Clay Particle Dispersion in Organic Media

The dispersion of approximately 1.0% kaolin suspensions in various organic liquids was studied. Both individual and family effects were noted. Complete dispersion was found with higher alcohols, such as hexanol, and with glycols and glycerol. Sodium salts of the several alcohols were also employed to advantage as deflocculants. Complex alcohol formations with kaolin are believed to be absent or at least negligible. Results are compared with the typical effects obtained with water. Summary Optimum dispersion of kaolin was obtained in the higher alcohols and in the glycols. Both alcohols and glycols are known to behave similarly toward montmorillonite; the only difference is the degree of exactness of the complex formed. If glycol, which forms the strongest montmorillonite complex, is inert to kaolinite (and there is no evidence to the contrary), it follows that the other alcohols also are inert to kaolinite, at least very nearly so. These results agree with those of MacEwan.33 Although the glycol-montmorillonite complex is the most stable one formed, the glycol can be completely washed out, restoring the particles to their original condition, and regenerating the expansible lattice. Thus, with kaolinite, even assuming a limited type of complex formation with an alcohol, the particles may be retained unaltered and the alcohol may be removed by washing or by evaporation. Considering kaolinite surfaces as being analogous to montmorillonite edges, only a single-layer complex flat against the surface can be formed by C-H.O bonding or by O-H.O bonding. The maximum adverse effect on particle size under these circumstances would be the addit'on of approximately 3.0 a.u. to the radius of the particle. Applied to a particle 0.05 μ in diameter, this would result in an increase of only 1.2%; and with larger particles this percentage would be considerably reduced. Particle-size analyses based on Stokes’law and using an alcohol as the suspending medium thus could be expected to yield a more accurate picture of actual particle diameters, on the basis of complex formation alone. In the alcohols the intensity of Brownian motion was reduced from that exhibited in water and in some cases motion was not present at all. This was true even in methanol, with a viscosity much less than that of water. This reduced Brownian motion would tend to give closer adherence to Stokes’law, particularly in the portion of the kaolin particles less than 1.0 μ in diameter, and would result in more accurate particle-size determinations. A dispersed condition is not always required for handling clays in suspension. For instance, in processing a clay through a fractionation procedure, the several steps involved require at one point or another the development of both flocculation and dispersion. From the appropriate curves it is evident that by the proper selection of the particular alcohol almost any desired condition may be obtained (from complete flocculation to a nearly absolute dispersion). Table VI shows that these conditions may be attained over a wide range of viscosities, volatilities, densities, and many other physical properties. Note that oxygen was present as a part of the molecule of every liquid which gave even moderate dispersion, with the exception of aniline, in which nitrogen can be considered to replace the negative oxygen with the acceptance of an additional hydrogen. The presence of oxygen in the organic structure cannot be considered to ensure successful dispersion; however, without it no other compounds were even moderately successful. At present, the exact significance of the oxygen is not clear.