Chemical Recycling of Polyethylene Terephthalate (PET) Medical Waste for the Sustainable Production of Biomedical Materials

This study systematically evaluates the application prospects of three chemical recycling technologies for resource recovery from PET medical waste and the sustainable production of biomedical materials: catalytic pyrolysis, thermochemical recovery, and enzymatic hydrolysis. Orthogonal experimental designs and Box–Behnken response surface methodologies were used to optimise process parameters, and an extended assessment platform covering chemical purity, molecular weight distribution, biocompatibility, and mechanical properties was established. Under optimised conditions (200 °C, 3% w/w catalyst, 4 h, 6:1 ethylene-glycol-to-PET mass ratio), catalytic pyrolysis with zinc acetate achieved a terephthalic acid (TPA) recovery of 92.3 ± 1.8% at a product purity of 98.2 ± 0.5%, and retained 97.6% of the tensile strength and 97.4% of the elastic modulus of virgin PET. Although the enzymatic process was relatively long at 24 h, it had the best biocompatibility (L929 fibroblast viability 94.1 ± 2.2% and haemolysis 1.82 ± 0.28%) and reduced the carbon footprint by 46.5% compared to catalytic processing. Thermochemical recovery was completed in 1 h at 500 °C, achieving a TPA recovery of 71.2 ± 3.8%, and is suitable for large-scale processing of low-value medical waste streams. Biocompatibility tests showed that PET regenerated via the three paths met the ISO 10993 series of standards, with a cytotoxicity grade of 0–1 and an endotoxin content below 0.5 EU/mL. Gel permeation chromatography showed that the number-average molecular weight (Mn) of chemically recycled PET was between 21,200 and 24,100 g·mol−1 (compared to 24,500 g·mol−1 for virgin PET), approximately 86.5% to 98.4% of the virgin value, and significantly higher than mechanically recycled PET. The technical route and quality-control system established here provide a scientific basis for the closed-loop recycling of medical-grade PET and support the green transformation of the medical industry.