Document Detail

Investigating entropy changes during gas adsorption in ETS-4.
MedLine Citation:
PMID:  15919089     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Energetic heterogeneity has been investigated for Engelhard titanium silicate Na-ETS-4 adsorbent and its Sr-exchanged variant, Sr-ETS-4. Na-ETS-4 was nearly homogeneous, while Sr exchange seemed to induce some degree of energetic heterogeneity in the sample, which diminished upon dehydration at higher temperature. Analysis of the entropy change during adsorption showed that the adsorbate molecules at low as well as moderate loading possess entropy greater than that predicted by the 2-D mobile film model, the excess being attributed to vibrational freedom. The wavelength of this vibration decreased with increasing coverage, as expected. For oxygen, the observed entropy drops in Na-ETS-4 and in Sr-ETS-4 are comparable, whereas, for nitrogen and methane, Sr exchange resulted in a greater entropy drop than in Na-ETS-4, suggesting greater restriction to movement in the Sr-exchanged sample. This study presents a simplistic yet effective understanding of the energetic behavior of the adsorbed molecules in ETS-4 adsorbent. This is vital to a thorough energetic characterization and study of the adsorption phenomenon in these new, promising adsorbents.
R P Marathe
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of colloid and interface science     Volume:  290     ISSN:  0021-9797     ISO Abbreviation:  J Colloid Interface Sci     Publication Date:  2005 Oct 
Date Detail:
Created Date:  2005-08-26     Completed Date:  2006-11-06     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0043125     Medline TA:  J Colloid Interface Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  69-75     Citation Subset:  -    
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576.
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