Pyrolysis treatment of nonmetal fraction of waste printed circuit boards : Focusing on the fate of bromine

Advanced thermal treatment of electronic waste offers advantages of volume reduction and energy recovery. In this work, the pyrolysis behaviour of nonmetallic fractions of waste printed circuit boards was studied. The fate of a bromine and thermal decomposition pathway of nonmetallic fractions of waste printed circuit boards were further probed. The thermogravimetric analysis showed that the temperatures of maximum mass loss were located at 319°C and 361°C, with mass loss of 29.6% and 50.6%, respectively. The Fourier transform infrared Spectroscopy analysis revealed that the spectra at temperatures of 300°C–400°C were complicated with larger absorbance intensity. The nonmetallic fractions of waste printed circuit boards decomposed drastically and more evolved products were detected in the temperature range of 600°C–1000°C. The gas chromatography–mass spectrometry analysis indicated that various brominated derivates were generated in addition to small molecules, such as CH4, H2O and CO. The release intensity of CH4 and H2O increased with temperature increasing and reached maximum at 600°C–800°C and 400°C–600°C. More bromoethane (C2H5Br) was formed as compared with HBr and methyl bromide (CH3Br). The release intensity of bromopropane (C3H7Br) and bromoacetone (C3H5BrO) were comparable, although smaller than that of bromopropene (C3H5Br). More dibromophenol (C6H4Br2O) was released than that of bromophenol (C6H5BrO) in the thermal treatment. During the thermal process, part of the ether bonds first ruptured forming bisphenol A, propyl alcohol and tetrabromobisphenol A. Then, the tetrabromobisphenol A decomposed into C6H5BrO and HBr, which further reacted with small molecules forming brominated derivates. It implied debromination of raw nonmetallic fractions of waste printed circuit boards or pyrolysis products should be applied for its environmentally sound treating.© 2020 Sage. The article is protected by copyright and reuse is restricted to non-commercial and no derivative uses. Users may also download and save a local copy of an article accessed in an institutional repository for the user's personal reference.fi=vertaisarvioitu|en=peerReviewed

Surface free energy and mechanical performance of LDPE/CBF composites containing toxic-metal free filler

Heavy-metal contamination in children's toys is a widespread problem, and the international community has issued a series of safety standards to restrict and control the use of toxic metals in toys. In this work, a colored filler (CBF) was prepared using pearl oyster shell (POS) as the green raw material and azo dye as the colorant. Its surface properties were subsequently studied in comparison to those of POS powder using the inverse gas chromatography method. The dispersion surface free energy profiles for both CBF and POS showed that this component contributed the major part (> 70%) to the total surface free energy. The CBF possessed lower polar surface free energy and was relatively more hydrophobic. It also showed a lower thermodynamic work of cohesion, allowing its better dispersion in a low density polyethylene (LDPE) matrix. Mechanical performance studies showed that adding CBF could significantly increase the tensile strength, elastic modulus, flexural strength and flexural modulus of LDPE composites. The absence of toxic metals coupled with excellent mechanical performance makes the CBF an ideal candidate as a filler for children's toys fabrication.The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (Grant nos. 51606055 and 41373121) and Zhejiang Provincial Natural Science Foundation of China (Grant no. LY14D010009).info:eu-repo/semantics/publishedVersio

Editorial for the Special Issue on the Environmentally Friendly Management and Treatment of Solid Waste to Approach Zero Waste City

Cities around the world are expanding rapidly, taking up vast resources (e [...

The Resource Utilization of Water Hyacinth (Eichhornia crassipes [Mart.] Solms) and Its Challenges

The unchecked growth of Eichhornia crassipes can cause significant harm, including covering of the water surface, depletion of oxygen, clogging of river channels, and promotion of the breeding of flies and mosquitoes. These effects can significantly impact farmland irrigation, water transportation, and human health. However, methods for controlling its growth are not ideal, and control using biological and chemical agents can result in secondary pollution. The utilization of E. crassipes as a resource, for example, as animal feed or organic substrates, can not only turn waste into valuable resources, but it can also solve the problem of its growth, thus bringing about economic and ecological benefits. In this paper, the growth and ecological characteristics of E. crassipes, its nutrient composition, and resource utilization approaches were reviewed. The challenges associated with the large-scale utilization of E. crassipes were also analyzed in order to provide references for the control and resource utilization of the species. Regarding challenges such as the difficulty of cultivation and the high cost of harvesting and dehydrating, it is necessary to investigate the proper water surface and coverage characteristics of E. crassipes cultivation to assure adequate biomass and protect the ecological landscape. It is also necessary to evaluate the effect of E. crassipes cultivation on the health of aquatic ecosystems and the safety of the water environment in order to prevent the significant potential ecological and environmental risks. In addition, developing portable, high-efficiency facilities to promote the effectiveness of harvesting, transportation and dehydration are needed, as well as further improvement in the techniques of utilization and assessment of the economic value

Performance, emission and combustion characteristics of liquid fuel produced through catalytic co-pyrolysis of waste LDPE and Pongamia pinnata seeds: An experimental investigation in CI engine

As there is an urgent need to address the global problem of increasing plastic waste and decreasing petroleum-based fuels, it is possible to convert waste plastic and unused biomass seeds into fuels that can be utilized in transportation sector. The current study deals with blending pure diesel (D100) with the liquid fuel (PB2) obtained from the co-pyrolysis of Pongamia pinnata seeds and waste low-density polyethylene (LDPE) with Calcium oxide (CaO) as the catalyst. Three blends of D100, namely, PB2@10 (with 10 % blend), PB2@20 (with 20 % blend) and PB2@30 (with 30 % blend) were tested for performance, emission and combustion in an unmodified CI engine for an analytical comparative analysis using standard methods. The results showed that the BSFC was almost same (0.3 kg/kWh) at higher loads for all three blends, while the BTE was found to be equal or increased compared to D100 in the range of 27–30 % at higher loads for higher blends. NOx formation was found to decrease by 19.4 % and 13 % at the highest load for PB2@30 andPB2@30. The smoke formation also decreased for all blends (maximum 22.5 %) while the maximum difference of lambda was determined to have decreased in comparison to D100, close to 1 at higher loads. The maximum cylinder pressure and temperature were also found to have increased during combustion by approximately 1 % for PB2@10 while that of PB2@20 and PB2@30 remained quite close to D100. The obtained renewable liquid fuel could certainly be utilized in blends with pure diesel for use in vehicles

Kinetic modeling study on the combustion treatment of cathode from spent lithium-ion batteries

Thermal treatment offers an alternative method for the separation of aluminum foil and cathode materials during spent lithium-ion batteries recycling. In this work, the combustion kinetic of cathode was studied based on six model-free (isoconversional) methods, namely Flynn-Wall-Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose, Starink, Tang, and Boswell methods. The possible decomposition mechanism was also probed using a master-plots method (Criado method). Thermogravimetric analysis showed that the whole thermal process could be divided into three stages with temperatures of 37-578 degrees C, 578-849 degrees C, and 849-1000 degrees C. The activation energy (E alpha) derived from these model-free methods displayed the same trend, gradually increasing with a conversion range of 0.002-0.013, and significantly elevating beyond this range. The coefficients from the FWO method were larger, and the resulted E alpha fell into the range of 10.992-40.298 kJ/mol with an average value of 20.228 kJ/mol. Comparing the theoretical master plots with an experimental curve, the thermal decomposition of cathode could be better described by the geometric contraction models

Comparative study on the pyrolysis kinetics of polyurethane foam from waste refrigerators

Thermal treatment offers advantages of significant volume reduction and energy recovery for the polyurethane foam from waste refrigerators. In this work, the pyrolysis kinetics of polyurethane foam was investigated using the model-fitting, model-free and distributed activation energy model methods. The thermogravimetric analysis indicated that the polyurethane foam decomposition could be divided into three stages with temperatures of 38 degrees C-400 degrees C, 400 degrees C-550 degrees C and 550 degrees C-1000 degrees C. Peak temperatures for the major decomposition stage (-1, respectively. The activation energy (Ealpha) from the Friedman, Flynn-Wall-Ozawa and Tang methods increased with degree of conversion (alpha) in the range of 0.05 to 0.5. The coefficients from the Flynn-Wall-Ozawa method were larger and the resulted E alpha values fell into the range of 163.980-328.190 kJ mol-1 with an average of 206.099 kJ mol-1. For the Coats-Redfern method, the diffusion models offered higher coefficients, but the E values were smaller than that from the Flynn-Wall-Ozawa method. The E alpha values derived from the distributed activation energy model method were determined as 163.536-334.231 kJ mol-1, with an average of 206.799 kJ mol-1. The peak of activation energy distribution curve was located at 205.929 kJ mol-1, consistent with the thermogravimetric results. The Flynn-Wall-Ozawa and distributed activation energy model methods were more reliable for describing the polyurethane foam pyrolysis process

Kinetic studies on the pyrolysis of plastic waste using a combination of model-fitting and model-free methods

In this work, the pyrolysis behavior of plastic waste-TV plastic shell-was investigated, based on thermogravimetric analysis and using a combination of model-fitting and model-free methods. The possible reaction mechanism and kinetic compensation effects were also examined. Thermogravimetric analysis indicated that the decomposition of plastic waste in a helium atmosphere can be divided into three stages: the minor loss stage (20-300 degrees C), the major loss stage (300-500 degrees C) and the stable loss stage (500-1000 degrees C). The corresponding weight loss at three different heating rates of 15, 25 and 35 K/min were determined to be 2.80-3.02%, 94.45-95.11% and 0.04-0.16%, respectively. The activation energy (E-a) and correlation coefficient (R-2) profiles revealed that the kinetic parameters calculated using the Friedman and Kissinger-Akahira-Sunose method displayed a similar trend. The values from the Flynn-Wall-Ozawa and Starink methods were comparable, although the former gave higher R-2 values. The E-alpha values gradually decreased from 269.75 kJ/mol to 184.18 kJ/mol as the degree of conversion (alpha) increased from 0.1 to 0.8. Beyond this range, the E-alpha slightly increased to 211.31 kJ/mol. The model-fitting method of Coats-Redfern was used to predict the possible reaction mechanism, for which the first-order model resulted in higher R-2 values than and comparable E-alpha values to those obtained from the Flynn-Wall-Ozawa method. The pre-exponential factors (lnA) were calculated based on the F1 reaction model and the Flynn-Wall-Ozawa method, and fell in the range 59.34-48.05. The study of the kinetic compensation effect confirmed that a compensation effect existed between E-a and lnA during the plastic waste pyrolysis

Recycling of typical difficult-to-treat e-waste: Synthesize zeolites from waste cathode-ray-tube funnel glass

The disposal of waste cathode ray-tubes (CRTs) from old televisions and discarded computer monitors has become a major environmental concern worldwide. In this work, an open-loop recycling method was developed to synthesize zeolites using CRT funnel glass as the raw material. The effects of hydrothermal temperatures and pressure, n(SiO2/Al2O3) molar ratios and hydrothermal time on the resulting products were investigated. The results indicated that hydrothermal temperatures and pressure played critical roles in zeolite synthesis. Amorphous phases were detected at lower temperatures (80-100 degrees C) and pressure (0.47-1.01 bar) with n(SiO2/Al2O3)=2.0. At the temperature of 110 degrees C (pressure 1.43 bar), NaA formed with a mixture of NaP1 and Faujasite. With further increase in the temperature and pressure, the unstable NaA and Faujasite disappeared, and Hydroxysodalite developed. The influence of n(SiO2/Al2O3) ratios on resulting products revealed a single phase of NaA was formed at the ratio of 1.5 and a mixture of NaA and Faujasite at the ratio of 2.0. Prolonging hydrothermal time, however, could promote zeolite crystallization, and NaA gradually developed with an increase in the time from 2 to 6 h at n(SiO2/Al2O3)=1.5. By comparison, crystallization phases were observed only when the time was longer than 8 h at n(SiO2/Al2O3)=2.0. (C) 2016 Published by Elsevier B.V