Master of Science (MS)
Geology and Geophysics
Past practices of applying creosote and coal tar preservatives to wood, such as unlined pits and trenches, have resulted in contamination of the surface and ground water at thousand of sites. The low aqueous solubility, volatility and bioavailability of many these constituents limit their degradation by natural attenuation and standard remediation techniques such as ground water flushing, soil vapor extraction, and bioremediation. While research has shown that cyclodextrin solutions have the ability to enhance the solubility of some of the components of creosote, additional work is needed to evaluate its potential as a remedial agent for these sites. Equilibrium batch studies were conducted to determine the solubility enhancement of eight different PAHs commonly present in creosote in aqueous solutions of three different types of cyclodextrin. Three highly soluble cyclodextrins were tested which vary in their internal cavity size (smallest to largest: hydroxypropyl-α-cyclodextrin (HPαCD), hydroxypropyl-β-cyclodextrin (HPβCD), and hydroxypropyl-γ-cyclodextrin (HPγCD). The results showed that all three types of cyclodextrin enhanced the apparent solubility of the tested PAHs. The degree of solubility enhancement ranged from 19.6 for naphthalene to 4136 for benzo (k) fluoranthene. Because previous research has shown that hydroxypropyl substitution does not favor forming complexes with low-polarity compounds, it is concluded that cyclodextrin with larger cavities slightly enhance the degree of PAH partitioning into their cavities and hence PAH apparent solubility. Comparison of the results also showed that the logarithm of the PAH solubility enhancement factor in the cyclodextrin solutions is inversely related to the logarithm of PAHs aqueous solubility, directly related to the mass of the PAHs, and directly related to the logarithm of the PAH hydrophobicity. Additional direct correlations were found between the logarithm of the ratio of molar concentration of the PAH to that of the cyclodextrins with the logarithm of PAHs aqueous solubility. These strong correlations enable the ability to project the enhancement of other PAHs present in creosote and coal tar. Additional research has to be performed, but cyclodextrin shows promise as a remedial agent for creosote and coal tar sites.
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Dutta, Monalisa, "Enhanced flushing with cyclodextrin for the remediation of creosote contaminated soil" (2004). LSU Master's Theses. 3031.
William J. Blanford