Abstract
The measured dynamic surface tension of a water drop in air saturated by heptane vapor shows a sharp decrease from about 60 mN m−1 to 40 mN m−1, and less after a certain adsorption time. The observed adsorption kinetics is analyzed by a theoretical model based on multilayer adsorption of alkanes from the vapor phase at the water surface. The model assumes a dependence of the kinetic coefficients of adsorption and desorption on the surface coverage and in equilibrium it reduces to the classical Brunauer–Emmett–Teller adsorption isotherm. The calculated time dependencies of adsorption and surface tension agree well with experimental data and predict a five-layer adsorption of heptane.
Highlights
Various experimental and theoretical studies of adsorption of alkanes from the gas phase on a water surface were previously reported [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
Experimental dynamic surface tension of water drops in air saturated by heptane vapor shows a sharp decrease at sufficFieignutlrye l8o.nDgyandamsoircpstoiof nthteimcoevse(r1a0g,e00o0f–L1a5y,0e0r0s s1,a2t 2a0nd◦C4, aatn3d05°0C0–fo7r00twsoatd5if0fe◦rCen).t Tbh2 ivsapluheesn. oFmorenon detailed discussion, see text
For the analysis of experimental data, we proposed a model of multilayer adsorption of alkanes from the vapor phase at the water surface
Summary
Various experimental and theoretical studies of adsorption of alkanes from the gas phase on a water surface were previously reported [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. Measurements and analysis of tensiometric data [7] demonstrated that the adsorption of alkanes on the surface of water drops can lead to a condensation of the alkane molecules at the surface and to the formation of liquid films It was shown [12] that the influence of hexane vapor on the surface tension of water depends essentially on the air humidity. Our previous studies [17,18] have shown that the rate of alkane adsorption at an aqueous surface is not limited by diffusion of alkane molecules in a gas (vapor) phase but has a kinetic limitation due to an energy barrier for adsorbing/desorbing molecules Such a process can be described in terms of kinetic equations. The model describes the variation of the measured surface tension with time and constrains the model parameters, in particular, the kinetic coefficients
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
