The synthesis of zeolite-P, Linde Type A, and hydroxysodalite zeolites from paper sludge ash at low temperature (80 °C): Optimal ash-leaching condition for zeolite synthesis
-
Takaaki Wajima
,
Keiko Kuzawa
Abstract
Typically, the ash from incineration of paper sludge contains a high percentage of Ca in the form of anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO7). The Ca in the sludge originates from calcite that is included in paper as fillers. We applied acid leaching with HCl on the ash to reduce its Ca content. Zeolite was then synthesized from the leached ash through reaction with 2.5 M NaOH solution at 80 ºC for 24 hours. The fraction of Ca and Al extracted from the ash correlates with the pH of the leachant. We determined the leachant pH (after 24 hours of leaching) associated with the Ca: Al:Si ratio in the leached ash that provided optimal production of zeolites with high cation-exchange capacity. During acid leaching, gehlenite dissolved out at higher pH than anorthite. In the case of pH > 5, both gehlenite and anorthite remained in the ash, and hydroxysodalite and LTA (Linde Type A) were synthesized in the product. In the case of pH = 1−5 in the leachant, gehlenite dissolved out but anorthite remained in the ash, and LTA and Na-P1 (zeolite-P) were produced. In the case of pH < 1, both gehlenite and anorthite dissolved out, and only Na-P1 was produced. The cation-exchange capacities of the products that contained hydroxysodalite, LTA, and Na-P1 were approximately 130, 200, and 120 cmol/kg, respectively. We conclude that acid leaching of paper sludge ash controls which of the three zeolite phases form, and that LTA and Na-P1 exhibit a higher cation-exchange capacity than hydroxysodalite. The most efficient production of zeolites with high cation-exchange capacity (about 220 cmol/kg) is obtained after leaching the sludge ash in solutions of around pH = 3. At this low pH, gehlenite has already dissolved out of the sludge ash, half the Ca content of the ash has been leached out, Si has not yet been leached, but Al has begun to be leached. After ash zeolitization, LTA coexists with Na-P1 in the product.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- First-principle study of polytype structures of 1:1 dioctahedral phyllosilicates
- Calorimetry of liquids in the system Na2O-Fe2O3-SiO2
- A Mössbauer study of the oxidation state of Fe in silicate melts
- Nanometer-scale measurements of Fe3+/ΣFe by electron energy-loss spectroscopy: A cautionary note
- The most reduced rock from the moon, Apollo 14 basalt 14053: Its unique features and their origin
- Quantitative analysis of ammonium in biotite using infrared spectroscopy
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- V oxidation state and coordination number in silicate glasses by XAS
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- Crystal nucleation in hydrous rhyolite: Experimental data applied to classical theory
- Investigation of polytypes in lepidolite using electron back-scattered diffraction
- Iron partitioning between basaltic melts and clinopyroxene as a function of oxygen fugacity
- The synthesis of zeolite-P, Linde Type A, and hydroxysodalite zeolites from paper sludge ash at low temperature (80 °C): Optimal ash-leaching condition for zeolite synthesis
- High-pressure viscometry of polymerized silicate melts and limitations of the Eyring equation
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- Site distribution of Fe2+and Fe3+in the axinite mineral group: New crystal-chemical formula
- Epidote-rich talc-kyanite-phengite eclogites, Sulu terrane, eastern China: P-T-fO₂estimates and the significance of the epidote-talc assemblage in eclogite
- Quantitative mineralogy of the Yukon River system: Changes with reach and season, and determining sediment provenance
- Exsolution of thortveitite, yttrialite, and xenotime during low-temperature recrystallization of zircon from New Caledonia, and their significance for trace element incorporation in zircon
- Mineralogical characterization and genesis of hydrothermal Mn oxides from the flank of the Juan the Fuca Ridge
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