Pyrolysis kinetic study of cathode material derived from spent lithium ion batteries (LIBs): Comparison of different models.

Separating cathode material and Al foil from spent lithium-ion batteries (LIBs) is a critical step for LIBs recycling. As compared to chemical dissolving and decomposition, the pyrolysis pretreatment is an alternative and simple method. In this work, the pyrolysis kinetics of cathode material were comparatively studied using various isoconversional methods, including Flynn-Wall-Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose, Starink, Tang, and Boswell. The thermal degradation mechanism was investigated by the Coats-Redfern (CR) and master-plot methods as well. The thermogravimetric analysis revealed that cathode material decomposition could be divided into three stages with mass losses of 1.51%, 0.787%, and 0.449%, respectively. Activation energy (Eα) calculated using the six model-free methods showed a similar trend, gradually increasing as the degree of conversion (α) increased from 0.001 to 0.009, and then significantly elevating. The FWO method gave the best fitting and Eα values first increased from 12.032 to 24.433 kJ·mol-1 with α elevating from 0.001 to 0.009, then increased further to 43.187 kJ·mol-1. Both CR and Criado methods indicated that the degradation of cathode material can be explained by the diffusion models.Implications: The rapid growth in the production and consumption of lithium-ion batteries (LIBs) for portable electronic devices and electric vehicles has resulted in an increasing number of spent LIBs. Thermal treatment offers advantages of high-efficiency and simple operation. Understanding the thermal process of spent LIBs and probing its kinetic are significant for the large-scale treatment. Through this study, it will be significant for the reactor designing and optimizing in practice.

Pyrolysis characteristics of cathode from spent lithium-ion batteries using advanced TG-FTIR-GC/MS analysis.

Thermal treatment offers an alternative method for the separation of Al foil and cathode materials during spent lithium-ion batteries (LIBs) recycling. In this work, the pyrolysis behavior of cathode from spent LIBs was investigated using advanced thermogravimetric Fourier transformed infrared spectroscopy coupled with gas chromatography-mass spectrometer (TG-FTIR-GC/MS) method. The fate of fluorine present in spent batteries was probed as well. TG analysis showed that the cathode decomposition displayed a three-stage process. The temperatures of maximum mass loss rate were located at 470 °C and 599 °C, respectively. FTIR analysis revealed that the release of CO2 increased as the temperature rose from 195 to 928 °C. However, the evolution of H2O showed a decreasing trend when the temperature increased to above 599 °C. The release of fluoride derivatives also exhibited a decreasing trend, and they were not detected after temperatures increasing to above 470 °C. GC-MS analysis indicated that the release of H2O and CO displayed a similar trend, with larger releasing intensity at the first two stages. The evolution of 1,4-difluorobenzene and 1,3,5-trifluorobenzene also displayed a similar trend-larger releasing intensity at the first two stages. However, the release of CO2 showed a different trend, with the largest release intensity at the third stage, as did the release of 1,2,4-trifluorobenzene, with the release mainly focused at the temperature of 300-400 °C. The release intensities of 1,2,4-trifluorobenzene and 1,3,5-trifluorobenzene were comparable, although smaller than that of 1,4-difluorobenzene. This study will offer practical support for the large-scale recycling of spent LIBs.

Kinetic study on the slow pyrolysis of nonmetal fraction of waste printed circuit boards (NMF-WPCBs).

In this study, the pyrolysis behaviour of nonmetal fraction of waste printed circuit boards (NMF-WPCBs) was studied based on five model-free methods and distributed activation energy model (DAEM). The possible decomposition mechanism was further probed using the Criado method. Thermogravimetric analysis indicated that the NMF-WPCBs pyrolysis process could be divided into three stages with temperatures of 37-330°C, 330-380°C and 380-1000°C. The mass loss at different heating rate was determined as 26.85-29.98%, 13.47-24.21% and 20.43-23.36% for these stages, respectively. The activation energy (Eα) from various model-free methods first increased with degree of conversion (α) increasing from 0.05 to 0.275, and then decreased beyond this range. The coefficient (R) from the Flynn-Wall-Ozawa (FWO) method was higher, and the resulting Eα fell into the range of 214.947-565.660 kJ mol-1. For the DAEM method, the average Eα value was determined as 337.044 kJ mol-1, comparable with 329.664 kJ mol-1 from the FWO method. The thermal decomposition kinetics of NMF-WPCBs could be better described by the second-order reaction.

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.

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°C, 578-849°C, and 849-1000°C. The activation energy (Eα) 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 Eα 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.

Geochemical Evidence of Metal-Driven Anaerobic Oxidation of Methane in the Shenhu Area, the South China Sea.

Anaerobic oxidation of methane (AOM) is a common biochemical process in the ocean and it plays an important role in global climate change, elemental circulation, and atmospheric evolution over geological time. In this paper, we analyzed of δ34S, Fe, Mn, Ca/Ti, and Sr/Ti ratios, and the date of carbon and sulfur from the site SH3 of Shenhu area. Result showed that (1) 0-6 mbsf (meter blow the sea floor) was mainly affected by OSR (anaerobic oxidation of organic matters) and 7-15 mbsf was a paleo-SMTZ (sulfate-methane transition zone) position. The modern SMTZ was mainly distributed at 19-25 mbsf. The barium sulfate precipitation above the modern SMTZ indicating that the current methane leakage was stable and lasted longer during geological history. (2) By studying the change of magnetic and the different carbonate minerals, results showed that there were two AOM stages. During the early stage, Fe2+ were mainly produced by sulfide abiotic reductive dissolution. During the later stage, Fe2+ were mainly produced by the metal-AOM. (3) Study of the mineral characteristics of the paleo-SMTZ and the modern SMTZ showed that the modern SMTZ carbonate minerals were mainly low-Mg calcite and aragonite, while the paleo-SMTZ carbon minerals were mainly high Mg minerals. The reason for this difference is that the modern SMTZ layer was only experienced the first stage of anaerobic oxidation of methane. In the paleo-SMTZ layer, it has experienced two stage of anaerobic oxidation of methane. During the last stage of metal-AOM, the low Mg carbonate minerals were converted into high Mg carbonate minerals. This research confirms the presence of metal-driven methane anaerobic oxidation at the bottom of sulfate-driven methane anaerobic oxidation and during the metal-driven methane anaerobic oxidation, methane and metal oxides or hydroxides would couple to convert the in situ metal oxides or hydroxides into metal ions, meanwhile the phosphorus adsorbed on the surface of the metal oxides is released into adjacent pore water, and convert to new P-bearing minerals under suitable conditions.

A critical review of cast-off crab shell recycling from the perspective of functional and versatile biomaterials.

Shellfish cultivation is an expanding economic activity worldwide. However, the rapid development of crab farming and processing result in a large number of crab shells (CS). Utilizing CS could not only benefit the environment and economy but also promote the sustainable development of aquaculture. In this work, it reviews and analyzes recent attempts in CS recycling, including extracting chitin and its derivatives, for use as adsorbent and flocculant and for preparing polymer composites and catalysts, as well as medical applications. The challenges in these utilizations are discussed, and future research directions are proposed as well. Extracting chitin and its derivates, for use as adsorbent and flocculant, are recent major recycling approaches. Preparing polymer composites and carbon materials has gained more and more attentions. Biotechnology is an alternative method for extracting chitin and its derivates from CS, and high-efficiency desalted and deproteinized bacteria need to be screened. Immobilizing the CS-based adsorbents is the key of treating wastewater in continuous systems. Using CS as a biofiller to prepare polymer composites is promising, and surface modification to improve the interfacial compatibility between CS-based fillers and matrix needs to be further studied.

Characteristics of Authigenic Minerals around the Sulfate-Methane Transition Zone in the Methane-Rich Sediments of the Northern South China Sea: Inorganic Geochemical Evidence.

Sediments at marine cold seep areas provide potential archives of past fluid flow, which allow insights into the evolution of past methane seepage activities. However, signals for anaerobic oxidation of methane (AOM) might be obscured in bulk sediments in cold-seep settings due to several factors, especially flood and turbidite deposition. Comprehensive inorganic data were gathered in this study to explore the availability of related records at cold seeps and to provide insights into the evolution of past methane seepage activities. Sediments collected from the site 973-4 in the Taixinan Basin on the northern slope of the South China Sea were characterized in terms of total carbon and sulfur, δ13C values of total organic carbon (δ13CTIC), δ34S values of chromium reducible sulfur (δ34SCRS), and foraminiferal oxygen and carbon isotopes. The results confirmed a strong correlation between formation of authigenic minerals and AOM. Moreover, the 34S enrichments and abundant chromium reducible sulfur (CRS) contents in the authigenic sulfides in the sulfate-methane transition zone (SMTZ) within 619-900 cm below seafloor (cmbsf) reflected past high methane fluxes supported by constant methane seepages. Lithological distribution and AMS (Accelerator Mass Spectra) 14C dating of planktonic foraminifera show that the turbidite (~35.14 ka) was related to a foraminifera-rich interval (Unit II: 440-619 cmbsf) and increased carbonate productivity during the last glacial maximum (LGM). Enrichment of Mo and U was observed accompanied by low contents of nutrient metals (Al, Ti, V, Ni, Fe, Mn, and Cu) in Unit II. The foraminifera-rich interval (Unit II) of cold seep sediments was probably linked to the phenomenon of inconsecutive sedimentary sequence due to the turbidites, which resulted in the lack of Fe, Mn, and Ba enrichment. There is no U enrichment but only Mo enrichment within Unit III, which might be related to H2S produced by AOM during the methane seepages. Based on the above results, it can be speculated that this area has experienced multiple-episodes of methane seep events. Further exploration of AOM should focus on the risks of rapid deposition, especially the impact of turbidity current on sediments.

Thermal treatment of flame retardant plastics: A case study on a waste TV plastic shell sample.

In this work, the combustion and pyrolysis characteristics of a waste TV plastic shell sample were investigated using a powerful Thermogravimetric-Fourier Infrared Spectrum-Mass Spectrum (TG-FTIR-MS) technique. The decomposition mechanisms of plastic waste and fate of bromines in both thermal processes were probed as well. The TG analysis revealed that the combustion rate was larger than that of pyrolysis at temperature of 456 °C below, whereas it decreased at temperature of 456-605 °C. As a result, the total weight loss was equivalent at temperature of 605 °C for both processes. The FTIR analysis indicated the plastic combusted vigorously at 300-500 °C and 800-900 °C. As a comparison, it decomposed drastically at 300-400 °C and 500-900° in pyrolysis. The MS analysis showed that the release of brominated products HBr, CH3Br, C2H5Br, C3H5Br, C3H7Br and C3H5BrO increased with an increase of temperature and reached maximum at 400-600 °C in both thermal processes. The release intensities of larger molecules C6H5Br, C6H5BrO and C6H4Br2 were in the descending order of C6H5Br > C6H4Br2 > C6H5BrO. It was not significant in the evolved products and decomposition pathway for both thermal processes. The entire decomposition of TV plastic shell sample could be divided into three stages, taking account of the evolved products. The backbone in acrylonitrile butadiene styrene resin and tetrabromobisphenol A first broke at 350 °C below, resulting in the form of 2-bromophenol, styrene, acrylonitrile and polybutadiene. Subsequently, the resulted 2-bromophenol debrominated forming HBr, which further reacted with hydrocarbons resulting in various brominated derivates. In addition, many small molecules, including CO2, CO and CH4 were generated in this stage. Further increasing temperature to 550 °C above, larger brominated derivates decomposed and smaller molecules predominated.

Experimental and Numerical Simulation of the Formation of Cold Seep Carbonates in Marine Sediments.

Cold seep emissions of low temperature fluid from the marine sediment basins are mainly comprised of methane and other hydrocarbons. A series of biogeochemical processes related to methane lead to the formation of authigenic carbonate minerals. In this study, a self-built experimental device was used to study the formation process of carbonate minerals under cold seep conditions. The concentrations of pore water chemicals, HCO3- and Ca2+ at different heights of the reactor under flow conditions can be observed. According to the experimental results, the formation process of carbonate minerals under cold seep conditions was estimated, that 1 m carbonate growth needs 12,000 and 7000 years, respectively, under fast (5 mL·min-1) and slow emission (1 mL·min-1) conditions. Furthermore, TOUGHREACT was used to simulate the diagenesis process. A 1D unsteady react-transport model was developed, and the experimental data was used to constrain the simulation. The results of simulation show that the carbonates need 17,000 and 9700 years to grow 1 m under the condition of fast and slow flow scenarios, respectively. The results of this work will contribute to the study of foundation on the formation of authigenic minerals in cold seep areas, and for the physical properties of sedimentary media as well.

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°C) and pressure (0.47-1.01bar) with n(SiO2/Al2O3)=2.0. At the temperature of 110°C (pressure 1.43bar), 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 6h at n(SiO2/Al2O3)=1.5. By comparison, crystallization phases were observed only when the time was longer than 8h at n(SiO2/Al2O3)=2.0.

[Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.