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Kinetics of localized adsorption of charged colloid particles on homogeneous solidlliquid interfaces was analyzed. Limiting analytical equations were formulated for the maximum surface concentration e ,, the blocking parameterB(O), and adsorption kinetics in terms of the lateral interaction parameter h* depending on the ionic strength of the colloid suspension. In the general case particle adsorption kinetics proceeding according to the random sequential adsorption (RSA) mechanism was simulated numerically by using the Monte Carlo method. The theoretical predictions were experimentally tested by applying the direct observation method based on the stagnation point flow cell. Monodisperse suspensions of negatively charged latex particles of micrometer size range were used with freshly cleaved mica sheets as the adsorbing surfaces. The theoretical predictions were quantitatively confirmed showing that the RSA model describes well the kinetics of localized adsorption of interacting colloid particles especially for higher flow intensity. The widely used Langmuir model was found inappropriate for colloid particle adsorption from liquid phases.

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A detailed description of the flow distribution in the radial impinging-jet (RIJ) cell was attained by solving the governing Navier-Stokes equation numerically. It was shown that for tangential distances r/R < 0.25 the flow configuration in the vicinity of the solid interface approached the stagnation point flow with the perpendicular velocity component independent of the radial distance. The intensity of this quasi-stagnation point flow, governed by the α parameter, was calculated numerically as a function of the Reynolds number. It was also found that the flow pattern in the RIJ cell resembled the flow occurring near a sphere immersed in a uniform flow. Knowing the fluid velocity field the convective diffusion equation was formulated. This equation, describing a two-dimensional transport of particles, was solved numerically by using the implicit finite-difference method. In this way the particle deposition rate for the low coverage regime (initial flux) can be determined for various parameters such as particle size, Reynolds number, distance from the stagnation point, etc. The validity of the theoretical predictions was verified experimentally using direct microscope observation of polystyrene latex particles of size 0.87 µm. The initial flux near the stagnation point was measured as a function of Reynolds number and ionic strength of the suspension. The dependence of the local mass transfer rate on the distance from the stagnation point was also determined experimentally. This enabled one to estimate the error associated with indirect (optical) measurements of protein absorption in the RIJ cell. A good agreement between predicted and measured flux values was found, which validates the applicability of the numerical solutions of the flow field and mass transfer in the RIJ cell. It was suggested that by measuring the initial flux for colloid particles microscopically one can determine in a direct way the local mass and heat transfer rates for the impinging-jet configuration used widely in practice. C 2001 Academic Press