Valorization of mixed multilayer plastic waste: an exploratory study

Multilayer plastic packaging waste (MPPW) represents a significant fraction of plastic waste disposed of in landfills and incinerated due to its complex composition. This study explores the use of density separation, dissolution-precipitation, delamination, and chemical depolymerization through hydrolysis for the valorization of a mixed MPPW sample from a plastic recycling facility composed mainly of polyethylene (PE) and poly(ethylene terephthalate) (PET), with smaller amounts of polypropylene (PP), polystyrene (PS), polyamide (PA), several plastic additives, aluminum, and paper. The study demonstrates that dissolution-precipitation effectively recovered good-quality PE at an average yield of 38.8 wt%, which increased to 55.5 wt% when preceded by density separation to remove heavier films rich in PET, PA, and PS. PET targeted chemical depolymerization through alkaline hydrolysis yielded 10.9 wt% of high-quality terephthalic acid with 97.9 % purity when directly applied to MPPW, increasing to 14.8 wt% with 98.6 % purity after density separation. The delamination strategy was inefficient due to the numerous film structures in the mixed MPPW, whilst density separation was a helpful pretreatment step for subsequent recycling through dissolution-precipitation and chemical depolymerization. Combining density separation, dissolution-precipitation, and chemical depolymerization offers a promising pathway to transform complex MPPW into a source of PE and PET monomers.