Effect of ionic strength on adsolubilization of toluene and acetophenone into CTAB adsorbed on precipitated silica

Abstract

In this study, the effects of ionic strength on adsorption and adsolubilization were studied using a quaternary ammonium cationic surfactant, cetyltrimethylammonium bromide or CTAB, and precipitated silica as a solid oxide surface. The adsolubilization of the model organic compounds, toluene and acetophenone, was investigated both in single-solute and mixed-solute systems. For both adsorption and adsolubilization, batch experiments were carried out at two different pH values (5 and 8) under various ionic strengths (1, 10 and 100 mM). The results showed that the adsorption of CTAB on the silica surface increased with increasing ionic strength. In the single-solute system, increasing ionic strength had little effect on the adsolubilization of toluene. However, the adsolubilization of acetophenone significantly increased with increasing ionic strength, especially at 100 mM. In the mixed-solute system, the synergetic effect was observed in the adsolubilization of acetophenone in the presence of toluene and the effect was more pronounced with increasing ionic strength. In contrast, the presence of acetophenone had little effect on the adsolubilization of toluene.