建構適用於電解質和非電解質溶液之活性係數模型

Abstract

本作藉由結合Pitzer-Debye-Hückel (PDH)理論和COSMO-SAC模型發展一通用於預測電解質和非電解質溶液中化學物質活性係數的熱力學模型。其中Pitzer-Debye-Hückel理論著重於描述溶液中帶電物質（如鈉離子、硝酸根）具有的遠程庫倫作用力。同時，利用分子電位分布(Molecular Electrostatic Potential Map, MESP)決定氫鍵方向性的COSMO-SAC模型則用於計算分子間短程交互作用力。該模型僅需要系統中物質的分子結構、每個原子的半徑以及一組通用參數來確定分子之間的交互作用力。利用計算出的交互作用力即可進一步求得活性係數以及相關的熱力學性質。除此之外，吾等發現如將單原子離子周邊的水合分子考慮至模型中，則能一定程度地改善電解質水溶液中熱力學性質的預測。因此，此模型能應用於幾乎所有種類的化學物質。本作使用大量電解質、非電解質和離子液體的相平衡數據評估此方法，包括氣液相平衡、液液相平衡、無限稀釋下的活性係數、辛醇-水分配係數、離子活性係數和滲透係數等熱力學性質，以確保模型的通用性。此方法能在缺少實驗數據的情況下，提供化工程序開發者一個更廣泛適用於各種溶液的活性係數模型。

A general model is developed for the prediction of activity coefficient of chemicals in both electrolyte and nonelectrolyte solutions. The method combines the thermodynamically consistent Pitzer–Debye-Hückel (PDH) theory for describing long-range Coulomb interactions that are important for charged species (e.g. Na+ and Cl-) and the COSMO-SAC model for short-range interactions. The model only requires the structure of molecules, the radius of each atom, and a universal set of parameters to determine the interactions between molecules. The activity coefficients and other relevant thermodynamics properties can then be obtained based on these interactions. It is worth mentioning that we consider the water hydration shell of monatomic ion in aqueous solution to improve the prediction from our former method. Therefore, the model is widely applicable to nearly all kinds of chemical species. We have validated the method using a large set of phase equilibrium data, including vapor−liquid equilibrium (VLE), liquid−liquid equilibrium (LLE), the infinite dilution activity coefficient (IDAC), the mean ionic activity coefficient (γ_±), the osmotic coefficient (ϕ^((m))) and the octanol−water partition coefficient (K_ow), encompassing nonelectrolytes, electrolytes, and ionic liquids. Thus, the method is very useful for the development of chemical processes involving both neutral and charged species when no experimental data is available.