Unveiling synergistic mechanisms and kinetic behaviors in co-pyrolysis of polyethylene terephthalate and balsa wood from waste wind turbine blades

For the recycling of waste wind turbine blades (WWTBs), pyrolysis has been proven to be a promising method for the recovery of organic components. This study systematically investigated the co -pyrolysis of polyethylene terephthalate (PET) and balsa wood (BW) blends by integrating thermogravimetry-mass spectrometry (TG-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) to explore their characteristics, kinetics, and underlying reaction mechanisms. Thermogravimetric analysis revealed significant interactions, evidenced by a decrease in the maximum decomposition temperature of PET and an increase in that of BW in the blends. A notable synergistic effect, optimally achieved at a 1:1 blending ratio, enhanced mass loss and reduced the apparent activation energy, as determined by model-free kinetic methods. Kinetic analysis via the distributed activation energy model (DAEM) indicated that the pyrolysis of PET and BW conformed to the single-Gaussian DAEM (SG-DAEM) and double Gaussian DAEM (DG-DAEM), respectively, with the mixture necessitating a triple Gaussian DAEM (TG-DAEM). The fitting further deconvoluted the co-pyrolysis process into distinct reaction stages corresponding to the decomposition of cellulose/hemicellulose, lignin, and PET. Moreover, their weighting factors effectively reflecting the contribution of each component. Py-GC/MS results demonstrated that co-pyrolysis significantly altered product distribution, promoting the formation of aromatics and aldehydes while suppressing phenols, esters, and ketones. A reaction mechanism was proposed, indicating that radicals and acids derived from BW pyrolysis catalyze PET depolymerization and facilitate secondary reactions, such as decarboxylation and esterification, thereby shaping the final product slate. This work provides fundamental insights and experimental data crucial for developing efficient pyrolysis-based recycling strategies for WWTBs.