Kinetics Study of alkaline hydrolytic degradation of PET Plastic bottle Waste into Useful Products

Every year, 56 million tons of polyethylene terephthalate (PET) are produced (McArthur 2017). It is used in everyday single-use disposable materials such as plastic water bottles, metalized candy wrappers, and food containers. A significant proportion of which, is improperly disposed of, ending up in landfills, oceans, and even as microplastics in our bodies; taking years to decompose. In our lab, we developed sustainable and green chemical reactions for degrading PET post-consumer plastic bottles into their value-added monomers; terephthalic acid (TPA) and ethylene glycol (EG) under conventional heating. The hydrolytic reaction process was optimized using Box Behnken Design (BBD) to maximize the yields of PET degradation and obtained TPA monomer. In the current study, the kinetics and mechanism of the degradation reaction are investigated to determine how the rate of the PET hydrolysis varies with temperature and calculate the reaction activation energy. Two kinetics studies are explored; the first studies the effect of varying the plastic bottle particle size on the rate of the reaction while the second study evaluates the applicability of the used TPA purifying agent as a catalyst. During the course of the reaction, the residual PET obtained after specific reaction times is characterized via FTIR and DSC instrumentation. Chemical and physical changes that occur on the surface of the PET plastic are tracked during the reaction to understand the mechanism by which the hydrolysis process takes place and consequently explore ways to improve the PET depolymerization process for large scale applications. McArthur, E. The New Plastics Economy: Rethinking the Future of Plastics & Catalysing Action; Ellen MacArthur Foundation: Cowes, UK, 2017; p. 68.
Additional Co-Authors: Vasilisa Palkova, Peter Boldyrev