SURFACE-CHARGE AND STABILITY OF AN AEROSIL IN AQUEOUS-SOLUTIONS OF ETHOXYLATED ALKYLPHENOL AND POLYACRYLAMIDE

A study is made of the adsorption of ethoxylated alkylphenols (R9 phi E10) and polyacrylamide (PAA) from aqueous solutions of KCl on the sur face of an Aerosil. It is shown that the adsorption isotherm of (R9 ph i E10) reaches saturation in the region of the CMC (critical micelle c oncentration), while the adsorption isotherm of PAA passes through a m aximum. The method of continuous potentiometric titration is used to s tudy the charging of the surface of Aerosil particles covered by adsor ption layers of (R9 phi E10) and PAA. In the case of (R9 phi E10), the re is a decrease in the surface charge of SiO2 compared to the KCl sol utions throughout the investigated interval of pH. This decrease is gr eater, the greater the ionic strength of the solution. No such decreas e in charge is seen in PAA solutions. Adsorption measurements made in mixed solutions of (R9 phi E10) and PAA show that the adsorption of th e surfactant and the surface charge of SiO2 are determined solely by t he presence of (R9 phi E10) in the solution and are independent of the presence of PAA macromolecules in same. The results of the adsorption studies are compared with data from the study of the stability of a s ol of an Aerosil in solutions of the investigated substances. The sol of an Aerosil which is aggregatively stable in a 10(-3) solution of KC l coagulates in solutions of (R9 phi E10) in the region of the CMC, wh ile solutions of PAA within this condition range have almost no effect on stability.