Application of the Taguchi method to investigate the effects of experimental parameters in hydrothermal synthesis of Na-P1 zeolite from coal fly ash

摘要

The aim of this study is to optimize the hydrothermal parameters to maximize Na-P1 (Na6Al6Si10O32 center dot 12H(2)O) zeolite crystallization from fly ash using the L9 orthogonal Taguchi methodology. The operational parameters considered were the hydrothermal temperature, synthesis duration, NaOH concentration, and liquid/solid (L/S) ratio. Analyses of the mean and variance were applied to investigate the effects of the selected parameters on the crystallization of Na-P1 zeolite. The resulting crystals were characterized by X-ray diffraction analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, laser granulometry, and cation exchange capacity measurements. The results showed that fly ash undergoes chemical and morphological changes indicating its transformation to zeolite materials. The hydrothermal temperature was found to be the most important parameter contributing to crystallization of Na-P1 zeolite. High NaOH concentration can cause a small decrease in the Na-P1 zeolite content due to the appearance of other zeolites such as hydroxysodalite, Na-X, and chabazite. The content of Na-P1 zeolite was enhanced by increasing the hydrothermal temperature, NaOH concentration, and liquid/solid (L/S) ratio, while variation of the synthesis duration had less effect on Na-P1 zeolite crystallization. The optimum conditions to obtain the maximum content of Na-P1 zeolite were found to be high temperature level (150 degrees C), NaOH concentration (3 M), and L/S ratio (20), and medium duration (24 h).