Kinetics of colloid particle adsorption at heterogeneous surfaces

Adsorption kinetics of negatively charged polystyrene latex particles (average size 1.38 mum) over a heterogeneous surface was studied experimentally. The substrate of a controlled heterogeneity was produced by covering natural mica sheets by smaller (average size 0.55 mum) positively charged latex particles. The direct microscope observation method combined with the impinging jet technique was used to determine particle adsorption kinetics. The initial flux of particles (the slope of the kinetic curves in the limit of short adsorption time) was determined quantitatively as a function of the coverage of smaller particles. It was demonstrated that the initial flux attains the limiting values for the smaller particle (heterogeneity) coverage as small as a few percent The experimental results were interpreted in terms of the generalized random sequential adsorption model by considering the coupling between the bulk and surface transfer steps. A good agreement was found which seems to confirm the validity of the theoretical model for predicting particle adsorption at heterogeneous surfaces.