英在内的氯二恶英可以在厌氧环境中充当电子受体。

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