Abstract:

Significance Under the concept of sustainable development, recycling waste polyester (PET) textiles has gained growing attention. Many countries have legislated to encourage this, and some renowned clothing brands aim to use 100% recycled PET in products by 2030. As a major PET fiber producer, China's efforts not only help reduce the environmental impact, lower resource waste, but also stimulate the technology advancement. However, it faces challenges such as low recycling rates and limited high-value use. This paper reviews the advancements in chemical recycling of PET textiles, summarizes their characteristics and challenges, and highlights the development trends of waste PET textile recycling technologies to promote sustainable utilization in the PET recycling industry.

Progress Chain extension and polycondensation technologies, classified under physical-chemical recycling, significantly enhance the melt viscosity of PET, thereby improving the quality of recycled fibers. Current research primarily focuses on the development of highly efficient chain extenders. Diguaiacyl oxalate, a reactive extender with high efficacy, not only increases the molecular weight of recycled PET but also allows for complete removal of post-reaction, effectively addressing traditional residue challenges. True chemical recycling involves depolymerizing waste PET into monomers, which can then be re-polycondensed to produce virgin-quality fibers. This process can be achieved through either bio-chemical or purely chemical depolymerization methods. Chemical approaches, such as methanolysis, glycolysis, and hydrolysis, aim to maximize monomer yield while optimizing catalyst performance. For example, the magnetic CoFe₂O₄ catalyst facilitates easy separation and maintains its activity after five cycles. Potassium carbonate enables PET methanolysis at room temperature, achieving a 93.1% dimethyl terephthalate (DMT) yield within 24 h. A novel acetic acid-based process developed in 2024 successfully depolymerizes PET at 280 ℃ within 2 h, yielding 95.8% terephthalic acid (TPA) with 99.7% purity and 95.3% ethylene glycol diacetate with 98.0% purity. Bio-chemical depolymerization emphasizes the use of highly efficient enzymes. The LCC quadruple mutant (LCCICCG) demonstrates the ability to depolymerize 90% of pretreated PET at 72 ℃ within 10 h. Furthermore, the computationally engineered LCC-A2 variant enhances efficiency, achieving over 99% TPA and ethylene glycol (EG) yields.

Conclusion and Prospect Currently, the recycling rate of waste PET textiles in China remains relatively low, with the majority being disposed of through landfill or incineration. Physical recycling is currently the predominant method, whereas chemical recycling plays a minor role. In physical-chemical recycling, there is a need for low-toxicity and residue-free chain extenders. Chemical catalytic depolymerization has made significant progress, particularly in the development of efficient catalysts for methanolysis, glycolysis, and hydrolysis. Bio-chemical depolymerization, which is environmentally friendly, encounters challenges such as enzyme thermal instability and low degradation efficiency for highly crystalline PET, with most studies still confined to laboratory settings. Future research should focus on optimizing chemical reactions to reduce costs and improve yields, as well as exploring bio-chemical depolymerization through protein engineering and machine learning techniques to enhance enzyme performance and achieve effective degradation of crystalline PET.

Key words: waste polyester, waste textiles, polyester recycling, polyester chain extending technology, catalytic depolymerization of polyester, polyester degradation enzyme, chemical regeneration