PhD Oral Exam - Rengyu Yue, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Marine oil spills can cause serious environmental damage. When the spilled oil reaches the coast, it can result in negative implications for the coastal ecosystems. Coastal oil cleanup operations are often expensive and time-consuming. Surface washing can be used following an oil spill to enhance the removal of stranded oil from coastal surfaces. Surface Washing Agents (SWAs) are typically applied directly on stranded oils and oil is then flushed with ambient water to remove the oil and direct it to a controlled area for physical recovery. However, there is still a gap between the available SWAs and the increasing application need. Many SWAs have been produced for the treatment of oiled shorelines. Although the toxicity of some SWAs is moderate, they can still have a potentially adverse impact on the shoreline environment after application. Moreover, the effluents after washing can be further recovered through appropriate disposal to avoid secondary pollution.

This thesis presents the development of multiple environmentally friendly surface washing fluids that demonstrate commendable performance, reusability, and remarkable stimuli-responsiveness. The efficacy of these washing fluids was meticulously assessed under various environmental conditions. To gauge their impact on selected species, biotoxicity experiments and modeling were conducted. Molecular dynamic and thermodynamic modeling was utilized to unveil the intricate mechanism of oil removal. Additionally, post-treatment methods were explored to curtail potential secondary pollution stemming from washing sludge. Notably, the stimuli-responsive nature of these washing fluids played a pivotal role in generating clean supernatants with minimal turbidity and oil content. In a bid to harness water motion for both physical and chemical actions, a piezocatalytic washing fluid was also conceived. This innovative fluid demonstrated the capability to degrade oil into low molecular-weight hydrocarbons. Overall, this thesis holds immense value in significantly benefiting shoreline oil spill response by enriching cleanup techniques, reducing environmental impact, and enhancing cost-efficiency. Moreover, this thesis contributes to enhancing oil spill preparedness and response capacity and safeguarding valuable coastal regions.