Abstract ：

The pyrolysis treatment of waste polyesterimide enameled wire offers significant advantages such as continuous processing, non-hazardous nature, and high resource recovery rate. However, research on its pyrolysis process and mechanism remains insufficiently explored. In this study, techniques including thermogravimetry (TG), Fourier transform infrared spectroscopy(FT-IR), pyrolysis-gas chromatography-mass spectrometry(Py-GC/MS) were employed to investigate pyrolysis temperature, weight loss rate, pyrolysis and kinetic parameters, composition and distribution of pyrolysis products, and changes in functional groups under different temperatures and heating rates. The pyrolysis of polyesterimide enameled wire can be divided into three stages: volatilization of specific components (314.8 degrees C,1.6 %), rapid decomposition of polyesterimide (435.2 degrees C, 44.7 %), and generation of small organic molecules with the fixation of pyrolytic carbon (750 degrees C, 9.0 %). The main components of the pyrolysis gas products include aromatic compounds, ethers, aromatics, ketones, and carbon dioxide. At 400 degrees C, a substantial amount of pyrolysis gas products and free radicals are produced, with an increase in aromatic hydrocarbons. The carbon distribution in the pyrolysis products mainly focuses on C6-C10 and C11-C15, and many organic compounds such as benzoic acid, phenol, and aniline are generated. Based on density functional theory, the bond dissociation energies in the polyesterimide were calculated. This clarified the possible thermal decomposition pathways of the polyesterimide and provided the energy barrier values, elucidating the generation mechanism of pyrolysis products during thermal decomposition. The copper atom in specific location reduces the negative ESP of O and increases the positive ESP of H in EPI, which makes H more likely to attach to O. The presence of Cu increases the ESP range and promote the pyrolysis process. This study provides a theoretical basis for the high-value recycling of waste polyesterimide enamelled wire.

Keyword ：

Pyrolysis mechanism Density functional theory Polyesterimide enameled wire Pyrolysis Organic coatings

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Abstract ：

Waste liquid crystal display (LCD) panels contain a significant amount of rare precious metal In, and In extraction is also the industry's driving force There are currently many reports on the recovery of In from waste LCD panels, but there are not many on the recovery of organic components from waste LCD panels, particularly polarizing film recovery. Pyrolysis is one of the most promising technologies for organic waste recycling. This work utilized TG, TG-FTIR, and Py-GC/MS to examine the pyrolysis properties and product distribution of the polarizing film. Additionally, a range of kinetic analysis methods and density functional theory calculation were utilized to examine the pyrolysis kinetics and mechanism of the polarizing film. Polarizing film are mainly composed of cellulose triacetate (CTA), triphenyl phosphate (TPHP), polyvinyl alcohol (PVA) and polyacrylate. The results showed that CTA first breaks the glycosidic bond through a synergistic reaction to form an active CTA with a low degree of polymerization, and then forms small molecule compounds such as glucan triacetate analog, methylglyoxal, and allyl benzoate, among others, through free radical reactions. PVA first forms long-chain olefins through a dehydration process, and then short-chain olefins by a free radical reaction. TPHP may merely undergo melting and evaporation rather than undergoing a chemical reaction. Polyacrylate generates esters and aldehydes mainly through free radical reactions. This study provides a theoretical foundation and comprehensive reference for the pyrolysis and recycling of waste LCD panels.

Keyword ：

Polarizing film Reaction mechanisms Density functional theory (DFT) Liquid crystal display (LCD) Pyrolysis

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Abstract ：

In recent years, scientists have become increasingly concerned in recycling electronic trash, particularly waste printed circuit boards (WPCBs). Previous research has indicated that the presence of Cu impacts the pyrolysis of WPCBs. However, there may be errors in the experimental results, as printed circuit boards (PCBs) with copper and those without copper are produced differently. For this experiment, we blended copper powder with PCB nonmetallic resin powder in various ratios to create the samples. The apparent kinetics and pyrolysis properties of four resin powders with varying copper concentrations were compared using nonisothermal thermogravimetric analysis (TG) and thermal pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). From the perspective of kinetics, the apparent activation energy of the resin powder in the pyrolysis reaction shows a rise (0.1 <alpha < 0.2)-stable (0.2 <alpha < 0.4)-accelerated increase (0.4 <alpha < 0.8)- decrease (0.8 <alpha < 0.9) process. After adding copper powder, the apparent activation energy changes more obviously when (0.2 <alpha < 0.4). In the early stage of the pyrolysis reaction (0.1 <alpha < 0.6), the apparent activation energy is reduced, but when alpha = 0.8, it is much higher than that of the resin sample without copper. Additionally, it is discovered using thermogravimetric analysis and Py-GC/MS that copper shortens the temperature range of the primary pyrolysis reaction and prevents the creation of compounds containing bromine. This inhibition will raise the temperature at which compounds containing bromine first form, and it will keep rising as the copper level rises. The majority of the circuit board molecules have lower bond energies when copper is present, according to calculations performed using the Gaussian09 software, which promotes the pyrolysis reaction.

Keyword ：

Copper Kinetic study Pyrolysis Waste printed circuit boards Density functional theory (DFT)

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Abstract ：

The emission of chlorinated pollutants is one of the main problems when recovering copper (Cu) via pyrolysis from waste enameled wires. This is mainly attributed to other wastes which possess high poly(vinyl chloride) content, such as electrical wires and cables, which are often recycled together with enameled copper wires. In this research, to control the chlorinated pollutants, copper(II) oxide (CuO) was chosen and demonstrated to be an efficient dechlorinating agent, and CuO did not introduce any impurities that influence the quality of the recovered Cu. The pyrolysis and co-pyrolysis of polyester enameled wires, PVC, and CuO were investigated, and special attention was paid to chlorinated compounds in released pyrolytic products. In particular, the co-pyrolysis of this ternary mixture was studied for the first time, and some new pyrolysis behaviors were discovered. For example, the results of Py-GC/MS analyses showed that the addition of CuO removed about 75% of the chloro-organic products, the main types of which were chloroaromatic compounds rather than the more toxic chloroesters. Moreover, pyrolysis gases were collected and characterized via ion chromatography, and the results showed that the chlorine content in the pyrolysis gases decreased by about 71%. TG analysis indicated that CuO only minimally affected the pyrolysis of polyester paint. However, through the chlorine fixation effect, CuO influenced the dechlorination and dehydrochlorination of PVC, as well as secondary reactions between HCl and pyrolysis products of polyester paint, therefore changing the products and behaviors of co-pyrolysis. Mechanism of reducing chlorine-containing pollutants and reaction mechanism of forming typical pyrolysis products closely correlated to the effects of CuO were also proposed, providing theoretical guidance for the recycling of waste enameled wires.

Keyword ：

polyvinyl chloride polyester enameled wire dechlorination co-pyrolysis copper(II) oxide

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Abstract ：

For the recovery of enameled wire, pyrolysis is a resource-friendly and effective process. However, because waste enameled wires are typically recovered from e-waste, a minor number of wires and cables are usually present. As a result, co-pyrolysis of the paint film and wire and cable sheaths is inevitable during the pyrolysis recovery of waste enameled wires. Polyethylene terephthalate (PET) polyester enameled wire and polyvinyl chloride (PVC) were chosen as representatives of enameled wire and cable sheath materials, respectively. The pyrolysis characteristics and pyrolysis kinetic parameters of enameled PET (EPET) wire paint, PVC, and Mixture (a mixture of the two materials, mEPET: mPVC = 9:1) were investigated using TG and various kinetic analysis methods. The combined pyrolysis index and Py-GC/MS were used to assess the co-pyrolysis of EPET and PVC and the products. The pyrolysis of EPET is adversely affected by the presence of PVC throughout the process; however, the presence of Cu in EPET may facilitate the HCl removal reaction of PVC. The co-pyrolysis products of EPET and PVC are more complex, and according to the different main functional groups, can be divided into monocyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons, phenols, ketones, aldehydes, alcohols, esters, carboxylic acids, chlorides, and others. Finally, density functional theory calculations were used to explore the co-pyrolysis mechanism of PET and PVC as well as the creation mechanism of various pyrolysis products. The catalytic mechanism of Cu contained in EPET on PET and PVC was explained from the perspective of electrostatic potential. This study provides a theoretical foundation and comprehensive reference for the pyrolysis and recycling of waste enameled wires.

Keyword ：

Reaction mechanisms Pyrolysis Waste enameled wires Density functional theory Polyvinyl chloride

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Abstract ：

Anaerobic digestion generates a significant amount of byproduct known as digestate, necessitating resourceful disposal. However, the digestate biochar may exert certain impacts on the pyrolysis of sludge, especially regarding the release of N/S/Cl during the pyrolysis process. This may lead to environmental risks and impose restrictions on the recycling of digestate. There is limited existing research on this topic. In this study, the impact and mechanism of digestate biochar on pyrolysis products were analyzed through kinetic analysis, TG-MS, and Py-GC/MS, with a specific focus on the release characteristics of polluting elements during the pyrolysis process. The findings indicate that the Fe-containing digestate biochar, owing to the larger specific surface area, richer functional groups and catalytic activity associated with Fe3+, enhances the production of C/H/O gases during pyrolysis while reducing the release of NH3, NO2, and H2S. Particularly, Fe-containing digestate biochar significantly enhances the release of Cl-containing gases. The decrease in tar content indicates that Fe-containing digestate biochar promotes the catalytic removal of tar. A comprehensive comparison and analysis of the reaction mechanism were conducted in this study, providing a theoretical basis for the release of pollutants from digestate pyrolysis while enhancing the control and management of pollutants containing N/S/Cl.

Keyword ：

Digestate biochar Sludge pyrolysis products Anaerobic digestion N/S/Cl

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Abstract ：

Pyrolysis is an effective method for waste tire disposal. However, it has rarely been used to recycle specific highly valuable components (such as benzene, toluene, and xylene (BTX)) from tire rubbers, owing to complicated pyrolytic reactions. This study investigated the pyrolysis process of passenger-car-waste-tires (PCWT) with the help of TG-DTG and Py-GC/MS. Based on response surface methodology (RSM), the effect of pyrolytic parameters on the yields of pyrolytic oil and BTX is evaluated. Furthermore, the BTX generation mechanisms are discussed from the perspective of aliphatic and aromatic hydrocarbon transformations. Additionally, pyrolytic conditions including temperature, rubber particle size, pressure, and gas flow rate were systemically investigated and the optimum pyrolytic condition for yield of BTX (26.5 g per 100 g tire rubber) was obtained [765 K, 0.7 mm, 0.52 MPa and 2.5 mL (g min)-1]. Therein, yield of benzene, toluene and xylene were 1.07, 5.03 and 20.40 g per 100 g tire rubber, respectively. During PCWT pyrolysis, BTX is primarily obtained via the Diels-Alder reactions of small-chain alkenes and transformations of limonene and aromatics. This study elucidates the BTX generation mechanisms during PCWT pyrolysis and clarifies the effects of varying pyrolytic conditions on BTX generation.

Keyword ：

Pyrolysis mechanism Response surface methodology BTX Waste tire

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Abstract ：

The waste light-emitting diode (WLED) is a new type waste electrical and electronic equipment (WEEE). The volume of waste WLEDs is huge and effective recycling and treatment have attracted widespread attention. However, it's difficult to handle the WLED packaging materials in the recycling process because of the complex structure. Few studies have been conducted to analyze the efficient recycling of WLED packaging materials. In this study, the pyrolysis characteristics, pyrolysis kinetics and product composition of light-emitting diode (LED) packaging materials methyl phenyl silicon (MPS) were investigated using TG analysis, kinetic analysis, TG-FTIR analysis and Py-GC/MS analysis. Density functional theory (DFT) calculation was further combined to study the pyrolysis process of MPS. The TG analysis showed that the MPS pyrolysis was divided into two stages: 310-561 degrees C and 499-980 degrees C. The apparent activation energies of MPS pyrolysis were calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods to be 144.68-149.76 kJ center dot mol(-1) (Stage I) and 95.99-105.47 kJ center dot mol(-1) (Stage II), respectively. The pyrolysis kinetic reaction model of MPS was determined by the Coats-Redfern (CR) method: D1 for Stage I, C2 for Stage II. According to the TG-FTIR and Py-GC/MS analysis results, 8 major gaseous products in the MPS pyrolysis process were identified, including CO2, benzene, HCl, biphenyl, chlorobenzene, styrene, ethylbenzene and chlorodimethylphenylsilane. Finally, the formation mechanism of different pyrolysis products was determined by DFT calculation. The pyrolysis characteristics and pyrolysis mechanism of WLED packaging materials may be helpful for the optimization of WLEDs pyrolysis recycling process and the regulation of pyrolysis products.

Keyword ：

Methyl phenyl silicon (MPS) Density functional theory (DFT) Waste light emitting diodes (WLEDs) Pyrolysis Reaction mechanisms

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Abstract ：

Waste enameled copper wire is an important secondary source of copper and often recovered by removing their organic paint layer through pyrolysis. This research focused on studying co-pyrolysis behaviors of poly(ethylene terephthalate) (PET) paint of waste enameled wires, mixed with a small amount of polyvinyl chloride (PVC) which is part of electric wires or cables. The results indicated that mixing PVC with a mass fraction of 10% into enameled PET wire paint (EPET) would significantly affect pyrolysis products, especially the chlorinated compounds, as well as increase energy consumption of the pyrolysis process. TG-FTIR and Py-GC/MS analyses showed that the chlorinated organics were mainly generated in the second stage of pyrolysis. Chloroesters such as terephthalic acid, di(2-chloroethyl) ester were dominant over other chloroorganic compounds, and their formations were attributed to the addition reaction of aromatic vinyl esters with HCl which formed from PVC pyrolysis. It is also worth mentioning that the chemically active acid chlorides including propanoyl chloride and benzoyl chloride were detected in the products, and they were proposed to be formed from the HCl acidolysis of esters that produced from pyrolytic EPET. Besides pyrolysis products, energy consumption of pyrolysis process also was closely correlated to the interactions between pyrolytic PVC and EPET. The average co-pyrolysis activation energy was calculated by Kissinger-Akahira-Sunose (KAS) method and was about 15 kJ/mol higher than that of EPET. These should be consequences of reactions between HCl and EPET. Since PVC is the minority component in the pyrolysis mixture that HCl eliminated from the few PVC was mostly consumed by EPET to form chloroorganic compounds, which negatively influences EPET degradation.

Keyword ：

Polyester enameled wire Polyvinyl chloride Chlorinated organic compounds Co -pyrolysis

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Abstract ：

Recent advancements in renewable energy have enabled a reduction of fossil fuel usage. However, the so-called energy waste, such as end-of-life (EoL) photovoltaic (PV) modules, has become a simultaneous emerging issue in the field of solid waste management. Debonding of ethylene-vinyl-acetate (EVA) copolymer is critical for recycling EoL PV modules. The separation of organic substances may be done effectively using pyrolysis technology. Therefore, in this work we investigated the pyrolysis characteristic and mechanism of EVA. Based on TG, TGFTIR, and Py-GC/MS, the pyrolysis products and pyrolysis characteristics of EVA were examined. Activation energies and reaction mechanisms were determined through iso-conversional model-free and model-fitting methods. Combined with density functional theory (DFT) calculations, the pyrolysis mechanism of EVA was discussed. Our research shows that the pyrolysis technology can almost completely decompose EVA without residue and the EVA pyrolysis can be divided into two stages. Combined with DFT calculation, it was found that in the stage I, acetoxy was removed to generate acetic acid, and in the stage II, the main chain of EVA was broken to generate olefins. The recycling strategy based on two-step pyrolysis of Eol PV modules was accordingly proposed.

Keyword ：

Photovoltaic (PV) Density functional theory (DFT) Recycling Pyrolysis Ethylene -vinyl -acetate (EVA)

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