Chem. J. Chinese Universities ›› 2023, Vol. 44 ›› Issue (11): 20230316.doi: 10.7503/cjcu20230316

• Physical Chemistry • Previous Articles     Next Articles

Surface Adsorption of Water-alcohol Binary Solutions

YU Xianchao1, QI Wenshuai1, DENG Quanhua2, HOU Wanguo1,3()   

  1. 1.Key Laboratory of Colloid & Interface Chemistry,Ministry of Education
    2.School of Chemistry and Chemical Engineering
    3.National Engineering Technology Research Center of Colloidal Materials,Shandong University,Jinan 250100,China
  • Received:2023-07-05 Online:2023-11-10 Published:2023-09-11
  • Contact: HOU Wanguo E-mail:wghou@sdu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(22272088)

Abstract:

Algebraic equations of the Gibbs surface excess(Γ2) and adsorption layer thickness(τ) were developed for binary liquid mixtures based on the surface aggregation adsorption(SAA) model and the Gibbs differential equation, which can predict the change of Γ2 and τ with the bulk composition(such as the molar fraction of component 2, x2,b) in the whole concentration range. The model equations were used to investigate the surface adsorption of water(1)-alcohol(2) binary solutions. The alcohols involved include methanol(MeOH), ethanol(EtOH), iso-propanol(iPrOH), n-propanol(nPrOH), and tert-butanol(tBuOH). It was found that their adsorption trend on the water surface increases in turn, consistent with the enhancement trend of their hydrophobicity. Their Γ2 and τ increase in turn in the low x2,b region, while decrease in turn in the high x2,b region, which arise from the differences in adsorption trend and molecular size between alcohols. In addition, for a given alcohol system, with an increase in x2,b from 0 to 1, its Γ2 initially sharply increases and then decreases, showing a maximum, but its τ exhibits a continuous reduction. This work provides a better understanding of the surface adsorption behavior of water-alcohol liquid mixtures.

Key words: Liquid mixture, Surface adsorption, Surface aggregation, Adsorption layer thickness, Thermodynamic model

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