Adsorption Kinetics of Polyvinyl Acetate Adsorbed at the Solid-Liquid Interface

The kinetics of adsorption of polyvinyl acetate at the solid-liquid interface has been studied to verify the correctness of a description in a paper [Peterson and Kwel, J.Phys.Chem. 65, 1330(1961)]: “the initial rate of adsorption of polyvinyl acetate was found to be rapid”. This is inconsistent with the widely accepted knowledge that polymer adsorption is a slow process. Polyvinyl acetate (Mw = 124,800) was adsorbed from benzene (0.001 to 0.05 mg ml−1) onto mica at 295.5 K. The adsorbed amount per unit area i.e. adsorbance has been determined as a function of incubation time using an ultramicrobalance [Mettler UM3]. The results obtained show that the adsorbance rises rapidly at the beginning of adsorption and then reaches an apparent plateau, where the adsorbance still increases at negligibly slow rate in comparison with the initial rate. The Peterson and Kwei’s results have been confirmed to be correct. We regarded the plateau as an adsorption equilibrium and constructed adsorption isotherms, in which the Peterson and Kwei’s results were incorporated. These isotherms are found to be less dependent on concentration in the dilute region concerned. This dependency is in agreement with the prediction of the Scheutjens and Fleer theory based on the loop-train-tail model.