Mikhailova I. Adsorption of cationic surfactants and proteins and its influence on stability of suspensions of highly dispersed silica

3. The dissertation devoted to the study of adsorption properties of highly dispersed silica and stability of its suspensions in the presence of some physiologically active substances. It was experimentally established that the interaction of silica surface with the molecules of cationic surfactants - mono- and bis-quarternary ammonium compounds - takes place simultaneously on two types of the surface centres (charged and neutral) that corresponds to the monolay adsorption model. The disturbance of aggregative stability of suspensions of highly dispersed silica takes place both due to neutralization of negative charge of surface and phloculating action of cationic surfactants. The adsorption of cationic surfactants on highly dispersed silica make be accompanied by the aggregation of molecules on the surface that results in the rate increase of suspensions phloculation.There have been studied the conformity of suspensions phloculation of highly dispersed silica in the presence of some albumins, human hemoglobin and gelatin. It was found that in the presence of proteins the silica suspensions stability is described with the help of electrostatic mechanism. It was determined that at low covering of the surface and at pH approaching to isoelectric point of silica, maximum is observed on the concentration dependence of suspensions phloculation rates. With increasing of protein adsorption simultaneously with phloculation the decomposition of aggregates of silica particles takes place in suspensions at low pH. The character of phloculating action of serum albumins depends on the way of their production. The presence of admixture of lipids probably increases of proteins adsorption and results in the phloculation rate increasing, especially at high pH in the condition of electrostatic repulsion from surface.