Electrokinetic properties of barite nanoparticles suspensions in different electrolyte media

In this study, electrokinetic properties of barite nanoparticles have been investigated in water. A series of systematic zeta potential measurements have been performed to determine the isoelectric point (iep) and potential-determining ions (pdi), and the effect of mono-, di-, and trivalent anions sodium salts such as NaCl, NaNO3, NaCH3COO, Na2SO4, Na2CO3, and Na3PO4 on the zeta potential of barite nanoparticles. Barite nanoparticles yields an isoelectric point at pH 7.8. The zeta potential for the barite nanoparticles has ranged from +15.5 mV at pH ∼ 3 to −19.8 mV at pH ∼ 9.5 at 25 ± 1 °C in water. It is proved that the valency of the ions greatly influence on the electrokinetic behavior of the suspension. Monovalent anions were found to have a weak effect on the zeta potentials. The negative zeta potentials were observed in the presence of di- and trivalent anions. Charge reversal was observed for divalent anions at 1 × 10−2 M and for trivalent anions at 1 × 10−1 M. It was considered that monovalent anions are indifferent ions and di- and trivalent anions are potential-determining ions. A schematic adsorption model which accounts for the adsorption of mono- and multivalent anions in the electrical double layer of barite nanoparticles is proposed.