Selective formation of Na-X zeolite from coal fly ash by fusion with sodium hydroxide prior to hydrothermal reaction

Analysis of the influence of fusion synthesis parameters on the SO2sorption properties of zeolites produced out of fly ash

“…It was stated that formatted zeolite phases in the 6-hour hydrothermal aging, were dissolved and the secondary crystallization took place as a result of which sodalite was formed. Confirmation of this fact are available literature data [6] as well as the fact that in case of presence of different than sodalite zeolite phases (also present in the sample subjected to 6-hour hydrothermal aging), the reflections intensity of this different phase is lower than for analogical sample subjected to 6-hour hydrothermal aging process.…”

“…In part of the samples zeolite X was present, however it was noticed, based on the analysis of area under the most intensive reflections characteristic for X zeolite phases, that along with the appearance of sodalite reflections, the intensity of reflections characteristic for zeolite X is decreasing, what in approximation gives idea of the amount of formatted zeolite. It is believed that in the 24-hour aging the secondary dissolution of silicaalumina sources takes place (also from zeolite phases) and the recrystallization in the form of sodalite is observed [6]. It was discovered that the used fly ash/base ratio influences the formation of zeolite phases.…”

“…The comparison of literature data of particular methods allowed for the selection of fusion method for the research presented in this work. Adoption of this method was dictated by the reports stating that highly efficient zeolite synthesis process can be expected [5,6].…”

Thermogravimetry applied to characterization of fly ash-based MCM-41 mesoporous materials

“…In order to extract silicon (in the form of sodium silicate) from FA, a method consisting in the fusion of FA with sodium hydroxide was used [1], followed by dissolving the formed solid substance in water. According to this methodology, FA (25 g) and sodium hydroxide (30 g) were used for the sintering of FA with sodium hydroxide so as to obtain an NaOH:ash weigh ratio of 1.2.…”

“…Studies on the modification of fly ashes (FA), which have been carried out in recent years, have confirmed the possibility of obtaining on their basis microporous materialszeolites with very good ion-exchange and sorption properties [1,2]. This fact encouraged searches for new possibilities of using FA as a source of silicon and aluminium.…”