Solubility and partitioning studies on buckminsterfullerene carbon-60
Abstract
The potential large scale production of fullerene C60 and its widespread use in consumer products may translate into occupational and public exposure and in long term environmental exposure. In this study, the solubility of C60 was measured in mixtures of toluene-acetonitrile, toluene-ethanol, toluene-tetrahydrofuran, and acetonitrile-tetrahydrofuran and the solubility data were modeled using Wohl's equation. The estimated crystal energy term for C60 in tetrahydrofuran was different than that in the other solvents indicating that C60 may form solvates in tetrahydrofuran. The log Kow of C60 was measured to be 6.67, and the toluene-water partition coefficient was measured at log Ktw = 8.44. From these values and the respective solubilities of C60 in water-saturated octanol and water-saturated toluene, C60's aqueous solubility was calculated to be 7.96 ng/L. Because it is widely known that clusters form in aqueous solutions upon mixing crystalline C60 with water, this value can be regarded as the hypothetical solubility in water, as the activity of C60 in water at this concentration will result in the more thermodynamically favorable clusters in which C 60 has a lower activity, resulting in an associated lower dissolved aqueous concentration of molecular C60 at equilibrium. Additionally, solubility of C60 was measured in mixtures of ethanol-water and tetrahydrofuran-water and modeled with Wohl's equation, to confirm the accuracy of the "hypothetical" solubility value. Results of a generator column experiment strongly support the notion that clusters form at aqueous concentrations below the solubility limit. The Kow value is compared to those of other hydrophobic organic compounds such as p,p'-DDT, and bioconcentration factors for C60 were estimated based on Kow. In this study, some widely used solubility models, their assumptions, and accuracy for predicting solubility of PAHs are discussed. Solubility data for naphthalene, phenanthrene, pyrene, and perylene in alcohol-water mixtures were compared with predicted solubilities using the log-linear cosolvency model and the Wohl's equation. The interaction parameters in Wohl's equation were regressed against each solutes log Kow and the relationship was used to estimate interaction parameters and solubility of similar PAHs in alcohol-water mixtures. Further, the model was extended to predict solubility of C60 in ethanol-water and propanol-water mixtures.
Degree
Ph.D.
Advisors
Jafvert, Purdue University.
Subject Area
Civil engineering|Environmental engineering
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