The effect of deposition of negatively charged particles on the electrokinetic behaviour of oppositely charged surfaces

Two models have recently been proposed to explain the electrokinetic properties of surfaces with electrostatically deposited particles (R. A. Hayes, Colloids Surf., A, 1999, 146, 89, and M. Zembala and Z. Adamczyk, Langmuir, 2000, 16, 1593). However, supporting experimental data is sparse. In this study, the effects of particle size, particle coverage and ionic strength on the electrokinetic behaviour of positively charged surfaces with negatively charged particles deposited were investigated by streaming current measurements. Results confirm that deposition of oppositely charged particles decreases the magnitude of the zeta potential of the underlying surface. Reversal of the zeta potential was observed at all particle sizes with larger particles reversing the potential at lower coverages. The results presented are fitted to the respective models, and the relative merits of each are discussed