Preferential Adsorption of Cationic Surfactant Mixture Studied by Bromide Ion Selective Total-Reflection XAFS Measurement

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• 作者：Kaoru Kashimoto ; Kinue Shibata ; Takashi Matsuda ; Mayumi Hoshide ; Yukari Jimura ; Iwao Watanabe ; Hajime Tanida ; Hiroki Matsubara ; Takanori Takiue ; Makoto Aratono
• 刊名：Langmuir
• 出版年：2008
• 出版时间：July 1, 2008
• 年：2008
• 卷：24
• 期：13
• 页码：6693 - 6697
• 全文大小：144K
• 年卷期：v.24,no.13(July 1, 2008)
• ISSN：1520-5827

文摘

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 X_j^H 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 f_i^H,p of component i and excess Gibbs energy of adsorption ĝ_pr^H,E. Then, the magnitude of ĝ_pr^H,E was compared with that of ĝ_in^H,E attributable to intrinsic interaction between ions.