Cationic surfactants on silica

Goloub, T.P. et al.. Adsorption of cationic surfactants on silica. Surface charge effects, Langmuir, 12, 3188, 1996. 

M. Chorro, C. Chorro, O. DoUadiUe, S. Partyka, R. Zana, Adsorption mechanism of conventional and dimeric cationic surfactants on silica surface effect of the state of the surface. J. Colloid Interface Sci. 210(1), 134-143 (1999). doi 10.1006/jcis.l998.5936 R. Chaghi, L.-C. de Menorval, C. Chamay, G. Derrien, J. Zajac, Interactions of phenol with cationic micelles of hexadecyltrimethylammonium bromide studied by titration calorimetry, conductiraetry, and IH NMR in the range of low additive and surfactant concentrations. J. Colloid Interface Sci. 326(1), 227-234 (2008). doi 10.1016/j.jcis.2008.07.035... 

Kibbey, T.C.G., and Hayes, K.F. (1993). Partitioning and UV adsorption studies of phenanthrene on cationic surfactant-coated silica. Environ. Sci. Technol, 21, 2168-2173. 

Zhou Q, Somasundaian P (2009) Synergistic adsorption of mixtures of cationic gemini and ntmitmic sugar-based surfactant on silica. J Colloid Interface Sci 331 288-294... 

Adsorption of cationic surfactants (cationic soaps) on silica has been studied by Ter-Minassian-Sarage (88) and by Bijsterbosch (89), who have shown that either a monolayer or a bi-layer may be formed. Similar complexities may exist with some micelle-forming dyes, and special conditions would have to be worked out for each adsorbate to eliminate confusion. Also, the adsorption of these ionic species is affected by pH and by aluminosilicate ion impurities on the silica surface. Use of cationic dyes and surfactants is generally restricted to rapid comparison of surface areas of a series of silica powders of the same type. 

Therefore, using capillary electrokinetics one can in principle investigate the adsorption of cationic surfactant on a silica surface and explain the results obtained on the basis of Langmuir-type isotherms of adsorption. 

Abstract The adsorption of ionic surfactants on different soil components such as silica, clay minerals, and humic acids was studied. The adsorption processes were controlled by flow microcalorimetry to determine the molar adsorption enthalpies of surfactant accumulation on clay and silicate surfaces. The evaluation of adsorption results for cationic surfactants has shown different mechanisms for solids having permanent (kaolinite, illite, montmorillonite) and pH-dependent surface charges (silica gels and powders). The adsorption mechanism for surfactants on silica surfaces with pH-dependent charges has been explained in terms of the development of charges on the surfaces and their interaction with... 

Soderlind E and Stilbs P 1993 A Fl NMR study of two cationic surfactants adsorbed on silica particles Langmuirs 2024-34... 

In this experiment a zeta-meter is used to determine the variation in the zeta potential of silica at constant pH (5.7) over a range of concentrations of a cationic surfactant CTAB, which should adsorb on the ionized silanol groups on the silica particle surface. 

The common gangue material quartz (silica) is naturally hydrophilic and can be easily separated in this way from hydrophobic materials such as talc, molybdenite, metal sulphides and some types of coal. Minerals which are hydrophilic can usually be made hydrophobic by adding surfactant (referred to as an activator ) to the solution which selectively adsorbs on the required grains. For example, cationic surfactants (e.g. CTAB) will adsorb onto most negatively charged surfaces whereas anionic surfactants (e.g. SDS) will not. Optimum flotation conditions are usually obtained by experiment using a model test cell called a Hallimond tube . In addition to activator compounds, frothers which are also surfactants are added to stabilize the foam produced at the top of the flotation chamber. Mixtures of non-ionic and ionic surfactant molecules make the best frothers. As examples of the remarkable efficiency of the process, only 45 g of collector and 35 g of frother are required to float 1 ton of quartz and only 30 g of collector will separate 3 tons of sulphide ore. 

When the wall is made hydrophobic by treatment with alkylsilane, it is possible to separate proteins that tend to adsorb at the surface of bare fused silica. Ultimately, it is possible to recuperate one type of ion depending on the direction of the electric field. Finally, if a cationic surfactant is added to reverse the polarity of the inner wall, it is possible to reverse the direction of the electro-osmotic flow (Fig. 8.6). 

Surfactant extractions have been attempted previously, but mainly for HMS materials (mesoporous silicas, prepared using neutral amines as the surfactant). Due to the much weaker S°I° interaction, compared to the S+I interaction, these surfactants can be extracted relatively easily [6], Some reports have been published on the extraction of the cationic surfactant, but the resulting material is mostly inferior to the calcined one and in most cases, still a posttreatment at high temperatures is required [7], We describe an extraction procedure for MCM-48, that does not require a post-treatment and that produces materials with a better quality than the calcined ones. 

---