Physical and chemical properties of sorbents based on bentonite clay, modified with iron (III) and aluminum polyhydroxocations by the «coprecipitation»
Abstract
Sorption is a promising method in water treatment. A variety of materials can be used as sorbents but, nowadays, the interest in environmentally safe natural sorbents is growing. The purpose of this work was to develop effective sorbents based on bentonite modified with iron (III) and aluminum polyhydroxocations by coprecipitation to enhance their sorption capacity for anions. Natural bentonite was modified with iron
(III) and aluminum polyhydroxocations by coprecipitation. Some samples were subjected to heat treatment in an inert atmosphere of argon.
The chemical and mineral composition of the modified sorbents was studied. The introduction of aluminum and iron (III) polyhydroxocations into bentonite by coprecipitation was shown not to change the mineral and phase composition of bentonite (the minerals montmorillonite, α-cristobalite, and plagioclase were found in all cases). Annealing of the samples under study led to changes in their mineral composition. The mineral illite instead of montmorillonite appeared in both the source bentonite and its samples modified with iron polyhydroxocations. Bentonite modification increases the number of micropores and mesopores and decreases that of macropores as compared with the source clay. The 1.5–8.0 nm poresadd up to the majority of the pores in our modified samples. A similar relationship is also kept for the modified sorbent samples annealed at 550°C.
The specific surface area of the modified sorbents significantly increases in comparison with the initial bentonite. A significant rise in the specific surface area is observed for the iron-modified samples, it reaches 227 m2/g when 10 mmol/g of iron (III) has been added. Chromates, arsenates, and selenite anions were chosenas test ones to study sorption on the modified sorbents. Bentonite modification results in a considerable increase in the limiting adsorption of these anions. Of all the studied anions, arsenat esexhibitthe highest sorption activity: the limiting sorption on the iron-modified sorbent reaches 21.3 mg/g. Hightemperature annealing reduces the adsorption activity of the sorbent surface. Thus, bentonite modification with aluminum and iron (III) polyhydroxocations by coprecipitation allows obtaining small-pore (nanostructured) sorbents with a developed surface (the predominant pore sizes within 1.5–8.0 nm). The specific surface area of such sorbents depends on the amount of the introduced modifying component (iron
(III) and aluminum). The modification of bentonite with aluminum and iron (III) polyhydroxocations was shown to lead to an increase in the sorption capacity of the sorbents prepared in relation to chromates, arsenates, and selenites.
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References
2.Smirnov A.D., Sorbcionnaya ochistka vody. L., Ximiya, 1982, 169 p.
3.Tarasevich Yu.I., Prirodnye sorbenty v processax ochistki vody, Kiev, Naukova dumka, 1981, 207 p.
4.Komov D.N., Nikitina N.V., Kazarinov I.A., Izvestiya Saratovskogo universiteta. Novaya Seriya. Seriya Ximiya. Biologiya. E'kologiya, 2015, Vol. 15, No 2, pp. 27-34.
5. Pechenyuk S.I., Sorbtsionnye i khromatograficheskie protsessy, 2008, Vol. 8, No 3, pp. 380-429.
6.Narayanan S., Deshpande K., Applied Catalysis A: Genegal., 2000, Vol. 193, No 1-2, pp. 7-27.
7.Brindley G.W., Sempels R.E., Clays and Clay Minerals, 1977, Vol. 12, No 3, pp. 229237.
8.Komarov V.S., Kolloidnyj zhurnal, 1995, Vol. 57, No 1, pp. 51-54.
9.Savel'ev G.G., Jurmazova T.A., Shahova N.B., Izv. vuzov. Himija i himicheskaja tehnologija, 2011, Vol. 53, No 3, pp. 36-39.
