• plastic
• carboxylic acids
• wet air oxidation
• tertiary recycling
• feedstock recycling
• chemical recycling
• benzoic acid
• succinic acid
• propionic acid
• acetic acid
• polyethylene terephthalate
• polypropylene
• hdpe
• polystyrene
• ldpe
• green chemistry
• sustainability

Increasing waste streams compel our society to rethink how we manage products' end-of-life stages. Today we had better be aware of recycling technologies and develop those to generate valuable products to be reintroduced on the market. Such a practice enables two beneficial advantages: avoiding disposal, and preserving the material and energetic value of the waste thus avoiding extraction of new raw materials. However, plastic waste is a challenging share of Municipal Solid Waste (MSW) to be effectively recycled. This is mainly due to the heterogeneous chemical nature of polymers that form plastic products. Reuse of plastics and standard mechanical recycling may prove insufficient while tertiary recycling that adopts a chemical approach is a novel approach that may guarantee unlimited renewal into valuable chemicals. Pyrolysis, gasification, solvolysis, and biological digestion have been tested as possible technologies to turn plastic waste into valuable feedstock for the chemical industry. HTPs (Hydro-Thermal Processes) can represent an emerging technique to deal with the problem. Out of many HTPs, we put our focus on the Wet Oxidation (WO) technique, an AOP (Advanced Oxidation Process) that may provide a solution to convert mixed plastic waste into major industrial chemicals, namely carboxylic acids such as acetic, propionic, benzoic and others. Furthermore, wet oxidation is operated using water as the reaction medium. This means that harmful organic solvents can be avoided resulting in a process managed according to the requirements of a green and sustainable chemistry. Furthermore, since WO is by istself a wet technique costly dewatering pretreatments can be neglected.
This study has focused on assessing how to implement through WO the degradation of the polymers representing the main commodities ending up as plastic waste, namely polyethylene (PE), polypropylene (PP), poly(styrene) (PS) and poly(ethylene terephthalate) (PET), looking for optimal temperature, pressure, and residence time along with the preservation of valuable chemicals as the WO products. Kinetic, qualitative, and quantitative assessments are brought into this work.