Effects of Zeta Potential and Electrolyt

This study investigates the relative motion between colloidal particles deposited on an electrode subjected to alternating current (ac) polarization, focusing on the effects of zeta potential and electrolyte conditions. The objective was to understand how variations in zeta potential, electrolyte composition, concentration, and frequency influence particle interactions. Using experimental setups, the researchers observed that at a frequency of 100 Hz, both sodium bicarbonate and sodium chloride resulted in particle aggregation, while sodium hydroxide facilitated their separation. At 1000 Hz, separation was noted in bicarbonate and hydroxide solutions, although the separation rate was slower in hydroxide solutions compared to 100 Hz. The findings indicated that zeta potential had a negligible effect, suggesting that the relative motion was primarily governed by a convective mechanism. Interestingly, electrolyte concentration did not significantly alter particle behavior. These experimental results align with predictions from an electrohydrodynamic theory, which postulates that particle motion is influenced by electrohydrodynamic flow induced by ionic concentration gradients and the electric field. Notably, the interparticle separation velocity in hydroxide solutions, as predicted by the theory, aligns well with measured values.