Conversion of coal fly ash to zeolite utilizing microwave and ultrasound energies: A review

This paper presents a sub-pilot scale process of synthesis of Na-P1 zeolite from the coal fly ash. After establishing the appropriate synthesis conditions (20 kg of fly ash, 12 kg of NaOH, 90 dm3 of water, the reaction temperature: 80 °C and reaction time: 36 h), the high-purity (81 wt%) Na-P1 zeolite product was obtained. Its chemical, mineralogical, and textural properties were determined (by means of XRD, XRF, SEM–EDS and ASAP 2020). The synthesized material has a specific BET surface area (88 m2/g) c.a. six times higher than the fly ash from which it has been derived (15 m2/g). The pore-size distribution indicates a mesoporous character of the obtained zeolite, with the following pores size contents: micropores (2.76 %), mesopores (61.81 %), and macropores (35.43 %). The presented technological/production line is fully automated and allows to regulate the conditions of the synthesis process, therefore different types of zeolite materials (including: Na-X, Linde-A, and Na-P1) can be obtained using the same equipment.

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The conversion technology of fly ash into zeolites

Recycling of industrial solid state waste is always the priority solution in the prospect of waste management. This work demonstrated a new method converting coal fly ash (CFA) industrial waste to anorthite-cordierite-based porous ceramic membrane supports (ACCMS), through high-temperature sintering with additions of dolomite mineral. Characterization of as-prepared ACCMS included phase composition, microstructure, pore structure, N2 and water permeability, and mechanical properties. From dilatometric measurements, the densification temperature of a sample with 28.43 wt.% dolomite addition was extended to 1100 °C compared to 1060 °C for that of a sample without any dolomite. For samples sintered at 1150 °C, their open porosity increased from 25.2 ± 0.5% to 46.5 ± 0.2% when dolomite addition increased from 0 to 28.43 wt.%. It is suggested that this level of dolomite addition significantly inhibited the sintering behavior of CFA.

Feasible recycling of industrial waste coal fly ash for preparation of anorthite-cordierite based porous ceramic membrane supports with addition of dolomite

Synthetic zeolites from fly ash as effective mineral sorbents for land-based petroleum spills cleanup

Synthesis of zeolite Na-P1 under mild conditions using Brazilian coal fly ash and its application in wastewater treatment

Synthesis of zeolites from coal fly ash using mine waters

The thermal stability of zeolites A and X synthesized from coal fly ash was studied by evaluation of TGA-DTA curves obtained on increasing the tem- perature and by in-situ temperature-programmed XRD analysis. It was found that zeolites A and X were both stable up to approximately 800 C and retained their characteristic diffraction peaks up to 440 C, meaning the crystal structure was still stable. Of particular interest was that zeolite X, which has a unique hierarchical morphology, was thermally stable and was, hence, suitable for applications requiring elevated temperatures, for example catalysis and pollution control.

Thermal stability studies of zeolites A and X synthesized from South African coal fly ash

This study was aimed at optimizing the synthesis conditions for pure phase zeolite Na-P1 from three coal fly ashes obtained from power stations in the Mpumalanga province of South Africa. Synthesis variables evaluated were: hydrothermal treatment time (12-48 hours), temperature (100-160°C) and varying molar quantities of water during the hydrothermal treatment step (H(2)O:SiO(2) molar ratio ranged between 0-0.49). The optimum synthesis conditions for preparing pure phase zeolite Na-P1 were achieved when the molar regime was 1 SiO(2): 0.36 Al(2)O(3): 0.59 NaOH: 0.49 H(2)O and ageing was done at 47°C for 48 hours. The optimum hydrothermal treatment time and temperature was 48 hours and 140°C, respectively. Fly ashes sourced from two coal-fired power plants (A, B) were found to produce nearly same high purity zeolite Na-P1 under identical conditions whereas the third fly ash (C) lead to a low quality zeolite Na-P1 under these conditions. The cation exchange capacity for the high pure phase was found to be 4.11 meq/g. These results highlight the fact that adjustment of reactant composition and presynthesis or synthesis parameters, improved quality of zeolite Na-P1 can be achieved and hence an improved potential for application of zeolites prepared from coal fly ash.

Optimization of hydrothermal synthesis of pure phase zeolite Na-P1 from South African coal fly ashes.

In situ ultrasonic monitoring of zeolite A crystallization from coal fly ash

The effect of using industrial waste brine solution instead of ultra pure water was investigated during the synthesis of zeolites using three South African coal fly ashes as Si feedstock. The high halide brine was obtained from the retentate effluent of a reverse osmosis mine water treatment plant. Synthesis conditions applied were; ageing of fly ash was at 47 ° C for 48 hours, and while the hydrothermal treatment temperature was set at 140 ° C for 48 hours. The use of brine as a solvent resulted in the formation of hydroxy sodalite zeolite although unconverted mullite and hematite from the fly ash feedstock was also found in the synthesis product.

Eric Hums

Papers

Synthesis of zeolites from coal fly ash using mine waters

Thermal stability studies of zeolites A and X synthesized from South African coal fly ash

Optimization of hydrothermal synthesis of pure phase zeolite Na-P1 from South African coal fly ashes.

In situ ultrasonic monitoring of zeolite A crystallization from coal fly ash

Synthesis of hydroxy sodalite from coal fly ash using waste industrial brine solution.