EFFECTS OF SURFACTANTS ON THE STABILITY OF CLAY SUSPENSIONS WITH SPECIAL REFERENCE TO THE CHANGES OF PH

Abstract

The anionic surfactant sodium dodecylbenzenesulfonate [SDBS] and nonionic surfactant (an alcohol ethoxylates with 12 carbons and 9 oxyethyl groups [A 12 E 9 ]) are widely used as major constituents of synthetic detergents in China and are becoming the most common environmental pollutants. Stability of clay suspensions based on examination of surfactant adsorption on the clays was examined. In addition, the effect of pH on the stability of clay suspensions in the presence of the surfactants was also considered. The data showed that SDBS significantly affected the stability of clays from Jiangxi (JX clay) suspensions at lower pH, whereas the effect on clays from Shanghai (SH clay) suspensions was minimal at all pH values studied, except for SDBS at higher concentration. The different effects possibly resulted from difference of adsorbed amounts of SDBS on JX and SH clays. With the increase in pH, the effect of SDBS on the stability of JX clay suspensions was gradually weakened. The stability of both the JX clay and SH clay suspensions decreased at lower concentration of A 12 E 9 , whereas it increased at higher concentrations, possibly resulting from changes of adsorption modes of A 12 E 9 on the clays. The A 12 E 9 had a more intensive effect on the stability of JX clay suspensions at moderate pH than at other pH values. At different pH values, the stability of SH clay suspensions had similar effects with the increase of A 12 E 9 concentration, possibly resulting from the observation that the amount of A 12 E 9 adsorbed on SH clay varied minimally with pH.