Lu Zhan

Synergistic physical deconstruction and radical oxidation depolymerization enable multi-component recovery of waste chips into valuable materials.

Ultrashort-chain per- and polyfluoroalkyl substances (USC-PFAS), defined by three or fewer carbon atoms in their backbone, represent an emerging class of environmental contaminants whose prevalence and hazards remain inadequately characterized. This study conducted a comprehensive survey of seven USC-PFAS and 37 other PFAS compounds in aquatic environments within the Integrated Demonstration Zone of the Yangtze River Delta, a region undergoing continued industrialization. Results showed that USC-PFAS overwhelmingly dominated PFAS profiles, with trifluoroacetic acid (TFA) representing the most abundant species. Mean concentrations of TFA reached 8.7 × 10⁴ ng/L in surface water, 8.0 × 10⁴ ng/L in source water, and 6.9 × 10⁴ ng/L in tap water, constituting 90.1% to 99.6% of total ∑₄₄PFAS across matrices. When TFA was excluded, the remaining ∑₆USC-PFAS contributed 44.0% to 58.8% of the total PFAS burden. Trifluoromethanesulfonic acid (TFMS) was the second most abundant in surface and source waters, while trifluoromethane sulfonimide (Ntf2) ranked second in tap water. Source apportionment analyses implicated battery electrolyte formulations as major contributors of TFMS and Ntf2. Hazard prioritization based on persistence, mobility, bioaccumulation, and toxicity (PMBT) metrics, alongside measured environmental levels, identified TFA, TFMS, perfluoro-2-(perfluoromethoxy)propanoic acid (PMPA), and perfluorooctanoic acid (PFOA) as high-hazard compounds. These findings suggest that USC-PFAS constitute a pervasive and underregulated class of pollutants, whose high mobility and recalcitrance challenge current assumptions regarding their environmental safety and call for urgent regulatory reevaluation.

Remanufacturing high-value vehicle parts is of substantial significance for the circular economy because it provides a second service life and reduces solid waste generation. Laser cleaning is a promising method in the remanufacturing industry owing to its high energy, precision, and efficiency. However, the pollution caused by laser cleaning remains unknown and has rarely been reported, limiting the application of this method. In this study, pollution removal and conversion using a high-energy laser were explored, and environmental life cycle and health risk assessments were conducted. The results showed that high-energy lasers might induce new organic pollutants, such as olefins, alkynes, and aldehydes. During laser cleaning, thermal elastic expansion and shock wave generation were the main mechanisms of rust removal, and evaporation and small-scope boiling were used for waste oil removal. The mean concentration of PM₁₀ was above 7000 µg/m³ in laser rust removal, and the total concentration of volatile organic compounds (VOCs) was the highest in laser oil removal (∼ 2568 µg/m³). Particulate matter contained high amounts of Fe, Al, and Mn. An environmental life cycle assessment indicated that laser cleaning for stain removal significantly reduced the total environmental impact compared with that of traditional solvent-ultrasonic cleaning (∼ 40.0%) and sandblasting (∼ 83.3%). This study provides an environmental protection basis for increasing the use of laser cleaning in the remanufacturing industry.

The extensive use and longevity of nylon plastics pose substantial challenges for plastic management, recycling, and pollution control. Depolymerization and monomer recycling are potential solutions for valorizing waste plastics, but they often rely on complex and costly catalysts. Additionally, various additives in nylon plastics can negatively impact the catalyst efficiency. To address these issues, we proposed a novel method of hydrothermal clean water depolymerization without any catalysts. In this study, high-purity monomers were successfully recovered from nylon plastics by utilizing the reversibility and hydrophilicity of amide bonds, with hydrothermal amphoteric hydrolysis applied as the method. On this basis, repolymerization of the monomer was completed, and new nylon was generated by one-pot solution polycondensation, thereby achieving a closed-loop recycling process. A depolymerization model was established for nylon in a hydrothermal system at both macro- and micro levels, revealing a unique mechanism of simultaneous surface and internal depolymerization. This process enables the closed-loop upcycling of nylon, transforming waste back into its starting materials, reducing carbon emissions, and promoting sustainability.

The pyrolysis process of waste printed circuit board (WPCB) with high economic benefit has been a black box problem, limiting the upgrading of pyrolysis processes. The resourcefulness and hazardous nature of WPCB will make it necessary for it to be treated properly. Multiphysics model was built to simulate the whole processes of WPCB pyrolysis and contaminants’ release. The circuit board samples containing six components were selected for pyrolysis in a tube furnace at a rate of 10[ ]C/min from room temperature to 600[ ]C, and the residual rate of Br- was determined by the oxygen bomb method. The results showed that the difference in temperature distribution could be attributed to thermal conductivity and surface area. Heat distribution would be more even from the inner material in areas where holes existed. The assembly method would affect the stress distribution around the components. Thermal stress at the pins might cause the separation of components from the substrate. The concentration of brominated contaminants was influenced by the material and assembly method. The instantaneous concentration around the pin was 3–4 times compared to the bare substrate, which was beneficial for the release and control of brominated organics. This study provided the research method for the in-depth understanding of the pyrolysis process of complex materials; and provided a basis for the upgrading of related processes.