Preparation and Characterization of Aluminum Lithium Hydroxide Carbonate Hydrate Obtained From Basic Aluminum Sulfate
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Preparation and Characterization of Aluminum Lithium Hydroxide Carbonate Hydrate Obtained From Basic Aluminum Sulfate César A. C. Soto1, Aurora P. Delgado1, Esthela R. Ramírez1, and Veridiana R. Zamudio1 1
Universidad de Guanajuato, Departamento de Química, Noria alta s/n, Col. Noria alta, Guanajuato, Gto., C.P. 36050, México. E-mail: [email protected]
ABSTRACT Aluminum lithium hydroxide carbonate hydrate, also known as Al-Li double hydroxide or Al-Li hydrotalcite-like compound [Al2Li(OH)6]2CO3•nH2O, was prepared from basic aluminum sulfate. This compound was prepared by precipitation in homogeneous solution of an aluminum bisulfite solution. A sodium aluminate aqueous solution was prepared by dissolving basic aluminum sulfate in 1M sodium hydroxide. The Al-Li double hydroxide was obtained after addition of lithium carbonate satured solution to the sodium aluminate solution, at 60 °C. The synthesized powder was characterized by thermal analysis (TG, DTG and DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By this method crystalline Li-Al hydrotalcite like compound with composition near to Al4Li2(OH)12CO3 •3H2O was obtained. Keywords: Chemical synthesis, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM).
INTRODUCTION Hydrotalcite-like compounds (HLC), also known as anionic clays or hydrotalcite (HT)like materials, are a layered double hydroxide that may be represented by the general formula [M2+1–xM3+x(OH)2]x+(An–)x/n mH2O, where M2+ (M = e.g. Mg, Fe, Co, Cu, Ni, or Zn) and M3+ (M = e.g. Al, Cr, Ga, Mn or Fe) are di- and trivalent cations respectively; the value of x is equal to the molar ratio of M2+/(M2+ + M3+) and is generally in the range 0.2–0.33; An– is an anion [1]. A1-Li hydroxycarbonate, [A12Li(OH)6]2CO3 • nH20, with laminar structure, belongs to the hydrotalcite-like compounds family, and is obtained by hydrolysis of A13 + in the presence of lithium carbonate solutions [2]. HLC possess very interesting properties with applications in catalysis, adsorption, pharmaceutics, and other areas [3-5]. Owing to its technical importance, several synthesis methods have been developed as for example co-precipitation, reconstruction, sol-gel technique, hydrothermal, microwave, and ultrasound treatments, anion-exchange reactions, among others [6]. In this work, the preparation and characterization of Al-Li hydrotalcite like compound using basic aluminum sulfate as a precursor is presented.
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EXPERIMENTAL The precursor basic aluminum sulfate (BAS) was prepared by precipitation in homogeneous solution by heating an aluminum bisulfite solution at 96 °C for 35 minutes. The as obtained solid was separated by vacuum filtration and dried at 80 °C in an electric oven. Then, the BAS was dissolved in 1M sodium hydroxide aqueous solution, at 80 °C in order to obtain a clear sodium aluminate solution. Subsequently, lithium carbonate saturated solution was added
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