Undergraduate Thesis Or Project
 

A Study on Physiochemical Oxidation and Bioremediation on Polyethylene Terephthalate

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https://ir.library.oregonstate.edu/concern/undergraduate_thesis_or_projects/pg15bq04m

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  • Plastic pollution is a widespread problem in the environment and one of the major plastics contributing to this issue is polyethylene terephthalate (PET). Like most plastics, PET does not readily biodegrade, and once it is in the environment it is stable for hundreds or thousands of years. Some esoteric and slow-growing organisms have been identified that cleave bonds in the PET polymer, but if PET is going to be made decomposable on any practical scale, its carbon must be accessible for metabolism by a much wider group of organisms. We sought to investigate whether physiochemical pretreatments could oxidize and depolymerize PET enough to expand the number of organisms that can degrade PET and improve biological decomposition rates. To do this we utilized a combination of physiochemical oxidation on the PET polymer using ultrasonication, chemical oxidants, and biological oxidation with a known PET-degrading bacterium and a wood degrading fungus. PET beads were oxidized by sonicating in 2%, 4%, 8%, and 16% solutions of KMnO₄, Zn(NO₃)₂, FeCl₂, MnCl₂, or CuSO₄. The PET beads showed the greatest alteration to their FT-IR spectra after treatment with the 8% KMnO₄ solution. This manifested as a drop in absorbance in at about ~1700 nm indicative of carbonyl groups. This could be attributed to polymer cleavage and decarboxylation. PET beads were also treated by ultrasonication and a Fenton system consisting of FeSO₄ and H₂O₂ at molar ratios, 1:1, 1:10, and 1:100. FT-IR analysis showed decreases in absorbance at around 1700 nm with the greatest decrease occurring when the highest concentration of FeSO₄ and H₂O₂ was present. While similar modifications were observed for the Fenton system and the KMnO₄, the latter seemed to produce a greater edect on the polymer. Because of this, an 8% solution of KMnO₄ was used to pretreat PET beads using an ultra-sonicator prior to exposure to different biological cultures. Pretreated plastic was exposed to Idionella sakaiensis, Pleurotus ostreatus, or combined cultures, then analyzed for further oxidation. As seen on the FT-IR, it had the greatest oxidation on the carbonyl group in the ~1700nm range. This was further supported through an increase in polymer cavitation, as seen on the laser microscope.
  • KEYWORDS: Physiochemical Oxidation, Idionella sakaiensis, Polyethylene Terephthalate, Bioremediation, Pleurotus ostreatus
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