Polycyclic Aromatic Hydrocarbons Formed During the Pyrolysis Process of Plastics – Characterization, Quantification and Risk Assessment

Abstract

Occurrence, distribution, and toxicity assessment of 16 Polycyclic Aromatic Hydrocarbons (PAHs) prioritized by the US Environmental Protection Agency in pyrolysis products – pyrolysis oil and pyrolysis wax – of different plastics are characterized. PP, HDPE, LDPE, PVC, PS (respectively, polypropylene, high- and low-density polyethylene, polyvinylchloride and polystyrene) and their mixture named 5P are chosen as a feed material for pyrolysis. Pyrolysis process is carried out in a custom-built laboratory batch reactor with the pyrolysis temperature of 450 °C for PP, PVC, PS and 500 °C for HDPE and LDPE. 5P mixture is pyrolyzed at 500 and 700 °C. PAHs quantification is used to determine the toxicity equivalency quantity TEQ(BaP) for each pyrolysis product and to establish the degree of toxicity. The highest total concentration of 16 PAHs in pyrolysis oil is found to decrease in the order of PVC > PP > PS > LDPE > HDPE. According to TEQ(BaP), the toxicity of the most toxic pyrolysis oils correlates with the aforementioned order of the total concentration, i.e., being lowest for HPDE and highest for PVC. For pyrolysis wax, the highest total concentration of 16 PAHs is for PVC > PS > LDPE > PP > HDPE, while TEQ(BaP) value decreases as PVC > LDPE > PP > PS > HDPE. The PAHs concentration and TEQ(BaP) values of 5P mixture show similar trends in both products (oil, wax), i.e., they both increase with increasing pyrolysis temperature.

Keywords

• pyrolysis of plastics
• polycyclic aromatic hydrocarbons (pahs)
• pyrolysis oil
• pyrolysis wax
• risk assessment