The Mathematical Institute, University of Oxford, Eprints Archive

The kinetics of surfactant desorption at the air–solution interface

Morgan, C. E. and Breward, C. J. W. and Griffiths, I. M. and Howell, P. D. and Penfold, J. and Thomas, R. K. and Tucker, I. and Petkov, J. T. and Webster, J. R. P. (2012) The kinetics of surfactant desorption at the air–solution interface. Langmuir . (Submitted)

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Abstract

The kinetics of desorption of the anionic surfactant sodium dodecylbenzene sulfonate at the air–solution interface have been studied using neutron reflectivity (NR). The experimental arrangement incorporates a novel flow cell in which the subphase can be exchanged (diluted) using a laminar flow whilst the surface region remains unaltered. The kinetics of the desorption is relatively slow and occurs over many tens of minutes compared with the dilution timescale of approximately 10–30 minutes. 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 timedependent adsorption data.

A key parameter of the model is the ratio of the depth of the diffusion layer, Hc , to the depth of the fluid, Hf, and we find that this is related to the reduced Péclet number, Pe*, for the system, via Hc/Hf, = C/Pe* 1/ 2 . Although from a highly idealised experimental arrangement, the results provide an important insight into the ‘rinse mechanism’, which is applicable to a wide variety of domestic and industrial circumstances.

Item Type:Article
Subjects:D - G > General
Research Groups:Oxford Centre for Collaborative Applied Mathematics
ID Code:1641
Deposited By: Peter Hudston
Deposited On:05 Jan 2013 10:31
Last Modified:29 May 2015 19:20

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