Reactive crystallization for purifying PET monomers from mixed plastic waste for food-grade packaging
A chemical recycling method that uses coordinating additives to selectively crystallize and purify terephthalic acid monomers from unsorted PET waste, enabling production of virgin-grade, food-safe packaging while reducing greenhouse gas emissions.
Overview
PET packaging is a significant source of greenhouse gas emissions, and current recycling methods struggle with contaminated or unsorted waste streams. Mechanical recycling requires clean inputs, while conventional chemical recycling from mixed waste produces low-grade monomers that fail food-contact standards. This solution applies reactive crystallization, a coordination-chemistry-based purification approach, to recover virgin-grade terephthalic acid monomers from complex plastics-digestion mixtures. By enabling circular use of dirty and unsorted PET waste, the technology supports sustainable packaging production and meaningful GHG reduction.
Technical specifications
- Coordinating additive purification: Inert metal ions are introduced into depolymerized PET mixtures, selectively bonding with terephthalic acid monomers to drive their crystallization out of solution.
- Selective precipitation: The approach exploits the unique ability of terephthalic acid to form extended coordination networks with the metal ions, allowing impurities such as dyes and contaminants to remain in solution.
- Additive recovery: Metal ions are recovered after monomer extraction, ensuring process circularity and preventing additive contamination of the final product.
- Analytical quality verification: Monomer purity is confirmed using NMR, HPLC, and UV-Vis characterization techniques, with demonstrated results exceeding standard solid-liquid separation benchmarks on dyed PET fiber model wastes.
- Applicable feedstock: Designed for unsorted, dirty PET bottles sourced from landfills and waste collectors, expanding the range of recyclable input materials.
Technology readiness level
The concept has been validated on dyed PET fibers as model waste streams, demonstrating that reactive crystallization outperforms conventional solid-liquid separation in producing high-purity monomers. A manuscript documenting these results is in preparation. The next development phase involves validating the process on real-world unsorted waste bottles and quantifying circularity through energy-mass balance analysis, with the goal of producing food-grade packaging and generating patentable intellectual property around the additive recovery workflow.
About Cornell University
Cornell University is a comprehensive private, land-grant research university with campuses in Ithaca and New York City, combining significant scale with cross-disciplinary breadth. Industry connects through open-access user facilities and prototyping labs, pilot-scale testbeds, and a research and technology park that provide pathways from discovery to demonstration. A statewide extension network and integration with a major hospital system enable real-world deployment, while a graduate campus embedded in New York City’s tech corridor provides direct access to startups, venture investors, and corporate R&D teams. Research is supported by competitive federal funding from agencies such as the National Science Foundation, National Institutes of Health, the Department of Energy, and the U.S. Department of Agriculture. A dedicated technology transfer office streamlines IP management, licensing, startup formation, and corporate partnerships across campuses.
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