Abstract
The object of research is bentonite clays, the main rock-forming mineral of which is montmorillonite. This natural silicate exhibits sorption capacity for heavy metal ions due to its high cation exchange capacity and specific surface area. One of the most problematic uses of montmorillonite in sorption processes is the ability to swell in aqueous media. This greatly complicates the separation of the spent sorbent from purified water. To eliminate this drawback, granulation is most often used, followed by heat treatment. Moreover, various polymer compounds are used as a structure-forming agent. This technique leads to a significant decrease in the specific surface of bentonite clays, and, therefore, deterioration in their sorption properties. In the course of the study, the method of surface modification of montmorillonite iron oxide-hydroxide (ferrihydrite) is used. The resulting materials are distinguished by manufacturability and increased sorption ability with respect to uranium compounds. This is due to the fact that when treating the surface of bentonite clays with ferrihydrite, effective sorbents can be obtained that lose their ability to swell without heat treatment. The deposition of a layer of iron oxide compounds on the surface of montmorillonite led to a change in the parameters of the porous structure of the resulting composite. So, the specific surface of the modified sample is 250 m2/g, which is significantly higher than that for the output mineral (89 m2/g). At the same time, the average pore size increased 2.8 times. It has been shown that as a result of surface treatment of montmorillonite with ferrihydrite, the sorption capacity of materials for uranium compounds increases with an increase in the iron content on the surface: from 0.42 mg/g for the initial montmorillonite to 10.13 mg/g for the modified sample. It is found that the presence of competitive metals (As, Mn, Co, Cd, Cr) in mineralized waters in equimolar amounts does not lead to a significant change in the values of uranium adsorption on bentonite/iron oxide composites.
Highlights
The development of the uranium mining and uranium processing industries causes significant environmental pollution, in particular the water basin
As a result of the use of acid leaching in hydrometallurgical processes, in addition to the high content of U(VI) compounds, groundwater in places of uranium ore mining and processing is characterized by increased mineralization, which amounts to several grams per liter [9]
The prospects of using sorbents based on iron and its compounds for the extraction of uranium and heavy metals from polluted waters are described in a significant number of works
Summary
The development of the uranium mining and uranium processing industries causes significant environmental pollution, in particular the water basin. As a result of the use of acid leaching in hydrometallurgical processes, in addition to the high content of U(VI) compounds, groundwater in places of uranium ore mining and processing is characterized by increased mineralization, which amounts to several grams per liter [9]. In such waters, U(VI) is predominantly in the form of negatively charged sulfate or carbonate complexes [10], while the solubility of uranium in mineralized waters increases [8]. The development of composites based on natural clay minerals by modifying them with iron compounds for the effective extraction of uranium compounds and other inorganic toxicants from contaminated mineralized waters is a timely and relevant task, and is the subject of this research
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