A Laboratory Investigation on Oil-Mineral Interactions: The Role of Mineral Type in Oil-Mineral Flocculation and Oil Entrapment

Abstract:

Understanding natural cohesive sediment interactions with spilled oil has become increasingly important because the presence of oil can significantly alter the properties of mineral flocculation in marine environments. Moreover, the presence of minerals and their ability to attach to or enclose oil droplets can also affect the fate of oil. One property of significance that requires further investigation is the temporal evolution of flocculation because it can be used to quantify the stickiness of certain types of floc. To fully investigate the role oil plays in this process, it is also necessary to understand the interplay between sediment type and concentration, mixing time, and seawater turbulence level with regards to controlling the flocculation rate. Preliminary laboratory observation has suggested that the most efficient method to test this interplay is to first observe the significance that different types of sediment (Bentonite and Kaolinite), as well as different concentrations of Texas crude oil (Dynamic viscosity: 7.27×10^-3 Pa·s at 20 ℃) hold while controlling the homogeneous flow turbulence (turbulence dissipation rate estimated to be about 0.02 m²·s^-3) and flocculation time.

Our goal is to quantify the role of sediment type on multiple oil mineral flocculation properties, including flocculation rate, floc size, and the ability of floc to entrap oil. Oil-mineral flocs have been generated in a custom designed jar using a magnetic stirrer. Floc samples were transferred from the jar to a digital microscope with a pipette at set time intervals over the two hour testing period. Furthermore, floc sampled at later time stamps were also analyzed for their size and composition. Preliminary findings have verified previous research in showing that Bentonite is significantly more cohesive than Kaolinite, and therefore forms both larger and more stable floc, even under the influence of oil. Moreover, Bentonite is more efficient at entrapping free oil droplets, implying that sediment type can potentially alter spilled oil’s removal from the environment. Future experimentation and analysis will aim to quantify more interactions, such as the use of diverse concentrations and types of sediment, oil, and organic material that are often present in a marine environment.