Electron transfer to direct oxidation of aqueous organics by perovskites

The residual of oxidant chemicals in advanced oxidation processes(AOPs)resulted in both economic cost and secondary pollution.Herein,we report a direct oxidation of phenolic pollutants induced by Ca-Mn-O perovskites without using an oxidant.Governed by one-electron transfer process(ETP)from the phenolics to the Ca-Mn-O perovskites,this direct oxidation proceeds in fast reaction kinetics with activation energy of 51.4 kJ/mol,which was comparable with those AOPs-based catalytic systems.Additionally,mineralization and polymerization reactions occurred on the Ca-Mn-O surface and ensured the complete removal of phenolics.The high spin state Mn(III)within Ca-Mn-O structure was the dominant active site for this ETP.The elongated axial Mn(III)–O bonds within the[MnO_(6)]octahedron facilitated the acceptance of the electrons from the phenolics and thus promoted the initiation of the direct oxidation process.Mn(III)in the high spin state can also activate dissolved O_(2)to produce singlet oxygen(^(1)O_(2))for a fast removal of phenolics.The mixed Mn(III)/Mn(IV)within Ca-Mn-O accelerated the ETP by enhancing the electrical conductivity.This efficient Ca-Mn-O-induced ETP for removal of organic contaminants casts off the dependence on external chemical and energy inputs and provides a sustainable approach for transforming the toxic organic pollutants into value-added polymers.

Formation Mechanism of Nanoparticles in Fe-Cr-Al ODS Alloy Fabricated by Direct Oxidation Method

This study presents the fabrication of 14CrFe-Cr-Al oxide dispersion strengthened(ODS)alloy by a direct oxidation process.In order to explain how oxide nanoparticles are formed in the consolidation process,the powders after oxidation are subjected to vacuum thermal treatment at high temperatures.Differential scanning calorimeter,X-ray photoelectron spectroscopy,scanning electron microscopy and transmission electron microscopy techniques are used to detect the generation,evolution of oxides on both the surface and interior of the powder,as well as the type of oxide nanoparticles in the fabricated ODS alloy.It is found that an iron oxide layer is formed on the surface of the powder during low temperature oxidation.And the iron oxide layer would be decomposed after thermal treatment at high temperature.In the consolidation process,the oxygen required by the reaction of alumina and yttrium oxide to produce nano scale Y-Al-O particles mainly derives from the decomposition of iron oxide layer at elevated temperature and the inward diffusion of oxygen.Using the direct oxidation process,YAlO_(3) nanoparticles are dispersed in the grains and at the grain boundaries of Fe-Cr-Al ODS alloy.

Fabrication of Ceramic Composites by Directed Metal Oxidation

To explain the growth mechanism of Al 2O 3/Al Lanxide composites,the dynamics of the directed oxidation of Al-Mg-Si alloys are analyzed.The experimental methods to produce Lanxide composites by directed oxidation of metal melts at high temperatures are presented.The effect of the processing factors on the microstructures and properties of Al 2O 3/Al composites and enforced Al 2O 3/Al composites is also analyzed.Compared with sintering ceramic composites,the advantages of Lanxide process and Lanxide materials are as following:it is a near net shaped process;the process is very simple;the microstructures and properties of Lanxide materials can be adjusted;and this process can be used to infiltrate ceramic fiber or particle preforms.

Preparation of SiC_p/Al_2O_3-Al Composites by Directed Metal Oxidation

SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM） and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.

Different Performances of H_2O_2 to Oxidise Aldicarb and Hexazinone in the Advanced Oxidation Process of Ozone/Hydrogen Peroxide

The degradations of hexazinone and aldicarb by direct ozonation combined an advanced oxidation process( AOP) of O3/H2O2 were investigated in this study focusing on the oxidation mechanism by identifying the hydrogen peroxide consumption during the oxidation process of the two chemicals. The results showed that H2O2 could enhance the removal rate of the triazine herbicide hexazinone,and it was consumed along with the variation of removal rate in the light of different pH levels. The addition of H2O2 contributed little to the removal of the thiocarbamate herbicide aldicarb and H2O2 content kept constantly throughout the degradation process. Tert-butyl alcohol( TBA) effectively scavenged the ·OH radical for hexazinone,but had no effect on the removal rate of aldicarb. Aldicarb removal was mainly attributed to direct ozonation molecule in both O3( 97.00%) and O3/H2O2( 96.76%)systems. Moreover,sole O3 could hardly oxidize hexazinone whereas·OH radicals contribute respective 74.70% and 97.50% of removal in O3 system and O3/H2O2 AOP. All of these findings suggest that the mechanism of ·OH radical generation and the chain reaction in O3/H2O2 AOP should be further discussed.

Two-dimensional PtRu Nanoclusters Carbon Based Electrocatalysts for Methanol Oxidation

A novel method to prepare an electrocatalyst with a new structure and high catalytic performance was reported. Two-dimensional（2 D） PtRu nanoclusters have been successfully deposited on graphene oxide and carbon black supports. Compared with the commercial 3 D E-TEK PtRu samples, the prepared 2 D PtRu composites have larger electrochemically active surface area and display much higher catalytic activity toward methanol oxidation reaction. The preparation method mainly includes the following procedures： oxidation of carbon matrix, Pb^（2＋） adsorption on the surface of carbon support, Pb^（2＋） electrochemical reduction and galvanic displacement of Pb^0 by Pt^（2＋） and Ru^（3＋）. The method developed in this study could be viable for solving the problem of low electrocatalytic activity in direct methanol fuel cell anodes.

A review:Advances in microbial remediation of trichloroethylene (TCE)

Research works in the recent past have revealed three major biodegradation processes leading to the degradation of trichloroethylene. Reductive dechlorination is an anaerobic process in which chlorinated ethenes are used as electron acceptors. On the other hand, cometabolism requires oxygen for enzymatic degradation of chlorinated ethenes, which however yields no benefit for the bacteria involved. The third process is direct oxidation under aerobic conditions whereby chlorinated ethenes are directly used as electron donors by microorganisms. This review presented the current research trend in understanding biodegradation mechanisms with regard to their field applications. All the techniques used are evaluated, with the focus being on various factors that influence the process and the outcome.

Ce-Fe-O mixed oxide as oxygen carrier for the direct partial oxidation of methane to syngas

The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...

A method for recovery of iron,titanium,and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures： low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200°C, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70 wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.

Investigation of Nickel Oxide Used for Alloying in BOF Steelmaking

Direct alloying of nickel oxide in a hot simulator of LD converter was investigated in laboratory.Reduction rate of nickel oxide in steelmaking process was analyzed with the test results. Under the condition oflower slag viscosity, the reduction rate of NiO increases and the [Ni] yield rises. When the slag viscosity is higher, a lot of metal particles with higher Ni content are contained in the slag so as to decrease the [Ni] yield.

Modulating reaction pathways of formic acid oxidation for optimized electrocatalytic performance of PtAu/CoNC

Formic acid oxidation(FAO)is a typical anode reaction in fuel cells that can be facilitated by modulating its direct and indirect reaction pathways.Herein,PtAu bimetallic nanoparticles loaded onto Co and N co-doping carbon nanoframes(CoNC NFs)were designed to improve the selectivity of the direct reaction pathway for efficient FAO.Based on these subtle nanomaterials,the influences of elemental composition and carbon-support materials on the two pathways of FAO were investigated in detail.The results of fuel cell tests verified that the appropriate amount of Au in PtAu/CoNC can promote a direct reaction pathway for FAO,which is crucial for enhancing the oxidation efficiency of formic acid.In particular,the obtained PtAu/CoNC with an optimal Pt/Au atomic ratio of 1:1(PtAu/CoNC-3)manifests the best catalytic performance among the analogous obtained Pt-based electrocatalysts.The FAO mass activity of the PtAu/CoNC-3 sample reached 0.88 A·mg_(Pt)^(-1),which is 26.0 times higher than that of Pt/C.The results of first-principles calculation and CO stripping jointly demonstrate that the CO adsorption of PtAu/CoNC is considerably lower than that of Pt/CoNC and PtAu/C,which indicates that the synergistic effect of Pt,Au,and CoNC NFs is critical for the resistance of Pt to CO poisoning.This work is of great significance for a deeper understanding of the oxidation mechanism of formic acid and provides a feasible and promising strategy for enhancing the catalytic performance of the catalyst by improving the direct reaction pathway for FAO.

Microstructure and High-Temperature Oxidation Behavior of Dy-Doped Nb–Si-Based Alloys

Microstructures and oxidation behaviors of four Dy-doped Nb-Si-based alloys at 1250 ℃ were investigated. The nominal compositions of the four alloys are Nb-15Si-24Ti-4Cr-2Al-2Hf-xDy （at.%）, where x = 0, 0.05, 0.10 and 0.15, respectively. Results showed that the four alloys all consisted of Nbss, αNbsSi3 and γNbsSi3, and the addition of Dy produced no obvious effect on the phase constitution and the microstructures of Nb-Si-based alloys. After oxidation at 1250 ℃ for 58 h, it was found that the addition of Dy accelerated the oxidation rate of Nb-Si-based alloys and caused a larger weight gain, accompanied by the formation of a more porous and less protective oxide scale. The oxides of Nb2O5, Ti2Nb10O29, TiNb2O7, Ti0.4Cr0.3Nb0.302 and glassy SiO2 were formed on Dy-doped Nb-Si-based alloys. The high- temperature oxidation mechanism of Dy-doped Nb-Si-based alloys was discussed.

SnNi nanoneedles assembled 3D radial nanostructure loaded with SnNiPt nanoparticles： Towards enhanced electrocatalysis performance for methanol oxidation

A desirable methanol oxidation electrocatalyst was fabricated by metal atom diffusion to form an alloy of an assembled three-dimensional （3D） radial nanostructure of SnNi nanoneedles loaded with SnNiPt nanoparticles （NPs）.Herein,metal atom diffusion occurred between the SnNi support and loaded Pt NPs to form a SnNiPt ternary alloy on the catalyst surface.The as-obtained catalyst combines the excellent catalytic performance of the alloy and advantages of the 3D nanostructure;the SnNiPt NPs,which fused on the surface of the SnNi nanoneedle support,can dramatically improve the availability of Pt during electrocatalysis,and thus elevate the catalytic activity.In addition,the efficient mass transfer of the 3D nanostructure reduced the onset potential.Furthermore,the catalyst achieved a favorable CO poisoning resistance and enhanced stability.After atomic interdiffusion,the catalytic activity drastically increased by 45%,and the other performances substantially improved.These results demonstrate the significant advantage and enormous potential of the atomic interdiffusion treatment in catalytic applications.

Recent progress in Ru(Ⅱ)-catalyzed C-H activations with oxidizing directing groups

In this review, we highlight the recent development in Ru（II）-catalyzed C-H activations under redox neutral conditions. After a brief introduction of the C-H activations with oxidizing direct group by different transition metal catalysts, the examples with Ru（ll） catalyst were classified and introduced according to different internal oxidants used in the system. The features of each methodology will be highlighted and the plausible reaction mechanism will be presented if available.

Rare earth metal oxides as BH_4^--tolerance cathode electrocatalysts for direct borohydride fuel cells

Rare earth metal oxides（REMO） as cathode electrocatalysts in direct borohydride fuel cell（DBFC） were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm 2.The DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V.

Effect of Oxidizing Atmosphere on the Surface of Titanium Dental Implant Material

Direct oxidation is a simple and effective method for titanium surface treatment.In this research,a titanium sample was directly oxidized at the high temperature in two different atmospheres,air and pure oxygen,to obtain better atmosphere for titanium surface treatment.The results of the Raman spectroscopy indicated that in both atmospheres,the rutile bioactive phase(TiO2)has been formed on the titanium surface.The results of X-ray diffraction(XRD)also revealed that the surface of oxygen-treated sample was composed of the rutile phase and titanium monoxide(TiO),while at the surface of the air-treated sample,the rutile phase and titanium dioxide had been formed.Further,the results of Field Emission Scanning Electron Microscopy(FE-SEM)showed that by the surface treatment of titanium in both atmospheres,some micro-features including cracks thinner than 30 nm were formed on the surface.Because of more apatite forming ability and fewer water contact angle and more L-929 cell attachment of the air-treated titanium,it seemed that air,in comparison to the pure oxygen,is more promising atmosphere for the direct oxidation of titanium and improving its biofunctionalization.

Rhodium-catalyzed formal[4+3]annulation reaction of N-methoxybenzamides with gem–difluorocyclopropenes:A combination of experimental and theoretical studies

A rhodium-catalyzed[4+3]cycloaddition reaction between N-methoxybenzamides and gem–difluorocyclopropenes is described.The reaction offers a mild and efficient approach towards the synthesis of fluorinated 2 H-azepin-2-ones with broad substrate scope.A consecutive HOAc-assisted C–N bond formation and fluorine elimination are involved as key steps for success as illustrated by detailed DFT studies.