Thermo-delamination of metallised composite plastic: An innovative approach to generate Aluminium from packaging plastic waste

Abstract

Metallised packaging plastics are combination of various plastics and aluminium. Each year, large amounts of aluminium-plastics packaging waste are being generated with record up to 20,000 tons worldwide and this value is continuously growing. However, its recycling rate is still restricted in 20% due to lack of appropriate separation technology. In this study, a cleaner and sustainable thermo-delamination process of metallised plastic waste into high quality aluminium and hydrocarbon fuel gases is presented. Commonly used metallised composite plastic, post-consumer face mask sheet packaging bags, composed of polypropylene, polyethylene terephthalate and a layer of aluminium foil is investigated as raw metallised plastic packaging waste material. Thermo-delamination of this waste above temperature of 500 °C can achieve approximate 67 wt% gasification and left a 33 wt% solid residue constituted by black char and aluminium. Followed by a refinement treatment, a high-quality metallic aluminium weight around 30 wt% of the raw waste was finally isolated. This aluminium product was proved to have a high purity up to 95 wt% and a nanoscale oxidation surface by scanning electron microscopy-energy dispersive spectroscopy, X-ray photoelectron spectrometer, X-ray diffractometer and inductively coupled plasma techniques. Meanwhile, the gaseous products generated from decomposition of the plastic components contained in the waste are mainly composed of aromatic and methylene group hydrocarbons which can be easily reformed into high efficient fuel gases like methane, hydrogen and carbon monoxide for energy uses. This innovative thermo-delamination process offered a cleaner route for production of high quality aluminium from metallised plastic packaging waste and achieved 97 wt% transformation of waste into value-added resources.