Effect of crystallization time on the hydrothermal synthesis of zeolites from kaolin and bauxite

Abstract

Kaolin and bauxite were used as alumina and silica sources to synthesize zeolites hydrothermally. The source mate-rials as well as the synthesized zeolites were characterized by X-ray diffraction (XRD) scanning electron microscopy (SEM), en-ergy dispersive x-ray analysis (EDX) and Fourier transformed infrared spectroscopy (FTIR). XRD spectra of the bauxite showed Gibbsite phase whereas that of kaolin gave 32.4 % quartz and 67.6 %. The main phases of zeolites obtained after hydrothermal crystallizations were zeolite types LTA, analcime and zeolite X. Longer crystallization time resulted in phase change of the zeo-lites into sodalite. Hence, natural raw materials such as bauxite and kaolin have the attractive features of providing the staring reagents for the synthesis of ultrapure synthetic zeolites.