The concentration effect of surfactants on zeta-potential in non-aqueous dispersions

Effect of alkyl functionalization on charging of colloidal silica in apolar media

“…Both untreated and C16-treated particles had negative surface charge. In both cases, the particle mobilities exhibited a maximum as a function of surfactant concentration consistent with commonly reported results [2,17,38]. At low surfactant concentrations, the particle mobilities were below the instrument limit of 0.001 lm cm/ s V and are represented as zero on the graph.…”

Determination of the effective charge of individual colloidal particles

“…Hsu et al [21] found higher values around −100 mV for PMMA particles in dodecane with charging agent AOT. This shows the high influence of the charging agent and the type of particle on the resulting zeta potential, as also reported by Kitahara et al [32]. The calculated values for the zeta potential are also of the same magnitude as those found in many aqueous systems.…”

Effect of particle and surfactant acid–base properties on charging of colloids in apolar media

“…Although the decline in zeta potential at high surfactant concentration is commonly reported, it is not always observed [23,26,31]. When such a decline was seen, the cause of such decrease remains unanswered.…”

“…Morrison noted that it has generally been assumed that the decrease in the potential could not be caused by the compression of the electrical double layer since there are too few charge carriers in medium to do so [7]. Therefore, many reports proposed that the reduction in the zeta potential was caused by ''neutralization" of charge on the particle surface by adsorption of oppositely charged species from the medium [22,26,[48][49][50]. However, recent studies also have shown that charged micelles in the medium could effectively screen the electrostatic interaction between colloidal particles in apolar media.…”

“…In fact, the dependence of zeta potential on surfactant concentration in apolar media is an unsettled issue, and many types of relationships have been reported. The most commonly reported picture is one that shows zeta potential going through a maximum as surfactant concentration increases [26][27][28][29][30]. However, there have been reports that zeta potential is constant [23,31], increases [32] or decreases monotonically [33], and even switches sign as the surfactant concentration increases [22].…”