Aluminum oxides have been especially useful in such
The adsorption of sodium dodecylsulfate (SDS) and the costudies since their surface charge and electrical double adsorption of SDS and 1-butanol from aqueous electrolyte solulayer properties are well characterized and controlled by tions and from microemulsions containing heptane onto acidic the pH (3, 4).
and basic aluminum oxide were measured. The aluminum oxides
In contrast to the large amount of literature on surfaccontain quasi-spherical highly porous particles with an amorphous tant / cosurfactant association and micellar solubilization, structure. The measurements were carried out just above the considerably less work has been done on adsorption at Krafft temperature at 26ЊC. It is shown that the adsorption capacity of SDS and butanol onto the acidic alumina is slightly higher solid / liquid interfaces of surfactant systems containing than that onto the basic. The adsorption of SDS decreases while additives. However, some previous papers have investibutanol adsorption increases upon increasing alcohol concentragated the mutual adsorption of anionic surfactants and tion. The alcohol to surfactant mol ratio on the oxide surface nonionic cosurfactants onto solid oxide surfaces ( 5 -10 ) . reaches 2.3 for the acidic oxide and 2.1 for the basic oxide in These works show that surfactant ions adsorb readily onto solutions containing 0.8 M butanol. The result indicates that to a oppositely charged oxides and form a characteristic isocertain degree, SDS becomes gradually replaced by butanol on therm ( 11 ) . Moreover, adsorption of cosurfactants only the alumina surface. In order to describe the surfactant/alcohol takes place if the surfactant already is present on the solid exchange on the surface, a simple model is proposed and fitted to surface, and a decrease in the surfactant adsorption level the obtained adsorption data. According to this model, the alcohol to surfactant area ratios in the adsorbed patches are 0.48 and 0.71 is observed with increasing cosurfactant adsorption. on the acidic and basic oxide respectively. Addition of heptane Thus, the results indicate that the cosurfactant adsorbs does not show any considerable alteration in the adsorption density onto the preadsorbed surfactant colloids present on the of the surfactant and alcohol, which indicates that heptane does oxide surface.
not solubilize to any appreciable extent in the adsorbed aggregates
In an aluminum oxide / water system, the OH groups on on the oxide surface.