Recovering\nValuable\nChemicals from Polypropylene Waste\nvia a Mild Catalyst-Free Hydrothermal Process

Waste\npolypropylene (PP) presents a significant environmental\nchallenge,\nowing to its refractory nature and inert C–C backbone. In this\nstudy, we introduce a practical chemical recovery strategy from PP\nwaste using a mild catalyst-free hydrothermal treatment (HT). The\ntreatment converts 64.1% of the processed PP into dissolved organic\nproducts within 2 h in an air atmosphere at 160 °C. Higher temperatures\nincrease the PP conversion efficiency. Distinct electron absorption\nand emission characteristics of the products are identified by spectral\nanalysis. Fourier transform-ion cyclotron resonance-mass spectrometry\n(FT-ICR-MS) reveals the oxidative cracking of PP into shorter-chain\nhomologues (10–50 carbon atoms) containing carboxylic and carbonyl\ngroups. Density functional theory (DFT) calculations support a reaction\npathway involving thermal C–H oxidation at the tertiary carbon\nsites in the polymer chain. The addition of 1% H<sub>2</sub>O<sub>2</sub> further enhances the oxidation reaction to produce valuable\nshort-chain acetic acids, enabling gram-scale recycling of both pure\nPP and disposable surgical masks from the real world. Techno-economic\nanalysis (TEA) and environmental life cycle costing (E-LCC) analysis\nsuggest that this hydrothermal oxidation recovery technology is financially\nviable, which shows significant potential in tackling the ongoing\nplastic pollution crisis and advancing plastic treatment methodologies\ntoward a circular economy paradigm.