Recent Advances in Pre-Treatment of Plastic Packaging Waste

Abstract

There is an urgent need to close the loop of plastic waste. One of the main challenges towards plastic packaging waste recycling is the presence of a variety of contaminants. These contaminants include organic residues, additives, labels, inks and also other plastic types that can be present in the waste stream due to missorting or in multimaterial structures (e.g. multilayer films in packaging). In this context, pre-treatment processes are a promising route to tackle the difficulties that are encountered in mechanical and chemical recycling due to these contaminants. This chapter gives better insight on the already existing pre-treatment techniques and on the advances that are being developed and/or optimized in order to achieve closed-loop recycling. Some of these advanced pre-treatments include chemical washing to remove inks (deinking), extraction methods to remove undesired plastic additives and dissolution-based pre-treatments, such as delamination and dissolution-precipitation techniques.

Towards high-quality petrochemical feedstocks from mixed plastic packaging waste via advanced recycling: The past, present and future

“…Sorting, separation and other pre-treatment methods, which are also performed in mechanical recycling will not be discussed in detail, neither will surface treatment techniques such as de-inking. The interested reader is herewith referred to the respective specialized literature [34,[41][42][43][44][45][46][47][48]. The most important waste pre-treatment techniques for thermochemical recycling are dehalogenation and the removal of residues and additives prior to pyrolysis to produce a feedstock more suitable for petrochemical processes.…”

Critical Evaluation of Life Cycle Assessment Analyses of Plastic Waste Pyrolysis

“…For example Zhao and You (2021) used experimental data collected through pyrolysis experiments performed with 2 g of high-density polyethylene (HDPE) and considered that the results would remain the same for reactors of 2 t/h, although it is not well-known how product yields and compositions in small scale reactors would change in large scale ones due to mass and heat transfer effects and possible modifications of the reactor configuration. Furthermore, it is also known that upstream and downstream processes also affect the product quality and LCA scores. ,− For instance, heating a plastic material in an extruder can be less energetically demanding and can remove hydrochloric acid. Or the use of catalysts in a secondary reactor can crack further the pyrolysis products, changing product specifications.…”

Toward More Universal Prediction of Polymer Solution Viscosity for Solvent-Based Recycling

“…Solvent-based techniques can be categorized into two groups: solid–liquid extraction techniques and dissolution–precipitation technique. , In the dissolution–precipitation technique, which is the focus of the present work, the polymer is dissolved in a suitable solvent, followed by one or more separation processes, e.g., filtration or centrifugation, to remove the contaminants. Finally, the addition of an antisolvent induces precipitation of the polymer .…”