%0 Journal Article
%A Kiraly, Z.
%A Findenegg, G. H.
%A Klumpp, E.
%A Schlimper, H.
%A Dekany, I.
%T Adsorption calorimetric study of the organization of sodium n-decyl sulfate at the graphite/solution interface
%J Langmuir
%V 17
%@ 0743-7463
%C Washington, DC
%I ACS Publ.
%M PreJuSER-46882
%P 2420 - 2425
%D 2001
%Z Record converted from VDB: 12.11.2012
%X The material and enthalpy balances of the adsorption of sodium n-decyl sulfate from aqueous solutions onto graphitized carbon black were determined between 288 and 318 K by using an automated flow sorption/microcalorimeter system. At low concentrations, the surfactant molecules form a flat monomolecular film on the graphite plane, in consequence of surface-directed ordering. A mechanism is proposed in which two adsorbed phases coexist during the formation of this surfactant monolayer. The enthalpy of adsorption in the monolayer region is ca. -42 kJ mol(-1), which does not depend appreciably on the temperature or on the surface coverage. At higher concentrations, the ordered monolayer induces surface aggregation to produce half-cylindrical hemimicelles as the critical micelle concentration is approached. The enthalpies of surface aggregation at 288, 298, and 318 K are -10, -16, and -26 kJ mol(-1), respectively. As the temperature is increased from 288 to 318 K, the average number of surfactant molecules in the cross section of a half-cylinder drops from ca. 5.4 to 3.4. Calorimetric evidence is provided that cationic and anionic surfactant adsorption on graphite follow the same mechanism in the low-density and high-density adsorbate regions.
%K J (WoSType)
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000168100700025
%R 10.1021/la001552y
%U https://juser.fz-juelich.de/record/46882