THE INFLUENCE OF SURFACTANT IMPURITIES ON COLLOID STABILITY AND DISPERSION OF POWDERS IN AQUEOUS SUSPENSIONS

Citation
M. Colic et Dw. Fuerstenau, THE INFLUENCE OF SURFACTANT IMPURITIES ON COLLOID STABILITY AND DISPERSION OF POWDERS IN AQUEOUS SUSPENSIONS, Powder technology, 97(2), 1998, pp. 129-138
Citations number
28
Categorie Soggetti
Engineering, Chemical
Journal title
ISSN journal
00325910
Volume
97
Issue
2
Year of publication
1998
Pages
129 - 138
Database
ISI
SICI code
0032-5910(1998)97:2<129:TIOSIO>2.0.ZU;2-5
Abstract
Surfactants have been used for different industrial and cosmetic purpo ses for decades. Most industrial formulations are complex mixtures of many different chemicals. Often, more than one component is surface ac tive. In this paper we present the results of studies on the colloid s tability and dispersion of metal oxide powders in anionic surfactant s olutions with nonionic or long chain anionic surface-active impurities . Dodecanol dramatically influenced anionic surfactant adsorption and powder dispersion in mixed surfactant solutions. The enhancement of an ionic surfactant adsorption modified the colloid stability of disperse d metal oxides. At the same concentrations where powders were floccula ted in the presence of pure anionic surfactants, stable dispersions we re observed after addition of less than 1 wt.% of dodecanol, Similar e ffects were observed in the presence of 1 wt.% of long chain anionic s urfactant impurities. The modified flocculation/dispersion behavior is caused by the enhanced coadsorption of nonionic and anionic surfactan ts at the oxide-water interface, Even more interesting behavior was ob served at pH values above the isoelectric point of oxides where partic les and surfactants bare negative charge. Pure anionic surfactants can not stabilize oxides at such pH values, but mixtures containing less t han 1 mol% of dodecanol significantly stabilized hematite and anatase at pH values above the isoelectric point. (C) 1998 Elsevier Science S. A. All rights reserved.