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.