Mechanisms that affect the wettability of quartz exposed to coal-derived non-aqueous phase liquids

The objective of this dissertation is to identify the primary mechanism causing quartz wettability to change upon exposure to environmental NAPLs. Coal tars and creosotes were the primary focus of this work. Specific tasks designed to meet this objective include the characterization of polar compounds in NAPLs, measurement of interfacial tension and oil receding contact angles under a range of conditions, and simulation of quartz wettability with DLVO theory. NAPLs recovered from field sites, as well as asphaltenes separated from these NAPLs, were investigated to facilitate the identification of the primary mechanisms controlling quartz wettability.; Coal-derived NAPLs and asphaltenes separated from them were characterized in terms of acid and base numbers.; Primary mechanisms causing quartz wettability to change were identified in environmental systems contaminated by coal-derived NAPLs. It was found that DLVO (Derjagum, Landau, Verwey and Overbeek) mechanisms are predominantly responsible for changes in wetting behavior under lower asphaltene concentrations irrespective of the solvent characteristics.; The two primary mechanisms that are responsible for change in the quartz wettability in environmental aquifer systems have great significance on the effectiveness of remediation technologies. In the case where no precipitation occurs, pH of the ground water should be maintained well above PZC, where quartz wettability is intermediate to water wet. Fortunately, under environmental conditions where neutral pH's are frequently observed, quartz surfaces are not oil-wetting as predicted by DLVO theory. Under these wetting conditions, recovery efficiency is expected to be high. It can be inferred from this study that in co-solvent remediation practices, care must be paid that the addition of the co-solvent into the system might decrease the solvent power of the original NAPL solvent matrix and thus increase the possibility of asphaltene precipitation. Precipitation of asphaltene on the aquifer media can change the wettability via the precipitation mechanism. (Abstract shortened by UMI.)...