摘要 ：

Fe-N-C has a high number of FeNx active sites and has thus been regarded as a high-performance oxygen reduction reaction (ORR) catalyst, and combining Fe3C with Fe-N-C typically boosts ORR activity. However, the catalytic mechanism remains unknown, limiting further research and development. In this study, a precipitation-solvothermal process was used in conjunction with pyrolysis to produce a series of Fe-N-C catalysts derived from a zeolitic imidazolate framework (ZIF) that was composited with Fe3C. The prepared catalysts had a multiscale structure of ZIF-like carbon particles and rod-like structures, as well as bamboo-like carbon nanotubes (CNTs) and carbon layers wrapped with Fe3C particles while a series of studies revealed the origin of the rod-like structures and Fe3C phase. The hierarchical structure was beneficial to the enhanced electrocatalytic performance of catalysts for ORR. The optimal sample had the highest half-wave potential of 0.878 V vs. RHE, which was higher than that of commercial Pt/C (0.861 V vs. RHE). The ECSA of the optimal sample was 1.08 cm(2) mu g(-1), with an electron transfer number close to 4, and functioning kinetics. The optimal sample exhibited high durability and methanol tolerance for the ORR. Finally, blocking different Fe active sites with coordination ions demonstrated that Fe(ii) was the main active site, indicating that Fe3C primarily served as a cocatalyst to optimize the electron structure of Fe-N-C, thereby synergistically improving the ORR activity.

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Removal of steroid hormones from aqueous environment is of prevailing concern because of their adverse impact on organisms. Using biochar derived from biomass as adsorbent to remove pollutants has become more popular due to its low cost, effectiveness, and sustainability. This study evaluated the feasibility of applying corn straw biochar (CSB) and dewatered sludge biochar (DSB) to reduce 17 beta-estradiol (E2) from aquatic solutions by adsorption. The experimental results showed that the adsorption kinetics and isotherm behavior of E2 on the two biochars were well described by the pseudo-second-order (R-2 > 0.93) and Langmuir models (R-2 > 0.97). CSB has higher E2 adsorption capacity than DSB, and the maximum adsorption capacity was 99.8 mg/g obtained from Langmuir model at 298 K, which can be attributed to the higher surface area, porosity, and hydrophobicity of this adsorbent. Higher pH levels (>10.2) decreased the adsorption capacities of biochar for E2, while the ionic strength did not significantly affect the adsorption process. The regeneration ability of CSB was slightly better than that of DSB. The possible adsorption mechanism for E2 on biochar is suggested as pi-pi interactions, H-bonding, and micropores filling. These results indicated that CSB has more potential and application value than DSB on reducing E2 from aqueous solutions when considering economy and removal performance.

关键词 ：

adsorption 17 beta-estradiol sludge pyrolysis biochar

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Plastics are now essential components in our daily life, but they have also raised a waste crisis and environmental pollution issues. The traditional plastic waste treatments rely on high-energy input and are environmentally unfriendly. The emergence of nanocatalyzed chemical upcycling of plastic waste approaches, aiming to convert wastes to value-added chemicals, is encouraging and may enable a circular-plastics economy. Thus, in this Review, we first briefly summarize the background of the plastic waste treatments by introducing the most common plastic types and the traditional treatment methods. We then review the chemical upcycling of plastics in terms of nanocatalyzed pyrolysis, pyrolysisgasification, solvolysis, hydrocracking and the light/electrochemical-induced processes from a historical account to recent achievements. Coordination chemistry aspects are emphasized in these processes, particularly in the plastics depolymerization mechanism. Emphasis is placed on highlighting the encouraging results recently obtained, especially on the rational design of nanocatalysts with tunable active metals, size, support, and coordination environments for improved catalytic performances. Indications towards further research and applications for value-added products synthesis are also proposed. In addition, some other emerging technologies for waste plastic treatments are introduced. Finally, perspectives for further developments towards a circular-plastic economy are highlighted.(c) 2022 Published by Elsevier B.V.

关键词 ：

Circular plastic economy Nanocatalysts Coordination Chemical upcycling Plastic wastes

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Fe-N4 single-atom catalysts (SACs) have been investigated extensively in various energy conversion reaction. However, large amount of untouchable Fe-N4 sites buried in the dense carbon skeletons greatly restrict the maximization of catalytic performance. Therefore, rational construction of catalyst nanostructure to effectively expose Fe-N4 single atom sites is eagerly desired. Here, we report a one-step gradient pyrolysis method by using quaternary ammonia polysulfone (QAPS) polymer with a lower carbonization temperature to segregate precursor particles (ZIF-8 and polyaniline) to construct mesopores at 4-9 nm, thereby tellingly increasing the accessibility of Fe-N4 single atom sites. Nitrite reduction method revealed that the prepared catalyst had a three-fold increase in active sites density compared to catalyst without QAPS. Thus, it exhibits a terrific peak power density (1.15 W cm-2) in proton exchange membrane fuel cells and a superior CO partial current density (121 mA cm-2) with 99 % Faradaic efficiency for CO at 0.5 V in flow cells.

关键词 ：

the Fe -N 4 sites utilization CO 2 electroreduction Proton exchange membrane fuel cells Fe -N 4 single atoms

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The pyrolysis of passenger-car-waste-tires (PCWT) has recently attracted widespread attention because it is a highly effective disposal method. However, a comprehensive understanding of real tire pyrolytic processes is limited owing to the complicated PCWT pyrolysis reaction system, particularly regarding the reaction mechanism. This study investigated the PCWT pyrolytic processes using a thermogravimetric analyzer coupled with mass spectrometry and analyzed all the pyrolytic products using pyrolysis-gas chromatography coupled with mass spectrometry. The composition and distribution of the PCWT pyrolytic products were investigated under a kinetic regime to eliminate other influences on the intrinsic reaction. The pyrolytic products mainly consisted of chain and cyclic alkenes, and monocylic aromatics. Importantly, an integral pyrolytic mechanism network for the PCWT was established based on the pyrolysis of single rubbers (natural, styrene butadiene, and butadiene rubbers). The reaction routes for the main products were determined according to the mechanism. Moreover, a kinetic study of the PCWT pyrolysis revealed the activation energy for this complicated reaction system.

关键词 ：

Mechanism network Rubber pyrolysis Kinetics regime Activation energy

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LiCoO2 (LCO) lithium-ion battery (LIB) is rich in valuable metals (cobalt and lithium), which has high recycling value. The existing process has basically realized the extraction of cobalt, but there are still shortcomings in harmless disposal of fluorine-containing electrolyte, binder and other organic matters, selective extraction of lithium and low-cost extraction of cobalt. In this context, a novel process was developed to realize the full-component recovery of spent LiCoO2 battery via environmentally friendly pyrolysis and hydrometallurgical leaching. The organic matters were recovered in the form of pyrolytic oil and gas, in which the harmful fluorine element was absorbed by Ca(OH)(2) solution. The current collectors (copper and aluminum) were recovered after the easy separation of electrode materials due to the degradation of binders. During pyrolysis the cathode material was deconstructed and reduced under the synergistic effect of pyrolytic gas and anode graphite. Selective recovery of lithium and cobalt was achieved through carbonated water leaching and reductant-free acid leaching. The leaching efficiencies of lithium and cobalt were respectively 87.9% and 99.1% under the optimal conditions. Lithium carbonate and cobalt sulfate were obtained by evaporative crystallization, respectively. The remaining residue was only graphite without impurity entrainment. The results in this research suggest that the process consisting of pyrolysis and hydrometallurgical leaching is inexpensive, efficient, and eco-friendly for full-component recycling of spent LiCoO2 battery.

关键词 ：

Carbonated water leaching Spent LiCoO2 lithium-ion battery Reductant-free acid leaching Reduction Full-component pyrolysis

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With the rapid growth in the number of passenger cars (PCs) in China over the past decades, more than ten million tons of used tires have already become solid wastes and subsequently caused serious environmental issues. Due to the presence of synthetic rubber in PC tires, waste PC tires cannot be disposed through rubber reclaiming technology. Thus, waste PC tires have become one of fastest growing solid wastes in China. First, the current disposal capacity of the pyrolysis method, regarded as a promising technology for the disposal of waste PC tires, is surveyed and compared with other disposal methods mentioned in previous papers. Second, this work establishes a model to predict the total number of waste PC tires in the next five years depending on the rate of PC growth and current waste tire disposal capacity. Moreover, pyrolysis is evaluated on 15 collected waste PC tires selected from the most representative tire brands in the Chinese market. The corresponding results imply that similar to 68.5% of S was into oil and similar to 44.3% N and large amount of heavy metals resided in solid carbon which severely limit further applications. Finally, a new pyrolysis technology is introduced that may represent a solution to the limits in the application of tire disposal methods and relief for the coming waste tire crisis. (c) 2021 Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.

关键词 ：

Pyrolysis Waste PC tire Disposal method Disposal capacity

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To solve the poor fireproof performance of plant fibers, one of the technical difficulties, and use more straw fibers as construction materials, wheat straw fibers (WSFs) have been subject to flame-retardant modification. Then, tests and analysis over the modified WSFs per the burning behavior and pyrolysis performance have been made. The physical and mechanical, and thermal insulation properties of wheat straw fiber cement-based composites (WSFCC) at high temperatures were characterized. The results are as follows: Ammonium polyphosphate (APP), magnesium hydroxide (MH), and aluminum hydroxide (ATH), three fire retardants, all affect the chemical structure of WSFs. P, Mg, and Al elements of the three retardants are successfully adsorbed onto the fibers' surface subject to modification. Flame-retardant WSFs significantly outperforms the non-flame-retardant ones per thermostability and flame retardancy. The heat release rate (HRR), total heat release (THR), effective heat of combustion (EHC), and mass loss rate (MLR) of most flame-retardant WSFs are obviously lower than those of non-flame-retardant ones. The APP-modified WSFs demonstrate higher total smoke production (TSP), while WSFs modified with composite flame retardants perform better in flame retardancy and smoke suppression. The MLR of WSFCC at high-temperature increases as the temperature goes higher. The compressive and flexural strengths of WSFCC decrease with the increase of temperature and the decrease mitigates after 350 degrees C. In terms of thermal conductivity, composite-flame-retardant fiber WSFCC are much higher than non-flame-retardant fiber and APP-modified fiber WSFCC. As the temperature rises, the thermal conductivity of composite-flame-retardant fiber WSFCC tends to decrease. (C) 2021 The Authors. Published by Elsevier B.V.

关键词 ：

Flame retardant modification Properties Wheat straw fiber High temperature Cement-based composite material

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Phosphorus is an indispensable element, while the existing phosphate rock resources are not enough to maintain the long-term demand of modern agricultural development. To ensure the sustainability of economic and social, it is necessary and urgent to seek the alternative phosphorus source of phosphate rock. In this study, calcined clam shell powder (CSP) was firstly used as a modifier and mixed with sewage sludge (SS) for co-pyrolysis to obtain sludge-derived pyrochars containing a large amount of bioavailable phosphorus. The effect of different temperatures (500, 600, 700, 800 degrees C) and dosages (0%, 10%, 20%, 30%) on the change in the form of phosphorus during the pyrolysis process were investigated. With the increase of temperature and the addition of CSP, the orthophosphate (Ortho-P) increased from 63.69% in the original SS to nearly 100%. Furthermore, the main phase of inorganic phosphorus (IP) changed, mainly in the form of apatite phosphorus (hydroxyapatite increased from 8.88% to 35.97%), and the concentration of easy-to-lose phosphorus reduced to 0.11 mg/g. After co-pyrolysis of SS with CSP, the passivation situation of heavy metals (HMs), such as Zn, Mn, Cr, Cu, Cd and Pb was significantly improved, thus reducing the potential environmental risk. The planting experiment proved that the sludge-derived pyrochars obtained by adding 20% CSP at 800 degrees C promoted the germination of seeds and the growth of seedlings. Consequently, the product of SS co-pyrolysis with CSP could be used as an excellently bioavailable and environmentally friendly phosphate fertilizer for agricultural production. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词 ：

Calcined clam shells Co-pyrolysis Heavy metals Phosphorus bioavailability Sewage sludge

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Wide application of NCM (LiNixCoyMnzO2) lithium-ion batteries (LIBs) for electric vehicles indicates their high scrap amount in the near future. Thus, spent NCM LIBs must be recycled from the economic and environment viewpoint. In this context, a novel process was developed to achieve efficient extraction of valuable metals and harmless treatment of organics in NCM LIBs through full-component pyrolysis. Organic substances, such as a separator and a binder, were recovered in the form of pyrolytic oil and gas, whereas the cathode material was simultaneously dissociated and reduced, realizing the subsequent extraction of valuable metals by acid leaching without a reducing agent. The leaching efficiencies of lithium, nickel, cobalt, and manganese were over 99.5% under optimum conditions: a pyrolysis temperature of 450 degrees C, a pyrolysis time of 60 min, and a nitrogen flow rate of 100 mL/min. In addition, the reduction mechanism of the cathode material was investigated by experimental design and analysis of pyrolytic gas.

关键词 ：

full-component pyrolysis recovery of metals reduction of cathode powder spent NCM lithium-ion battery

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