Fluorescence spectroscopy analysis of aromatic naphtha surrogates diffusing from bitumen to the aqueous phase of oil sands tailings

A cheap, reliable, rapid fluorescence spectroscopy method was developed to determine the partitioning of naphtha surrogates, o-xylene and 1-methyl naphthalene (1-MN), from bitumen to the aqueous phase in mature fine tailings (MFT) in oil sand tailing ponds (OSTPs). The method gave reproducible results when volatilization of the surrogates was minimized by using a co-solvent (20 % (vol/vol) high-performance liquid chromatography (HPLC) methanol), by reducing sample exposure to open air and by analyzing samples within 6 days of preparation. It was found that the overlap of the fluorescence spectra of both surrogates with water-soluble bitumen compounds increased with contact time of bitumen; while the presence of salts found in MFT decreased the fluorescence response of 1-MN but not o-xylene; and there was interference between surrogates at certain mass ratios. However, with appropriate controls, quantification of low concentrations of naphtha surrogates diffusing from bitumen to an aqueous phase under a variety of pond conditions and bitumen characteristics were achieved. Such experiments can be used to study what factors can affect the diffusion of bitumen-solubilized components across the oil-water interface and can be broadly applied to any biphasic system. This knowledge will contribute to our fundamental understanding of the fate of these components and can influence the development of strategies to mitigate or minimize their environmental impact.