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There and Back Again: Recovery of Terephthalic Acid from Enzymatically Hydrolyzed Polyesters for Resynthesis
Chiara Siracusa1,2, Virginia Celestre3, Felice Quartinello1,2
1acib GmbH, Konrad-Lorenz-Strasse 20, 3430 Tulln an der Donau, Austria.
This study demonstrates enzymatic depolymerization of plastic waste using Humicola insolens cutinase, enabling high-purity terephthalic acid (TPA) recovery. The recovered TPA was successfully repolymerized into polyethylene terephthalate (PET).
Area of Science:
- Biotechnology
- Polymer Science
- Environmental Science
Background:
- Poly(ethylene terephthalate) (PET) is a widely used plastic, primarily for packaging.
- Current production of terephthalic acid (TPA), a key PET monomer, relies on fossil fuels.
- TPA is also a component in biodegradable polymers like poly(1,4-butylene adipate-co-1,4-butylene terephthalate) (PBAT).
Purpose of the Study:
- To explore an environmentally friendly method for depolymerizing PET and PBAT.
- To recover high-purity terephthalic acid (TPA) from plastic waste, including mixed plastics.
- To investigate the feasibility of repolymerizing recovered TPA into PET.
Main Methods:
- Enzymatic depolymerization of PET, PBAT, and mixed plastic waste using Humicola insolens cutinase.
- Isolation and purification of terephthalic acid (TPA) via acidification.
- Characterization of purified TPA using Fourier Transform-Infrared Spectroscopy, 1H-NMR spectroscopy, and Thermogravimetric analysis.
- Synthesis of bis(hydroxyethyl) terephthalate (BHET) and subsequent repolymerization to PET.
Main Results:
- Successful depolymerization of plastics and recovery of TPA.
- High purity of isolated TPA confirmed by spectroscopic and thermal analyses.
- Identified challenges in PET precursor synthesis due to contaminants in TPA.
- Repolymerization of recovered TPA yielded PET, with molecular weight influenced by TPA purity and catalyst.
Conclusions:
- Humicola insolens cutinase offers an eco-friendly alternative for plastic depolymerization and TPA recovery.
- TPA recovery from mixed plastic waste is feasible.
- TPA purity is critical for successful repolymerization and achieving desired polyester molecular weights.
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