大学化学 >> 2018, Vol. 33 >> Issue (10): 91-96.doi: 10.3866/PKU.DXHX201803038

师生笔谈 上一篇    下一篇

溶液表面吸附实验的再讨论

许新华*(),吴梅芬,王晓岗   

  • 收稿日期:2018-03-19 发布日期:2018-11-01
  • 通讯作者: 许新华 E-mail:xxh01@tongji.edu.cn
  • 基金资助:
    中国高等教育学会高等教育科学研究"十三五"规划课题(16SY004)

Revisiting the Solution Adsorption Experiment

Xinhua XU*(),Meifen WU,Xiaogang WANG   

  • Received:2018-03-19 Published:2018-11-01
  • Contact: Xinhua XU E-mail:xxh01@tongji.edu.cn
  • Supported by:
    中国高等教育学会高等教育科学研究"十三五"规划课题(16SY004)

摘要:

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σ-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σ-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σ-lnc关系曲线;求出各点的导数(∂σ/lncT;采用吉布斯吸附等温式Γ=-(∂σ/lncT/(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。

关键词: 溶液表面吸附, 数据拟合, 吉布斯吸附等温式, 朗格缪尔吸附等温式

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 re-plotting the σ-lnc curve; calculating the first derivatives at these data points (i.e., (∂σ/lnc)T); calculating surface adsorptions by Gibbs adsorption isotherm, Γ=-(∂σ/lnc)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.

Key words: Solution adsorption, Data fitting, Gibbs adsorption isotherm, Langmuir adsorption isotherm

MSC2000: 

  • G64