Related Experiment Video
Updated: Jul 16, 2026
06:53
Additive Manufacturing of Functionally Graded Ceramic Materials by Stereolithography
Published on: January 25, 2019
Nonaqueous suspensions of surface-modified kaolin
Yan Zhang1, David I Gittins, David Skuse
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 20, 2007
Summary
Surface treatments enhance kaolin clay dispersibility in nonpolar solvents. Combined silane and amine treatments, or a polyisobutylene-based stabilizer (SAP230), significantly improved suspension stability compared to individual treatments.
Area of Science:
- Materials Science
- Colloid Science
- Surface Chemistry
Background:
- Natural kaolin clay particles are hydrophilic and poorly dispersible in nonpolar solvents.
- Kaolin surfaces contain silanol and aluminol groups, with aluminol sites exhibiting acidity.
- Effective dispersion requires rendering kaolin particles hydrophobic via surface modification.
Purpose of the Study:
- To evaluate various stabilizers for rendering kaolin clay hydrophobic and dispersible in nonpolar solvents.
- To understand the interaction between stabilizers and kaolin surface sites.
- To correlate surface treatment with suspension stability and particle characteristics.
Main Methods:
- Chemical characterization of kaolin surface acidity using a Hammett indicator.
- Adsorption studies to confirm chemical bonding of stabilizers.
- Preparation of kaolin suspensions in heptane and polydecene.
- Assessment of suspension stability via sediment density.
- Particle size analysis using small-angle light scattering.
- Rheological measurements to determine Bingham yield stress.
Main Results:
- Silanes did not neutralize acidic aluminol sites, while amines did.
- Both silane + amine and SAP230 treatments neutralized acid sites.
- Suspension stability followed the order: silanes < amines < silane + amine < SAP230.
- Stability trends were consistent across heptane and polydecene solvents.
- Increased stability correlated with higher surface coverage, smaller particle size, and reduced yield stress.
Conclusions:
- Surface neutralization of acidic sites is crucial for effective kaolin stabilization.
- Advanced treatments like combined silane/amine or SAP230 offer superior hydrophobicity and dispersibility.
- Stabilizer efficacy is linked to surface coverage, particle size reduction, and rheological properties.
More Related Videos
Related Concept Videos
01:09Colloidal precipitates
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
03:22Colloids
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
01:29The Colloidal State
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...
04:01Factors Affecting Solubility
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
01:17Colloids and Suspensions
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
01:23Factors Affecting Dissolution: Particle Size and Effective Surface Area
Dissolution kinetics, an essential aspect of oral drug delivery, is significantly influenced by the drug's particle size. According to the Noyes-Whitney dissolution model, the dissolution rate correlates directly with the drug's surface area. The larger the surface area, the higher the drug's solubility in water, leading to a faster drug dissolution rate. Reducing particle size increases the effective surface area, enhancing the dissolution process. Micronization and nanosizing are employed to...