Preferential adsorption of cationic surfactant mixture studied by bromide ion selective total-reflection XAFS measurement.
The total-reflection XAFS measurement possessing bromide ion selectivity at the interfacial region was applied to the adsorbed film of hexadecyltrimethylammonium chloride (HTAC) and dodecyltrimethylammonium bromide (DTAB) mixture. The surface compositions XjH of individual ions j ( j = HTA+, Cl(-), DTA+, and Br (-)) were evaluated by combining the surface excess concentration of Br(-) estimated from the XAFS with the surface composition of the respective surfactants from the surface tension results. It is clearly shown that HTA+ and Br(-) are preferentially adsorbed to DTA+ and Cl(-) at the air/water interface. The preferential adsorption was estimated numerically in terms of activity coefficient fi+/-(H,p) of component i and excess Gibbs energy of adsorption ĝprH,E. Then, the magnitude of ĝprH,E was compared with that of ĝprH,E attributable to intrinsic interaction between ions.
Department of Chemistry and Physics of Condensed Matter, Graduate School of Sciences, Kyushu University, Fukuoka 812-8581, Japan. kaoru_k@kyudai.jp
Kaoru
K
Kashimoto
Kinue
K
Shibata
Takashi
T
Matsuda
Mayumi
M
Hoshide
Yukari
Y
Jimura
Iwao
I
Watanabe
Hajime
H
Tanida
Hiroki
H
Matsubara
Takanori
T
Takiue
Makoto
M
Aratono