Assessment of Supercritical CO2 Extraction as a Method for Plastic Waste Decontamination

• Published in: Polymers Vol. 12; no. 6; p. 1347
• Main Authors: Alassali, Ayah, Aboud, Noor, Kuchta, Kerstin, Jaeger, Philip, Zeinolebadi, Ahmad
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 15.06.2020; MDPI
• Subjects: Adhesion tests; Carbon dioxide; Containers; Contaminants; Contamination; Decontamination; Fluids; Food contamination & poisoning; High density polyethylenes; Infrared analysis; Lubricants & lubrication; Near infrared radiation; plastic waste; Plastics; Polycyclic aromatic hydrocarbons; Polyethylene; Polymers; Product safety; Quality assessment; Recycling; supercritical extraction; Supercritical gas extraction; United States > US; Europe; Germany
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym12061347

Due to the lack of advanced methods to clean plastic waste from organic contaminants, this study aimed at evaluating supercritical extraction as a decontamination method. Oil-adhesive high-density polyethylene (HD-PE) oil containers were subjected to supercritical extraction using supercritical carbon dioxide. The extraction was conducted at 300 bar, applying various temperatures (i.e., 70, 80 and 90 °C). The study assessed the impact of temperature on the decontamination efficiency. The variation in the samples’ quality was first analyzed using near infrared (NIR) spectroscopy. An analysis of the content of polycyclic aromatic hydrocarbons (PAHs) was followed. Samples treated at 70 and 80 °C showed higher extraction efficiencies, in spite of the lower extraction temperatures. The NIR analysis showed that the plastic specimens did not experience degradation by the supercritical decontamination method. Moreover, the NIR spectra of the extracted oil showed the presence of a wide range of compounds, some of which are hazardous. This has been confirmed by a GC-MS analysis of the extracted oil. Based on the provided assessment, the quality of the decontaminated HD-PE plastic samples—from a contamination point of view—is enhanced in comparison to untreated samples. The level of PAHs contamination decreased to be within the allowed limits defined by the REACH regulation, and also met the specifications of the German Product Safety Committee. This study proved the effectiveness of the supercritical extraction using CO2 in extracting organic contaminants from plastics, while maintaining their quality.