Publication: Microwave-assisted pyrolysis of plastic waste
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Date
2025-08-08
Authors
Ng, Xiang Han
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Abstract
Plastic waste has raised significant environmental concerns especially due to plastic pollution and its degradation into microplastics in the atmosphere. Pyrolysis process is a sustainable thermochemical recycling method that decomposes plastic waste in an oxygen-deficient environment to produce valuable and alternative energy sources products. Microwave-assisted pyrolysis (MAP) is a promising alternative to conventional pyrolysis (CP), offering faster reaction times and improved heat transfer. However, MAP requires microwave absorbers as plastics are transparent to microwaves. Common absorbers like silicon carbide and activated carbon suffer from reduced efficiency with reuse, contamination of products, and recovery challenges. This study explores the use of spent carbon, a cost-effectiveness industrial waste as a reusable microwave absorber in MAP to provide thermal energy to the plastic samples. The effects of spent carbon ratios (1:1, 1:0.8, 1:0.6, 1:0.4) and microwave power levels (120W, 230W, 385W) were investigated. Results showed that the yield of residue increased when the ratio of spent carbon decreased as lower spent carbon ratios reduced microwave energy conversion and heating rate. At a fixed ratio but different microwave power level supplied, the sample at 385W produced better yields as higher microwave power enhanced the heating rate to the plastic sample. Pyrolysis products were analyzed using X-ray fluorescence (XRF) and Fourier Transform Infrared Spectroscopy (FTIR). Residue contained elements such as Al, Si, Ti, and Fe from food packaging coatings, and P, K, and Ca from spent carbon impurities. The liquid oil mainly comprised hydrocarbons (alkanes, alkenes, aromatics) which indicated the potential of MAP for waste-to-energy conversion.