Study of the sorption properties of zeolite-containing tripolite from the Khotynets deposit in the Orel Region

Abstract

The purpose of the study was to evaluate the possibility of using zeolite-containing tripolite from the Khotynets deposit of a specific mineral composition for purification of ground and surface waters from anthropogenic Ni²⁺ and Zn²⁺ and as a geochemical barrier. We studied the sorption and filtration properties of zeolite-containing tripolite samples with a pre-determined mineralogical and chemical composition in accordance with known GOST standards and industry methods. The total cation exchange capacity of the studied zeolite-containing tripolite samples was determined by the ammonium ions. It amounted to 1.53 meq/g. The kinetics of sorption of the above ions from solutions of different mineralisation (0.003 N CaCl₂ and 0.06 N CaCl₂) was studied by the limited volume method. Taking into account the equilibration time, we obtained isotherms of Ni²⁺ and Zn²⁺ sorption by zeolite-containing tripolite from 0.003 N CaCl₂ and 0.06 N CaCl₂ solutions. In the range of the studied concentrations of pollutant ions (2-10 mg/dm³), the isotherms of sorption of Zn²⁺ and Ni²⁺ were linear. We studied the sorption of nickel and zinc ions depending on the pH. It was determined that at рН=6, the sorption of Ni²⁺ from 0.003N CaCl₂ decreased by 23%, and the sorption of Zn²⁺ decreased by 13%. At the same time, it was shown that after 3 weeks of solution contact with an initial pH=6.7, the equilibrium pH increased to 7.7-7.8. It may be due to the presence of other minerals (calcite, cristobalite, smectite, etc.) in the initial rock. The filtration rate decreased approximately 4 times in 5 months. The data obtained allowed us to conclude that the studied zeolite-containing tripolite of the known mineralogical and chemical composition could be used to solve environmental problems (purification of surface and ground water of low mineralisation (0.003 N) from Ni²⁺ and Zn²⁺ ions).