Separation of hematite from banded hematite jasper (BHJ) by magnetic coating

The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.     

Significance of interface barrier at electrode of hematite hydroelectric cell for generating ecopower by water splitting

Recent increase in energy demand and associated environmental degradation concern has triggered more research towards alternative green energy sources. Eco‐friendly energy in facile way has been generated from abundantly available iron oxides using only few microliters of water without any external energy source. Hydroelectric cell (HEC) compatible to environment benign, low cost oxygen‐deficient mesoporous hematite nanoparticles has been used for splitting water molecules spontaneously to generate green electricity. Hematite nanoparticles have been synthesized by coprecipitation method. Chemidissociated hydroxyl group presence on hematite surface has been confirmed by infrared spectroscopy (IR) and X‐ray photoelectron spectroscopy (XPS). Surface oxygen vacancies in nanostructured hematite have been identified by transmission electron microscopy (TEM), XPS, and photoluminescence (PL) measurement. Hematite‐based HEC delivers 30 mA current with 0.92 V emf using approximately 500 μL water. Maximum off‐load output power 27.6 mW delivered by 4.84 cm² area hematite‐based HEC is 3.52 times higher than reported 7.84 mW power generated by Li‐magnesium ferrite HEC. Electrochemistry of HEC in different irreversible polarization loss regions has been estimated by applying empirical modeling on V‐I polarization curve revealing the reaction and charge transport mechanism of cell. Tafel slope 22.7 mV has been calculated by modeling of activation polarization overvoltage region of 0.11 V. Low activation polarization indicated easy charge/ion diffusion and faster reaction kinetics of Ag/Zn electrode owing to lesser energy barrier at interface. Dissociated H₃O⁺ ions diffuse through surface via proton hopping, while OH^? ions migrate through interconnected defective crystallite boundaries resulting into high output cell current.     

铁矿石浮选过程中矿物的交互影响及机理研究

复杂矿石浮选体系中矿物间会产生交互影响,研究了在油酸钠浮选体系中,不同粒级的磁铁矿、赤铁矿和石英的交互影响,并讨论了其机理。结果表明:-45+18μm粒级磁铁矿会显著降低赤铁矿的回收率,主要是因为微细粒级矿物消耗了大量捕收剂;-18μm粒级磁铁矿能够大幅度降低石英的回收率,其原因是-18μm粒级磁铁矿在石英粗颗粒表面发生了罩盖;不同粒级磁铁矿,对赤铁矿和石英混合矿浮选会有不同的影响,由于-106+18μm粒级磁铁矿被抑制进入浮选精矿,使浮选精矿铁品位略有提高,-18μm粒级磁铁矿降低浮选精矿铁品位与矿物罩盖有关。     

非洲某特大型铁矿工艺矿物学研究

非洲某特大型铁矿高品位赤褐铁矿矿石铁品位为52.73%,铁主要以赤铁矿、褐铁矿的形式存在,铁在赤褐铁矿中的分布率为90.06%。矿石主要有用矿物为赤褐铁矿,脉石矿物主要为黏土、石英、辉石、水铝氧石。为了给选矿工艺流程的确定提供依据,对高品位赤褐铁矿的矿石进行了工艺矿物学研究。矿石构造主要为块状构造和层状构造,矿石结构主要为斑状结构、粒状结构、针状结构、脉状结构、包含结构。赤铁矿、褐铁矿和含铁黏土工艺嵌布粒度分布较细,在-0.07 mm分布率分别为79.26%、62.93%和58.42%。褐铁矿颗粒中常包裹一些细粒脉石矿物,包体粒径30μm的颗粒占到70%,这部分褐铁矿与脉石关系紧密,不利于褐铁矿的单体解离。通过对高品位赤褐铁矿矿石的工艺矿物学研究可知,样品属于较难选矿石。采用物理选矿方法,回收率应在75%～80%之间,精矿品位很难超过64%。     

Electrochemical reduction of CO2: Two- or three-electrode configuration

Electrocatalytical conversion of CO₂ into various chemicals like hydrocarbons and CO is regarded as a promising approach to mitigate carbon emission and, meanwhile, to provide sustainable energy and value-added chemicals. Two different reactors are used in this work. One is based upon the two-electrode configuration powered by a DC power supply or Si solar cell, which is suitable for practical applications. Another is three-electrode one powered by a potentiostat, which is feasible to study the electrode performance. Polycrystalline Cu electrode is used as the cathode, and hematite is the anode. Performance of CO₂ reduction using the two- and three-electrode configurations is studied by measuring electrode potential, cell voltage, current density, Faradaic efficiency, and reduction selectivity of CO₂. Cu cathode used here exhibits a low overpotential for CO₂ reduction, specifically for the cell with two-electrode configuration. No obvious difference can be observed between the two types of configurations at a low bias like −0.3 and −0.4 V; while the reactor with two-electrode configuration exhibits better performance at a high bias like −0.8 V than the one with three-electrode configuration. Thus, the reactors with two-electrode configuration are desirable for practical applications, specifically considering solar cells can be used as the power source to provide green and sustainable energy.     

鲕状赤铁矿微波碳热还原-磁选提铁脱磷实验研究

采用微波碳热还原-磁选工艺对鲕状赤铁矿提铁脱磷进行了研究,考察了还原温度、碱度、添加剂用量和原矿粒度等因素对提铁脱磷效果的影响。结果表明,最佳还原条件为:还原温度1 150 ℃、碱度0.8、配碳量1.0、钠盐添加剂用量15%、原矿粒度0.15 mm;将还原所得球团磨至-0.15 mm,在65 mT磁场强度下磁选,可得到全铁含量87.98%、铁回收率95.48%、脱磷率69.42%的指标。     

Augmented photoelectrochemical response of CdS/ZnS quantum dots sensitized hematite photoelectrode

A visible light active and stable photoelectrode has been developed by depositing a passivating layer of ZnS QDs on CdS QDs sensitized hematite photoelectrode (Hematite‐CdS/ZnS) for PEC generation of hydrogen. Photoelectrochemical properties, in terms of stability and efficiency, have been investigated on the various hematite photoelectrodes sensitized with CdS QDs and CdS/ZnS QDs by varying number of SILAR cycles. I–V characteristics show that two layers of ZnS QDs deposited over three layers of CdS could enhance PEC response of hematite and efficiency by a factor of 3 and 11 respectively. Chronoamperometry measurement ensures that after adding a layer of ZnS QDs, CdS sensitized hematite film turns out to be a stable photoelectrode in the electrolyte. Prepared photoelectrodes have been characterized by XRD, SEM, HRTEM and UV–Vis spectrophotometer for various structural, morphological and optical properties to analyze PEC results. Mott–Schottky analysis and incident photon to current conversion efficiency (IPCE) measurements of sensitized hematite photoelectrode supported the improved PEC response of CdS/ZnS QDs sensitized hematite thin films. Copyright © 2016 John Wiley & Sons, Ltd.     

Mill scale as a potential additive to improve the quality of hematite ore pellet

Hematite pellet is required to be indurated at very high temperature to achieve its good strength as there is no exothermic heat of oxidation unlike magnetite. As mill scale contains mainly FeO and Fe₃O₄, any minor amount of its addition in pellet can provide in situ heat and enhance diffusion bonding and sintering. In this study, the mill scale generated in steel plant is added as magnetite input in hematite pellet both in acidic and in basic condition. It has been found that in fluxed pellet, mill scale can improve the properties of pellet. In acidic pellet, the induration temperature has been reduced to a great extent (1250–1275°C) and all properties have been found to be improved due to the addition of 15% mill scale. Mill scale shows enough potential to eliminate the flux addition in producing blast furnace quality pellet from hematite ore. Thus, the flux free acidic pellet has been developed even at very low temperature (1275°C) of induration.     

改性淀粉抑制赤铁矿反浮选石英的作用机理研究

通过矿物浮选试验、动电位测定以及吸附量测试,考察了4种淀粉抑制剂对赤铁矿和石英浮选性能的影响,并探讨了其作用机理。在碱性条件下,改性淀粉抑制剂对赤铁矿抑制效果明显,且以改性玉米淀粉效果最佳,改性磷酸酯淀粉、改性羧甲基淀粉的抑制效果次之,而普通淀粉抑制作用一般。同时4种淀粉抑制剂对主要脉石矿物石英的抑制效果均不明显。pH=10~12.5条件下,改性玉米淀粉因其羟基氧和裸露在赤铁矿表面的铁元素发生了化学键合,因而选择性抑制能力最佳。分子动力学模拟表明,改性玉米淀粉片段与赤铁矿作用更为紧密,验证了改性淀粉能更好地抑制赤铁矿。     

配加高磷铁矿的小型烧结试验研究

应用压块、焙烧方法,结合试样的显微结构及X射线衍射（XRD）分析,在固定的烧结温度与碱度的条件下,研究了不同高磷铁矿配比对烧结试样的显微结构和矿物组成的影响。结果表明：随着高磷铁矿配比的增加,试样的显微结构由非均相结构向均相结构过渡;赤铁矿由粒状转变为熔蚀结构,铁酸钙由板状转变为针状;赤铁矿含量逐渐减少,铁酸钙含量逐渐...