An Introduction to Clay Colloid Chemistry

Olphen, H. van; Hsu, Pa Ho

doi:10.1097/00010694-196404000-00013

Cited by 701 publications

(232 citation statements)

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“…25,26 However, other types of clays may have the properties of pH-dependent charges due to the presence of the amphoteric edges with Al-OH and Si-OH groups and permanent negative charges by isomorphic substitutions (e.g., Al 3+ for Si 4+ or Mg 2+ for Al 3+ ). 26, 27 When there is a low percentage of amphoteric edges 26,28,29 in total surface area, the clay may not have a pH-dependent zeta potential. With a significantly different charge behavior from Na + -MMT, the zeta potentials of the exfoliated platelets exhibited an isoelectric point (IEP) at pH 6.4.…”

Section: Resultsmentioning

confidence: 99%

First Isolation of Individual Silicate Platelets from Clay Exfoliation and Their Unique Self-Assembly into Fibrous Arrays

et al. 2006

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Thin silicate platelets in a dimension of approximately 80 × 80 × 1 nm 3 are isolated for the first time by a newly developed process involving one-step exfoliation of natural montmorillonite clay and toluene/aqueous NaOH extraction. The platelets are observed to be polygon shape by transmission electron microscopy (TEM) and round bent-leaf shape by dynamic force microscopy (DFM). Individual platelets possessing high-aspectratio dimension and ionic character are able to self-assemble into microscale fiber bundles after water evaporation. The self-stacking mechanism indicated strong face-to-face ionic charge stacking propensity in triggering a vertical growth. Regularity of fibrous bundles in an average 5 µm length has been observed.

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Section: Resultsmentioning

confidence: 99%

First Isolation of Individual Silicate Platelets from Clay Exfoliation and Their Unique Self-Assembly into Fibrous Arrays

et al. 2006

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“…[2][3][4] Moreover, clay particles are also used as carriers of pesticides, decolorizing agents, and environmental pollutants. 5 We demonstrated that the absolute number of MG molecules transferring from the PSS particles to the clay particles can be measured in real time. The effect of the clay particle density on the transfer kinetics was also observed.…”

Section: Introductionmentioning

confidence: 87%

“…It is known that the basal surfaces of the particles are negatively charged, but the edge surfaces are positively charged. 5 The organic cations, MG, prefer to adsorb on the negatively charged basal plane. However, the top and bottom of the basal plane of a clay particle is separated by the thickness of the disk, ∼10 nm, which is much smaller than the wavelength of the light.…”

Section: Adsorption Of Mg On Polystyrene Particles and Clay Particlesmentioning

confidence: 99%

“…[18][19] It was shown that the adsorptive and electrostatic properties 18 as well as the rotational dynamics 19 of the clay particles in aqueous solutions can be probed by the SHG method. Because montmorillonite has a structure that is centrosymmetric, 5 there is no SHG generated from the bulk of the montmorillonite. A montmorillonite particle is composed of about 10 unit layers, and each layer consists of an octahedral sheet of alumina sandwiched between two tetrahedral sheets of silica.…”

Section: Introductionmentioning

confidence: 99%

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In Situ Studies of Molecular Transfer between Microparticles by Second-Harmonic Generation

2001

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We have demonstrated that second-harmonic generation (SHG) can be used to investigate the in situ transfer of molecules between colloidal microparticles. The transfer kinetics of organic cations, malachite green (MG) initially adsorbed on to spherical polystyrene sulfate (PSS) microparticles, to disk-shaped clay particles in aqueous solution was obtained. The surface population of MG on the PSS particles during the transfer process can be measured in real time. In the present studies, the adsorption free energy and the number of adsorption sites were found from the adsorption isotherm measured by the SHG method (Wang, H.; Yan, E. C. Y.; Liu, Y.; Eisenthal, K. B. J. Phys. Chem. B 1998, 102, 4446). The kinetics of transfer was observed to depend linearly on the particle density of clay. The observed transfer was biexponential with decay times of 17 ( 1 s and 217 ( 4 s for the case of a clay particle density of 3 × 10 9 /cm 3 . This method was further applied to study the transfer of MG between PSS microparticles. At a PSS density of 4 × 10 8 /cm 3 , the decay time was 40 s. Because of the coherent nature of the SHG signal, the transfer kinetics can be obtained in situ by the SHG method. A kinetic model is used to describe the transfer process from which the desorption and adsorption rate constants of MG from and onto PSS particles were obtained.

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“…[1][2][3] Clay particles have long been recognized as important catalysts in petroleumforming reactions and in the chemical evolution of certain organic compounds related to the origin of life. 4,5 The large surface area make them excellent adsorbents and is the basis for their increasing use to remove organic and inorganic environmental pollutants.…”

Section: Introductionmentioning

confidence: 99%

Probing the Interface of Microscopic Clay Particles in Aqueous Solution by Second Harmonic Generation

Yan

Eisenthal

1999

J. Phys. Chem. B

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Second harmonic generation (SHG) is applied for the first time to study the surfaces of clay particles. An SHG signal was detected from an aqueous suspension of disk-shaped montmorillonite clay particles of 0.5 µm diameter and 0.01 µm thickness. The origin of the SHG signal is the polarization of water molecules by surface charges located in the edge region of the clay particles. On addition of the organic molecule 4-(2-pyridylazo)resorcinol (PR) to the clay aqueous suspension, a strong SHG signal originating from the PR molecules adsorbed onto the edge surfaces of the clay particles was obtained. The PR adsorbed on the basal planes do not contribute to the SHG signal because of cancellation effects. These experimental results demonstrate the applicability of the SHG method for studying molecular adsorption and the electrostatic properties of clay particles.

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An Introduction to Clay Colloid Chemistry

Cited by 701 publications

References 0 publications

First Isolation of Individual Silicate Platelets from Clay Exfoliation and Their Unique Self-Assembly into Fibrous Arrays

First Isolation of Individual Silicate Platelets from Clay Exfoliation and Their Unique Self-Assembly into Fibrous Arrays

In Situ Studies of Molecular Transfer between Microparticles by Second-Harmonic Generation

Probing the Interface of Microscopic Clay Particles in Aqueous Solution by Second Harmonic Generation

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