GIS-type zeolite synthesis from Greek lignite sulphocalcic fly ashes promoted by NaOH solutions

• Published in: Microporous and mesoporous materials 2003-07, Vol.61 (1), p.57-67
• Main Authors: Mouhtaris, Th, Charistos, D., Kantiranis, N., Filippidis, A., Kassoli-Fournaraki, A., Tsirambidis, A.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; Fly ash; General and physical chemistry; GIS-type zeolite; Gobbinsite; Ion-exchange; NaP1; Surface physical chemistry; Zeolite synthesis; Zeolites: preparations and properties
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/S1387-1811(03)00355-X

GIS-type zeolite (gobbinsite–NaP1) was synthesized from sulphocalcic lignite fly ashes, from the Agios Dimitrios and Amynteon-Filotas power plants of the Lignite Center of Ptolemais-Amynteon, Macedonia, Greece. The fly ash samples were treated with 0.1 and 0.5 mol dm −3 NaOH solutions at 90 °C and at room temperature. Both fly ash samples contained calcite, quartz, anhydrite and lime as major mineral phases, and mainly consisted of SiO 2, CaO, Al 2O 3. Their Si/Al ratio was 2.08 and 2.28, respectively. The experiments (duration 95–260 h) were conducted under continuous rotational stirring. The solid experimental products have been analyzed by means of X-ray diffraction, FT-IR, and scanning electron microscopy–energy dispersive spectrometer. The treatment of both fly ashes at 90 °C with 0.5 mol dm −3 NaOH resulted in GIS-type zeolite (gobbinsite–NaP1) with a 10–15% yield. FT-IR absorption bands assigned to CaCO 3, CaSO 4, CaO, and silicates were observed in the starting materials, whereas bands attributed to CaCO 3, amorphous silicate polymers (intermediate products of zeolitization), hydrated aluminum silicates, and increased amount of silicates, attributed to the zeolite synthesis, were identified in the solid experimental products.