In Ukrainian

Abstract

Surface modifiсation of clay minerals from Cherkasy deposit (Ukraine) montmorillonite (layer silicate) and palygorskite (fibrous silicate) was performed using the cationic surfactant hexadecyltrimethylammonium bromide (HDTMA). The successful modification of the surface of montmorillonite and palygorskite clays after treatment with HDTMA was confirmed by X-ray analysis and IR-spectra. The ζ-potential measurements of the organo-clays showed even a zeta potential reversion from negative to positive in the whole acidic pH range. In this case, the adsorbed surfactant molecules can form both mono and double layers on the surface of clay particles. The uranium(VI) sorption from mineralized groundwater on montmorillonite and palygorskite clays modified by HDTMA was investigated. The composition of the mineralized groundwater according to the main anionic components corresponded to the composition of the underground mineralized waters near the uranium ore mining and processing sites of the State Enterprise Eastern Mining and Processing Plant (Zhovty Vody, Ukraine), the total dissolved solids content was 5280 mg/l, pH 7.2. It has been shown that in contaminated mineralized groundwater, uranium(VI) is predominantly in anionic form, namely in the form of carbonate and sulfate complexes. Unmodified clays had no affinity to negative charged complexes while samples of HDTMA-modified clay minerals showed significant removal of uranium from mineralized water. The experimental data were applied to the Langmuir model of monomolecular adsorption and a good fit was obtained. It has been found that adsorption capacity increased with increasing HDTMA content in modified clays. The maximum sorption values in samples with a high degree of surface coverage and the formation of predominantly double layers of surfactants (ratio of surfactants exchange capacity 5) were obtained. These values for montmorillonite were higher (about 31 mg/g) than those for palygorskite, having a much smaller exchange capacity (about 28 mg/g). The method of organophilization of clays can be effectively used in environmental technologies for the removal of negatively and positively charged complexes of uranium from groundwater, for example, in the construction of permeable reaction barriers.