Surface Activity And Adsorption Of Some Surfactants At Aqueous / Air Interface At Different Temperatures
[Full Text]
AUTHOR(S)
Alzahraa A. El Feky, Magda N. Shalaby, Omnia A.A. El-Shamy, Suzy A. Selim
KEYWORDS
Surface activity, Surface excess concentration, minimum surface area per molecule, surface tension, surfactants.
ABSTRACT
The adsorption of a series of ethoxylated nonionic and anionic surfactant molecules at aqueous / air interface at different temperature ranges [298, 308, 318, 328 and 338K] was studied. Different surface parameters were evaluated from surface tension measurements at different temperatures. The effectiveness of adsorption, Гmax, for all nonionic and anionic surfactants was discussed with respect to their hydrophilic and hydrophobic characters. Ethoxylated stearate had the lowest effectiveness of adsorption at 298K comparing to other nonioics. Minimum surface area per molecule, Amin, was calculated which provides information on the degree of packing and orientation of the adsorbed surfactant molecules. Amin decreased through increasing the hydrophobicity. Also, the effectiveness of surface tension reduction, πcmc was discussed concerning on surfactant structures. The dependence of surface parameters (Гmax and Amin) on temperatures was explained in details. For the most investigated nonionic and anionic surfactants πcmc were slightly affected by temperature.
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