Adsorption and Desorption Kinetics of Mixtures on Planar Surfaces under Flow Conditions

The adsorption isotherms and the adsorption/desorption kinetics of a mixture of nonionic water-soluble associative polymers with different molecular weights on silicon wafers and polystyrene films under flow conditions were studied. Equations were derived to calculate the parameters characterizing the kinetic-diffusive-convective-controlled adsorption and desorption processes under flow conditions: (a) the equilibrium adsorption, (b) the thickness of the adsorbed layer, (c) the activation energy of adsorption, (d) the rate constant, (e) the effective coefficients of diffusion in the adsorbed layer, and (f) the time needed to attain the equilibrium state for the adsorption and desorption processes for individual components and mixtures. We also studied the competitive adsorption kinetics of water-soluble nonionic polyurethane polymer based on poly(ethylene glycol), with an average molecular weight of 12 000, 62 000, and 120 000 g/mol and with a C 16 H 33 linear alkyl group on each end of the molecule, from aqueous solution onto the silica (SiO 2 ) and polystyrene films by ellipsometry.