ABSTRACT This work represents the results of comparative assessment of sorption capacity of enriched and modified alkaline forms of montmorillonite containing clay deposit of Belgorod region (Russia). The process of complex activation of montmorillonite containing clay consists in isolation of fine-grained fraction and subsequent activation of matrix by solutions of alkali metal chlorides (lithium, sodium and potassium). It is shown that during salt treatment the average diameter of clay particles is decreased, which is explained by dispersing action of solutions of alkali and alkaline earth metal chlorides. At the same time, the texture characteristics of the materials remain almost unchanged. The results of mathematical treatment of isotherms of sorption of Cu2+ ions andFe3+ from model aqueous solutions on experimental materials are given in this work. The correlation coefficients of R2 in the conversion of isotherms of sorption of metal ions into linear form, indicating compliance of the sorption with the Langmuir model, are 0.99. The highest amount of marginal adsorption among alkaline forms is the sodium form of clay. The relatively low absorption activity of the K-form of clay is due to the lower mobility and hence the possibility of surface dissociation of K+ ions in aqueous solutions. In general, in terms of their capacity to absorb heavy metal cations (Cu2+ and Fe3+) the activated samples are superior to the enriched clay form on the 20 - 40%.