Lee Namkyu, Mohanakumar Shilpa, Briels W J, Wiegand Simone
IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, Jülich D-52428, Germany.
Department of Mechanical Engineering, Yonsei University, Seoul, Korea.
Phys Chem Chem Phys. 2024 Feb 28;26(9):7830-7836. doi: 10.1039/d3cp06061f.
We investigate the thermodiffusive properties of aqueous solutions of lithium chloride, using thermal diffusion forced Rayleigh scattering in a concentration range of 0.5-2 mole per kg of solvent and a temperature range of 5 to 45 °C. All solutions exhibit non-monotonic variations of the Soret coefficient with a concentration exhibiting a minimum at about one mole per kg of solvent. The depth of the minimum decreases with increasing temperature and shifts slightly towards higher concentrations. We compare the experimental data with published data and apply a recent model based on overlapping hydration shells. Additionally, we calculate the ratio of the phenomenological Onsager coefficients using our experimental results and published data to calculate the thermodynamic factor. Simple linear, quadratic and exponential functions can be used to describe this ratio accurately, and together with the thermodynamic factors, the experimental Soret coefficients can be reproduced. The main conclusion from this analysis is that the minimum of the Soret coefficients results from a maximum in the thermodynamic factor, which appears itself at concentrations far below the experimental concentrations. Only after multiplication by the (negative) monotonous Onsager ratio does the minimum move into the experimental concentration window.
我们利用热扩散强迫瑞利散射，在每千克溶剂0.5 - 2摩尔的浓度范围以及5至45°C的温度范围内，研究了氯化锂水溶液的热扩散性质。所有溶液的索雷特系数均呈现非单调变化，在每千克溶剂约1摩尔的浓度处出现最小值。最小值的深度随温度升高而减小，并略微向更高浓度偏移。我们将实验数据与已发表的数据进行比较，并应用了基于重叠水化层的最新模型。此外，我们利用实验结果和已发表的数据计算了唯象昂萨格系数的比值，以计算热力学因子。简单的线性、二次和指数函数可用于准确描述该比值，并且结合热力学因子，可以重现实验索雷特系数。该分析的主要结论是，索雷特系数的最小值源于热力学因子的最大值，而该最大值本身出现在远低于实验浓度的浓度处。只有在乘以（负的）单调昂萨格比值后，最小值才会进入实验浓度窗口。
