Kinetics of Surfactant Desorption at an Air鈥揝olution Interface

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• 作者：C. E. Morgan ; C. J. W. Breward ; I. M. Griffiths ; P. D. Howell ; J. Penfold ; R. K. Thomas ; I. Tucker ; J. T. Petkov ; J. R. P. Webster
• 刊名：Langmuir
• 出版年：2012
• 出版时间：December 18, 2012
• 年：2012
• 卷：28
• 期：50
• 页码：17339-17348
• 全文大小：598K
• 年卷期：v.28,no.50(December 18, 2012)
• ISSN：1520-5827

文摘

The kinetics of re-equilibration of the anionic surfactant sodium dodecylbenzene sulfonate at the air鈥搒olution interface have been studied using neutron reflectivity. The experimental arrangement incorporates a novel flow cell in which the subphase can be exchanged (diluted) using a laminar flow while the surface region remains unaltered. The rate of the re-equilibration is relatively slow and occurs over many tens of minutes, which is comparable with the dilution time scale of approximately 10鈥?0 min. A detailed mathematical model, in which the rate of the desorption is determined by transport through a near-surface diffusion layer into a diluted bulk solution below, is developed and provides a good description of the time-dependent adsorption data. A key parameter of the model is the ratio of the depth of the diffusion layer, H_c, to the depth of the fluid, H_f, and we find that this is related to the reduced P茅clet number, Pe*, for the system, via H_c/H_f = C/Pe*^1/2. Although from a highly idealized experimental arrangement, the results provide an important insight into the 鈥渞inse mechanism鈥? which is applicable to a wide variety of domestic and industrial circumstances.