Microcrystalline paraffin wax, biogas, carbon particles and aluminum recovery from metallised food packaging plastics using pyrolysis, mechanical and chemical treatments

Metallised food packaging plastics waste (MFPW) is the most complex part of plastic waste ever with poor recyclability. In order to close the circle loop of MFPWs and to increase their economic and environmental benefits according to the zero waste principle, this research aims to convert MFPWs into energy products (Microcrystalline paraffin wax and biogas) and raw materials (carbon particles and aluminum) using three combined approaches: pyrolysis, mechanical and chemical treatments. The thermal treatment using mini-pyrolysis plant (capacity of 250 g) was applied as the main treatment to convert MFPWs into three main energy products: biooil, biogas, and char mixed with aluminum flakes (Al/char) at 25 degrees C/min up to 500, 600, and 700 degrees C, while the mechanical treatment using milling process was used to break the bonds between char and Al flakes, thus liberating Al flakes after sieving process. Finally, the leaching process using hydrochloric acid was employed to extract the remaining Al particles from the milled Al/char and to recover the carbon particles simultaneously, using a density separation method. The experiments were performed on a mixture of five types of equal shares of packages (potato chips, chocolate, bakery, coffee, and biscuits). The obtained energy products and recovered materials were analyzed by GC, FTIR, ICP, and SEM-EDS. The results showed that MFPWs can be decomposed thermally into Al/char (99.4%) only up to 500 degrees C, while in case of 600 and 700 degrees C, they can be converted into microcrystalline paraffin wax (19.5%), biogas (63%), and Al/char (17.8%). Also, the mechanical and chemical treatments were succeeded by leaching >90 wt% of Al and extraction of carbon particles on a micro-scale (10-50 mu m). Finally, the assessment of economic performance and greenhouse gases showed that application of the developed approach on an industrial scale can provide an economic return up to 610 $/ton of MFPWs and decrease carbon footprint by -984 kg CO2-eq/t of MFPWs. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

By utilizing a combination of pyrolysis, mechanical, and chemical treatments, MFPWs can be converted into energy products and raw materials. The experiments demonstrated that MFPWs can be thermally decomposed into Al/char at temperatures up to 500 degrees C, with higher temperatures resulting in the production of additional energy products. Mechanical and chemical treatments proved successful in extracting aluminum and carbon particles.