INVESTIGATION OF SURFACE-REACTIONS ON AN INTERFACE OF SIO2 WITH AN AQUEOUS-SOLUTION OF POLYETHYLENIMINE

The surface reactions and state of adsorbed layers on the interface of aerosol with an aqueous solution of polyethylenimine (PEI) were inves tigated by potentiometric titration. The dependences of the surface ch arge density of SiO2, as well as the charge density of the dense and d iffuse portions of the adsorbed PEI layer, on the pH of the PEI soluti ons were obtained and used to estimate the constants of the surface re actions of complex formation according to the Davis-James-Leckie model of binding sites. It was shown that the adsorption of PEI on aerosol is accompanied by an increase in the native charge of the SiO2 surface , an increase in the constant of complex formation of the surface sila nol groups, and also a change in the binding constant of PEI adsorbed in the dense portion of the adsorption layer. The constant of the bind ing of PEI in the diffuse portion of the adsorption layer is virtually the same as the binding constant of PEI in the free solution. An anal ysis of the dependences of the charge density of th e dense and diffus e portions of the adsorbed layer of PEI on the pH of the solutions ind icates a redistribution of adsorbed PEI between the dense and diffuse portions of the adsorption layer with changing pH of the solution.