Kinetic and Thermodynamic Characteristics of the Sorption of Fluoride Ions Using a Composite Based on Cellulose and Alum
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ICAL CHEMISTRY OF SURFACE PHENOMENA
Kinetic and Thermodynamic Characteristics of the Sorption of Fluoride Ions Using a Composite Based on Cellulose and Alumina A. V. Dolganova, A. V. Balandinaa,b,*, D. B. Chugunova, A. S. Timoninaa, L. A. Klimaevaa, V. V. Shinginaa, and A. V. Knyazevb a National
b
Research Mordovia State University, Saransk, 430005 Russia Faculty of Chemistry, Lobachevsky State University, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received March 16, 2020; revised March 16, 2020; accepted March 17, 2020
Abstract—The adsorption of fluoride ions by a composite material based on aluminum oxide and cellulose is studied in detail. Adsorption equilibrium constants K, parameter Г∞, and ΔG0ad are calculated from Langmuir adsorption isotherms. The sorption characteristics are determined along with the kinetics and mechanism of the processes. The high sorption ability of the composite material based on alumina and cellulose is compared to that of sorbents described earlier. Keywords: cellulose, alumina, fluoride, AСО technology, adsorption DOI: 10.1134/S0036024420100076
INTRODUCTION With the growth of our civilization, water pollution has become a major problem that requires immediate solutions [1]. The use of water with fairly high fluoride contents continues in Russia and around the world. Different filters in which sorbents have low lifetimes, low absorption capacity, and very high cost are used for its defluorination. Drinking water with high fluoride contents is harmful to human health [2]. The long-term use of water with excess fluoride can lead to the destruction of tooth enamel in children and the deformation of limbs in adults [3]. Various ways of removing fluoride have different limitations, but adsorption is considered the most promising approach, due to its ease and low cost [4]. In recent years, the use of aluminum oxide to remove fluoride ions from water has been actively studied, since it has a mesoporous structure and low toxicity [5–8]. However, all sorbents based on aluminum oxide have a considerable drawback: low sorption capacity. The search for new sorbents containing alumina and having high sorption capacities is currently of interest. In this work, we proposed using thin films (100 nm) of alumina deposited on surfaces of microcrystalline cellulose as a sorbent. The kinetic and thermodynamic parameters of the sorption of fluoride ions from water are studied in detail for the obtained composite material. EXPERIMENTAL Microcrystalline cellulose was used as a sorbent on which Al2O3 films of different thicknesses was depos-
ited using ALD technology. In the deposition of thin films by ALD, a substrate inside a vacuum chamber at the operating temperature is subjected to alternate impacts of two reagents (precursors) in the form of steam. The precursors, which react only on the surface of the substrate, create a monolayer of a thin-film compound that forms as a result of their interaction. The thickness of the deposited layers is determined using the calibration graphs
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