Synthesis and Characterization of Zeolites Produced by Ultrasonication of Coal Fly Ash/NaOH Slurry Filtrates

Abstract

Studies were conducted to determine if crystalline zeolites could be obtained from the filtrates of coal fly ash (CFA)/NaOH slurries through sonication. The CFA/NaOH slurries were obtained by aging CFA in 3 M NaOH for 24 h at 50°C using a solid/ liquid (S/L) ratio of 15 g/120 mL. FT-IR studies indicated that the 'Lo' regime ultrasonicated zeolite had higher intensities than that of the 'Hi' frequency ultrasonicated zeolite. The bands associated with the 'Lo' regime ultrasonicated zeolite were observed at 1066 cm-1 , 1400 cm-1 and 3600 cm-1 , which were identified as Si-O asymmetric stretch, Al-O asymmetric stretch, O-H bend and O-H asymmetric stretch, respectively. Based on PXRD studies, the zeolitic phases were most intense for the 90 min ultrasonicated zeolite. Powder X-ray diffraction studies showed that the phases initially in CFA, such as quartz and aluminosilicate, were converted into gismodine zeolite Na-P1. Morphological changes were seen as ultrasonication period was increased. At short ultrasonication times, irregularly shaped fused-like grain structures were observed, while at longer times separate grain-like structures became more apparent. Energy dispersive X-ray spectroscopy studies on the 90 min ultrasonicated zeolite indicated the presence of Na, O, Si and Al, which were important building-blocks for the zeolites.

Ultrasonic-pretreated hydrothermal synthesis of less dense zeolite CHA from the transformation of zeolite T

“…Li et al [62] have prepared a high-quality MER-rich product from coal fly ashes by KOH direct conversion method under optimal activation conditions. Mokgehle et al [63] have obtained GIS product from the ultrasonication of coal fly ash/NaOH slurry filtrates. It seems that MER phase is easy to be formed in the KOH-rich condition and GIS phase is inclined to the produced in the NaOH-rich condition from the same original materials.…”

Modification of Coal Fly Ash Waste into Manganese-Oxide-Coated-Zeolite (MOCZ) to Adsorb Heavy Metal Ions Ni2+

“…Meanwhile, the -OH group from Si-OH was also proven by the absorption wave numbers of 1640.53 and 1446.67 cm -1 , which showed that there was a -OH bending vibration from Si-OH. The appearance of spectra at around 3019.69 cm -1 and 1640.53 cm -1 , which showed stretching vibrations and bending vibrations of water molecules in zeolite, was evidence of the formation of zeolite through an alkaline hydrothermal process 26 .…”