Bentonite Rock from Oglanlynski Field (Turkmenistan) and Composites Based on It as Sorbents for 90Sr

Abstract

Removal of 90Sr from aqueous media by sorbents prepared from bentonite from the Oglanlynski field and by their composites with magnetite is studied. It is shown that the sorbents can be used for purification of large volumes of radioactively contaminated waters. Here, we study bentonite rock material (a natural mineral), montmorillonite in Na-form derived from it, clinoptilolite and cristobalite (impurities in bentonite), and composites obtained by depositing magnetite onto the surface of listed materials. The 90Sr sorption is effective in a broad pH range (3.7–9). The developed composites can be successfully used in purification of radioactively contaminated aquatic environments. The magnetite in sorbents functions exclusively as a magnetically active component, which enables us to use an external magnetic field in separation of sludge resulting from water purification process. The maximum adsorption of strontium ions, as calculated from the Langmuir equation, is obtained for montmorillonite in Na-form and the initial rock material: 20.8 and 14.5 mg/g, respectively. For the composites based on these materials, the values are smaller: 18.5 and 10.6 mg/g, respectively. The effectiveness of sorbents for removal of 90Sr from natural waters and liquid radioactive wastes is shown to be determined mostly by the mineral content of media to be purified, i.e., the type and concentration of macro elements: Na+, K+, and Ca2+. Among the indicated competing ions, calcium affects the removal of strontium from aquatic environments to the largest extent.