Ping Cheng

Polyethylene (PE) accounts for 36% of the total plastic waste by mass. However, its inherent chemical stability poses significant challenges for chemical recycling, including energy‐intensive processing, costly catalysts, and thermodynamic constraints that result in low‐value hydrocarbon products. Herein, we present a catalyst‐free, one‐pot hydrothermal oxidation strategy for the efficient upcycling of waste PE into high‐value oxidized polyethylene wax (OPEW). Notably, under optimized conditions (160°C, 1.5 MPa O ₂ ), low‐density polyethylene (LDPE, 1.0 g) is converted to OPEW within 0.5 h, achieving an OPEW/PE mass ratio of 103.3% and a carbon yield of 99.8%. The resulting OPEW exhibits a tunable acid number (20–70 mg KOH/g) and saponification number (5–80 mg KOH/g), covering industrial specifications for commercial wax products. Mechanistic studies reveal that the superoxide radical (·O ₂ ⁻ ) plays a key role in mediating the reaction. Furthermore, 30‐fold scale‐up trials and successful application to various types of PE waste feedstocks demonstrate the great potential of this methodology for industrial viability. This strategy establishes a sustainable, catalyst‐free pathway for upcycling plastic waste into functional materials.

Polyethylene (PE) accounts for 36% of the total plastic waste by mass. However, its inherent chemical stability poses significant challenges for chemical recycling, including energy‐intensive processing, costly catalysts, and thermodynamic constraints that result in low‐value hydrocarbon products. Herein, we present a catalyst‐free, one‐pot hydrothermal oxidation strategy for the efficient upcycling of waste PE into high‐value oxidized polyethylene wax (OPEW). Notably, under optimized conditions (160°C, 1.5 MPa O ₂ ), low‐density polyethylene (LDPE, 1.0 g) is converted to OPEW within 0.5 h, achieving an OPEW/PE mass ratio of 103.3% and a carbon yield of 99.8%. The resulting OPEW exhibits a tunable acid number (20–70 mg KOH/g) and saponification number (5–80 mg KOH/g), covering industrial specifications for commercial wax products. Mechanistic studies reveal that the superoxide radical (·O ₂ ⁻ ) plays a key role in mediating the reaction. Furthermore, 30‐fold scale‐up trials and successful application to various types of PE waste feedstocks demonstrate the great potential of this methodology for industrial viability. This strategy establishes a sustainable, catalyst‐free pathway for upcycling plastic waste into functional materials.

Polypropylene (PP) is widely used in microwavable food containers, but the simultaneous release of volatile organic compounds (VOCs) and nanoplastics (NPs) during microwave heating is poorly understood. In this work, we developed two mass spectrometry techniques: low-pressure assisted microwave plasma ionization time-of-flight mass spectrometry (LAMP-TOFMS) for the real-time monitoring of VOC emissions and argon-assisted internal-tube sampling enhanced microwave plasma ionization linear ion trap mass spectrometry (AIS-EMPI-LTQMS) for the rapid, pretreatment-free detection of NPs. Simultaneous monitoring of the representative VOCs styrene and 2-methylpentane revealed dynamic release profiles characterized by a time-dependent increase. The concentrations of styrene and 2-methylpentane from the rectangular plastic container were measured at 3.99 ± 0.65 and 4.43 ± 0.19 ppbv after 180 s of microwave heating. Meanwhile, the AIS-EMPI-LTQMS exhibited a satisfactory analytical performance for PP NPs. The linear correlation (R² = 0.989) was observed between the characteristic ion intensity and the PP NPs concentration. Additionally, our findings highlight container geometry as a significant factor affecting NPs release, with rectangular containers generating the highest PP NPs concentration, up to 2.04 ± 0.32 μg/L under 180 s of microwave heating. This study offers a comprehensive, real-time evaluation of dual pollutants from PP containers and establishes a practical, concise analytical platform for the rapid safety evaluation of food-contact materials.

Low-cost MnO ₂ efficiently upcycles mixed plastics into high-performance additives in one pot, turning waste into value without costly purification.

The fundamental challenge in degrading diverse odorous compounds lies in their low concentration and varied chemical reactivity, which complicates the elucidation of underlying degradation mechanisms. This study investigates the plasma‐driven reaction pathways and synergistic effects in a microwave plasma‐catalytic system, designed for the degradation of representative odorous compounds including oxygenated volatile organic compounds (OVOCs), benzene derivatives, and sulfur compounds. An end‐face enhanced reactor design significantly improved plasma excitation efficiency and stability, enabling effective degradation (> 90%) at low power (50–80 W). Crucially, we report the first mechanistic study on the simultaneous degradation of mixed organic and inorganic sulfur compounds using microwave plasma catalysis. Real‐time online monitoring of reaction intermediates and products was achieved via a custom low‐pressure assisted microwave plasma time‐of‐flight mass spectrometry (LAMP‐TOFMS) instrument. Target compounds included butanal, ethyl acetate, benzene, toluene, dimethyl sulfide, dimethyl disulfide, methanethiol, and carbon disulfide. The system demonstrated not only high degradation efficiency but also a pronounced control over by‐product formation. The introduction of a catalyst was found to critically alter the reaction selectivity, suppressing the formation of undesirable oxygenates (e.g., formic acid) and nitrogen‐containing intermediates (e.g., nitromethane), thereby promoting the complete mineralization pathway. This work provides fundamental insights into the plasma‐catalytic reaction mechanisms governing the degradation of complex odorant mixtures, offering a novel molecular‐level perspective on nonthermal plasma chemistry relevant to environmental remediation.

The practical application of non‐thermal plasma‐catalysis hybrid systems for industrial off‐gas treatment faces significant challenges due to unavoidable generation of deleterious by‐products. In this study, a novel post‐plasma catalytic system was developed, incorporating an α‐MnO2/Cordierite honeycomb monolithic heterogeneous catalyst designed for the simultaneous removal of toluene and styrene. Experimental results revealed that the plasma‐catalyst system achieved almost 100% degradation efficiency and exhibited a COx selectivity of 51.8%, thereby effectively reducing the formation of by‐products. Notably, during co‐processing, the removal efficiency of toluene was diminished, whereas the conversion of styrene remained stable under comparable conditions. The integration of the catalyst imparted strong resilience to variations in pollutant concentration and gas flow rates, demonstrating significant adaptability for industrial‐scale emission control. The synergistic and inhibitory interactions governing the co‐degradation of binary volatile organic compounds (VOCs), along with the pathways of by‐product formation, were elucidated through real‐time mass spectrometric analysis of transient intermediates. This work represents a pioneering advancement in the integration of monolithic catalysts with plasma technology, offering fundamental mechanistic insights into the co‐elimination of multicomponent VOCs and facilitating the accelerated industrial implementation for the treatment of complex waste gas streams.