Adsorption of Pure Nonionic Alkylethoxylated Surfactants down to Low Concentrations at a Silica/Water Interface as Determined Using a HPLC Technique
✍ Scribed by P.L. Desbene; F. Portet; C. Treiner
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 126 KB
- Volume
- 190
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
Investigations on the determination of the quantities of
The adsorption of pure nonionic alkylethoxylated surfactants surfactant adsorption and on the behavior of pure nonionic of the C 12 E n series at silica/water interface has been determined surfactants at solid/liquid interfaces are necessary for the using a very precise HPLC technique. The number of ethoxylated analysis of complex commercial surfactants which contain groups was varied from 2 to 9. The adsorption isotherms were within a given chemical series a large number of different constructed with special attention to the very low surface coverage oligomers. They are particularly important when environdomain. It is shown that at very low concentration, the adsorption mental conditions are considered. It has been recently shown amounts are higher as the number of ethoxylated groups increases that at very small surface coverage, ethoxylated surfactants but the reverse trend is found at higher surfactant concentration and above the critical micelle concentration. It is shown that this at a silica/water interface adsorb flat on the hydrophilic behavior is the consequence of the interplay of the primary and surface (12). Adsorption is dominated by primary interacsecondary adsorption mechanisms depending upon the length of tions involving hydrogen bonds between the oxygen atoms the ethoxylated chain. The maximum adsorption quantities is not of the surfactant ethoxylated moieties and the surface silanol a linear function of the number of ethoxylated groups. This and groups (13). As the surface coverage increases, another type other observations confirm the viewpoint that the behavior of nonof interaction occurs which induces generally a very large ionic surfactant aggregates adsorbed at a hydrophilic surface carincrease of adsorption on silica. This secondary process inries many similarities with the properties of this class of nonionic volves lateral interaction between the surfactants lipophilic surfactant aggregates in bulk aqueous solutions. ᭧ 1997 Academic Press moieties (10, 14). Finally at an equilibrium (free) concen-Key Words: nonionic surfactants adsorption at solid/liquid intertration close to the critical micelle concentration (cmc), the faces; silica/water interface; dodecylpolyethoxylated surfactants; HPLC technique for nonionic surfactants.
adsorption stops to increase. Any new addition of surfactant takes part in the formation of free micelles in solution even if the silica surface is not saturated (15). These very general