Development of a thermodynamic model to predict reduced surface excess adsorption isotherms in liquid phase adsorption based on a new method for characterisation of surface groups

该项目的目的是预测减少表面过量吸附等温线与验证的热力学模型。活性炭表面上的化学表面基团的表征形成了这些预测的基础。在第一步中，具有不同表面功能的活性炭将通过不同的方法表征。此外，这些碳中的一些将被氧化化学品改性。然后将在选定的活性炭上测量探针分子（甲苯、甲基环己烷和丙酮）的二元混合物的过量等温线。借助这些等温线，可以评估探针分子吸附到表面基团的竞争。初步研究表明，该实验可以定性描述活性炭表面的极性、非极性和芳香性。减少表面过剩以及探针分子的优选吸附区域的大小的详细解释预计将产生进一步的见解。附加的物质性质，如PI电子的数量，偶极矩，极化率和汉森参数将用于进一步的定性讨论。此外，表面基团的定量描述是有意的。这将导致活性炭上过量等温线的热力学建模。基于表面基团的分布，将开发基团贡献模型。该模型应考虑吸附剂的官能团以及活性炭表面。然后，该模型可以拟合到实验过量等温线。除了将模型拟合到实验数据之外，该研究还应该朝着预测模型的方向进展，从而打开预测未经实验检验的探针分子的过量等温线的可能性。

The aim of this project is the prediction of reduced surface excess adsorption isotherms with a validated thermodynamic model. The characterization of the chemical surface groups on the surface of the activated carbons forms the basis for those predictions. In a first step, activated carbons with different surface functionalities will be characterized by different methods. Additionally some of these carbons will be modified by oxidizing chemicals. Then excess isotherms of binary mixtures of probe molecules (toluene, methylcyclohexane and acetone) will be measured on a selection of activated carbons. With the help of these isotherms, the competition of the probe molecules for adsorption to the surface groups can be assessed. Preliminary studies showed that such experiments can qualitatively describe the polar, nonpolar and aromatic character of the activated carbon s surface. A detailed interpretation of the reduced surface excess as well as the size of the region of preferred adsorption of the probe molecules is expected to yield further insights. Additional substance properties like the number of PI-electrons, dipole moments, polarizabilities and Hansen parameters will be used to further the qualitative discussion. Also, a quantitative description of the surface groups is intended. This will lead to a thermodynamic modeling of excess isotherms on activated carbons. A group contribution model will be developed, based on the distribution of surface groups. This model is supposed to take into account functional groups of the adsorptives as well as the activated carbon surface. The model can then be fitted to the experimental excess isotherms. Besides fitting the model to the experimental data, the research is supposed to progress in the direction of a predictive model, opening the possibility of predicting excess isotherms of not experimentally examined probe molecules.