Influence of the thermal treatment of palygorskite on the adsorption of tritium from water solutions

English

https://doi.org/10.15407/mineraljournal.40.03.097

UDC 549.67:54-116:54.027

I.M. Rudenko 1, O.V. Pushkar’ov 1, A.M. Rozko 2, V.Vik. Dolin 1
1 Institute of Environmental Geochemistry of the NAS of Ukraine
34-a, Acad. Palladin Ave., Kyiv, Ukraine, 03142
E-mail: Irina_mihalovna@ukr.net
2 M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
E-mail: al.rozko@gmail.com
Influence of the thermal treatment of palygorskite on the adsorption of tritium from water solutions
Language: Ukrainian
Mineralogical journal 2018, 40 (3): 97-104

Abstract: An experimental study was made of the change in the adsorption properties of palygorskite due to thermal treatment of the mineral under thermostatic conditions at 110 °C. For the experiment, the Palygorskite Cherkassy deposit (Ukraine) and tritiated water NTO were used. The experiment was carried out under stationary conditions in a closed system for 400 days. Under such conditions, an equilibrium distribution of tritium between the components of the system was achieved. The redistribution of tritium between the mineral phase and NTO is determined by measuring the specific activity of tritium in the aqueous residue and in the mineral mass. Using the indicator of the specific stock of tritium normalized to the amount of mineral mass (Bq/g), a 7-fold improvement in the adsorptive capacity of palygorskite was established due to thermal treatment compared to the original (untreated) mineral. To determine the distribution of tritium between different structural positions of palygorskite, moisture fractions were isolated at fixed temperature intervals according to DTA data: 1 fraction (up to 105 °C), 2 (105-240 °C), 3 (240-350 °C), 4 (350-1000 °C). Fractions of moisture were released from the mineral mass after the completion of the experiment using specialized thermogravimetric equipment. It has been established that most of tritium (up to 78 %) accumulates in surface adsorbed form due to more intensive attraction and retention of NTO molecules due to the realization of adsorption-desorption processes on the thermally activated surface of mineral particles. The residual part of the tritium of the initial solution in the molecular form of NTO is exchanged with the H2O channel water molecules (16 %), replaces the polarized molecules of the coordinated OH2 (3.1 %), and participates in the OT → OH exchange in the structural positions of the octahedral mineral grid (29 %). It is established that the thermal activation of palygorskite facilitates the fractionation of hydrogen isotopes in the redistribution of tritium between different structural positions of the mineral. This made it possible to determine the effectiveness of the thermal modification of palygorskite in improving its ability to adsorb tritium from aqueous solutions. Using the thermogravimetric method and equipment, regularities in the distribution of tritium between different structural positions of palygorskite and the degree of fractionation of hydrogen isotopes in the water-mineral system were determined.

Keywords: palygorskite, tritium, thermal treatment, adsorption, fractionation of hydrogen isotopes.

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