Organotemplate-free synthesis of MOR zeolite from coal fly ash through simultaneously effective extraction of Si and Al

Solvent-free synthesis of FAU zeolite from coal fly ash

“…Notably, impurities such as Fe 2 O 3 , TiO 2 and K 2 O do not influence the synthesis of FAU zeolite, and do not need to be removed in the synthesis. The mineral phases present in CFA were identified by XRD as quartz (SiO 2 ) and mullite (3Al 2 O 3 •2SiO 2 ), together with some amorphous silica, as shown in Fig.S1, † in good agreement with the literature 34,[39][40][41]. Fig.…”

“…S1,† in good agreement with the literature. 34,39–41 Fig. S2† shows SEM images of CFA, indicating spherical particles with different diameters.…”

Novel process for high value utilization of high-alumina fly ash: valuable metals recovery and mesoporous silica in situ preparation

“…During the combustion process, these elements are further enriched in fly ash. The content of alumina 6 and silica is more than 80%, of which the mass fraction of alumina can reach 35–50 wt%, the grade of associated element Li can reach 200–400 ppm, and the grade of Ga 7 is 50–100 ppm, which is of great value for extraction of valuable elements.…”

“…In the previous work, alumina could be efficiently leached from coal fly ash by an atmospheric acid leaching process after mineral transformation of stable mullite and quartz into nepheline. 6 There is no further study on pore structure regulation and the pore forming mechanism of silica materials. Furthermore, the crystalline structure of nepheline and kaliophilite would be different under different reaction conditions, which could inevitably lead to the difference of metal leaching behaviors and pore structure of silica materials.…”

Green and Moderate Activation of Coal Fly Ash and Its Application in Selective Catalytic Reduction of NO with NH3

“…Nevertheless, as the internal active components of CFAs were covered by vitreous shells formed under high temperature, a series of fusion assistants were essential to destroy these stable shells, of which HCl or NH 4 HSO 4 was usually used for aluminum dissolution and NaOH or Na 2 CO 3 was generally applied for silicon extraction. For example, Zhou et al prepared CFA-derived mordenite (MOR) zeolites by extracting Si and Al components sequentially from CFA particles with the assistance of NH 4 HSO 4 and NaOH, and 90% of NO conversion was achieved when loading 3.36% of Mn over the CFA-derived MOR zeolites. Nevertheless, the use of these fusion assistants generated large amounts of waste effluents and residues with high risks of secondary pollution to the environment. − Moreover, the nucleation with a duration of at least 12 h was required in the process of hydrothermal crystallization, which also was the obstacle to the utilization of CFA-derived zeolites.…”