Precipitation of calcium surfactants. Part 3

Abstract

The precipitation of calcium surfactants has been shown to proceed by the same mechanisms that apply to the precipitation of inorganic salts. As the rates of precipitation of the latter are retarded by the addition of polyelectrolytes it was expected that they may have a similar effect on surfactant precipitation. In this paper the influence of polyelectrolytes and non-ionic surfactants on the precipitation of calcium dodecyl sulphate were investigated. The precipitation was affected by polymeric additives, only through interaction between the polymers and the precipitating species in solution. No evidence was found for adsorption of the polymers on specific growth sites of the crystals. This may have been a result of the adsorption energy arising mainly from hydrophobic rather than electrostatic forces.

Non-ionic surfactants also have no specific effect on the precipitation of calcium surfactants, except through the normal mixed micelle formation. In the absence of mixed micelle formation, non-ionic surfactants have no influence on the precipitation of calcium dodecyl sulphate.