Chemisorption of divalent cations onN-(2-pyridyl)acetamide immobilized on silica gel — a thermodynamic study
✍ Scribed by Claudio Airoldi; Edésio F.C. Alcântara
- Book ID
- 102968850
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 515 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0021-9614
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✦ Synopsis
N-(2-Pyridyl)acetamide covalently immobilized on silica gel (''0Si-pa'') has a great ability to chemisorb cations from propanonic or ethanolic solutions through the amount of substance divided by mass 1.57•10 -4 mol•g -1 of bidentate groups attached to this inorganic support. The chemisorption isotherms obtained with MCl2 (M: Ni, Co, Cu, Zn, Cd, Hg) in each solvent are similar and adjustable to a modified Langmuir equation. The sequence of the maximum capacity is Cu q Co q Zn in propanone and Hg q Cd q Zn q Co q Cu q Ni in ethanol. The enthalpies of chemisorption of the cations by ''0Si-pa'' at T=(298.1520.02) K showed larger values in ethanol. With the exception of cobalt {DHm=+(6.1220.01) kJ•mol -1 } in propanone, all other cation-surface interactions are enthalpically favourable in both solvents. The enthalpic sequence is Cu q Zn q Co in each solvent and the complete series Cu q Cd q Hg q Ni q Zn q Co was found in ethanol. The standard molar Gibbs free energies are in agreement with the spontaneity of the proposed reactions between a cation and a basic centre, which has a favourable enthalpic contribution to these chelating processes.