Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation-low-temperature reduction

Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore.However,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery via weak magnetic separation.We systematically studied and proposed the fluidized preoxidation-low-temperature reduction magnetization roasting process for siderite.We found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550℃due to the unstable intermediate product magnetite(Fe_(3)O_(4)).Stable magnetite can be obtained through maghemite reduction only at low temperature.The optimal fluidized magnetization roasting parameters included preoxidation at 610℃for 2.5 min,followed by reduction at 450℃for 5 min.For roasted ore,weak magnetic separation yielded an iron ore concentrate grade of 62.0wt%and an iron recovery rate of 88.36%.Compared with that of conventional direct reduction magnetization roasting,the iron recovery rate of weak magnetic separation had greatly improved by 34.33%.The proposed fluidized preoxidation-low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.

Influence of chromium modification on the properties of MnO_x-FeO_x catalysts for the low-temperature selective catalytic reduction of NO by NH_3

Catalytic properties of MnOx-FeOx complex oxide （hereafter denoted as Mn-Fe） catalysts modified with different loadings of chromium oxide were investigated by using the combination of physico-cbemical techniques, such as N2 physisorption, X-ray diffraction （XRD）, high-resolution transmission electron microscope （HRTEM）, in situ Fourier transform infrared spectroscopy （in situ FT-IR） and temperature-programmed reduction （TPR） and their catalytic activities were evaluated with the selective catalytic reduction （SCR） of NOx by NH3. It was found that with the addition of Cr, more NO could be removed in the low-temperature window （below 120 ℃）. Among the tested catalysts, Mn-Fe- Cr （2 ： 2 ： 1） catalyst exhibited the best catalytic performance at 80 ℃ with the NO conversion higher than 90%. The combination of the reaction and characterization results indicated that （1） the strong interaction among tertiary metal oxides existed in the catalysts when Cr was appropriately added, which made the active components better dispersed with less agglomeration and sintering and the largest BET specific surface area could be obtained; （2） Cr improved the low-temperature reducibility of the catalyst and promoted the formation of the active intermediate （-NH3＋）, which favored the low-temperature SCR reaction.

Synthesis of novel MnO_x@TiO_2 core-shell nanorod catalyst for low-temperature NH_3-selective catalytic reduction of NOx with enhanced SO_2 tolerance

In this study,a MnOx@TiO2 core‐shell catalyst prepared by a two‐step method was used for the low‐temperature selective catalytic reduction of NOx with NH3.The catalyst exhibits high activity,high stability,and excellent N2 selectivity.Furthermore,it displays better SO2 and H2O tolerance than its MnOx,TiO2,and MnOx/TiO2 counterparts.The prepared catalyst was characterized systematically by transmission electron microscopy,high‐resolution transmission electron microscopy,X‐ray diffraction,Raman,BET,X‐ray photoelectron spectroscopy,NH3 temperature‐programmed desorption and H2 temperature‐programmed reduction analyses.The optimized MnOx@TiO2 catalyst exhibits an obvious core‐shell structure,where the TiO2 shell is evenly distributed over the MnOx nanorod core.The catalyst also presents abundant mesopores,Lewis‐acid sites,and high redox capability,all of which enhance its catalytic performance.According to the XPS results,the decrease in the number of Mn4+active centers after SO2 poisoning is significantly lower in MnOx@TiO2 than in MnOx/TiO2.The core‐shell structure is hence able to protect the catalytic active sites from H2O and SO2 poisoning.

TiO_2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NO_x with NH_3

Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order：Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order：Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h？ 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared（FTIR）spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.

Photocatalytic Cr(Ⅵ) reduction and organic-pollutant degradation in a stable 2D coordination polymer

A new coordination polymer,Zn(bpy)L(BUC‐21),(H2L=cis‐1,3‐dibenzyl‐2‐imidazolidone‐4,5‐dicarboxylic acid,bpy=4,4′‐bipyridine),has been synthesized under hydrothermal conditions,and characterized by single‐crystal X‐ray analysis,Fourier transform infrared spectroscopy,thermogravimetric analyses,CNH elemental analysis and UV‐Vis diffuse reflectance spectroscopy.BUC‐21exhibited an excellent performance for photocatalytic Cr(VI)reduction with a conversion efficiency of96%,better than that of commercial P25(39%),under UV light irradiation for30min.BUC‐21could also be used to conduct photocatalytic degradation of organic dyes including methylene blue,rhodamine B,methyl orange and reactive red X‐3B.Also,the photocatalytic activity of BUC‐21remained high across a wide pH range from2.0to12.0.It is interesting to note,however,that BUC‐21was unable to achieve simultaneous reduction of Cr(VI)and degradation of an organic pollutant in a mixed matrix,which can be attributed to the competition between Cr(VI)and the organic dyes for access to the photo‐excited electrons.

Low-Temperature Selective Catalytic Reduction of NO with NH_3 over Fe–Ce–O_x Catalysts

In this study, we used a simple impregnation method to prepare Fe-Ce-O x catalysts and tested them regarding their low-temperature (200-300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94-99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h−1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80-98% between 200 and 300 °C at a space velocity of 204,000 h−1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200-300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance.

The Preparation of Mn-Fe/CNTs Catalyst at the Low-Temperature Selective Catalytic Reduction of NO with NH₃

The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH3 was investigated. The results showed that the active components were loaded suc-cessfully and easily on the carriers by impregnation. The Mn-Fe/CNTs catalyst was chose 10% Fe(NO3)3 solution to impregnate Mn-Fe/CNTs. The species of active components loaded on the catalyst were Fe2O3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.

Low-temperature synthesis of ultrasmall spinel MnxCo3-xO4 nanoparticles for efficient oxygen reduction

Spinel-type manganese-cobalt oxides have been regarded as important class of electrocatalysts for oxygen reduction reaction(ORR).However,they are usually synthesized through oxidation-precipitation under aqueous ammonia and then crystallization at high temperature(150–180℃),which not only increases the energy consumption but also induces the growth of particles that is unfavorable for ORR.Herein,through a facile precipitation-dehydration method,ultrasmall spinel manganese-cobalt oxide nanoparticles(~5 nm)homogeneously dispersed on conductive carbon black(MnxCo3-xO4/C)were fabricated at low temperature(60℃).And the bimetallic composite oxide(Mn1.5Co1.5O4/C)with cubic spinel structure and high Mn content exhibits remarkable enhancement of ORR activity and stability compared with single metal oxide(both Mn3O4/C and Co3O4/C).The essential reason for the enhancement of activity can be attributed to the presence of the mixed Mn^3+ and Mn^4+ cations in Mn1.5Co1.5O4/C.Moreover,the ORR activity of Mn1.5Co1.5O4/C is comparable to that of commercial 20 wt% Pt/C,and the relative current density only decreases 1.4% after 12 h test,exceeding that of Pt/C and most reported manganese-cobalt oxide electrocatalysts.

Relationship between the state of reduction-oxidation and protein degradation in the soleus muscle after scalding in rats

One hind leg(about 7% TBSA)of a rat was scalded and the changes of thereduction-oxidation state and protein degradation in the soleus muscle were observed inthe 72nd h after scalding both in vitro and in vivo.It was found that the lactate/pyruvate(L/P)and malate/pyruvate(M/P)ratios in the soleus muscle were significantly lower andthe protein degradation rate significantly higher in the scalded rats than those in the controland in the unscalded legs.After the addition of insulin to the medium,significant eleva-tion of L/P and M/P ratios and reduction of the protein degradation rate were observedin the soleus muscle.These findings suggest that there is a good correlation between thechanges of the reduction-oxidation and the protein degradation rate in the cytosol of thesoleus muscle after scalding in rats.

Density Functional Theory Study of Marine Polybrominated Diphenyl Ethers in Anaerobic Degradation

Polybrominated diphenyl ethers(PBDEs)are a kind of serious pollutants in the ocean.Biodegradation is considered as an economical and safe way for PBDEs removal and reductive debromination dominates the initial pathway of anaerobic degradation.On the basis of experimental study,Octa-BDE 197,Hepta-BDE 183,Hexa-BDE 153,Penta-BDE 99 and Tetra-BDE 47 were selected as the initial degradation objects,and their debromination degradation were studied using density functional theory.The structures were optimized by Gaussian 09 program.Furthermore,the molecular orbitals and charge distribution were analyzed.All C-Br bond dissociation energies at different positions including ortho,meta and para bromine atoms were calculated and the sequence of debromination was obtained.There is a close relationship between molecular structure,charge,molecular orbital and C-Br bond.All PBDEs exhibited similar debromination pathways with preferential removal of meta and para bromines.

Life-cycle assessment of batteries for peak demand reduction

At present,a life-cycle assessment of energy storage systems(ESSs)is not widely available in the literature.Such an assessment is increasingly vital nowadays as ESS is recognized as one of the important equipment in power systems to reduce peak demands for deferring or avoiding augmentation in the network and power generation.As the battery cost is still very high at present,a comprehensive assessment is necessary to determine the optimum ESS capacity so that the maximum financial gain is achievable at the end of the batteries’lifespan.Therefore,an effective life-cycle assessment is proposed in this paper to show how the optimum ESS capacity can be determined such that the maximum net financial gain is achievable at the end of the batteries’lifespan when ESS is used to perform peak demand reductions for the customer or utility companies.The findings reveal the positive financial viability of ESS on the power grid,otherwise the projection of the financial viability is often seemingly poor due to the high battery cost with a short battery lifespan.An improved battery degradation model is used in this assessment,which can simulate the battery degradation accurately in a situation whereby the charging current,discharging current,and temperature of the batteries are intermittent on a site during peak demand reductions.This assessment is crucial to determine the maximum financial benefits brought by ESS.

Using Ferrous Ion for the Reductive Degradation of Hexavalent Chromium

This paper discusses the toxicity and mobility of chromium species. And it presents the extent and kinetics of reductive remediation of hexavalent chromium, Cr+ using ferrous ion, Fe2+. Molar ratios of 1:3 and 1:6 of Cr (VI) to Fe (II) were used. Integral method of data analysis showed reaction followed second-order kinetics with R square values near unity. Reaction was initially fast but with a rapid precipitation attributed to Cr (III)-Fe (III) in previous studies. This colloidal precipitate ultimately stops the reaction, which explains while conversion efficiency increases with increased molar ratio of Cr (VI) to Fe (II). The impact of pH was investigated by adjusting the Cr (VI)-Fe (II) medium to pH 2.78, 5.24, 7.00, 9.00 and 11.96 using predetermined drops of acid or base. Reaction was more rapid under alkaline conditions with higher extent of degradation consistent with previous research. In soil system, mass transfer limitation was hardly noticed as high extent of reduction was recorded relative to aqueous phase. The high solubility of Cr (VI) aided the release into the aqueous media for reduction by ferrous sulfate.

A multi-scale framework for life reduction assessment of turbine blade caused by microstructural degradation

The prolonged thermal exposure with centrifugal load results in microstructural degradation,which ultimately leads to a reduction in the fatigue and creep resistance of the turbine blades.The present work proposes a multi-scale framework to estimate the life reduction of turbine blades,which combines a microstructural degradation model,a two-phase constitutive model,and a microstructure-dependent fatigue and creep life reduction model.The framework with multi-scale models is validated by a Single Crystal(SC)Ni-based superalloy at the microstructural length-scale and is then applied to calculate the microstructural degradation and the fatigue and creep life reduction of turbine blades under two specific service conditions.The simulation results and quantitative analysis show that the microstructural degradation and fatigue and creep life reduction of the turbine blade are heavily influenced by the variations in the proportion of the intermediate state,namely,the maximum rotor speed status,in the two specific service conditions.The intermediate state accelerates the microstructural degradation and leads to a reduction of the life,especially the effective fatigue life reserve due to the higher temperature and rotational speed than that of the 93%maximum rotor speed status marked as the reference state.The proposed multi-scale framework provides a capable approach to analyze the reduction of the fatigue and creep life for turbine blade induced by microstructural degradation,which can assist to determine a reasonable Time Between Overhaul(TBO)of the engine.

Stabilizing perovskite precursors with the reductive natural amino acid for printable mesoscopic perovskite solar cells

Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.

Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs:Effect of molecular weight of the cross-linking agent

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the application of temporary plugging agents(TPAs)for their efficient development.TPAs can expand the stimulated reservoir volume(SRV)and facilitate the flow of oil and gas to the bottom of the well.Particle-gels used as temporary plugging agents have the characteristics of the simple injection process,good deformation,high plugging strength,and complete self-degradation performance,which have been widely applied in recent years.In this paper,five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared.In addition,infrared spectroscopy analysis,differential calorimetry scanning(DSC)analysis,static particle gel swelling and degradation performance evaluation experiments,and dynamic temporary plugging performance experiments in cores were conducted at 34°C.Results show that as the molecular weight of the cross-linking agent(at 0.01 g)in the DPPG molecule decreased from 1,000 to 200 Da,the fewer cross-linking sites of DPPG,the looser the microscopic three-dimensional mesh structure formed.The swelling ratio increased from 7 to 33 times.However,the complete degradation time increased from 40 to 210 min.Moreover,the DSC results confirmed that the higher the molecular weight of the cross-linking agent,the worse is chemical stability and the more prone it to self-degradation.DPPG samples had good temporary plugging performance in reservoir cores.DPPGs prepared by the cross-linking agent with smaller molecular weight has a stronger swelling ratio,higher gel strength,and greater plugging strength in the core permeabilities.Moreover,the degraded DPPG is less damaging to the cores.However,their slower degradation rates take a slightly longer times to reach complete degradation.The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-type temporary plugging agents(TPA)with controllable degradation time in low-temperature reservoirs.It can help to expand the application range of existing DPPG reservoir conditions.

Fe-Mn/Al_2O_3 catalysts for low temperature selective catalytic reduction of NO with NH_3

A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactivation of the catalysts were studied. N2 adsorption‐desorption, X‐ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, H2 temperature‐programmed reduction, NH3 temperature‐programmed desorption, X‐ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis and Fourier transform infrared spectroscopy were used to character‐ize the catalysts. The 8Fe‐8Mn/Al2O3 catalyst gave 99%of NO conversion at 150？？ and more than 92.6%NO conversion was obtained in a wide low temperature range of 90–210？？. XPS analysis demonstrated that the Fe3＋was the main iron valence state on the catalyst surface and the addition of Mn increased the accumulation of Fe on the surface. The higher specific surface area, enhanced dispersion of amorphous Fe and Mn, improved reduction properties and surface acidity, lower binding energy, higher Mn4＋/Mn3＋ratio and more adsorbed oxygen species resulted in higher NO conversion for the 8Fe‐8Mn/Al2O3 catalyst. In addition, the SCR activity of the 8Fe‐8Mn/Al2O3 cata‐lyst was only slightly decreased in the presence of H2O and SO2, which indicated that the catalyst had better tolerance to H2O and SO2. The reaction temperature was crucial for the SO2 resistance of catalyst and the decrease of catalytic activity caused by SO2 was mainly due to the sulfate salts formed on the catalyst.

Comparative Studies on Degradation of Methyl Orange by Nanostructured Zinc and Zinc Oxide Films

Nanostructured zinc and zinc oxide films were prepared by magnetron sputtering processes and succeeded air annealing treatments. Comparison of reductive degradation rate of methyl orange （MO） by zinc films and photocatalytic degradation rate of MO by zinc oxide films was carried out. Both reductive degradation and photocatalytic degradation process of MO by zinc and zinc oxide films can be described by first order kinetic model. It was found that although MO liquid was most quickly decolorized by metallic zinc films, the mineraliza- tion of MO was not thorough. Observation of extra ultraviolet absorption peaks indicated the formation of aromatic intermediates. On the other hand, although the photocatalytic degradation rate of MO liquid by ZnO films was only as about 1/4 large as the reductive degradation rate by zinc films, no signs of aromatic intermediates were found. Moreover, it was found that partially oxidized zinc oxide film showed higher photocatalytic efficiency than the totally oxidized ZnO films. Synergy effect between zinc and zinc oxide phase in the partially oxidized films was considered to be responsible for the higher photocatalytic efficiency.

Electrochemical degradation of p-nitrophenol with different processes

The electrochemical degradation ofp-nitrophenol （PNP） under different conditions was investigated. The electrochemical behavior of PNP and its reduction product p-aminophenol （PAP） on stainless steel cathode and Ti/Pt anode through cyclic voltammetry were observed. Electrochemical degradation process was performed in an undivided cell and 92% PNP was removed corresponding to a 22% total organic carbon removal. A divided cell was also used and it was found that PNP degradation was mainly attributed to cathodic reduction, while anodic oxidation was responsible for PNP removal due to the reaction with hydroxyl radicals and surface oxide generated on the anode. The sequential electrolytic processes, reduction-oxidation and oxidation-reduction, were compared in the divided cell. In the case of reduction-oxidation process, the total organic carbon removal reached 40%, but PNP removal was the same with the undivided cell. A black deposit was found in the effluent and identified by Fourier transform infrared spectroscopy as a polymer of PAP produced by the 1,4-addition reaction of quinoneimine. Intermediates left in the solution such as hydroquinone, p-benzoquinone and PAP were determined by high performance liquid chromatography. Whereas, the oxidation-reduction process proved unsatisfying.

Low-Temperature SCR of NO with NH_3 on Mn-Based Catalysts Modified with Cerium

A series of Mn-based catalysts, MnOx, MnOx-CeO, Pd-Mn-Ce, MnOx/AC were prepared. And their performances for NO low-temperature SCR were investigated in this study. The NO conversion is about 90% at 100 ℃ on MnOx-CeOand almost all NO can be converted at 120 ℃. Similar results are also observed in the tests on MnOx-CeO/AC. The excellent low-temperature catalytic activity of modified Mn-based catalysts, which may be mainly due to the oxygen storage function of CeO, can improve the oxygen flow on the catalysts surface. Then the oxidation of NO to NO2 is accelerated, which is the key step of NO SCR.

Doped graphene/carbon black hybrid catalyst giving enhanced oxygen reduction reaction activity with high resistance to corrosion in proton exchange membrane fuel cells

Nitrogen doping of the carbon is an important method to improve the performance and durability of catalysts for proton exchange membrane fuel cells by platinum–nitrogen and carbon–nitrogen bonds. This study shows that p-phenyl groups and graphitic N acting bridges linking platinum and the graphene/carbon black(the ratio graphene/carbon black = 2/3) hybrid support materials achieved the average size of platinum nanoparticles with(4.88 ± 1.79) nm. It improved the performance of the lower-temperature hydrogen fuel cell up to 0.934 W cm^(-2) at 0.60 V, which is 1.55 times greater than that of commercial Pt/C. Doping also enhanced the interaction between Pt and the support materials, and the resistance to corrosion, thus improving the durability of the low-temperature hydrogen fuel cell with a much lower decay of 10 mV at 0.80 A cm^(-2) after 30 k cycles of an in-situ accelerated stress test of catalyst degradation than that of 92 mV in Pt/C, which achieves the target of Department of Energy(<30 mV). Meanwhile,Pt/Nr EGO_(2)-CB_(3) remains 78% of initial power density at 1.5 A cm^(-2) after 5 k cycles of in-situ accelerated stress test of carbon corrosion, which is more stable than the power density of commercial Pt/C, keeping only 54% after accelerated stress test.