Synthesis of a Ca/Na-aluminosilicate from kaolin and limestone and its use for adsorption of CO2

Qusay Bkour, Naim Faqir, Reyad Shawabkeh*, Anwar Ul-Hamid, Hans Jörg Bart

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

A Ca/Na-aluminosilicate was synthesized from kaolin and limestone via the hydrothermal reaction and was used for CO2 capture from a gas stream. Synthesis was performed at several combinations of temperature, pressure, kaolinite to limestone mass ratio, and the reaction time. The products were characterized by determining the crystalinity, surface morphology, surface area, and the pore size distribution. When the reaction temperature and pressure are increased, the sodium hydroxide concentration has a significant effect on the formation of novel Ca/Na-aluminosilicate phases. X-ray diffraction shows that a mixture of Gehlenite Ca2Al(Al1.22Si0.78O6.78)OH0.22 (43 wt %) and Stilbite Na5.76Ca4.96(Al15.68Si56.32O144) (57 wt%) is produced in 36 M NaOH at 200 °C and 15 bar. The adsorption capacity of the above product for CO2 from a gas stream increased with temperature, reaching a CO2 uptake of 294.7 mg/g at an equilibrium pressure of 45 bar and a temperature of 150 °C. Thermodynamic studies show spontaneous and endothermic adsorption behavior with a ΔHads of 4.64 kJ/mol, ΔSads of 25.25 J/mol.K, and ΔGads of -6.09 kJ/mol obtained at 150 °C. The CO2 adsorption/cycling process were repeated and it was found that the capacity of the novel adsorbent decreases in the second cycle and remains constant after that. This suggests chemisorption process took place on the fresh adsorbent and physical adsorption occurred at higher cycles.

Original languageEnglish
Pages (from-to)973-983
Number of pages11
JournalJournal of Environmental Chemical Engineering
Volume4
Issue number1
DOIs
StatePublished - 1 Mar 2016

Bibliographical note

Publisher Copyright:
© 2015 Elsevier Ltd. All rights reserved.

Keywords

  • Adsorption
  • CO capture
  • Kaolinite
  • Thermodynamics

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Waste Management and Disposal
  • Pollution
  • Process Chemistry and Technology

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