Accession Number : ADA183459

Title :   Effect of Nonionic Surfactants on the Stability of Hydrophobic Colloids.

Descriptive Note : Technical rept.,

Corporate Author : TUFTS UNIV MEDFORD MA DEPT OF CHEMICAL ENGINEERING

Personal Author(s) : Botsaris,Gregory D ; Glazman,Yuli M ; Beronja,Gregory P

PDF Url : ADA183459

Report Date : 30 Jul 1987

Pagination or Media Count : 12

Abstract : This paper reports recent findings in our continuing investigation on the preparation of stable dispersions in the presence of relatively high concentrations of electrolytes. Typical practical examples of such dispersions are those prepared with ocean water as the liquid phase. Previous investigations have shown that the nature of aggregative stability of hydrophobic sols changes drastically in the presence of nonionic surface active agents (NSAA); the ionically stabilized sols are converted into hydrophilic ones. This transition manifested by an extremely sharp rise in the resistance of the sol towards the coagulating effect of electrolytes, takes place at relatively low NSAA concentrations. This work studied the effect of a certain type of NSAA, i.e., polyoxyethylated octyland nonyhlphenols with different degrees of oxyethylation, on the stability of silver iodide hydrosols. The above mentioned steep rise in stability was observed also with this type of NSAA. However, the certain cases at surfactant concentrations below those causing the steep rise, a peculiarity was discovered: a peak appeared in the curve representing the dependence of the electrolyte coagulation value on the surfactant concentration. It is important to emphasize that at these low NSAA concentrations, the sol remains hydrophobic, or in other words, it is still stabilized by an electric double layer mechanism. The phenomenon of the above peak is explained by a possible modification of the electric double layer by the benzene ring of the non-polar chain of the surfactant molecules which are adsorbed on the sol particles. Keywords: Colloidal stability, Coagulation, Solvation stabilization, Nonionic surfactants.

Descriptors :   *COLLOIDS, *SURFACE ACTIVE SUBSTANCES, BENZENE, RINGS, STABILITY, ELECTRIC DOUBLE LAYER, ELECTROLYTES, HYDROPHOBIC PROPERTIES, COAGULATION, CONCENTRATION(COMPOSITION), HIGH RATE, LIQUID PHASES, SEA WATER, DISPERSIONS, PREPARATION, STABILITY, STABILIZATION, PARTICLES, SOLVATION, CONCENTRATION(COMPOSITION)

Subject Categories : Organic Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE