Development of Magnetic Nanocomposites Based on Beta Zeolites and Study of Their Sorption Properties
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velopment of Magnetic Nanocomposites Based on Beta Zeolites and Study of Their Sorption Properties E. Yu. Brazovskayaa, * and O. Yu. Golubevaa aGrebenshchikov
Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, 199034 Russia *e-mail: [email protected] Received March 2, 2020; revised March 20, 2020; accepted April 10, 2020
Abstract—Core–shell type magnetic nanocomposites based on Beta zeolites and magnetite (Fe3O4) nanoparticles have been synthesized under hydrothermal conditions. It has been revealed that the magnetic nanocomposites obtained have a high sorption capacity for the organic dye methylene blue. It has been found that the maximum absorption of methylene blue on a Beta–Fe3O4 sample is 186 mg/g, with the adsorption equilibrium being reached within 90 min. The mechanisms and characteristic parameters of the adsorption process have been analyzed using the Langmuir and Freundlich isotherm models. Sorption kinetic curves have been evaluated using the diffusion model and the pseudo-first and pseudo-second order models. The results indicate that the adsorption process has a chemisorption nature, since it obeys the pseudo-secondorder rate law. Keywords: zeolites, magnetite, sorption, methylene blue DOI: 10.1134/S0965544120080046
Any industry consumes a huge amount of water and thereby produces significant amounts of wastewater, which usually contains various pollutants due to the textile, pharmaceutical, and paper industries [1]. Dyes can absorb sunlight, thereby inhibiting the photosynthetic activity of aquatic plants and creating a serious threat to the entire ecosystem [2]. Therefore, wastewater must be appropriately treated before discharging into natural water bodies. However, as a rule, the removal of dyes is a laborious process due to their high solubility in water, complex structure, and synthetic origin [3]. For wastewater treatment, physical, chemical, and biological methods are used, which include precipitation [4], ion exchange, photocatalytic decomposition [5], biological oxidation [6], adsorption [7], and membrane filtration [8]. Among these processes, adsorption is considered the most commonly used method of water purification because of its low cost, ease of operation, and safety [9]. Magnetic sorbents are widely used in wastewater treatment processes. The essence of obtaining magnetic materials is to incorporate a discrete magnetic phase into weak or nonmagnetic carriers to increase their magnetic susceptibility, prevent agglomeration of magnetic nanoparticles, and remove the magnetic nanocomposite from an aqueous medium after its use [10]. Using this approach, 99.9% of organic dyes can be removed [11].
In this study, synthetic zeolites have been selected as a nonmagnetic matrix, as they represent a great potential for wastewater treatment. Zeolites, due to their peculiar structure, are unique sorbents that allow efficient adsorption of various molecules. The object of study was zeolite Beta, which is one of the macroporous zeolites with the largest pore size d
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