溶液表面吸附实验的再讨论

Revisiting the Solution Adsorption Experiment

在溶液表面吸附实验中,乙醇和正丁醇水溶液具有不同的吸附行为,但是从?–c曲线上很难判断,实验测量条件选择不当可能导致错误的结果。鉴于吉布斯吸附等温式与朗格缪尔吸附等温式并不具有相容性,不宜采用任何数学方程或物理模型进行数据拟合。建议实验数据处理方法如下:对?–nc关系手工拟合曲线,做到单调、平滑;在拟合曲线上密集读点后重新绘制?–lnc关系曲线;求出各点的导数(?σ/?lnc)T;采用吉布斯吸附等温式(38)=-(?σ/?lnc)T/(RT)计算表面吸附量。在计算溶质分子横截面积时,应考虑本体溶液浓度c对表面层溶质分子密度的影响。

Abstract： In the solution adsorption experiment, different adsorption mode has been observed for aqueous ethanol and aqueous n-butanol, respectively. However, it is difficult to make an adjustment by the profiles of σ-c relationship. Choosing the experimental conditions improperly will give wrong results. Since there is no consistency between the Gibbs adsorption isotherm and Langmuir adsorption isotherm, the experimental data should not be fitted by using any algebraic equations or physical models. The data fitting for this experiment should be carried out according to the following steps： fitting the σ-lnc curve manually, making it monotonic and smooth; retrieving more data from this fitting curve, and replotting the σ-lnc curve; calculating the first derivatives at these data points （i.e., （σσ/σlnc）T）; calculating surface adsorptions by Gibbs adsorption isotherm, σ = σ（σσ/σlnc）T/RT. As for the calculation of the cross-section area for the solute molecule, the effect of concentration of bulk solution （i.e., c） on the surface molecular density should be taken into account.