Institute of Geology of the Komi Science Centre UB RAS (Russia):

Kotova O. B., Doctor of Geology and Mineralogy, Professor, Head of Chair, kotova@geo.komisc.ru

Shushkov D. A., Ph. D. in Geology and Mineralogy, Senior Reseacher, dashushkov@geo.komisc.ru

Fly ash, formed in burning of coal, is mineral wastes, accumulated in huge quantities, and constituting a serious environmental threat. In connection with this, development of promising technologies for fly ash utilization and its transformation into new products remains to be a critical task. One of solutions may be synthesis of zeolites from fly ash, with subsequent utilization as sorbents, widely used in the mining-and-chemical industry. Fly ash, formed in burning of coal at thermal power plants of the Pechora Coal Basin, was studied by the state-of-the-industry analytical techniques. The laboratory experiments were performed with a view to produce zeolites from fly ash. The experiments included magnetic separation and autoclave hydrothermal synthesis. In the first series of the experiments, hydrothermal reaction effect upon synthesis of zeolites was investigated (reaction temperature: 80, 95, 140 and 180 °С, reaction duration: 12 hr, the ratio NaOH : fly ash = 1 : 1, concentration of NaOH – 3.0 mole/dm³). In the second series of the experiments, reaction duration and alkali concentration effects upon synthesis of zeolites were studied (reaction temperature: 140 °С, reaction duration: 2, 4, 6 and 8 hr). As a result of hydrothermal reaction, several types of zeolites were synthesized from fly ash: analzim, zeolites of faujasite type (zeolite X) and gismondite (zeolite P). As the final product, powders were produced, mostly representing zeolites mixture in various quantitative ratios, its yield being 70–80 % from the starting ash mass. The produced powder bulk density is 0.78–0.83 g/cm³. It is shown that the experimental conditions (temperature, reaction duration and alkali concentration) have a significant effect upon type of zeolite and its content in reaction products. As a result of the experiments, an approximate field of zeolites and other phases crystallization was built as the first stage in formation of new products (molecular sieves, sorbents, etc.).
The work was performed with the financial aid for the Ural branch of the Russian Academy of Sciences Projects (Project No. 15-18-5-45).

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