Opoka from Russian deposits as natural sorbent for wastewater treatment: Mineralogical and chemical compositions, adsorptive and structural properties

Adsorptive treatment is one of the most efficient methods to remove biologically stable pollutants from production wastewater. It is urgent to increase resources of inexpensive natural sorbents suitable for water treatment. The aim of this study is to find general patterns of mineralogical and chemical compositions, and adsorptive and structural properties of opoka from a number of deposits in Russia as a basis for the opoka application as a sorbent without preliminary thermochemical treatment. The samples of opoka from the Kamenogorsk, Saratov, Artyom and Sukhoy Log deposits, as well as Inzena diatomite were investigated and compared with quartz sand and bentonite. The chemical composition analyses used the energy dispersive X-day spectroscopy, the mineralogical study used the X-ray phase analysis and electron microscopy, and the adsorptive and structural characteristics were examined using the low-temperature isothermal curves of nitrogen adsorption (Brunauer–Emmett–Teller (BET) theory and Langmuir method), and the sorption activity was investigated in adsorption of methylene blue. It is found that the chemical composition is uniform in terms of rock-forming oxides: the coefficient of variation in the contents of SiO2 and Al2O3 was not higher than 7% both within a deposit and in the class of dispersion silica in general. It is shown that the adsorption capacity grows with an increase in the contents of alumina, clayey minerals, and oxides of alkaline and alkaline earth metals, and decreases with an increase in the content of silica. The mesoporous character of opoka (type IV isotherms) is proved, and the influence of grinding on the pore structure is determined. It is substantiated that native opoka is usable in pressure filters without thermochemical modification, which reduces the cost of the sorbent at preservation of physicochemical properties. 

Vurdova N. G., Ovchinnikova T. I., Meshchanova V. D., Vurdov P. Y. Opoka from Russian deposits as natural sorbent for wastewater treatment: Mineralogical and chemical compositions, adsorptive and structural properties. MIAB. Mining Inf. Anal. Bull. 2026;(12):18-31. [In Russ]. DOI: 10.25018/0236_1493_2026_12_0_18.

N.G. Vurdova¹, Dr. Sci. (Eng.), Professor, EMBA, e-mail: nadya_vurdova@mail.ru, ORCID ID: 0009-0001-4624-1569,
T.I. Ovchinnikova¹, Dr. Sci. (Eng.), Professor, Head of Chair, e-mail: ovchinnikova_ti@mail.ru, ORCID ID: 0000-0001-5849-6473,
V.D. Meshchanova¹, Graduate Student, e-mail: Meschanova.valera@yandex.ru, ORCID ID: 0009-0007-2832-7709,
P.Y. Vurdov¹, Graduate Student, e-mail: prod@yandex.ru, ORCID ID: 0009-0003-4302-8783,
¹ NUST MISIS, 119991, Moscow, Russia. 

N.G. Vurdova, e-mail: vurdova2019@gmail.com.

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