Science Letters:Simultaneous removal of nitrate and heavy metals by iron metal

Great attention should be paid now to simultaneously removing common pollutants, especially inorganic pollutants such as nitrate and heavy metals, as individual removal has been investigated extensively. Removing common pollutants simul- taneously by iron metal is a very effective alternative method. Near neutral pH, heavy metals, such as copper and nickel, can be removed rapidly by iron metal, while nitrate removal very much slower than that of copper and nickel, and copper can accelerate nitrate removal when both are removed simultaneously. Even a little amount of copper can enhance nitrate removal efficiently. Different mechanisms of these contaminants removal by iron metal were also discussed.

Sensitivity of Nanostructured Iron Metal on Ultrasonic Properties

The present investigation is focused on the influence of the nanocrystalline structure of pure iron metal on the ultrasonic properties in the temperature range 100 - 300 K. The ultrasonic attenuation due to phonon- phonon interaction and thermoelastic relaxation phenomena has been evaluated for longitudinal and shear waves along , and crystallographic directions. The second-and third-order elastic constants, ultrasonic velocities, thermal relaxation, anisotropy and acoustic coupling constants were also com- puted for the evaluation of ultrasonic attenuation in this temperature scale. The direction is most ap- propriate to study longitudinal sound waves, while , direction are best to propagate shear waves due to lowest values of attenuation in these directions. Other physical properties correlated with obtained results have been discussed.

Kinetics of hexavalent chromium reduction by iron metal

The kinetics of Cr(VI)reduction to Cr(III)by metallic iron(Fe0)was studied in batch reactors for a range of reactant concentrations,pH and temperatures.Nearly 86.8%removal efficiency for Cr(VI)was achieved when Fe0 concentration was 6 g/L(using commercial iron powder(<200 mesh)in 120 min).The reduction of hexavalent chro-mium took place on the surface of the iron particles following pseudo-first order kinetics.The rate of Cr(VI)reduction increased with increasing Fe0 addition and temperature but inversely with initial pH.The pseudo-first-order rate coeffi-cients(kobs)were determined as 0.0024,0.010,0.0268 and 0.0628 min−1 when iron powder dosages were 2,6,10 and 14 g/L at 25°C and pH 5.5,respectively.According to the Arrehenius equation,the apparent activation energy of 26.5 kJ/mol and pre-exponential factor of 3330 min−1 were obtained at the temperature range of 288−308 K.Different Fe0 types were compared in this study.The reactivity was in the order starch-stabilized Fe0 nanoparticles>Fe0 nano-particles>Fe0 powder>Fe0 filings.Electrochemical analysis of the reaction process showed that Cr(III)and Fe(III)hydroxides should be the dominant final products.

Preparation of Chromium-iron Metal Powder from Chromium Slag by Reduction Roasting and Magnetic Separation

Chromium slag（CS）has become one of the most hazardous solid waste containing chromium and iron.Based on its characteristics,the technology of reduction roasting and magnetic separation was employed to treat CS.The major impurity element of CS is magnesium and it exists in magnesium ferrite phase,which is hard to recover iron in the absence of additives.During reduction roasting,additives（Al2O3and CaF2）could destroy the structure of magnesium ferrite and improve the iron grade and recovery.The final product,i.e.chromium-iron powder,contains 72.54% Fe and 13.56% Cr,with the iron recovery of 80.34% and chromium recovery of 80.70%.

Formation and characterization of metallic iron grains in coal-based reduction of oolitic iron ore

To reveal the formation and characteristics of metallic iron grains in coal-based reduction, oolitic iron ore was isothermally re- duced in various reduction times at various reduction temperatures. The microstructure and size of the metallic iron phase were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and a Bgrimm process mineralogy analyzer. In the results, the re- duced Fe separates from the ore and forms metallic iron protuberances, and then the subsequent reduced Fe diffuses to the protuberances and grows into metallic iron grains. Most of the metallic iron grains exist in the quasi-spherical shape and inlaid in the slag matrix. The cumula- tive frequency of metallic iron grain size is markedly influenced by both reduction time and temperature. With increasing reduction temperature and time, the grain size of metallic iron obviously increases. According to the classical grain growth equation, the growth kinetic parameters, i.e., time exponent, growth activation energy, and pre-exponential constant, are estimated to be 1.3759 ± 0.0374, 103.18 kJ·mol^-1, and 922.05, respec- tively. Using these calculated parameters, a growth model is established to describe the growth behavior of metallic iron grains.

Growth of metallic iron particles during reductive roasting of boron-bearing magnetite concentrate

The growing characteristics of metallic iron particles during reductive roasting of boron-bearing magnetite concentrate under different conditions were investigated.The size of the metallic iron particles was quantitatively measured via optical image analysis with consideration of size calibration and weighted ratio of image numbers in the core,middle and periphery zones of cross-section of pellets.In order to guarantee the measurement accuracy,54 images were captured in total for each specimen,with a weighted ratio of 1:7:19 with respect to the core,middle and periphery section of the cross-section of pellets.Increasing reduction temperature and time is favorable to the growth of metallic iron particles.Based on the modification of particle size measurement,in terms of time(t)and temperature(T)a predicting model of metallic iron particle size(D),was established as:D=125−0.112t−0.2352T−5.355×10^−4t^2+2.032×10^−4t∙T+1.134×10^−4T^2.

Divalent metal transporter 1 expression and iron deposition in the substantia nigra of a rat model of Parkinson's disease

Extensive iron deposition has been observed in the midbrain substantia nigra （SN） of Parkinson＇s disease （PD） patients, but the mechanisms of iron deposition in the SN remain poorly understood. The present study investigated the relationship between dopaminergic neuronal damage, iron content changes, and divalent metal transporter 1 （DMT1） in the midbrain SN of PD rats to explore the relationship between time of iron deposition and DMT1 expression. Frozen midbrain SN sections from model rats were stained with Perls＇ iron. Results showed massive loss of tyrosine hydroxylase （TH）-positive cells in the SN and increased DMT1 expression in model group rats. No obvious iron deposition was observed in the SN during early stages after damage, but significant iron deposition was detected at 8 weeks post-injury. Results demonstrate that the loss of TH-positive cells in the SN appeared simultaneously with increased DMT1 expression. Extensive iron deposition occurred at 8 weeks post injury, which could be regarded as an early time window of iron deposition.

Chemical Forms of Heavy Metals in Carbonate-Derived Laterite and Enrichment of Its Iron Oxide Minerals

In this paper the seven-step continuous extracting method was employed in the studyof chemical forms of the six heavy metals Co, Zn, Pb, Cu, Cr and Mn. The result shows thatthe metals in the laterite are present in the chemical form of crystalline iron oxides andresidues, and they are transformed toward organic and exchangeable forms in the surface soil.Linear regression analysis indicates that the above heavy metals have a positive correlation withthe crystalline iron oxide minerals. The crystalline iron oxide minerals have a very importantrole to play in the enrichment of heavy metals, especially the solid components in the laterite.

Identifying the optimal HVOF spray parameters to attain minimum porosity and maximum hardness in iron based amorphous metallic coatings

Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.

Preparation of Nano-Sized γ-Al_2O_3 Supported Iron Catalyst for Fischer-Tropsch Synthesis by Solvated Metal Atom Impregnation Methods

Two types of small iron clusters supported on γ-Al2O3-RT（dehydroxylated at room temperature） and γ-Al2O3-800 （dehydroxylated at 800 ℃） were prepared by solvated metal atom impregnation （SMAI） techniques. The iron atom precursor complex, bis（toluene）iron（0） formed in the metal atom reactor, was impregnated into γ-Al2O3 having different concentrations of surface hydroxyl groups to study the effect of surface hydroxylation on the crucial stage of iron cluster formation. Catalysts prepared in this way were characterized by TEM, Mǒssbauer, and chemisorption measurements, and the results show that higher concentration of surface hydroxyl groups of γ-Al2O3-RT favors the formation of more positively charged supported iron cluster Fen/γ-Al2O3-RT, and the lower concentration of surface hydroxyl groups of γ-Al2O3-800 favors the formation of basically neutral supported iron cluster Fen/γ-Al2O3-800. The measured results also indicate that the higher concentration of surface hydroxyl groups causes the rapid decomposition of precursor complex, bis（toluene）iron（0）, and favors the formation of relatively large iron cluster. Consequently, these two types of catalysts show different catalytic properties in Fischer-Tropsch reaction. The catalytic pattern of Fen/γ-Al2O3-RT in F-T reaction is similar to that of the unreduced γ-Fe2O3 and that of Fen/γ-Al2O3-800 is similar to that of the reduced α-Fe2O3.

THE EFFECT OF TRANSITION METAL IONS-IRON ON HYDROGEN PEROXIDE BLEACHING

Hydrogen peroxide bleaching has been extensivelyused in high-yield pulp bleaching. Unfortunately,hydrogen peroxide can be decomposed underalkaline condition, especially when transition metalions exit. Experiments show that the valence oftransition metal ion is also responsible for thedecomposition of hydrogen peroxide.Iron ions are present in two oxidation states, Fe2+ andFe3+. They are both catalytically active to hydrogenperoxide decomposition. Because Fe3+ is brown, itcan affect the brightness of pulp directly, it can alsocombine with phenol, forming complexes which notonly are stable structures and are difficult to beremoved from pulp, but also significantly affect thebrightness of pulp because of their color.Sodium silicate and magnesium sulfate, when usedtogether, can greatly decrease hydrogen peroxidedecomposition. The optimum dosage of sodiumsilicate is about 0.1% (on solution) for Fe2~ and0.25% (on solution) for Fe3~. Adding chelants such asDTPA or EDTA with stabilizers simultaneously canobviously improve pulp brightness. For iron ions, thechelate effect of DTPA is better than that of EDTA.Under acidic conditions, sodium hyposulfite andcellulose can reduce Fe3+ to Fez+ effectively, and pulpbrightness is improved greatly. Adding sodiumthiosulfate simultaneously with magnesium sulfate,sodium silicate, and DTPA to alkaline peroxidesolution can result in higher brightness of pulp.pH is a key parameter during hydrogen peroxidebleaching, the optimum pH value should be 10.5-12.

Investigation on the Geochemical Distribution of REE and Heavy Metals in Western Part of Jalal-Abad Iron Ore Deposit, Zarand, SE of Iran

The Jalal-Abad iron ore deposit, with a reserve of more than 200 Mt ore, is located in NW of Zarand region, southeastern Iran. The ore deposit occurs in the form of an elongated lens-shaped body incorporated in a folded structure of Rizu volcano-sedimentary unit. Mineralization occurred mainly in siltstones, acidic volcanic rocks and dolomitized limestones. The ore minerals include magnetite, hematite, pyrite, chalcopyrite, goethite, malachite and azurite. Chloritization and silicification are the two most widespread alteration types in the Jalal-Abad area. Cu and Ti are among the associated elements with iron in the ore samples. In comparison, the concentrations of Cu, Ti and REE are relatively low in the samples analyzed. The combined concentrations of Ce, La and Y show that geochemical background values for most areas have been measured. The Pearson correlation coefficient values and the results of cluster and principal component analyses indicate a strong correlation between REE, La, Ce, and Y with Sr in the same geochemical group suggesting a common source for these elements. A close association between Cu and Cl with metasomatic host rock and among Pb, Zn and Ba with carbonate host rocks is observed.

Metallic Iron and Nickel in Cretaceous and Cenozoic Sediments: The Results of Thermomagnetic Analysis

With the aid of thermomagnetic analysis (TMA) up to 800&#186;С the composition and distribution of particles of native iron and Fe-Ni alloy was studied in 15 sections, Gams (Austria), Verhorechie and Selbuhra (Crimea), Kvirinaki and Tetritskaro (Georgia), Aimaki, Bass, Dzhengutaj, Madzhalis and Gergebil (North Caucasus, Russia), Klyuchi and Tep-lovka (Volga Region, Russia), Koshak (Kazakhstan), Kara-Kala and Khalats (Turkmenistan). The age of sediments varies from Miocene to Early Cretaceous. Iron particles are present at 521samples out of 921studied. Their percentage varies from 10-5% to 0.05%. The distribution consists of two groups: 1) “zero” group (iron is not found by TMA);2) group of logarithmic normal distribution with a differing modes. The global enrichment by iron particles in synchronous deposits of Miocene, Maastrichtian-Danian, Santonian and Cenomanian was discovered. With respect to nickel content, the iron particles fall into two groups: 1) nearly pure iron without nickel;and 2) iron with nickel content up to 20%, with modal value of 5%. The source of iron particles is the cosmic dust. Particles of pure nickel and the alloy containing more of 20% of nickel are very rare. Possibly, such particles are related mainly with impact events. A peak of elevated iron content with nearly constant nickel of 5-6% was found in almost all studied sections. It is a global effect which is not dependent of place and time of deposition of iron particles.

Geobacter metallireducens异化还原铁氧化物三种方式

异化金属还原菌通过络和剂、电子传递中间体、直接接触三种方式异化还原金属氧化矿.以Geobactermetallireducens还原铁氧化物为实验体系,利用微生物燃料电池考察了以上三种方式对异化还原铁氧化物的影响.结果表明,微生物异化还原铁氧化矿时,NTA,AQDS在初始阶段显著加速铁氧化物的还原,但也加速磁铁矿的生成,阻碍反应继续进行;直接接触方式起着重要作用,吸附形成的生物膜是一个关键因素,其形成是一个相对较长的过程.生物膜的形成阻碍电子传递中间体发挥作用.

基于磁记忆技术的海洋出水铁质文物状态评估与监测——以南海Ⅰ号出水铁器为例

为评估南海Ⅰ号出水铁器的保存状态,运用磁记忆检测技术对铁条(锻钢)进行4通道双分量线扫,对比了置于大气环境中三年后未经保护修复和经过保护修复铁条的保存状态;对铁锅残片(过共晶白口铸铁)进行4通道单分量面扫,并与X射线照相结果进行比较。研究结果表明:磁记忆检测与X射线照相结果相匹配,良好指示裂隙、锈蚀发展区,能有效检出海洋出水铁器内部风险程度较高的应力集中区。风险位置的判据为:(1)磁场强度法向分量方向相对于基线改变,切向分量出现极值;(2)磁场梯度值高,超过检测区段均值的四倍。风险程度量化评估参数为:(1)磁记忆信号特征值,如磁场强度、磁场梯度(G)的平均值、最大值、峰-谷值等;(2)理论应力集中系数m=G_(max)/G_(ave)。量化评估参数的值越大,表明铁质文物的风险程度越高。磁记忆技术能对铁质文物病害的发生和发展进行早期预警,为海洋出水铁质文物的保存状态评估和监测、保护修复流程的安全性监测和有效性评估提供便捷有效的手段,为文物保护工作提供有力的参考。

UV/Fe(Ⅲ)工艺对络合态重金属的去除效果及机理

UV/Fe(Ⅲ)工艺是一种处理络合态重金属的新型组合工艺,该工艺先通过Fe(Ⅲ)的置换作用释放游离重金属离子,然后通过UV辐照对有机配体进行降解,最后通过碱性沉淀去除络合态重金属。以Cu(Ⅱ)-EDTA、Ni(Ⅱ)-EDTA为目标污染物,采用UV/Fe(Ⅲ)工艺对其进行去除,通过去除效果对比和机理分析,对组合工艺去除效果差异的内部机理进行阐述,并提出相应的优化方案。结果表明,UV/Fe(Ⅲ)工艺对Cu(Ⅱ)-EDTA、Ni(Ⅱ)-EDTA的去除效果存在较大差异,对两种络合态重金属中Cu、Ni的去除率分别为70%和41%。通过高效液相色谱(HPLC)、分光光度法、苯甲酸(BA)探针实验,确定Cu(Ⅱ)-EDTA、Ni(Ⅱ)-EDTA去除效果差异的主要原因是Fe(Ⅲ)对Cu(Ⅱ)、Ni(Ⅱ)的置换效果有明显差异,置换率分别是85%、22%。对Ni(Ⅱ)-EDTA置换过程分别进行Fe(Ⅲ)投加量和反应温度优化,结果表明,反应温度优化可以显著提升Fe(Ⅲ)对Ni(Ⅱ)-EDTA的置换效率。将反应温度提升至35℃,Ni去除率从41%提升至60%。反应温度在UV/Fe(Ⅲ)工艺中对Ni(Ⅱ)-EDTA的去除至关重要,适当升温有助于提高置换率,进而提升去除率。

Effects of Cu， Ni， Mn and Mo on the austemperability， microstructures and mechanical properties of ADI weld metal

Effect of Cu. ni. Mn and,mo on the austemperability, Inicroslruclures and Inechanlcal properlies of auslempered duclile iron(ADI) weld metal have been investigated it has been demonslrated foal Mn and.Mo obviously enhance the austemperablity of weld metal. but a exdcess of Mn or Mo impairs the mechanical properties of ADI weld metal because of the formation or carbide at cell boundaries. Cu and Ni can improve the plasticity of ADI weld metal by suppressing the formation of carbide and by increaxsing the amount of austemite,.in order to obtain the weld having both the high austemperability and exceptional combination of mechanical properties. it is advantageous that welds is alloyed withe tWo Or more elements in relalivelv.small amounts.

Effects of CaO and Na2CO3 on the Reduction of High Silicon Iron Ores

The effects of CaO and Na2CO3 on the reduction of high silicon iron ores at 1 250 ℃ were studied. The experimental results showed that the metallization rate was significantly hindered by the addition of CaO and Na2CO3, particularly at the early stage of roasting, compared to the rate without additives. In the absence of additives, iron oxides were quickly reduced to metallic iron, and fayalite was difficult to form. When CaO and Na2CO3 were added, the low reducible iron-containing silicate compounds formed and melted, subsequently retarding the metallization process. The inhibition of Na2CO3 was more noticeable than that of CaO, and higher Na2CO3 doses resulted in stronger inhibition of the increased metallization rate. However, when Na2CO3 was added prior to CaO, the liquid phase formed, which facilitated the growth of the metallic phase. To reinforce the separation of the metallic phase and slag, an appropriate amount of liquid phase generated during the reduction is necessary. It was shown that when 10% CaO and 10% Na2CO3 were added, a high metallization rate and larger metallic iron particles were obtained, thus further decreasing the required Na2CO3 dosage.

Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid–solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation（LPS） prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.