Yoshida Yuma, Shimada Tetsuya, Ishida Tamao, Takagi Shinsuke
Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University 1-1 Minami-ohsawa Hachioji-shi Tokyo 192-0397 Japan.
Research Center for Gold Chemistry, Tokyo Metropolitan University 1-1 Minami-ohsawa Hachiohji-shi Tokyo 192-0397 Japan.
RSC Adv. 2020 Jun 4;10(36):21360-21368. doi: 10.1039/d0ra03158e. eCollection 2020 Jun 2.
In this study, the adsorption behavior of mono-cationic acridinium derivatives on a synthetic clay mineral (Sumecton SA) was investigated. The acridinium derivatives were adsorbed on the clay surface without aggregation, as found from the changes in the absorption spectra of the acridinium derivatives with SSA and without SSA represented by two-component equilibrium systems of adsorbed and non-adsorbed components. Following the Langmuir isotherm analysis, the adsorption equilibrium constants and maximum adsorption amounts were determined for acridinium derivatives, and the Gibbs free energy change (Δ) was calculated to be in the range of -33.8 to 40.0 kJ mol from the adsorption equilibrium constants. These results indicated that the adsorption of acridinium derivatives on the clay surface was an exergonic reaction. Moreover, thermodynamic parameters such as enthalpy change (Δ) and entropy change (Δ) were obtained from the temperature effect experiments. For all acridinium derivatives, Δ (from -7.82 to -26.0 kJ mol) and Δ (0.047-0.088 kJ mol K) were found to be negative and positive, respectively. It was suggested that not only electrostatic interactions, but also van der Waals forces and hydrophobic interactions played an important role in the adsorption of cationic aromatic molecules on the clay surface. Because these thermodynamic parameters showed a strong correlation with the molecular cross-sectional area of acridinium derivatives, it was suggested that the contribution of hydrophobic interactions became smaller as the molecular cross-sectional area became larger.
在本研究中，研究了单阳离子吖啶鎓衍生物在合成粘土矿物（Sumecton SA）上的吸附行为。由吸附和未吸附组分的两组分平衡体系表示，通过有无SSA时吖啶鎓衍生物吸收光谱的变化发现，吖啶鎓衍生物在粘土表面吸附而不聚集。根据朗缪尔等温线分析，测定了吖啶鎓衍生物的吸附平衡常数和最大吸附量，并根据吸附平衡常数计算出吉布斯自由能变化（Δ）在-33.8至40.0 kJ/mol范围内。这些结果表明，吖啶鎓衍生物在粘土表面的吸附是一个放能反应。此外，通过温度效应实验获得了焓变（Δ）和熵变（Δ）等热力学参数。对于所有吖啶鎓衍生物，发现Δ（-7.82至-26.0 kJ/mol）为负，Δ（0.047 - 0.088 kJ/(mol·K)）为正。结果表明，静电相互作用以及范德华力和疏水相互作用在阳离子芳香分子在粘土表面的吸附中都起着重要作用。由于这些热力学参数与吖啶鎓衍生物的分子截面积有很强的相关性，因此表明随着分子截面积增大，疏水相互作用的贡献变小。
