Herding Oil Slicks with Fatty Alcohol and Carbonaceous Particles
2022
Earnden, Laura | Foster, Sierra Eckel | Tchoukov, Plamen | Stoyanov, Stanislav R. | Pensini, Erica
Oil slicks occurring during petroleum transportation or production are major sources of surface water pollution, and spread over large areas. Herders are interfacially active species that reduce the spread of oil slicks on water surfaces, facilitating slick recovery. Here, octanol (a readily biodegradable fatty alcohol) is used as a herder to facilitate the recovery of diluted bitumen and conventional crude oil spilled onto the surface of fresh and synthetic marine water. While octanol promptly decreases the area of simulated oil slicks in Petri dishes, over time it partitions into the oil phase and lowers its interfacial tension. As a result, low-viscosity hydrocarbons (toluene and conventional crude oil) re-spread. This study uses charcoal to suppress re-spreading and facilitate the mechanical recovery of oil slicks. Charcoal partitions into the crude oil phase and does not stabilize crude oil in water emulsions upon mixing, as demonstrated using optical microscopy. This ensures that charcoal particles are not lost to the water phase and do not promote hydrocarbon dispersion. Charcoal prevents herded slicks from re-expanding by rigidifying the crude oil–water interface (demonstrated using a Langmuir trough) and potentially due to the affinity of crude oil for charcoal. Therefore, charcoal facilitates the physical removal of crude oil slicks after herding, as qualitatively assessed by retrieving them from Petri dishes with the aid of a spatula. While charcoal also facilitates the recovery of herded low-viscosity conventional crude oil, it has only a marginal effect on the recovery of herded bitumen, which has high viscosity.
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