| Summary: | Reliance on plastic by society has resulted in large volumes of waste requiring treatment. Often, this waste is disposed of in ways that harm the environment or prevent the re-use of the material, such as landfill or incineration. Therefore, the plastic value chain is often described as being linear because of the poor end-of-life strategies currently in place.
It is crucial to introduce some circularity into the plastic value chain, to increase the useful lifespan of plastic material and to minimise plastic pollution of the natural environment. One route to achieve this is to recycle plastic.
Chemical recycling, an umbrella term used to describe a plethora of recycling strategies, describes the deliberate breakdown of a plastic material by a controlled process to yield monomers, or other low-molecular weight products. These products can then be used to produce fresh, high-quality plastic, or other valuable materials.
However, many chemical recycling processes suffer from drawbacks such as poor product selectivity and purification steps requiring large volumes of solvents. Both issues have led to challenges surrounding the proper cleaning and disposal of solvents used in the synthetic and purification steps, meaning that chemical recycling processes often find themselves in violation of the first Principle of Green Chemistry - it is better to prevent waste than to treat or clean up waste after it has been created.
In this work, two novel projects are undertaken to develop routes to chemically recycle polyethylene terephthalate with little to no solvent waste. Supercritical carbon dioxide is employed as a key solvent in both projects, whilst microwave heating is also exploited as an energy source for plastic degradation.
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