Synthesis and characterization of a single phase zeolite A using coal fly ash

Abstract

Zeolitization of coal fly ash (CFA) provides a potential alternative for creating high-added-value products from this hazardous solid waste. In this work, a single phase zeolite A with high crystallinity was successfully synthesized from CFA via the alkali fusion hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR) spectroscopy, N₂ physisorption, and solid-state MAS NMR spectra were applied to characterize as-synthesized zeolites. Results indicated that the type and purity of zeolite were closely related to the synthesis conditions and parameters. A well-defined cubic shape of zeolite A with a specific surface area of 43.7 m² g⁻¹ was obtained at a low temperature of 75 °C during hydrothermal treatment for 18 h. The ammonium cation exchange capacity (CEC) test showed an impressive value of 232.2 mmol 100 g⁻¹ over prepared zeolite A, which was about 22 times that of the original CFA and close to commercial zeolite A. These results pave the way for the exploitation and utilization of the CFA.