05/30/2023
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a doctoral dissertation defense by Taofeng Lu on “Advanced Recycling of Mixed Plastic Waste Using Safer Solvents and Supercritical Water.”

Candidate Name: Taofeng Lu
Degree: Doctoral
Defense Date: Friday, June, 9, 2023
Time: 10 a.m. to noon
Location: Perry Hall 215

Committee:

  • Advisor Wan-Ting Chen, Plastics Engineering, UML
  • Margaret J. SobkowiczKline, Plastics Engineering, UML
  • Hsi-Wu Wong, Chemical Engineering, UML
  • Fanglin Che, Chemical Engineering, UML

Brief Abstract:

Plastics are widely used because they are robust and cost-effective materials. However, improper disposal of plastics has become a serious environmental issue. Particularly, plastic waste is composed of different types of immiscible plastics and polymer additives. Conventional plastic recycling methods such as mechanical recycling cannot handle mixed plastics and usually lead to down-cycling, mainly due to the inferior properties of recycled products. To address this problem, hydrothermal liquefaction (HTL) and a solvent-based recycling process were researched in this PhD dissertation to convert the plastic waste into valuable products using supercritical water or safer solvents. In HTL, reaction temperatures and reaction times were first studied on polyethylene-based ocean plastic waste. The polymer degradation mechanism was explored by characterizing the gas, oil, and solid products. In addition, a dissolution-precipitation process, coupled with density separation, was developed to extract acrylonitrile butadiene styrene (ABS) from toy waste using safer solvents and antisolvents. The properties and chemical composition of recovered ABS were compared to feedstock ABS for understanding if any degradation may take place during the dissolution-precipitation process. Compared to producing virgin ABS material, the dissolution-precipitation process could potentially reduce embodied energy by 58%. Finally, inspired by the remarkable performance of catalysts in hydrogenolysis and pyrolysis of polyolefins, catalytical hydrothermal liquefaction of plastic is investigated, with the goal to improve the energy efficiency and/or to fine tune the product selectivity converted from HTL. Results from this study would contribute to developing efficient and potentially profitable recycling methods for challenging heterogeneous plastic waste.

All interested students and faculty members are invited to attend the defense.