Abstract
Nowadays, using fly ash for zeolites production has become a well-known strategy aimed on sustainable development. During zeolite synthesis in a hydrothermal conversion large amount of post-reaction solution is generated. In this work, the solution was used as a substrate for Na-A and Na-X zeolites synthesis at laboratory and technical scale. Obtained materials were characterized using particle size analysis, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), and nitrogen adsorption/desorption isotherm. Produced zeolites revealed high purity (>98%) and monomineral zeolitic phase composition. The SiO2 content was in the range 39–42% and 40–38%, whereas Al2O3 content was 23–22% and 25–26% for Na-X and Na-A, respectively. TEM and BET analyses revealed Na-X zeolite pores were almost identical to commercial 13X with SBET in the range 671–734 m2/g. FTIR indicated slight differences between materials obtained at laboratory and technical scale in Si-O-(Si/Al) bridges of the zeolitic skeleton. The results showed good replicability of the laboratory process in the larger scale. The proposed method allows for waste solution reusability with a view to highly pure zeolites production in line with circular economy assumptions.
Highlights
Fly ash is one of the most common pollution in the world
New technologies introduced in power plants and thermal power plants have a negative impact on the chemical composition of fly ash, e.g., by increasing the content of unburned coal that excludes their use in the construction industry [2,4]
Waste solution used for the production of ultrapure Na-X and Na-A zeolites was obtained after the hydrothermal synthesis of zeolites using a technological line described by Wdowin et al [30]
Summary
Fly ash is one of the most common pollution in the world It comes from combustion of coal in power plants and thermal power plants. The most common way of its disposal is using them in civil engineering (as an additive in cement industry) [3]. This application imposes certain limitations related to the chemical composition of the ash. New technologies introduced in power plants and thermal power plants have a negative impact on the chemical composition of fly ash, e.g., by increasing the content of unburned coal that excludes their use in the construction industry [2,4]. Fly ashes are comoposed of aluminosilicate glaze (65–78%) and a crystalline part in the form of mullite, quartz, and hematite, magnetite, or calcite [5,6]
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