Abstract ：

The current study aims to investigate the effects of thermal radiations in a porous bulb-shaped enclosure. The cavity is filled with Casson fluid, the upper highlighted section represents the hot wall, while the lower highlighted part signifies the cold wall, and the bottom section corresponds to the adiabatic wall. The research takes into account several key variables such as the Hartmann number (varying from 0 to 20), Lewis number (ranging from 0.1 to 10), Rayleigh number (Ra 10(3)-10(5)), Casson fluid parameter (varying from 0.1 to 10), buoyancy ratio (ranging from 0 to 2), Darcy number (ranging from 0.1 to 0.001) and thermal radiation parameter (varying from 0 to 5). In two dimensions, the governing formulation is written as a set of balancing equations for velocities, pressures, energies and concentrations. The nonlinear governing PDEs are solved using numerical approach based on finite element method (FEM). The discretization is performed using the stable finite element pair P-2/P-1. To analyze the effects of flow distribution changes, we graphically display those using streamlines, isothermal profiles and isoconcentration patterns. Information on kinetic energy, local heat and mass flux is also provided in the form of graphs and tables. The findings suggest that thermal radiation and porosity factors have profound impact on the flow pattern, isothermal and isoconcentrating contours. The study demonstrates the applications in solar thermal power conversion, energy deficiency systems and many other application of electronics designs.

Keyword ：

Bulb-shaped cavity Double diffusive Finite element method Thermal radiation

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Abstract ：

The inefficient electron transfer and Fe(III)/Fe(II) cycle remain significant obstacles in the electro-fenton process. Herein, a nitrogen-doped graphite felt (NGF)-supported CoFe/CoFe2O4 heterostructure is synthesized that achieves highly efficient interfacial electron transfer and stable Co/Fe redox cycle. Theoretical calculations demonstrate that the CoFe/CoFe2O4 heterointerfaces induce local charge redistribution benefiting from the electronic communication between electron acceptor (CoFe2O4) and electron donor (CoFe). Analysis of the Fermi level indicates that the introduction of CoFe alloy enhances the electron density of the catalyst. The CoFe/ CoFe2O4@NGF cathode can remove bisphenol A (BPA) completely in 90 min, and the pseudo-first-order kinetic constant (0.0625 min(-1)) is 23 times higher than the GF system. Notably, the CoFe/CoFe2O4@NGF electrode maintains excellent catalytic capability and stability within a broad pH range (3-11). The construction of the CoFe/CoFe2O4 heterostructure reduces the adsorption energy of oxygen, which ultimately increases the yield of reactive oxygen species (ROS). Quenching experiments revealed that hydroxyl radical (center dot OH) played a dominant role in the degradation of BPA, and significantly reduced the biotoxicity of intermediate products. This work offers a dependable approach for developing bimetallic catalysts with high catalytic activity.

Keyword ：

Heterogeneous electro-Fenton Heterointerface Electron transfer Bimetallic catalyst

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In the present paper, we studied the forces on a spherical particle of radius R moving in the vicinity of the plane wall in a shear flow of free molecular regime. We consider that the distance ratio between the plane wall and the particle (L) and the particle radius (R) is large (e.g., L/R > 5), and the gas molecular mean free path (lambda) is much higher than the particle size (lambda/R >> 1). An analytical formula for the forces is obtained based on gas kinetic theory and certain simplifying assumptions, and is verified by using Direct Simulation Monte Carlo Method. It is found that the forces acting on the particle can be affected by the momentum accommodation coefficients (sigma) of the wall and particle surfaces, the wall/gas temperature ratios (T-w/T), and the velocity gradient (G) of the gas flow. In the cases of specular reflections (sigma = 0), the near-wall effect can be neglected. With the increase of the momentum accommodation coefficients, the near-wall effect can be enhanced. When near-wall particles move in the direction parallel to the plane wall, there is a lift force which is perpendicular to the wall due to the near-wall effect and the shear flow. For T-w/T < 1, the lift force for the near-wall particles is in the direction against the wall. While for T-w/T > 1, the force is in the direction away from the plane wall. The findings presented in this paper can provide theoretical guidance for the application of near-wall particles in shear flows.

Keyword ：

Gas kinetic theory Shear lift forces Near -wall particles Free molecular regime

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Iodinated aromatic disinfection byproducts have attracted much attention owing to their high toxicity. However, little has been known about the iodination mechanism to date. In this study, the iodination of model aromatic precursors, tyrosine (Tyr) and its model dipeptides, by HOI and other iodinating agents was explored using a quantum chemical computational method, and the halogenation of Tyr by HOX (X = Cl, Br, and I) was compared. The results indicate that the phenolate salt plays a key role in the iodination of the phenol ring in Tyr compounds by HOI via the classic SEAr mechanism and the second deprotonation becomes the rate-limiting step, which explains why the kinetic isotope effect (KIE) was observed in the iodination of aromatic compounds. Among the seven possible iodinating agents present in chloramination, HOI is the predominant one, and I2 is the second in the iodination of the phenol ring under typical chloramination conditions. In the further investigation of bromination and chlorination, the KIE was found to also occur in the bromination of Tyr. More importantly, the different reactivity orders of HOX reacting with the phenol ring and the amino group in Tyr are related to the hardness of both HOX and substrates, which can be evaluated from the energy gap (ELUMO-HOMO) between the LUMO and HOMO energies. Following the "like-attracts-like" principle, the halogenating agent prefers the substrate with a similar ELUMO-HOMO value. The results are helpful in further understanding the iodination mechanism and identifying various halogenated products. The iodination mechanism of Tyr compounds by HOI and other iodinating agents was studied using the DFT method, and the halogenation of Tyr by HOX (X = Cl, Br, and I) was compared.

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Layered Li2MnO3 exhibits great potential as a high-capacity cathode used in lithium -ion batteries, but materials synthesized by traditional solid-phase methods exhibit poor activity and poor cycling stability. In this work, Li2MnO3 nanoparticles were synthesized by solid state method combined with high-energy ball milling, in which Fe was doped at transition metal sites to obtain a Li-rich cathode material (Li1.32Fe0.034Mn0.64O2). We systematically studied the effects of Fe doping and calcination temperature on the crystal structure and electrochemical properties and conducted kinetic studies using the galvanostatic intermittent titration technique (GITT), electrical impedance spectroscopy (EIS) and density functional theory (DFT) calculations. Our results demonstrate that the performance was significantly improved, its discharge capacity is about 235 mAh g-1 after 10 cycles compared 138 mAh g-1 of the pristine sample. The GITT and EIS results show that the Fe-doped sample had smaller charge transfer impedance, larger lithium -ion diffusion coefficient and lower internal polarization than the pristine. The activation energy results show the Fe-doped sample has larger activation energy at the late discharging period due to the anion redox reaction activation, indicting its O activation is more active than Li2MnO3. Moreover, the DOS results showed that the Fe-doped sample had a narrow band -gap, indicating good electrical conductivity. The CI-NEB results showed that the Fe-doped sample had a high transition metal ion migration energy barrier, indicating that its structure was stable. In conclusion, Fe doping is helpful to active the anion redox reaction in Li2MnO3 and improve its electrochemical performance as a low cost and high-capacity cathode materials.

Keyword ：

Nanostructured material Fe doping kinetics Li2MnO3

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Abstract ：

Partial nitrification (PN) has great significance in promoting both anaerobic ammonium oxidation (anammox) and advanced nitrogen removal. However, the kinetics of PN have not been sufficiently studied. Deterioration of PN often occurs due to nitrite-oxidizing bacteria (NOB) outgrowth, for which the dissolved oxygen (DO) is a critical factor. This study investigated the kinetic parameters of ammonia-oxidizing bacteria (AOB) and NOB by varying the DO concentration. The partial nitrification-anammox (PNA) process was operated under sequentially low (0.3-0.8 mg/L) and high (4.0-5.0 mg/L) DO. The results show that AOB could not adapt to low DO, resulting in a significant decrease in the maximum AOB activity (Vmax,AOB) and a slightly altered oxygen half-saturation constant of AOB (KO,AOB). Conversely, KO,NOB decreased and Vmax,NOB maintained, indicating that the main NOB genus, Nitrospira, was more adaptable to DO changes. Under high DO, AOB growth was weaker than NOB, leading to a low Vmax,AOB - Vmax,NOB value; KO,AOB increased and was larger than KO,NOB and PNA was eventually destroyed. The aerobic starvation was then adopted to restore PN. AOB recovered faster and dominated, with Vmax,AOB greatly exceeding Vmax,NOB. Finally, NOB were inhibited and PN was recovered. During this process, KO, NOB increased and was higher than KO,AOB. Changes in the kinetic parameters, especially the Vmax,AOB -Vmax,NOB value, have specific guiding significance for DO regulation during PNA. This work helps better understand the effect of DO variations on the nitrifying microbial community, which influences oxygen affinity and maximum activity.

Keyword ：

Dissolved oxygen Oxygen affinity Partial nitrification Nitrifying microbial community Maximum nitrification activity

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In producing electrolytic manganese and manganese-based lithium batteries, Manganous sulfate solution serves as a crucial intermediate material. During the preparation of manganese sulfate solution by acid leaching, the removal of impurities such as zinc, nickel, and cobalt ions by sulfide precipitation is essential for obtaining high-quality metallic manganese and high-purity manganese sulfate. The results show that when the temperature is 45 degrees C, the pH is 5.60, the ammonium sulfide dosage is 40 %, the time is 5 min, and the rotation speed is 650 rpm, the sulfidation rates of zinc, nickel and cobalt are 99.07 %, 89.30 %, and 87.70 % respectively. At this time, the loss rate of manganese in the solution after sulfide impurity removal is 11.45 %, and the manganese-impurity ratio is 80.00. Response surface methodology analysis revealed that temperature, pH, and ammonium sulfide concentration significantly affected the manganese loss rate. After process optimization, at a temperature of 32.70 degrees C, a pH of 5.20, and an ammonium sulfide concentration of 32.73 %, the manganese loss rate decreased to 6.05 %, while the removal rates of Ni, Co, and Zn were 75.35 %, 60.80 %, and 99.51 %, respectively. In the Manganous sulfate electrolyte with or without ammonium sulfate, the sulfide precipitation processes of zinc, nickel and cobalt ion are all first-order reactions, and the reaction order is zinc > nickel > cobalt. More importantly, the density functional theory (DFT) calculation results also confirmed the formation sequence of zinc sulfide > nickel sulfide > cobaltous sulfide, which supported the experimental results well. This study will lay the foundation for process optimization and mechanism elucidation of impurity ions in ammonium sulfate electrolyte precipitated by ammonium sulfate.

Keyword ：

Impurities metals ions MnSO4 electrolyte (NH4)(2)S Kinetic

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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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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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The rational design of efficient bimetallic nanoparticle (NP) catalysts is challenging due to the lack of theoretical understanding of active components and insights into the mechanisms of a specific reaction. Here, we report the rational design of nanoreactors comprising hollow carbon sphere-confined PtNi bimetallic NPs (PtNi@HCS) as highly efficient catalysts for hydrogen generation via ammonia borane hydrolysis in water. Using both density functional theory calculations and molecular dynamics simulations, the effects of an active PtNi combination and the critical synergistic role of a hollow carbon shell on the molecule diffusion adsorption behaviors are explored. Kinetic isotope effects and theoretical calculations allow the clarification of the mechanism, with oxidative addition of an O-H bond of water to the catalyst surface being the rate-determining step. The remarkable catalytic activity of the PtNi@HCS nanoreactor was also utilized for successful tandem catalytic hydrogenation reactions, using in situ-generated H2 from ammonia borane with high efficiency. The concerted design, theoretical calculations, and experimental work presented here shed light on the rational elaboration of efficient nanocatalysts and contribute to the establishment of a circular carbon economy using green hydrogen.

Keyword ：

ammonia borane nanoreactor hydrogen solid catalyst nanoalloy

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