The results of the study of the processes of adsorption of cationic flocculants of the “Praestol” brand on sorbents obtained by non-chemical processing of clays of the Astrakhan region, the Volga deposit are presented. The adsorption models of Langmuir, Freundlich, and Temkin were used to describe experimental adsorption isotherms. The parameters of the intensity and efficiency of the sorption process are calculated. A comparative analysis of the obtained constants corresponding to these models is carried out and the most preferred model is determined, taking into account the coefficient of determination. It is established that the Freundlich model is most preferable for adsorption in the cationic flocculant – clay system, which allows us to confidently assume that the surface of the natural materials under consideration contains a large number of energetically heterogeneous active centers and is heterogeneous. The results of the analysis of the adsorption of flocculants on clays showed that this process improves flocculation. The bigger value of parameter of intensity of n from Friendlich’s equation for Praestol 853BC flocculant, confirms a greater influence of sorption on flocculating effect that it is connected with formation of the strong high-viscosity sewed structures on a surface of a firm phase. Experiments on the purification of water from oil by test flocculation were also delivered and the degree of purification efficiency was calculated.