Abstract
In this study, NaA zeolite was successfully synthesized from coal gangue with high contents of iron and quartz as the main raw material. The results show that most iron ions can be removed from coal gangue after calcination at 700 °C for 2 h, leaching in hydrochloric acid with a mass fraction of 20% for 7 h and a liquid-solid ratio of 3.5:1. When m (acid leached residue of calcined gangue):m (Na2CO3) = 1.1 and melting at 750 °C for 2 h, the quartz and other aluminosilicates turn into nepheline, which dissolve in water. Finally, the optimum conditions of synthesis NaA zeolite are as follows: n(SiO2)/n(Al2O3) = 2.0, n(Na2O)/n(SiO2) = 2.1, n(H2O)/n(Na2O) = 55, aging at 60 °C for 2 h, and crystallization at 94 °C for 4 h. This shows that the high iron and quartz contents coal gangue can be used for the synthesis of NaA zeolite.
Highlights
Coal gangue is the main discharged waste of the coal industry [1,2]
Many products have been prepared from coal gangue, but the common utilization methods of coal gangue are as power plant fuel [8] and to prepare building materials [9], including brick [10], cement clinker products [11] and other products
Zeolite synthesis often uses cheap minerals or waste, which can save the cost of raw materials
Summary
Coal gangue is the main discharged waste of the coal industry [1,2]. The arbitrary stacking of it seriously influences the safety of the ecological environment [3,4]. Zeolites are micropore and mesoporous hydrated aluminosilicates containing alkali elements, alkaline earth metals, or other cations, whose structure is built up with a framework of tetrahedral molecules, which are linked with shared oxygen atoms [17] Due to their unique properties, zeolites have been used in many fields, such as in agriculture [18], chemical technology [19], oil refining [20], and others for their porous characteristics, ionexchange properties, and catalytic performance [21]. For further discussion of the mechanism of phase transformations, the gangue, acid-leached residue, alkali-melted intermediate products, and the NaA zeolite, which are prepared under different conditions, are detected by XRD; the phase transformation laws are obtained; and the suitable technological conditions for preparing NaA zeolite from high iron and quartz contents coal gangue are determined
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