Papers by Keyword: Hematite

Abstract: Chemical synthesis of nanocomposite particles based on titanium dioxide modified with iron and gold was carried out. It was shown that, depending on the mass content of the doping species, the phase transformation of titanium hydroxide at T = 700 °C proceeds with the formation of either anatase (2 wt.%) or anatase and rutile (8 wt.%). The doping species form a hematite phase and gold clusters on the metal-oxide surface. A weakly crystalline anatase obtained by the transformation of metatitanic acid (MTA), with a particle size of 8 nm and a sulfur content of 0.036%, was selected as the co-catalyst. The anatase co-catalyst exhibits photocatalytic activity in the destruction of organic dyes. Its introduction into the TiO₂&Fe₂O₃&Au nanocomposite suspension promotes the catalytic degradation of cationic and anionic dyes at temperatures ranging from 35 to 60 °C. It was observed that the degradation degree of the solutions after 150 min of catalytic process is the following: Methyl Orange (MO) – 72 %, Methylene Blue (MB) – 71.5 %, Rhodamine B (RhB) – 63.5 %, and Orange G (OG) – 47 %. The reaction rate constant depends on the composition of the dye, varying from 6.5·10^-4 min^-1 for OG to 2.56·10^-3 min^-1 for MB. The prospect of creating heterostructures based on TiO₂ modified with hematite and gold, and their further adaptation for photocatalytic hydrogen production, is considered.

Abstract: Nature has blessed Pakistan with abundant reserves of various ores/minerals. Among these; ores of Chromium, Manganese and Silicon like; Chromite, Manganite, Hausmannite, Braunite and Quartz are phenomenal in metallurgical perspective particularly for ferroalloys production, metals extraction and steel making industry. Unfortunately, Pakistan has been unable to realize the potential associated with these natural assets and therefore adequate mining, ore-beneficiation and value-additive measures are still missing. This paper briefly describes the locations, size and concentration of aforementioned ore/minerals in the country, local and international market trends, potential associated with value-addition of these raw materials and emphasizes the crucial and strategic need for the establishment of a ferroalloy production facility in the country.

Abstract: The article provides information about the initial elements in the waste and tailings of the copper processing plant of the Almalyk Mining and Metallurgical Combine and theoretical solutions for the extraction of metals. According to chemical data, the amount of iron in the waste is high (52.6%), and the most effective solution for extracting iron from the waste is the reduction process. An increase in the amount of iron to 88.9% was formed using coal and lime as reducing agents.

Abstract: This research aimed to study the recycling process and the feasibility of recovering iron as hematite or red oxide powder (Fe₂O₃) from spent pickling acid (hydrochloric acid). The spent hydrochloric acid waste from the pickling bath in the sheet rolling steel industry contains approximately 233 g of iron dissolved in one liter of the spent acid. To recover iron, 2 M NaOH was added to the spent acid until reaching pH 7. The iron was precipitated as iron oxide and/or hydroxide. Next, the oxidation of ferrous oxide was carried out by adding H₂O₂ 35%v/v to control the shade color. The precipitates were subsequently separated from the acid solution by a filter press. The precipitates were dried at 110°C for 24 h and calcined at 700°C for 2 h to synthesize and modify the crystallinity of ferric oxide. Ferric oxide was subject to water washing, where contaminating sodium chloride could be dissolved and filtered out. After drying at 110°C for 24 h, high-purity hematite was achieved. Hematite recovered from the spent pickling acid via this process provided more than 97% purity at 94.4% recovery.

Abstract: In this research, a homemade autoclave reactor was used for preparing iron oxide nanoparticles by hydrothermal technique at different reaction times by using ferric chloride, ferrous sulfate, and ammonium hydroxide as raw materials. The XRD characterization showed that the nanoparticles of the samples have high crystallinity with the crystal phase of magnetite, furthermore, the crystal phase of hematite appears clearly as the reaction time increased. The SEM results showed when the time of reaction increased the average particle size increased too from 28.1 to 49.2 nm. That means the reaction time is an effective parameter for the nanoparticle's growth, The EDX spectrum verified the confirmation of iron oxide nanoparticles by the appearance of Iron and Oxygen peaks. The FT-IR results showed that all samples have an absorption peak at about 578 cm^-1 corresponding to the Fe-O bond stretching modes of the in magnetite and the peak of hematite appeared as the reaction time increased above 2 hours which was confirmed with XRD results. Finally, the reaction time is a powerful tool for controlling in size and phase of nanoparticle preparation. Keywords: Hydrothermal, Iron Oxide, Reaction time, magnetite, and hematite.

Abstract: The annealing temperature dependent on the structural and magnetic properties of hematite (α-Fe₂O₃) powders synthesized via the sol-gel method was studied. The sol-gel method is used to prepare nanoparticles for this experiment. The annealing treatment of 200°C, 400°C, 600°C, and 800°C has been carried out to modify the physical properties. The obtained nanoparticles are characterized by their structural properties using X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Then, magnetic properties were evaluated using Vibrating Sample Magnetometer (VSM). XRD results have shown an increase in crystallite size with an increase in annealing temperature from 35.10 nm to 60.17 nm. The increase in crystallite size can be attributed to the increase in the crystal structure’s internal energy, which promotes atomic diffusion. The FTIR results show an absorption that appears at the peak around ~530 cm^-1. It indicates that the Fe³⁺ cation has successfully formed. The VSM results show an increase in the value of H_c with an increase in the annealing temperature from 117 Oe to 461.5 Oe. It is supported by the increase of anisotropy constant and increasing temperature annealing.

Abstract: Modification of nanometer size order in anode material of hematite nanoparticles is believed to be one of the keys to increasing the specific capacity of Li-ion batteries application. So that, the synthesis temperature dependence of nanocrystallite size properties in co-precipitated hematite nanoparticles is studied. Sample of Hematite nanoparticles is modified the physical properties by synthesis temperature and then annealed of 700°C for 4 hours. The crystallite size increase with the increase of the synthesis temperature i.e., 23.06 to 29.64 nm. It is indicated that the synthesis temperature affects crystallite formation. Furthermore, the magnetic properties show that the coercive field decrease from 869 to 211 Oe with the increase of the temperature synthesis. It is related to the change in the nanosize-order of the sample crystallite.

Abstract: Ultrasonic Spray Pyrolysis (USP) technique was used to prepare undoped and (2, 4, 6 and 10 at. %) Zn-doped iron oxide (Fe_xO_y:Zn) thin films for use in photocatalytic applications. The effect of Zn ion substitution on structural, optical, and electrical properties was studied. The X-ray diffraction patterns showed that there are two different phases of iron oxide, a hematite phase (α‑Fe₂O₃) and a magnetite phase (Fe₃O₄) that crystallized in the prepared samples. The nominal fractions of α‑Fe₂O₃ and Fe₃O₄ phases changed from 74 % to 42 % for the hematite phase and from 26 % to 58 % for the magnetite phase and this confirmed that the Zn doping favored the growth of Fe₃O₄ phase. The crystallite size decreased from 15.43 nm to 8.99 nm, while the micro-strain changed from 0.0056 to 0.0215 and the dislocation density from 0.0099 nm^‑2 to 0.0639 nm^‑2. The unit cell parameters were also improved when the doping rate was changed. Optical measurements showed that the energy gap decreased from 2.26 eV to 2.16 eV, the film thickness changed from 569 nm to 479 nm while the refractive index increased from 2.99 to 3.51 and the Urbach energy from 544 meV to 558 meV. Electrical measurements performed by the two-point probe method showed that the electrical conductivity increased directly with increasing Zn concentration reaching 18.5 10^‑15 (Ω.cm)^‑1 with 10 at. % Zn concentration. The variation of the electrical conductivity curves versus the sample heating temperature as well as the activation energy showed a semiconductor behavior of the films. Zinc doped iron oxide thin films exhibit 51.85 % photocatalytic degradation efficiency for methyl green organic dye.

Abstract: Hematite (α-Fe₂O₃) is a low-cost n-type semiconductor with significant absorption of visible light owing to its low bandgap energy of 2.1 eV. The wide applications of hematite in renewable energy and environmental remediation continuously entice more studies. However, the low absorbance of solar energy in the UV-range significantly limits the efficiency of many photocatalytic materials. In this study, we tried to dope α-Fe₂O₃ with silver via chemical precipitation method to lower the bandgap energy and widen its absorbance. The effects of doping hematite with Ag on the structure, morphology, elemental composition, and optical absorbance were determined by characterizing the samples via X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and UV-Vis spectroscopy, respectively. It was observed from the XRD patterns that the α-Fe₂O₃ crystallizes in hexagonal structure with lattice parameters a = 5.0380 Å and c = 13.7720 Å for the pure α-Fe₂O₃. Doping with 0.1M and 0.2M AgNO₃ leads to a greater value of the lattice parameters indicating successful doping. SEM images show that the hematite formed was composed of particles with irregular shapes that have sizes in the range 0.865-0.883 μm. Excess silver particles were deposited on the surface of hematite. UV-Vis spectra show that there is a red-shift in the absorption band of the Ag-doped hematite. A notable decrease in the bandgap energy of the undoped α-Fe₂O₃ was observed from ~2.2eV to ~2.0eV with the increase in the amount of the dopant in the hematite as determined using Tauc’s plot.

Abstract: In the research activities on the barium monoferrite pyrosynthesis, an important place is occupied by TG and DTA analysis. The effects of different hematite (α-Fe₂O₃) granulations on the BaFe₂O₄ pyrosynthesis temperature were followed. Four types of commercial hematite powders were used, the difference between them being the fineness of the powder granules and the purity. Only one type of commercial barium carbonate (BaCO₃) powder was also used as a barium additive in the BaFe₂O₄ pyrosynthesis. Each of the 4 types of α-Fe₂O₃ with BaCO₃ were subjected to the homogenization process in a planetary mill for a more intimate mixing of the powders in order to obtain error-free results regarding the pyrosynthesis reaction. To determine BaFe₂O₄ pyrosynthesis temperature, a derivatograph device was used. All the data obtained with this thermal device were digitally processed in order to extract the two TG and DTA curves. The protective atmosphere in the furnace was nitrogen. BaFe₂O₄ pyrosynthesis temperatures recorded different values for the four mixtures, depending on the particle size of the α-Fe₂O₃ powders, protective atmosphere from furnace and the mixing conditions. The effects of Fe₂O₃ oxides on the BaFe₂O₄ pyrosynthesis temperature is observed when are used very fine hematite powders in mixtures, obtaining a reduction of pyrosynthesis temperature up to 16% compared to the mixture where the size of the hematite is coarser.