ZEOLITE SYNTHESIS FROM PAPER SLUDGE ASH VIA ACID LEACHING |
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Authors: | Takaaki Wajima Yasuyuki Ikegami |
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Affiliation: | 1. Institute of Ocean Energy, Saga University , Saga, Japan wajima@ioes.saga-u.ac.jp;3. Institute of Ocean Energy, Saga University , Saga, Japan |
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Abstract: | Paper sludge ash (PSA) typically has a low Si abundance and significant Ca content due to the presence of calcite fillers. Acid leaching with HCl was used to reduce the Ca content so that a zeolitic product with a high cation exchange capacity (CEC) could be synthesized. Zeolitic products were synthesized from raw ash and leached ash through reaction with 2.5 M NaOH solution at 80°C. In the case of the original ash without acid leaching, the concentration of Al in the alkali solution always exceeded that of Si during the synthesis, and hydroxysodalite with a low Si/Al ratio (1:1) was formed. In the case of the leached ash, the concentration of Si always exceeded that of Al during the synthesis, and zeolite-P with a higher Si/Al ratio (5:3) was formed. Hydroxysodalite and zeolite-P crystallization was saturated after 6 h of reaction, and the product from leached ash had a higher CEC (approximately 150 cmol/kg) than that from original ash (approximately 40 cmol/kg). Both the decrease in the Ca phase in the leached ash and the corresponding increase in the Si and Al amorphous phases play an important role in zeolite synthesis. |
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Keywords: | Acid leaching Cation exchange capacity Hydroxysodalite Paper sludge ash Zeolite-P Zeolite synthesis |
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