Conversion of silica by-product into zeolites by thermo-sonochemical treatment

https://doi.org/10.1016/j.ultsonch.2020.105426Get rights and content
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Highlights

  • Silica by-product (the production of AlF3) was used for zeolite synthesis.

  • In silica by-product dominated amorphous SiO2 and crystalline AlF3·3.5H2O compound.

  • By using sonication (5–20 min) and hydrothermal treatment Na-P and Na-X zeolites formed.

  • The sonication efected to the formation of the diamond shape of Na–P zeolite.

  • In the synthesis products the total amount of zeolites was in the range of 89–93%.

Abstract

The fine powdered silica by-product of processing of aluminum fluoride (fertilizer plant, Lithuania) was used for zeolite synthesis as silica and aluminum source. The effect of sonication time and the time of hydrothermal synthesis on crystallinity of the synthesized zeolite were studied. This allowed the transformation of the by-product to the mixture of Na–P zeolite and Na–X zeolite. It was determined that ultrasonic-assisted hydrothermal action effected the “diamond” shape formation of Na–P zeolite with clear crystal edges. Na–P zeolite had the morphology of pseudo-spherical forms constituted by small plates when hydrothermal treatment (without sonication) was use for the preparation of zeolites. Moreover, it was determined that ultrasonic-assisted hydrothermal method effected a reduction in the crystal size compared with the zeolites which were synthesized only by using hydrothermal synthesis. The total amount of zeolites as high as 88–93% was achieved after 24 h of hydrothermal treatment followed or unfollowed by sonication. By using longer duration (20 min) of ultrasound pretreatment it is possible to reduce the duration of hydrothermal synthesis: from 24 h to 12 h of hydrothermal treatment. In this case, similar results of total amount of zeolites were detected. In the present work, low-cost raw materials, such as silica by-product have been investigated for the production of zeolites.

Keywords

Silica by-product
Thermo-sonochemical treatment
Na-P zeolite
Na-X zeolite

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