Dissolution kinetics of iron oxides in clay in oxalic acid solutions

Clay samples containing 8.15% iron oxides and 27.49% alumina were leached in oxalic acid. Leaching experiments were per-formed in aqueous solutions of oxalic acid of 0.2-2 mol/L at 40-80 C for up to 90 min. The mixed kinetic mechanism, i.e., t/τ=[（1 2X/3） （1 X）2/3 ]＋b[ 1 （1 X）1/3], seemed to be the most appropriate one to fit the kinetic data of leaching iron oxides contained in clay in the aqueous oxalic acid solutions. The Arrhenius activation energy for leaching in the 1.8 mol/L oxalic acid was found to be 41.035 kJ/mol.

Mathematical models and expert system for grate-kiln process of iron ore oxide pellet production(Part Ⅰ):Mathematical models of grate process

Grate process is an important step in grate-kiln pellet production.However,as a relatively closed system,the process on grate is inaccessible to direct detection,therefore,it is hard to control.As a result,mathematical models of temperature distribution,moisture distribution and oxidation degree distribution in pellet bed,with good universality,computation speed and calculation accuracy,are presented based on analysis of heat transfer and physical-chemical reactions during grate process.And real-time visualization of temperature,moisture and oxidation degree distribution in pellet bed during grate process is realized.Model validation is displayed,and the similarity of 91% is proved.The results can reveal real time status on grate,and provide a solid foundation for the subsequent study of artificial intelligence control system of pellet production.

Relationship between polymerization degree and cementitious activity of iron ore tailings

The aim of this study is to understand the relationship between the polymerization degree and cememitious activity of iron ore tailings. In light of the poor usage of iron ore tailings, stockpile samples from Tangshan were studied in terms of their ability to become cementitious materials. Compound thermal activation was used to improve the cementitious properties of the tailings, while analyzing methods, such as X-ray diffraction （XRD）, infrared spectroscopy （IR）, nuclear magnetic resonance （NMR）, and X-ray photoelectron spectrometer （XPS）, were employed to study the changes in phase and structure under different activation conditions. The results reveal clear relationships between the binding energies of Si2p and O 1 s, polymerization degree, and cementitious activity of iron ore tailings.

New Constraints on the Environmental Impact of Iron Oxides and Lead-Zinc Mines in Red Sea Hills,Egypt

Iron oxides and lead-zinc deposits in host rocks located in ten drainage basins in the coastal plain of the Red Sea,Egypt,have been subjected to important mining activities.The drainage basins were analyzed to estimate the transportations of these minerals. Fourteen soil samples and fifteen plant samples were collected from sites located in the basin and also in neighboring area and chemically analyzed.In

Characterization and Evaluation of Antibacterial Activities of Chemically Synthesized Iron Oxide Nanoparticles

The iron oxide nanoparticles have been synthesized in co-precipitation method using aqueous solution of ferric and ferrous ions with sodium salt. The synthesis of iron-oxide nanoparticles were validated by UV-Visible spectroscopy which showed higher peak at 370 nm as valid standard reference. An average size of iron oxide nanoparticle found by Diffraction Light scattering (DLS) particle size analyser, ranges approximately between 10 nm to 120 nm with mean particle size of 66 nm. The X-ray power diffraction (XRD) analysis revealed the crystallographic structure of magnetic particles. Characterization of the mean particle size and morphology of iron oxide nanoparticles confirmed that the iron oxide nanoparticles are nearly spherical and crystalline in shape. Further the antibacterial effect of iron oxide nanoparticles was evaluated against ten pathogenic bacteria which showed that the nanoparticles have moderate antibacterial activity against both Gram positive and Gram negative pathogenic bacterial strains and retains potential application in pharmaceutical and biomedical industries.

Photopolymerization of Cyclohexene Oxide Initiated with Iron-arene Complex

Two iron-arene complex photoinitiators with different substituents in arene ligands were synthesized, their activities in initiating photopolymerization of cyclohexene oxide (CHO) were compared with that of IRGACURE 261, a commercialized photoinitiator from Ciba-Geigy. A higher activity was found when the arene ligand was substituted with a stronger electron donating group. For the system initiated by IRGACURE 261 the concentration of active centers in CHO polymerization was determined and it was found that the concentration is maximum at around 35℃. The post (dark) polymerization was significant, the polymerization yield decreased with the increase of irradiation temperature and increased with the increase of post polymerization temperature. The results are interpreted based on the mechanism proposed by Lohse, et al..

Science Letters:Nitrogen doping of activated carbon loading Fe_2O_3 and activity in carbon-nitric oxide reaction

Nitrogen doping of activated carbon loading Fe2O3 was performed by annealing in ammonia, and the activity of the modified carbon for NO reduction was studied in the presence of oxygen. Results show that Fe2O3 enhances the amount of surface oxygen complexes and facilitates nitrogen incorporation in the carbon, especially in the form of pyridinic nitrogen. The modified carbon shows excellent activity for NO reduction in the low temperature regime （〈500℃） because of the cooperative effect of Fe2O3 and the surface nitrogen species.

Strengthening decomposition of oxytetracycline in DBD plasma coupling with Fe-Mn oxide-loaded granular activated carbon

A catalytic approach using a synthesized iron and manganese oxide-supported granular activated carbon(Fe-Mn GAC) under a dielectric barrier discharge(DBD) plasma was investigated to enhance the degradation of oxytetracycline(OTC) in water. The prepared Fe-Mn GAC was characterized by x-ray diffraction and scanning electron microscopy, and the results showed that the bimetallic oxides had been successfully spread on the GAC surface. The experimental results showed that the DBD?+?Fe-Mn GAC exhibited better OTC removal efficiency than the sole DBD and DBD?+?virgin GAC systems. Increasing the fabricated catalyst and discharge voltage was favorable to the antibiotic elimination and energy yield in the hybrid process. The coupling process could be elucidated by the ozone decomposition after Fe-Mn GAC addition, and highly hydroxyl and superoxide radicals both play significant roles in the decontamination. The main intermediate products were identified by HPLC-MS to study the mechanism in the collaborative system.

Efficiency of Iron Supported on Porous Material (Prepared from Peanut Shell) for Liquid Phase Aerobic Oxidation of Alcohols

Catalytic activity and selectivity of prepared catalysts (Fe2O3/ and Fe2O3/AC(KOH)) were investigated for liquid phase aerobic oxidation of primary and secondary alcohols, in a batch reactor, using solvent free condition and/or eco-friendly solvents. The catalysts were characterized by SEM, EDX, XRD, FTIR, TGA/DTA, and surface area and pore size analysis. Experimental data revealed that Fe2O3/AC(KOH) was an efficient catalyst for the oxidation (dehydrogenation) of alcohol while was found to show catalytic activity for both dehydration and dehydrogenation of alcohols. The catalysts were recycled by simple filtration, and used several times without any loss of catalytic activity.

Heterogeneous Oxidation of Methylene Blue with Surface-Modified Iron-Amended Activated Carbon

The present study aims to develop effective adsorption and oxidation of synthetic dye in wastewater by using the newly synthesized iron-amended activated carbon. Recently synthetic dye-containing wastewater has gained more attention due to its mass discharge, high toxicity and low biodegradation. For enhancing adsorption of dye and oxidative regeneration of dye-exhausted activated carbon, the novel amendment of iron-deposited granular activated carbon (GAC) was developed. It was to amend ferrous ion onto the acid-pretreated GAC when pH of iron solution was higher than the pH at point of zero charge (pH, pzc) of the GAC. Methylene blue (MB) in water was adsorbed onto the acid-treated iron- amended GAC (Fe-GAC) followed by single or multiple applications of H2O2. Batch experiments were carried out to study the adsorption isotherm and kinetics indicating adsorption of MB onto the Fe-GAC followed Langmuir isotherm and the pseudo-second order kinetics. The Fe-GACshowed the maximum adsorption capacity (qm) of 238.1 ± 0.78 mg/g which was higher than the virgin GAC with qm of 175.4 ± 13.6 mg/g at 20?C, pH 6 and the initial concentration of 20 - 200 mg/L. The heterogeneous Fenton oxidation of MB in the Fe-GAC revealedthat increasing the H2O2 loading from 7 to 140 mmol H2O2/mmol MB led to enhancing the oxidation efficiency of MB in the GAC from 62.6% to 100% due to the increased generation of hydroxyl radicals. Further enhancement of oxidation of MB in the Fe-GAC was made by the multiple application of H2O2 while minimizing OH radical scavenging often occurring at high concentration of H2O2. Therefore, the acid-treated iron-amended GAC would provide excellent adsorption capacity for MB and high oxidation efficiency of MB in the GAC with multiple applications of H2O2 and optimum iron loading.

Relationship Between Iron Oxides and Surface Charge Characteristics in Soils

The relationship between iron oxides and surface charge characteristics in variable charge soils ( latosol and red earth ) was studied in following three ways. ( 1 ) Remove free iron oxides ( Fed ) and amorphous iron oxides ( Feo ) from the soils with sodium dithionite and acid ammonium oxalate solution respectively. ( 2 ) Add 2% glucose ( on the basis of air-dry soil weight ) to soils and incubate under submerged condition to activate iron oxides, and then the mixtures are dehydrated and air-dried to age iron oxides. ( 3 ) Precipitate various crystalline forms of iron oxides onto kaolinite. The results showed that free iron oxides ( Fed ) were the chief carrier of variable positive charges. Of which crystalline iron oxides ( Fed-Feo ) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges, and did little influence on negative charges. Whereas the amorphous iron oxides ( Feo ) , which presented mainly as a coating with a large specific surface area, not only had positive charges, but also blocked the negative charge sites in soils. Submerged incubation activated iron oxides in the soils, and increased the amount of amorphous iron oxides and the degree of activation of iron oxide, which resulted in the increase of positive and negative charges of soils. Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide, and also led to the decrease of positive and negative charges. Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges. Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges. Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.

Green Oxygenation Degradation of Rhodamine B by Using Activated Molecule Oxygen

Iron(II) tetra-(1,4-dithin)-porphyrazine, (FePz(dtn)4) is able to activate molecule oxygen for oxygenation degradation of rhodamine B (RhB) in an extensive pH region without light excitation. Experiments indicate that the RhB can be degraded nearly 52% in alkaline aqueous solution, bubbling with dioxygen for seven hours in the presence of FePz(dtn)4 and the hydrogen peroxides as an active intermediate were determined by DPD method. The catalyst is recyclable and the catalyst activity was maintained after 10 recycles.

Effect of Fe_2O_3 on the crystallization behavior of glass-ceramics produced from naturally cooled yellow phosphorus furnace slag

CaO–Al2O3–SiO2(CAS) glass-ceramics were prepared via a melting method using naturally cooled yellow phosphorus furnace slag as the main raw material. The effects of the addition of Fe2O3on the crystallization behavior and properties of the prepared glass-ceramics were studied by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The crystallization activation energy was calculated using the modified Johnson–Mehl–Avrami equation. The results show that the intrinsic nucleating agent in the yellow phosphorus furnace slag could effectively promote the crystallization of CAS. The crystallization activation energy first increased and then decreased with increasing amount of added Fe2O3. At 4wt% of added Fe2O3, the crystallization activation energy reached a maximum of 676.374 kJ·mol−1. The type of the main crystalline phase did not change with the amount of added Fe2O3. The primary and secondary crystalline phases were identified as wollastonite (CaSiO3) and hedenbergite (CaFe(Si2O6)), respectively. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Preparation and Photocatalytic Activity of Nanocrystalline GdFeO_3

With Gd2O3, Fe （NO3）3· 9H2O, and nitric acid （ 1： 1 volume fraction） as starting materials, nanocrystalline material of rare-earth composite oxide GdFeO3 with perovskite-type structure was synthesized by sol-gel method in the system of citric acid. Structural characteristics were characterized by XRD and TEM, which indicate that the sample is nanocrystallite with uniform grain size distribution and the average grain size is about 21 nm. Its crystal structure includes a certain amount of lattice distortion due to decrease of grain size and increase of surface area. Photocatalytic properties of this material were tested by decolorization of various water-soluble dyes. Effects of irradiation time and amount of GdFeO3 on photocatalytic activity were also investigated. The results show that nano-sized GdFeO3 exhibits high photocatalytic activity and that increase of irradiation time and the amount of GdFeO3 can improve its photocatalytic activity.

Spectral Response of Different Eroded Soils in Subtropical China: A Case Study in Changting County, China

Hyper-spectral data is widely used to determine soil properties. However, few studies have explored the soil spectral characteristics as response to soil erosion. This study analysed the spectral response of different eroded soils in subtropical China, and then identify the spectral characteristics and soil properties that better discriminate softs with different erosion degrees. Two methods were compared： direct identification by inherent spectral characteristics and indirect identification by predictions of critical soft properties. Results showed that the spectral curves for different degrees of erosion were similar in morphology, while overall reflectance and characteristics of specific absorption peaks were different. When the first method is applied, some differences among different eroded groups were found by integration of associated indicators. However, the index of such indicators showed apparent mixing and crossover among different groups, which reduced the accuracy of identification. For the second method, the correlation between critical soil properties, such as soil organic matter （SOM）, iron and aluminium oxides and reflectance spectra, was analysed. The correlation coefficients for the moderate eroded group were primarily between -0.3 to -0.5, which were worse than the other twogroups. However, the maximum value of R2 was obtained as 0.86 and 0.94 for the non-apparent eroded and the severe group. Furthermore, these two groups also showed some differences in the spectral response of iron complex state （Fep）, Aluminium amorphous state （Alo） and the modelling results for soil organic matter （SOM）. The study proved that it is feasible to identify different degrees of soil erosion by hyperspectral data, and that indirect identification by modelling critical soil properties and reflectance spectra is much better than direct identification. These results indicate that hyper-spectral data may represent a promising tool in monitoring and modelling soil erosion.

Balanites aegyptiaca Oil Synthesized Iron Oxide Nanoparticles: Characterization and Antibacterial Activity

Antibacterial activity of iron oxide nanoparticles, an employing B. aegyptiaca oil (L.) Del., was used as natural stabilizer by modifying a co-precipitation method. In this work, we chose B. aegyptiaca oil as the new surfactant coating agent, and synthesized B. aegyptiaca oil coating with iron oxide nanoparticles which were characterized with a variety of methods, including Gas Chromatography (GC) to determine the fatty acids composition of the seeds oil, Fourier Transform-Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) equipped with Energy Dispersive Spectroscopy (EDS), X-ray Powder Diffractometer (XRD) and Vibrating Sample Magnetometer (VSM). In antibacterial studies, disk diffusion susceptibility test was used to measure efficacy of iron oxide nanoparticles against Gram-positive bacteria Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis) and Gram-negative bacteria Escherichia coli (E. coli) in terms of zone inhibition. The B. aegyptiaca coated on the surface of iron oxide nanoparticles;its particle size was found to be nanoscale below 50 nm, and the magnetization (δs) was 16.975 emu g-1. Antibacterial activity was measured. Efficacy of iron oxide nanoparticles against bacterial strains was found in Escherichia coli (E. coli). All these findings suggest that the nanoparticles synthesized from B. aegyptiaca oil may be a promising reagent for a wide variety of applications in biological fields as well as in nanomedicine.

Influence of rare earth ion substitutions on the structural,optical,transport,dielectric,and magnetic properties of superparamagnetic iron oxide nanoparticles

Superparamgnetic Fe_3O_4 and RE:Fe_3O_4(RE=Dy,Nd,La)nanoparticles with an average crystallite size in the range of 15–24 nm,were synthesized by co-precipitation method.The samples were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),vibrating sample magnetometer(VSM),UV–Vis spectroscopy,LCR bridge,and two-probe technique.X-ray diffraction patterns of all the investigated samples reveal the typical phase of magnetite structure,with a small contribution of orthoferrite(NdFeO_3)as a secondary phase in Nd:Fe_3O_4 sample.The saturation magnetization(M_s)of the samples has values in the range from 41.8 to 52.3 emu/g,and decreases with RE ion doping depending on the ionic radius.Negligible values of the coercivity H_c and remanenceM_r,indicate the superparamagnetic nature of the investigated samples.The calculated values of indirect optical band gap of Fe_3O_4 and RE:Fe_3O_4 nanoparticles are in the range of0.9–1.25 eV.The dielectric constant of the samples decreases,while their activation energy increases with the increasing of ionic radii of dopants.

Deciphering active biocompatibility of iron oxide nanoparticles from their intrinsic antagonism

Magnetite nanoparticles （Fe3O4 NPs） are a well proven biocompatible nanomaterial, which hold great promise in various biomedical applications. Interestingly, unlike conventional biocompatible materials （e.g., polyethylene glycol （PEG）） that are chemically and biologically inert in nature, Fe3O4 NPs are known to be catalytically active and exhibit prominent physiological effects. Herein, we report an ＂active＂, dynamic equilibrium mechanism for maintaining the cellular amenity of Fe3O4 NPs. We examined the effects of two types of iron oxide （magnetite and hematite） NPs in rat pheochromocytoma （PC12） cells and found that both induced stress responses. However, only Fe2O3 NPs caused significant programmed cell death; whereas Fe3O4 NPs are amenable to cells. We found that intrinsic catalase-like activity of Fe3O4 NPs antagonized the accumulation of toxic reactive oxygen species （ROS） induced by themselves, and thereby modulated the extent of cellular oxidative stress, autophagic activity, and programmed cell death. In line with this observation, we effectively reversed severe autophagy and cell death caused by Fe2O3 NPs via co-treatment with natural catalase. This study not only deciphers the distinct intrinsic antagonism of Fe3O4 NPs, but opens new routes to designing biocompatible theranostic nanoparticles with novel mechanisms.

Mechanisms of Exogenous Nitric Oxide and 24-Epibrassinolide Alleviating Chlorosis of Peanut Plants Under Iron Deficiency

Iron(Fe) is a crucial transition metal for all living organisms including plants; however, Fe deficiency frequently occurs in plant because only a small portion of Fe is bioavailable in soil in recent years. To cope with Fe deficiency, plants have evolved a wide range of adaptive responses from changes in morphology to altered physiology. To understand the role of nitric oxide(NO) and 24-epibrassinolide(EBR) in alleviating chlorosis induced by Fe deficiency in peanut(Arachis hypogaea L.) plants, we determined the concentration of chlorophylls, the activation, uptake, and translocation of Fe, the activities of key enzymes, such as ferric-chelate reductase(FCR),proton-translocating adenosine triphosphatase(H^+-ATPase), and antioxidant enzymes, and the accumulation of reactive oxygen species(ROS) and malondialdehyde(MDA) of peanut plants under Fe sufficiency(100 μmol L^(-1)ethylenediaminetetraacetic acid(EDTA)-Fe) and Fe deficiency(0 μmol L^(-1)EDTA-Fe). We also investigated the production of NO in peanut plants subjected to Fe deficiency with foliar application of sodium nitroprusside(SNP), a donor of NO, and/or EBR. The results showed that Fe deficiency resulted in severe chlorosis and oxidative stress, significantly decreased the concentration of chlorophylls and active Fe, and significantly increased NO production. Foliar application of NO and/or EBR increased the activity of antioxidant enzymes, superoxide dismutase,peroxidase, and catalase, and decreased the ROS and MDA concentrations, thus enhancing the resistance of plants to oxidative stress.Application of NO also significantly increased Fe translocation from the roots to the shoots and enhanced the transfer of Fe from the cell wall fraction to the cell organelle and soluble fractions. Consequently, the concentrations of available Fe and chlorophylls in the leaves were elevated. Furthermore, the activities of H^+-ATPase and FCR were enhanced in the Fe-deficient plants. Simultaneously,there was a significant increase in NO production, especially in the plants that received NO, regardless of Fe supply. These suggest that NO or EBR, and, especially, their combination are effective in alleviating plant chlorosis induced by Fe deficiency.

载铁活性氧化铝催化臭氧氧化处理废水COD的工艺研究

为了提高臭氧催化氧化技术对工业废水中有机污染物的去除效率,采用浸渍法,将铁负载于活性氧化铝上。当硝酸铁浓度为0.8 mol/L、臭氧量为5 g/h时,载铁活性氧化铝催化臭氧氧化工业废水有机污染物的去除率最大,约为56%。相比单独使用吸附和臭氧催化氧化技术,它大大提高了废水有机污染物的去除效果。因此载铁活性氧化铝催化臭氧氧化可作为高浓度工业废水去除有机污染物的一种有效方法。