Kinetics of colloid particles deposition under the influence of gravity

Kinetics of irreversible deposition of interacting colloid particles at solid/liquid interfaces has been investigated experimentally using the direct microscope observation technique coupled with an image analysing system. The new sedimentation cell enabled to study in real time both the number of particles deposited at a given surface area and the distribution of particles characterized in terms of the pair correlation function. Using the monodisperse colloid suspensions of melamine-formaldehyde latex particles with specific density of 1.5 g/cm(3) and the micrometer size range the effect of gravity has been evaluated quantitatively. It was found that particle deposition rate under gravity was considerably enhanced in comparison with the previously studied case of diffusion affected adsorption when the random sequential adsorption (RSA) mechanism was valid. Accordingly, the experimental results could be interpreted in terms of the ballistic adsorption model using the effective hard particle concept rather than in terms of the RSA model.