Cost-effective integrated strategy for the fabrication of hard-magnet barium hexaferrite powders from low-grade barite ore

Ultrafine barium hexaferrite (BaFe₁₂O₁₉) powders were synthesized from the metallurgical extracts of low-grade Egyptian barite ore via a co-precipitation route. Hydrometallurgical treatment of barite ore was systematically studied to achieve the maximum dissolution efficiency of Fe (~99.7%) under the optimum conditions. The hexaferrite precursors were obtained by the co-precipitation of BaS produced by the reduction of barite ore with carbon at 1273 K and then dissolved in diluted HCl and FeCl₃ solution at pH 10 using NaOH as a base; the product was then annealed at 1273 K in an open atmosphere. The effect of Fe3+/Ba2+ molar ratio and the addition of hydrogen peroxide (H₂O₂) on the phase structure, crystallite size, morphology, and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. Single-phase BaFe₁₂O₁₉ powder was obtained at an Fe3+/Ba2+ molar ratio of 8.00. The formed powders exhibited a hexagonal platelet-like structure. Good maximum magnetization (48.3 A·m2·kg–1) was achieved in the material prepared at an Fe3+/Ba2+ molar ratio of 8.0 in the presence of 5% H₂O₂ as an oxidizer and at 1273 K because of the formation of a uniform, hexagonal-shaped structure.     

Diffusion behavior and distribution regulation of MgO in MgO-bearing pellets

In this paper, the diffusion behavior between MgO and Fe₂O₃ (the main iron oxide in pellets) is investigated using a diffusion couple method. In addition, the distribution regulation of MgO in MgO-bearing pellets is analyzed via pelletizing experiments. The results illustrate that MgO is prone to diffuse into Fe₂O₃ in the form of solid solution; the diffusion rate considered here is 13.64 μm·min-1. Most MgO content distributes in the iron phase instead of the slag phase. The MF phase {(Mg_1-x Fe_x)O·Fe₂O₃, x ≤ 1} is generated in the MgO-bearing pellets. However, the distribution of MgO in the radial direction of the pellets is inconsistent. The solid solution portion of MgO in the MF phase is larger in the outer layer of the pellets than in the inner layer. In this work, the approximate chemical composition of the MF phase in the outer layer of the pellets is {(Mg_0.35-0.77·Fe_0.65-0.23) O·Fe₂O₃} and in the inner layer is {(Mg_0.13-0.45·Fe_0.87-0.55) O·Fe₂O₃}.     

一株嗜酸氧化亚铁硫杆菌的鉴定及浸矿性能

从西藏甲玛某多金属矿的酸性矿坑水中分离获得一株浸矿细菌(命名为XZ).该菌为革兰氏阴性菌,短杆状,菌体长约1~1.5μm,直径约0.5μm,两端钝圆,能够氧化Fe~(2+)和单质硫,最适生长pH为2.0,最适生长温度为30℃,经过对其生长特性进行研究及16S rRNA基因测序鉴定其为一株嗜酸氧化亚铁硫杆菌.利用XZ菌对西藏某低品位铜矿角岩矿进行了摇瓶浸出试验研究,结果表明,在接种量体积分数为10%,矿浆质量分数为10%,矿石粒度为-45μm占100%,培养温度30℃,振荡强度160 r/min的浸出条件下,经过15 d,Cu~(2+)的浸出率达72.15%.     

用磁选柱精选齐大山选矿厂磁选中矿的试验研究

介绍了用磁选柱选别齐大山选矿厂磁选中矿的实验室研究。试验证明：磁选柱可有效地将磁铁矿连生体颗粒从磁铁矿精矿中分选出来,从而获得高品位的铁精矿。     

Improved flotation performance of hematite fines using citric acid as a dispersant

In this study, citric acid was used as a dispersant to improve the flotation performance of hematite fines. The effect and mechanism of citric acid on the reverse flotation of hematite fines were investigated by flotation tests, sedimentation experiments, scanning electron microscopy (SEM), zeta-potential measurements, and X-ray photoelectron spectroscopy (XPS). The results of SEM analysis and flotation tests reveal that a strong heterocoagulation in the form of slime coating or coagulation in hematite fine slurry affects the beneficiation of hematite ores by froth flotation. The addition of a small amount of citric acid (less than 300 g/t) favorably affects the reverse flotation of hematite fines by improving particle dispersion. The results of sedimentation experiments, zeta-potential measurements, and XPS measurements demonstrate that citric acid adsorbs onto hematite and quartz surfaces via hydrogen bonding, thereby reducing the zeta potentials of mineral surfaces, strengthening the electrical double-layer repulsion between mineral particles, and dispersing the pulp particles.     

Acid Treatment Enables Suppression of Electron–Hole Recombination in Hematite for Photoelectrochemical Water Splitting

We report a strategy for efficient suppression of electron–hole recombination in hematite photoanodes. Acid‐treated hematite showed a substantially enhanced photocurrent density compared to untreated samples. Electrochemical impedance spectroscopy studies revealed that the enhanced photocurrent is partly due to improved efficiency of charge separation. Transient absorption spectroscopic studies coupled to electrochemical measurements indicate that, in addition to improved bulk electrochemical properties, acid‐treated hematite has significantly decreased surface electron–hole recombination losses owing to a greater yield of the trapped photoelectrons being extracted to the external circuit.     

Development of a Statistical Model for Selective Flocculation of Iron Ore Slimes

In this study, an attempt has been made to identify the significant factors that affect the selective flocculation of iron ore slimes using full factorial design. For this purpose, three factors pH, pulp density, and the flocculant dose were investigated. A 2³ factorial design was employed and the results were analyzed statistically. The result indicated that the pH, pulp density, and their interactions significantly affect the grade of the concentrate. Regression model using the design matrix showed that the predicted values are in well agreement with experimental values for grade and recovery. From the studies, it was possible to enhance the grade to 62.78% Fe with a recovery of 84.23% at pH 10, pulp density 1% and a flocculant dose of 0.03 mg/g.     

Controlled Aqueous Growth of Hematite Nanoplate Arrays Directly on Transparent Conductive Substrates and Their Photoelectrochemical Properties

Two‐dimensional (2D) hematite nanoplate arrays were synthesized directly on fluorine‐doped tin oxide (FTO)‐coated glass by using a facile and novel hydrothermal method. High‐temperature annealing retained the morphology of the nanoplate arrays while simultaneously introducing porosity. The thickness and length of the nanoplates could be tailored by adjusting the precursor composition. Photoelectrochemical (PEC) measurements showed that the photocurrent generated with bare hematite nanoplate photoelectrode under backside illumination was about four times of that under frontside illumination in the entire bias range used, which suggested that slow electron transport was a limiting factor for its PEC performance. Upon Sn doping and Co‐Pi co‐catalyst addition, the photocurrent increased significantly owing to the enhancement of electron conductivity and oxidation kinetics. Electrochemical impedance spectroscopy (EIS) measurements were conducted to understand the surface properties of the nanoplate arrays. Since this strategy is simple, cost‐effective, and highly reproducible, it provides exciting opportunities for the large‐scale growth of porous 2D metal oxide photoelectrodes for a variety of photoelectrochemical and photocatalytic applications.     

小秦岭金钼共生矿床地质特征及成矿规律研究

小秦岭地区是中国典型的以金矿为主的矿产地,在该地区罗山金矿发现与金矿共生的石英脉型钼矿床,对罗山金钼矿矿床地质特征和成矿规律进行研究,并对该矿床的最新研究等方面进行归纳。     

软锰矿还原酸浸制取金属锰电解液

对软锰矿还原酸浸过程进行了理论及实验研究,得出了最佳的浸出工艺条件：软锰矿：黄铁矿：硫酸为l：0．4：0．6～0.65,浸出温度95℃,浸出时间6h,液固比5：1。同时还讨论了电解液的净化过程。