The use of β-cyclodextrins to enhance the aqueous solubility of trichloroethylene and perchloroethylene and their removal from soil organic matter: Effect of substituents
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Media type:
E-Article
Title:
The use of β-cyclodextrins to enhance the aqueous solubility of trichloroethylene and perchloroethylene and their removal from soil organic matter: Effect of substituents
Contributor:
Shirin, Salma;
Buncel, Erwin;
vanLoon, Gary W
Published:
Canadian Science Publishing, 2003
Published in:
Canadian Journal of Chemistry, 81 (2003) 1, Seite 45-52
Language:
English
DOI:
10.1139/v02-205
ISSN:
0008-4042;
1480-3291
Origination:
Footnote:
Description:
This paper describes a systematic study for the evaluation of different substituted β-cyclodextrins (β-CDs), as agents for the enhancement of the aqueous solubility of two major organic pollutants, trichloroethylene (TCE) and perchloroethylene (PCE). The aqueous solubility enhancement occurs through the formation of hostguest inclusion complexes between the CD molecule (host) and the polychloroethylene (guest) and is driven primarily by hydrophobic forces. The CDs evaluated are: methyl-β-CD (Mβ-CD), hydroxypropyl-β-CD (HPβ-CD), carboxymethyl-β-CD (CMβ-CD1, CMβ-CD2), and sulfated-β-CD (Sβ-CD1, Sβ-CD2); the degree of substitution was also varied. Using a 5% (w/v) aqueous CD solution, solubility enhancement factors (St/So) up to 5.5 and 14 were determined for TCE and PCE, respectively. Binding constants (K11) for TCE with the substituted CDs were evaluated using an 1H NMR technique; these were found to range from 3 to 120 M1. It was shown that solubility enhancement, as well as the binding constant, is dependent on the type and degree of substitution of the β-CD molecule; the determining factors are discussed. The CDs are also capable of effective removal of PCE and TCE retained by soil organic matter. Thus, a suitably substituted β-CD may be a valuable additive in pump-and-treat protocols for site remediation of polychlorinated organics. Key words: Cyclodextrin, trichloroethylene, perchloroethylene, solubility enhancement, binding constant, soil and water remediation.