Kinetics of irreversible adsorption of latex particles under diffusion-controlled transport

Irreversible adsorption (deposition) of negatively charged later particles on silanized mica was studied by the optical microscopy method. The kinetics of this process, occurring under the diffusion-controlled transport regime, was determined by directly counting the number of particles as a function of adsorption time, reaching 80 h. Measurements were carried out for various ionic strengths of the suspension with the aim of determining both adsorption kinetics and the maximum coverage Theta(mx). The experimental data were interpreted in terms of the generalized RSA (random sequential adsorption) theory by considering the bulk transport of particles coupled with the transport through the adsorbed particle layer, forming a steric barrier. The resulting nonlinear boundary value problem was solved numerically by the finite difference method. A quantitative agreement of this model with experimental results was found, in respect to both adsorption kinetics and the maximum surface coverage. In contrast, the Langmuir model proved inadequate.