Markin Vladislav S, Volkov Alexander G, Volkova-Gugeshashvili Maya I
Department of Anesthesiology, UT Southwestern Medical Center, Dallas, Texas 75390-9068, USA.
J Phys Chem B. 2005 Sep 1;109(34):16444-54. doi: 10.1021/jp0529220.
Adsorption of hydrophobic and hydrophilic ions at the nonpolarizable interface between two immiscible electrolyte solutions was investigated. The results were analyzed in three different models: (i) Gouy-Chapman model, (ii) ions as hard spheres, and (iii) ion pair formation at the interface. In the Gouy-Chapman model, an analytical expression for the interfacial tension was obtained. It predicts that interfacial tension should be proportional to the square root of the electrolyte concentration, which does not agree with experimental data. Modeling ions as hard spheres only slightly improves the agreement. The third model of interfacial ion pairing as the main origin of adsorption was analyzed using the amphiphilic isotherm (Markin-Volkov isotherm). A good agreement between ion-pairing theory and experimental values was achieved. The MV isotherm takes into account the limited number of adsorption sites, final size of molecules, complex formation at the interface, and interaction between adsorbed particles. The analysis revealed repulsion between adsorbed tetraalkylammonium ions at the nitrobenzene/water interface and demonstrated linear dependence between adsorption site area and the size of a molecule.
研究了两种不混溶电解质溶液之间不可极化界面上疏水离子和亲水离子的吸附情况。结果在三种不同模型中进行了分析：（i）古依-查普曼模型，（ii）离子作为硬球，以及（iii）界面处的离子对形成。在古依-查普曼模型中，得到了界面张力的解析表达式。它预测界面张力应与电解质浓度的平方根成正比，这与实验数据不符。将离子建模为硬球仅略微改善了一致性。使用两亲等温线（马尔金-沃尔科夫等温线）分析了作为吸附主要来源的界面离子对形成的第三种模型。离子对理论与实验值之间取得了良好的一致性。MV等温线考虑了吸附位点的有限数量、分子的最终尺寸、界面处的络合物形成以及吸附颗粒之间的相互作用。分析揭示了硝基苯/水界面上吸附的四烷基铵离子之间的排斥作用，并证明了吸附位点面积与分子尺寸之间的线性关系。
