Hostname: page-component-848d4c4894-x5gtn Total loading time: 0 Render date: 2024-05-25T19:01:59.763Z Has data issue: false hasContentIssue false
  • English
  • Français

The Effect of Surface Modification by an Organosilane on the Electrochemical Properties of Kaolinite

Published online by Cambridge University Press:  28 February 2024

Belinda Braggs ,
Daniel Fornasiero ,
John Ralston  and
Roger St. Smart
Belinda Braggs
Affiliation:
School of Chemical Technology, University of South Australia, The Levels, S.A. 5095, Australia
Daniel Fornasiero
Affiliation:
School of Chemical Technology, University of South Australia, The Levels, S.A. 5095, Australia
John Ralston
Affiliation:
School of Chemical Technology, University of South Australia, The Levels, S.A. 5095, Australia
Roger St. Smart
Affiliation:
School of Chemical Technology, University of South Australia, The Levels, S.A. 5095, Australia
Get access Rights & Permissions [Opens in a new window]

Abstract

The electrochemical properties of kaolinite before and after modification with chlorodimethyl-octadecylsilane have been studied by electrophoretic mobility, surface charge titration, and extrapolated yield stress measurements as a function of pH and ionic strength. A heteropolar model of kaolinite, which views the particles as having a pH-independent permanent negative charge on the basal planes and a pH-dependent charge on the edges, has been used to model the data. The zeta potential and surface charge titration experimental data have been used simultaneously to calculate acid and ion complexation equilibrium constants using a surface complex model of the oxide-solution interface. The experimental data were modeled following subtraction of the basal plane constant negative charge, describing only the edge electrical double layer properties. Extrapolated yield stress measurements along with the electrochemical data were used to determine the edge isoelectric points for both the unmodified and modified kaolinite and were found to occur at pH values of 5.25 and 6.75, respectively. Acidity and ion complexation constants were calculated for both sets of data before and after surface modification. The acidity constants, pKa1 = 5.0 and pKa2 = 6.0, calculated for unmodified kaolinite, correlate closely with acidity constants determined by oxide studies for acidic sites on alumina and silica, respectively, and were, therefore, assigned to pH-dependent specific chemical surface hydroxyl groups on the edges of kaolinite. The parameters calculated for the modified kaolinite indicate that the silane has reacted with these pH-dependent hydroxyl groups causing both a change in their acidity and a concomitant decrease in their ionization capacity. Infrared data show that the long chain hydrocarbon silane is held by strong bonding to the kaolinite surface as it remains attached after washing with cyclohexane, heating, and dispersion in an aqueous environment.

Keywords

Acidity constantsElectrophoresisKaoliniteModelingSilaneSurface chargeSurface modification
Type
Research Article
Information
Clays and Clay Minerals , Volume 42 , Issue 2 , April 1994 , pp. 123 - 136
Copyright
Copyright © 1994, Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Bolland, M. D. A., Posner, A. M., and Quirk, J. P., (1980) pH-Independent and pH-dependent surface charges on kaolinite: Clays & Clay Minerals 28, 412–418.CrossRefGoogle Scholar
Buchanan, A. S., and Oppenheim, R. C., (1968) The surface chemistry of kaolinite: Aust. J Chem. 21, 2367–2371.CrossRefGoogle Scholar
de Bruyn, P. L., and Agar, G. E., (1962) Surface chemistry of flotation: in Froth Flotation, Fuerstenau, D. W., ed., 50th Anniversary Volume, AIME, New York, 91–134.Google Scholar
de Keizer, A., (1990) Adsorption of paraquat ions on clay minerals. Electrophoresis of clay particles. Progr. Colloid Polym. Sci. 83, 118–126.CrossRefGoogle Scholar
Diz, H. M. M., and Rand, B., (1989) The variable nature of the isoelectric point of the edge surface of kaolinite: Br. Ceram. Trans. J. 88, 162–166.Google Scholar
Greenland, D. J., and Mott, C. J. B., (1978) Surfaces of soil particles: in The Chemistry of Soil Constituents, Greenland, D. J., and Hayes, M. B. H., eds., John Wiley & Sons, New York, 330–333.Google Scholar
Hair, M. L., (1986) Silica surfaces: in Silanes, Surfaces and Interfaces, Leyden, D. E., ed., Gordon and Breach Science Publishers, New York, 25–41.Google Scholar
Hiemstra, T., de Witt, J. C. M., and van Riemsdijk, W. H., (1989) Multisite proton adsorption modeling at the solid/solution interface of (hydr)oxides: A new approach: J. Colloid Interface Sci. 133, 105–117.CrossRefGoogle Scholar
Hunter, R. J., (1981) Zeta Potential in Colloid Science: Academic Press, London, 298 pp.Google Scholar
Hunter, R. J., (1987) Foundations of Colloid Science. Vol. I: Oxford University Press, New York, 316–394, p. 557.Google Scholar
Hurlbut, C. S. Jr. 1971() Dana's Manual of Mineralogy, 18th Ed.: John Wiley & Sons, New York, 426 pp.Google Scholar
Israelachvili, J., (1992) Intermolecular and Surface Forces, 2nd Ed.: Academic Press, London, 128–133.Google Scholar
James, R. O., and Parks, G. A., (1982) Characterization of aqueous colloids by their electrical double-layer and intrinsic surface chemical properties: in Surface and Colloid Science, Vol. 12, Matijevic, E., ed., Plenum, New York, 119–216.CrossRefGoogle Scholar
Jepson, W. B., (1984) Kaolins: Their properties and uses: Phil. Trans. R. Soc. Lond. A 311, 411–432.Google Scholar
Kitchener, J. A., (1992) Minerals and surfaces: in Developments in Mineral Processing, Vol. 12: Colloid Chemistry in Mineral Processing, Laskowski, J. S., and Ralston, J., eds., Elsevier Science Publishers B.V., Amsterdam, p. 30.Google Scholar
Koopal, L. K., van Riemsdijk, W. H., and Roffey, M. G., (1987) Surface ionization and complexation models: A comparison of methods for determining model parameters: J. Colloid Interface Sci. 118, 117–136.CrossRefGoogle Scholar
Kramer, J. R., Collins, P., and Brassard, P., (1991) Characterization of multiple functional groups on kaolinite: Mar. chem. 36, 1–8.CrossRefGoogle Scholar
Messerschmidt, R. G., (1985) Complete elimination of specular reflectance in infrared diffuse reflectance measurements: Appl. Spectr. 39, 737–794.CrossRefGoogle Scholar
Morris, H. D., Shelton, B., and Ellis, P. D., (1990) 27Al NMR spectroscopy of iron-bearing montmorillonite clays: J. Phys. Chem. 94, 3121–3129.CrossRefGoogle Scholar
Nguyen, T. T., Janik, L. J., and Raupach, M., (1991) Diffuse reflectance infrared fourier transform (DRIFT) spectroscopy in soil studies: Aust. J. Soil Res. 29, 49–67.CrossRefGoogle Scholar
Ohshima, H., Healy, T. W., and White, L. R., (1983) Approximate analytic expressions for the electrophoretic mobility of spherical colloidal particles and the conductivity of their dilute suspensions: J. Chem. Soc., Faraday Trans. 2 79, 1613–1628.CrossRefGoogle Scholar
Pleuddemann, E. P., (1982) Silane Coupling Agents: Plenum Press, New York, p. 20.CrossRefGoogle Scholar
Pulfer, K., Schindler, P. W., Westall, J. C., and Grauer, R., (1984) Kinetics and mechanism of dissolution of bayerite (γ-Al(OH)3) in HNO3-HF solutions at 298.2 °K: J. Colloid Interface Sci. 101, 554–564.CrossRefGoogle Scholar
Rand, B., and Melton, I. E., (1977) Particle interactions in kaolinite: J. Colloid Interface Sci. 60, 308–329.CrossRefGoogle Scholar
Scales, P. J., Grieser, F., and Healy, T. W., (1990) Electrokinetics of the muscovite mica-aqueous solution interface: Langmuir 6, 582–589.CrossRefGoogle Scholar
Schindler, P. W., and Stumm, W., (1987) The surface chemistry of oxides, hydroxides, and oxide minerals: in Aquatic Surface Chemistry, Stumm, W., ed., John Wiley & Sons, New York, p. 97.Google Scholar
Schofield, R. K., and Samson, H. R., (1954) Flocculation of kaolinite due to the attraction of oppositely charged crystal faces: Discuss. Faraday Soc. 18, 135–144.CrossRefGoogle Scholar
Socrates, G., (1980) Infrared Characteristic Group Frequencies: John Wiley & Sons, New York, p. 27.Google Scholar
Stumm, W., Huang, C. P., and Jenkins, S. R., (1970) Specific chemical interaction affecting the stability of dispersed systems: Croat. Chem. Acta 42, 223–245.Google Scholar
Tadros, Th. F., (1989) Rheology of concentrated stable and flocculated suspensions: in Flocculation and Dewatering Proc. of the Engineering Foundation Conf., Palm Coast, Florida, Moudgil, B. M., and Scheiner, B. J., eds., Engineering Foundation, New York, 43–87.Google Scholar
van Olphen, H., (1977) An Introduction to Clay Colloid Chemistry, 2nd Ed.: John Wiley & Sons, New York, 92–110.Google Scholar
Westall, J., and Hohl, H., (1980) A comparison of electrostatic models of the oxide/solution interface: Adv. Colloid Interface Sci. 12, 265–294.CrossRefGoogle Scholar
Wierer, K. A., and Dobias, B., (1988) Exchange enthalpies of H+ and OH– adsorption on minerals with different characters of potential-determining ions: J. Colloid Interface Sci. 122, 171–177.CrossRefGoogle Scholar
Williams, D. J. A., and Williams, K. P., (1978) Electrophoresis and zeta potential of kaolinite: J. Colloid Interface Sci. 65, 79–87.CrossRefGoogle Scholar
Wood, R., (1990) The electrical double layer properties of oxides: Masters thesis, The South Australian Institute of Technology, 40–50.Google Scholar
Wood, R., Fornasiero, D., and Ralston, J., (1990) Electrochemistry of the boehmite-water interface: Colloids Surf. 51, 389–403.CrossRefGoogle Scholar