Effect of aspect ratio of elliptical stirred vessel on mixing time and flow field characteristics in the absence of baffles

Elliptical tanks were used as an alternative to circular tanks in order to improve mixing efficiency and reduce mixing time in unbaffled stirred tanks(USTs). Five different aspect ratios of elliptical vessels were designed to compare their mixing time and flow field. Computational fluid dynamics(CFD) simulations were performed using the k–ε model to calculate the mixing time and simulate turbulent flow field features, such as streamline shape, velocity distribution, vortex core region distribution, and turbulent kinetic energy(TKE) transfer. Visualization was also carried out to track the tinctorial evolution of the liquid phase. Results reveal that elliptical stirred tanks can significantly improve mixing performance in USTs. Specifically, the mixing time at an aspect ratio of 2.00 is only 45.3% of the one of a circular stirred tank. Furthermore, the secondary flow is strengthened and the vortex core region increases with the increase of aspect ratio. The axial velocity is more sensitive to the aspect ratio than the circumferential and radial velocity. Additionally, the TKE transfer in elliptical vessels is altered. These findings suggest that elliptical vessels offer a promising alternative to circular vessels for enhancing mixing performance in USTs.

Microplastics in Freshwater Aquaculture Fishpond System in Yichang,China:The Occurrence,Characteristics and Potential Risks

At present,microplastics have attracted much concern worldwide,but still few researches have focused especially on aquaculture fishponds.In this study,investigations were conducted in Zhijiang(ZJ)and Yidu(YD)areas of Hubei,China,typical freshwater aquaculture bases of the middle and lower reaches of the Yangtze River,on the occurrence and distribution characteristics of microplastics in fishpond system.It was found that microplastics presented in all samples from water,sediment,fish,and fish feed.Most microplastics detected had a diameter of<1.0 mm,blue and black were the most common colors,and fiber shape was the dominant type.The most common polymer types were polyethylene(PE)and polypropylene(PP).Microplastic abundance in fish was correlated with that in sediment and water.The potential ecological risk index values indicated that water,sediment,and fish samples were under moderate pollution risk.The results of this study illustrated the microplastics pollution situation in freshwater cultured fishpond systems,and the findings presented here will serve as a reference for future investigations of the environmental risks of microplastics in aquaculture environment.

Synthesis of Organic-Inorganic Hybrid Aluminum Hypophosphite Microspheres Flame Retardant and Its Flame Retardant Research on Thermoplastic Polyurethane

Aluminum hypophosphite microspheres(AHP) were synthesized by hydrothermal method using NaH2PO2·H2O and AlCl3·6H2O as raw materials, and then the AHP microspheres were polymerized by surface polymerization of micro-nanospheres with cyclic cross-linked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol)(PZS). A new organic-inorganic poly(phosphonitrile)-modified aluminum hypophosphite microspheres(PZS-AHP) were synthesized by encapsulation and applied to flame retardant thermoplastic polyurethane(TPU). The microstructure and chemical composition of the PZS-AHP microsphere were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray spectroscopy. The thermal stability of PZS-AHP microsphere was explored with thermogravimetric analysis. Thermogravimetric data indicate that the PZS-AHP microspheres have excellent thermal stability. The thermal and flame-retarding properties of the TPU composites were evaluated by thermogravimetric(TG), limited oxygen index tests(LOI), and cone calorimeter test(CCT). The TPU composite achieved vertical burning(UL-94) V-0 grade and LOI value reached 29.2% when 10 wt% PZS-AHP was incorporated. Compared with those of pure TPU, the peak heat release rate(pHRR) and total heat release(THR) of TPU/10%PZS-AHP decreased by 82.2% and 42.5%, respectively. The results of CCT indicated that PZS-AHP microsphere could improve the flame retardancy of TPU composites.

Hierarchical Reduced Graphene Oxide-MnO_(2)@Polypyrrole Coaxial Nanotube Composite Hydrogel as a Potential Adsorbent for Cr(Ⅵ)Removal

A hierarchical reduced graphene oxide-MnO_(2)@polypyrrole coaxial nanotube composite hydrogel was prepared via oxidative polymerization of pyrrole in the presence of MnO_(2)nanotubes,followed by the hydrothermal treatment of graphene oxide and MnO_(2)@polypyrrole coaxial nanotubes.The stable composite hydrogel with a hierarchical network was composed of one-dimensional MnO_(2)@polypyrrole coaxial nanotube and two-dimensional graphene nanosheet and characterized by scanning electron microscope,Fourier transform infrared spectroscopy,X-ray diffraction,Brunauer-Emmett-Teller surface,and X-ray photoelectron spectroscopy measurements.The composite hydrogel can be used as an efficient adsorbent for Cr(Ⅵ)removal due to the synergistic interaction between graphene and MnO_(2)@polypyrrole and the hierarchical structure of the hydrogel.Moreover,the composite hydrogel is easily separated because of its stable monolith,and it is reusable(76.8%of removal ability remaining after five adsorption-desorption cycles).The simple fabrication and cost-effective separation process together with the excellent absorption performance endow the composite hydrogel with great potential for practical wastewater treatment.

Construction of Mo/Mo_(2)C@C modified ZnIn_(2)S_(4)Schottky junctions for efficient photo-thermal assisted hydrogen evolution

Photocatalytic water splitting on noble metal-free photocatalysts for H_(2) generation is a promising but challenging approach to realize solar-to-chemical energy conversion.In this study,Mo/Mo_(2)C nanoparticles anchored carbon layer(Mo/Mo_(2)C@C)was obtained by a one-step in-situ phase transition approach and developed for the first time as a photothermal cocatalyst to enhance the activity of ZnIn_(2)S_(4)photocatalyst.Mo/Mo_(2)C@C nanosheet exhibits strong absorption in the full spectrum region and excellent photo-thermal conversion ability,which generates heat to improve the reaction temperature and accelerate the reaction kinetics.Moreover,metallic Mo/Mo_(2)C@C couples with ZnIn_(2)S_(4)to form ZnIn_(2)S_(4)-Mo/Mo_(2)C@C Schottky junction(denoted as ZMM),which prevents the electrons back transfer and restrains the charge recombination.In addition,conductive carbon with strong interfacial interaction serves as a fast charge transport bridge.Consequently,the optimized ZMM-0.2 junction exhibits an H2 evolution rate of 1031.07μmol g^(-1)h^-(1),which is 41 and 4.3 times higher than bare ZnIn_(2)S_(4)and ZnIn_(2)S_(4)-Mo2C,respectively.By designing novel photothermal cocatalysts,our work will provide a new guidance for designing efficient photocatalysts.

Preparation of ZIF-8@PEBAX/PVDF nanocomposite membrane by the combination of self-assembly and in-situ growth for removing thiophene from the model gasoline

Metal-organic frameworks(MOFs)have gained attention in the development of MOFs/polymer hybrid membranes for pervaporation.However,the agglomeration of MOFs particles and interfacial defects limit its further application.In this study,we present a novel approach to fabricate a ZIF-8@PEBAX/PVDF nanocomposite membrane for removing thiophene from the model gasoline by combination of selfassembly and in-situ growth.Firstly,a PVDF supporting membrane was modified to have a negative charge.Next,positively charged zinc ions were attracted onto the negatively charged PVDF supporting membrane through electrostatic interaction.Afterwards,the Zinc ions deposited PVDF membrane was immersed into dimethylimidazole solution to form a uniform ZIF-8 layer.Finally,the ZIF-8 layer was coated with poly(ether-block-amide)(PEBAX)using the pouring method.Experimental results showed that the separating efficiency of the ZIF-8@PEBAX/PVDF nanocomposite membrane was improved significantly compared to that of pristine PEBAX membrane.The optimal permeation flux and enrichment factor of membrane were 27.80 kg(m^(2)h)^(-1)and 6.9,respectively.

Concise Strategies to Enhance the High-Rate Performance of Li_(3)VO_(4) Anodes:Cl Doping,Carbon Coating,and Spherical Architecture Design

The safe operating voltage and low volume variation of Li_(3)VO_(4)(LVO)make it an ideal anode material for lithium(Li)-ion batteries.However,the insufficient understanding of the inner storage mechanism hinders the design of LVO-based electrodes.Herein,we investigate,for the first time,the Li-ion storage activity in LVO via Cl doping.Moreover,N-doped C coating was simultaneously achieved in the Cl doping process,resulting in synergistically improved reaction kinetics.As a result,the as-prepared Cl-doped Li_(3)VO_(4) coated with N-doped C(Cl-LVO@NC)electrodes deliver a discharge capacity of 884.1 mAh/g after 200 cycles at 0.2 A/g,which is the highest among all of the LVO-based electrodes.The Cl-LVO@NC electrodes also exhibit high-capacity retention of 331.1 mAh/g at 8.0 A/g and full capacity recovery after 5 periods of rate testing over 400 cycles.After 5000 cycles at 4.0 A/g,the discharge capacity can be maintained at 423.2 mAh/g,which is superior to most LVO-based electrodes.The Li-ion storage activity in LVO via Cl doping and significant improvement in the high-rate Li-ion storage reported in this work can be used as references for the design of advanced LVO-based electrodes for high-power applications.

Ultradurable fluorinated V_(2)AlC for peroxymonosulfate activation in organic pollutant degradation processes

Vanadium‐based catalysts are considered the most promising materials to replace cobalt‐based catalysts for the activation of peroxymonosulfate(PMS)to degrade organic pollutants.However,these traditional vanadium species easily leak out metal ions that can affect the environment,even though the of vanadium is much less than that of cobalt.Compared to other vanadium‐based cata‐lysts,e.g.,V_(2)O_(3),fluorinated V_(2)AlC shows a high and constant activity and reusability regarding PMS activation.Furthermore,it features extremely low ion leakage.Active oxygen species scavenging and electron spin resonance measurements reveal that the main reactive oxygen species was 1O_(2),which was induced by a two‐dimensional confinement effect.More importantly,for the real‐life application of tetracycline(TC)degradation,the introduction of fluorine changed the adsorption mode of TC over the catalyst,thereby changing the degradation path.The intermediate products were detected by liquid‐chromatography mass spectroscopy(LC‐MS),and a possible degradation path was proposed.The environmental impact test of the decomposition products showed that the toxicity of the degradation intermediates was greatly reduced.Therefore,the investigated ultradu‐rable catalyst material provides a basis for the practical application of advanced PMS oxidation technology.

Data-driven structural descriptor for predicting platinum-based alloys as oxygen reduction electrocatalysts

Owing to increasing global demand for carbon neutral and fossil-free energy systems,extensive research is being conducted on efficient and inexpensive electrocatalysts for catalyzing the kinetically sluggish oxygen reduction reaction(ORR)at the cathode of fuel cells.Platinum(Pt)-based alloys are considered promising candidates for replacing expensive Pt catalysts.However,the current screening process of Pt-based alloys is time-consuming and labor-intensive,and the descriptor for predicting the activity of Pt-based catalysts is generally inaccurate.This study proposed a strategy by combining high-throughput first-principles calculations and machine learning to explore the descriptor used for screening Pt-based alloy catalysts with high Pt utilization and low Pt consump-tion.Among the 77 prescreened candidates,we identified 5 potential candidates for catalyzing ORR with low overpotential.Furthermore,during the second and third rounds of active learning,more Pt-based alloys ORR candidates are identi-fied based on the relationship between structural features of Pt-based alloys and their activity.In addition,we highlighted the role of structural features in Pt-based alloys and found that the difference between the electronegativity of Pt and heteroatom,the valence electrons number of the heteroatom,and the ratio of heteroatoms around Pt are the main factors that affect the activity of ORR.More importantly,the combination of those structural features can be used as structural descriptor for predicting the activity of Pt-based alloys.We believe the findings of this study will provide new insight for predicting ORR activ-ity and contribute to exploring Pt-based electrocatalysts with high Pt utiliza-tion and low Pt consumption experimentally.

A multifunctional optoelectronic device based on 2D material with wide bandgap

Low-dimensional materials exhibit unique quantum confinement effects and morphologies as a result of their nanoscale size in one or more dimensions,making them exhibit distinctive physical properties compared to bulk counterparts.Among all low-dimensional materials,due to their atomic level thickness,two-dimensional materials possess extremely large shape anisotropy and consequently are speculated to have large optically anisotropic absorption.In this work,we demonstrate an optoelectronic device based on the combination of two-dimensional material and carbon dot with wide bandgap.High-efficient luminescence of carbon dot and extremely large shape anisotropy(>1500)of two-dimensional material with the wide bandgap of>4 eV cooperatively endow the optoelectronic device with multi-functions of optically anisotropic blue-light emission,visible light modulation,wavelength-dependent ultraviolet-light detection as well as blue fluorescent film assemble.This research opens new avenues for constructing multi-function-integrated optoelectronic devices via the combination of nanomaterials with different dimensions.

Durable flame-retardant,smoke-suppressant,and thermal-insulating biomass polyurethane foam enabled by a green bio-based system

Bio-based polyurethane foam has attracted increasing attentions due to eco-friendliness and fossil feedstock issues.However,the inherent flammability limits its application in different fields.Herein,we demonstrate a green bio-based flame-retardant system to fabricate polyurethane foam composite with durable flame retardancy,smoke suppression,and thermal insulation property.In this system,the green bio-based polyol(VED)with good reactivity and compatibility plays a role of flame retardant and EG acts as a synergistic filler.As a result,the LOI value of foam composite increased to 30.5 vol.%and it achieved a V-0 rating in the UL-94 vertical burning test.Additionally,the peak heat release rate(pHRR)and the total smoke production(TSP)decreased by 66.1%and 63.4%,respectively.Furthermore,the foam composite maintained durable flame retardancy after accelerated thermal aging test,whose thermal-insulating property was maintained even after being treated in high-humidity environment with 85%R.H.for a week.This work provides a facile strategy for durable flame retardancy and long-term thermal insulation performance,and creates opportunities for the practical applications of bio-based foam composites.

A 3D Ni_(8)-cluster-based MOF as a molecular electrocatalyst for alcohol oxidation in alkaline media

1.Introduction DAFCs offer significant promise for compact electric devices through the consumption of liquid fuels as one of the renewable energy sources,with minimal environmental effects and prominent energy density[1-4].Because of the fuel crossover phenomenon and sluggish kinetics of the alcohol oxidation.

Organophosphorus catalytic reaction based on reduction of phosphine oxide

The special electronic configuration of phosphorus atoms endows organophosphorus reagents with unique chemical properties,which enable them to be used to catalyze various organic reactions,such as the Wittig reaction,Staudinger reaction,Appel reaction and Mitsunobu reaction.However,the catalytic process will be accompanied by the generation of large amounts of phosphine oxide waste,resulting in the reduction of atom utilization of the reaction,and it is difficult to separate the product.Therefore,it is essential to explore a greener and more sustainable organic synthesis route based on the catalytic cycle of phosphine oxide as a model.This paper summarizes the catalytic cycle and recycling of phosphorus with or without reducing agents and reviews the related developments in recent decades:from the addition of stoichiometric strong reducing agents,to the design of ring phosphines with specific structures,to the development of new energy inputs(electrochemistry),to the addition of a series of compounds to activate the P(V)––O double bond,driving the catalytic cycle of phosphine oxide through chemical transformation.This review also points out the development potential of this field in the future,which will promote its development and progress in a greener direction.