Online TG-FTIR-MS analysis of the catalytic pyrolysis of polyethylene and polyvinyl chloride microplastics

Microplastics (MPs) are frequently detected in urban waters, which would pose a threat to human health through the food chain. Thus, efficient approaches to the elimination of MPs are urgently required. Pyrolysis is a powerful technique for the potential treatment of MPs. The online thermogravimetry-Fourier transform infrared reflection-Mass spectrometry (TG-FTIR-MS) is applied for tracking the pyrolysis process of representative polyethylene (PE) and polyvinyl chloride (PVC) MPs in urban waters, together with or without the FeAlO_x catalyst. TG could quantitatively determine the decomposition behavior and kinetics of MPs while FTIR and MS spectra would be capable of characterizing the pyrolysis products. The results revealed that FeAlO_x is an excellent carbon support, and the deposited carbon can be gasified to CO at higher pyrolysis temperatures. Moreover, more aromatic compounds were generated from the pyrolysis of PE MPs with the catalyzation of FeAlO_x. Large quantities of benzene were also produced in the PVC MPs pyrolysis with or without FeAlO_x. Also, FeAlO_x largely decreased the concentrations of chlorine-containing compounds in the liquid products of PVC MPs pyrolysis. This study provides a efficient technique for the online observation of the MPs' catalytic pyrolysis process, which would guide future upcycling of MPs into value-added products.