Adsorption behavior of cationic and nonionic surfactant mixtures at the alumina-water interface
- Columbia Univ., New York, NY (United States). Langmuir Center for Colloids and Interfaces
The solution and interfacial behavior of surfactant mixtures was investigated using a cationic surfactant, tetradecyl trimethyl ammonium chloride (TTAC), and a nonionic surfactant, pentadecylethoxylated nonyl phenol (NP-15), with alumina as the substrate. The cationic TTAC adsorbed at the alumina-water interface as a result of electrostatic attraction at pH {approximately} 10 whereas the nonionic NP-15 did not. Interestingly, in the mixed surfactant system, the tetradecyl trimethyl ammonium chloride forced adsorption of the NP-15 as a result of hydrophobic interactions between the adsorbed surfactant chains at the alumina-water interface. The adsorption behavior was dependent upon the ratio of the two surfactants in the mixture as well as the order of addition. With an increase in TTAC content, the adsorption density of NP-15 increased and the isotherm shifted to lower surfactant concentrations. The adsorption of TTAC decreased under conditions of saturation adsorption due to the bulkiness of the coadsorbed NP-15 as well as competition for common adsorption sites. However, below saturation adsorption conditions, the adsorption of TTAC was increased due to synergistic interactions between the cationic and nonionic heads leading to reduced repulsion among the cationic headgroups. Zeta potential measurements showed that, with an increase of NP-15 in the mixtures, the positive charge of the TTAC was partially screened by the coadsorbed NP-15. Surface tension of the surfactant mixtures was also measured, and regular solution theory was used to model the interactions between the surfactants.
- DOE Contract Number:
- AC22-92BC14884
- OSTI ID:
- 178328
- Journal Information:
- Journal of Colloid and Interface Science, Journal Name: Journal of Colloid and Interface Science Journal Issue: 1 Vol. 177; ISSN 0021-9797; ISSN JCISA5
- Country of Publication:
- United States
- Language:
- English
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