Interactions of ferro-nanoparticles(hematite and magnetite) with reservoir sandstone: implications for surface adsorption and interfacial tension reduction

There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy(strength) and adsorption of Fe2 O3 and Fe3 O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy(XPS) were used to monitor interaction of silicate species with Fe2 O3 and Fe3 O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3 O4 nanofluid,suggesting the intense adsorption of the Fe3 O4 with the crude oil.The measured IFT for brine/oil,Fe2 O3/oil and Fe3 O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3 O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2 O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3 O4 in reducing IFT.

Magnetite-Hematite Transformation: Correlation Between Natural and Sintetic Features

The iron-oxide system can be used as a marker of oxidized and reduced conditions in closed systems. However, natural rocks with iron-oxide minerals also exhibit such reactions, although the natural system is typically open. To understand the behaviour of this natural system, they were investigated the similarities, in terms of crystallographic textures, between the microstructures of two systems: natural open system and synthetic closed system of iron-oxide phase transformation.

The Hydrothermal Na-Ca Alteration at the Marginal Part of the Florina Granite and the Associated Magnetite-Hematite Bands With Thorium and Uranium Mineralization

The Oxia mineralized granite is the product of differentiation in the external parts of the Florina magmatic mass. Acidic hydrothermal solutions either of magmatic or of meteoric origin reacted with the upper tectonically fractured parts of the Florina granite and became enriched in iron, thorium, uranium, zircon and rare-earth elements. The most abundant alteration minerals are sericite and quartz, while the minerals of the mineralization bands include magnetite, hematite, thorite, monazite and zircon. The outer parts of the Oxia granite made it easy the percolation of hydrothermal solutions from the deeper heater to the upper cooler parts of the granite which acted as a hot spot.

Mechanism and kinetics of hydrothermal replacement of magnetite by hematite

The replacement of magnetite by hematite was studied through a series of experiments under mild hydrothermal conditions(140 -220℃, vapour saturated pressures) to quantify the kinetics of the transformation and the relative effects of redox and non-redox processes on the transformation. The results indicate that oxygen is not an essential factor in the replacement reaction of magnetite by hematite, but the addition of excess oxidant does trigger the oxidation reaction, and increases the kinetics of the transformation. However, even under high O_2(aq) environments, some of the replacement still occurred via Fe^(2+) leaching from magnetite. The kinetics of the replacement reaction depends upon temperature and solution parameters such as pH and the concentrations of ligands, all of which are factors that control the solubility of magnetite and affect the transport of Fe^(2+) (and the oxidant) to and from the reaction front. Reaction rates are fast at ~200℃, and in nature transport properties of Fe and,in the case of the redox-controlled replacement, the oxidant will be the rate-limiting control on the reaction progress. Using an Avrami treatment of the kinetic data and the Arrhenius equation, the activation energy for the transformation under non-redox conditions was calculated to be 26 ± 6 kJ mol^(-1).This value is in agreement with the reported activation energy for the dissolution of magnetite, which is the rate-limiting process for the transformation under non-redox conditions.

Growth behavior of the magnetite phase in the reduction of hematite via a fluidized bed

To understand the formation and growth mechanism of the magnetite phase during the fluidized reduction of hematite, a high-purity hematite ore was isothermally reduced using a 20vol% CO 80vol% CO2 gas mixture in a micro-fluidized bed to examine the process of the selective conversion of hematite to magnetite. The micro-structural characteristics of the magnetite phase were investigated using scanning electron microscopy (SEM) and the Brunauer, Emmett, and Teller (BET) method, and the thickness of the magnetite layer was measured and evaluated using statistical analysis. The experimental results showed that the fresh magnetite nuclei were dense needles of different lengths, and the original hematite grains became porous after complete reduction to the magnetite phase. The thickness of the mag- netite layer increased with an increase in reduction temperature and reduction time. The growth kinetics of the magnetite layer was investi- gated, and the value of the activation energy E was estimated to be 28.33 kJ/mol.

Effect of alumina occurrence form on metallurgical properties of hematite and magnetite pellets

The effect of alumina occurrence form on the metallurgical properties of both hematite and magnetite pellets was investigated at the same Al_(2)O level of 2 wt.%,including reduction index(RI),low-temperature reduction disintegration index(RDI),reduction swelling index(RSI),and high-temperature softening-dripping performance.The mineralogy of fired pellets was also studied to reveal the influence of alumina occurrence form on the phase composition and microstructure.From the results,the alumina occurrence form presents tremendous impacts on the metallurgical perfor-mance of both magnetite and hematite pellets.Addition of all alumina occurrence forms contributes to inferior reducibility of pellets,especially in the case of gibbsite for magnetite pellets with a RI of 58.4%and kaolinite for hematite pellets with a RI of 56.8%.However,addition of all alumina occurrence forms improves the RDI of magnetite pellets,while there is no significant difference among various alumina occurrence forms.In contrast,alumina occurrence forms have little influence on the RDI of hematite pellets.The presence of free alumina,gibbsite,and kaolinite tends to improve the RSI of hematite and magnetite pellets,whereas hercynite gives the opposite trend with a RSI of 25.6%.For softening-dripping performance of magnetite pellets,all alumina occurrence forms contribute to narrower softening-melting interval.Meanwhile,alumina,gibbsite,and kaolinite give narrower softening-dripping interval,at 229,217,and 88℃,respectively,whereas addition of hercynite results in the largest melting range at 276℃ due to its high melting point.Regarding hematite pellets,free alumina,gibbsite,and hercynite tend to enlarge melting range,whereas kaolinite contributes to lower dripping temperature of 1148℃ and narrow softening-dripping interval of 88℃ due to the formation of a greater amount of slag phase at high temperatures.

A Study of Rock Magnetism of High-Grade Hematite Ores

Rock magnetism is useful in various applications. Hematite is one of the two most important carriers of magnetism in the natural world and its magnetic features were mostly studied through laboratory experiments using synthetic hematite samples. A gap exists between the magnetic behaviors of hematite contained in the natural rocks and ores and those of synthetic hematite samples. This paper presents the results of a rock magnetism study on the natural hematite ores from the Whaleback mine in the Hamersley Province in the northwest of Western Australia. It was found that high-grade hematite ores carry a much higher remanent magnetization than induced magnetization. Hematite ores with less than 0.1% magnetite appear to have an exponential correlation between the bulk susceptibility and hematite content in weight percentage, different from the commonly accepted linear relationship between the bulk susceptibility and hematite content obtained from synthetic hematite samples. The new knowledge gained from this study contributes to a better understanding of magnetic behaviors of hematite, particularly natural hematite, and hence applications to other relevant disciplines.

鞍千磁赤铁矿石磁选-反浮选工艺优化研究

随着鞍千矿山入选矿石中磁性矿含量增加,为解决当前鞍千矿石联合分选工艺流程中重选精矿品位低、浮选提质困难、浮选尾矿铁损失严重等问题,以鞍千原矿为研究对象,开展原矿磨矿—两段弱磁选—强磁选—反浮选工艺优化实验研究。结果表明:原矿在最佳磨矿细度为-0.043 mm含量80%、两段弱磁选磁场磁感应强度均为0.1 T、强磁选磁场磁感应强度为0.7 T的条件下,得到高品位的弱磁选精矿,由弱磁选精选尾矿与强磁选精矿混合制备的混磁精矿,作为反浮选给矿;在反浮选最佳药剂制度为矿浆温度35±1℃、pH为11.5、淀粉用量800 g/t、CaO用量1000 g/t、粗选和精选捕收剂(TD-Ⅱ)用量分别为1000g/t和450 g/t的条件下,经一次粗选一次精选三次扫选反浮选闭路实验,获得了浮选精矿TFe品位为67.16%、对浮选给矿回收率为93.99%的技术指标。最终采用二段弱磁选—强磁选—反浮选工艺获得了产率为36.94%、铁品位为68.80%、铁回收率为88.19%的铁精矿。通过FTIR分析表明,淀粉可以通过物理吸附的方式选择性吸附在赤铁矿表面,抑制了捕收剂在赤铁矿表面的吸附。

Transformation of hematite in diasporic bauxite during reductive Bayer digestion and recovery of iron

The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate(desilication product,DSP)based on the differences of their surface properties.The results show that the differences of surface properties between magnetite and DSP in zeta potential,wettability and solvation trend facilitate magnetite to agglomerate,grow up and thus to dissociate from DSP.The increments of reductant amount and alkali concentration favor the transformation of hematite in digestion with the relative alumina recovery of98.91%.Processing the resultant red mud can obtain qualified iron concentrate with iron grade of approximate60%and recovery of about86%through magnetic separation,resulting in reduction of red mud emission higher than70%.The results are potential to develop a novel technology for processing high iron diasporic bauxite efficiently and provide references for comprehensive utilization of high iron red mud.

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.

成矿作用过程中赤铁矿-磁铁矿之间非氧化还原转变

自然界中铁氧化物的主要存在形式为赤铁矿和磁铁矿,两者之间的相互转变一直是人们关注和研究的热点。磁铁矿和赤铁矿之间的相互转变一直被认为是一个氧化还原反应的结果,反应的发生与一定的氧化剂或还原剂密切相关。然而,近年来一个铁氧化物之间的非氧化还原反应机制被提出,这种非氧化还原反应机制对于认识和了解复杂的成矿作用具有重要的意义。本文阐述了自然界中铁氧化物之间的相互交代结构,对BIF研究和实验学两方面的证据进行了综述,认为这种非氧化还原反应可能存在于很多不同类型的成矿作用过程之中。这种赤铁矿和磁铁矿之间的非氧化还原反应机制具有重要的理论和实际意义:一方面,仅靠地质作用过程中出现磁铁矿或赤铁矿现象不一定就能判别其形成流体的氧化还原状态;另一方面,它可以为勘探含后生赤铁矿的铁矿床提供新的找矿思路,进一步指导深埋在古风化面以下铁矿体的寻找。

磁选-阴离子反浮选工艺应用现状及展望

通过我国铁矿石资源与国外主要铁矿生产国铁矿石资源情况的对比 ,阐述我国铁矿石因具有储量大、品质差的特点必须加强选矿研究工作的重要性。介绍了国内一些选矿厂实施以“磁选 -阴离子反浮选”选别工艺为核心的工艺流程的研究过程及效果 ,分析了“磁选 -阴离子反浮选”选别工艺的特点 ,提出今后如何更加优化以“磁选 -阴离子反浮选”

α-Fe_2O_3/Fe_3O_4纳米复合材料的相变化及室温磁性质

为研究纳米α-Fe2O3和Fe3O4在受热过程中的物相变化过程和磁学性质,采用燃烧合成方法制备了含α-Fe2O3和Fe3O4不同尺寸的纳米复合材料.用XRD、TEM、穆斯堡尔谱和振动样品磁强计,表征纳米复合材料相变化过程中的性质.结果表明,低于450℃煅烧的复合材料样品中含有一定量的超顺磁相,该相影响着此温度以下煅烧得到的纳米复合材料的磁性质,晶粒尺寸在该温度附近也具有临界现象;复合材料中存在的超顺磁相是超细颗粒尺寸α-Fe2O3和Fe3O4的贡献;当复合材料中的超顺磁相消失后,随煅烧温度提高在复合材料中α-Fe2O3的质量分数不断增加,而Fe3O4的质量分数不断降低直至消失.

高铁赤泥悬浮磁化焙烧-弱磁选提铁工艺

高铁赤泥中的铁含量较多,是一种潜在的铁矿资源.因此,研发创新性工艺和技术以实现赤泥中铁的回收利用和赤泥减量很有必要.针对拜耳法高铁赤泥,制定了悬浮磁化焙烧-弱磁选的工艺流程,并研究了焙烧温度、焙烧时间、还原气CO浓度和总气量对磁化焙烧效果的影响.结果表明,在最佳焙烧条件下,焙烧矿经过弱磁选别,可获得磁选精矿TFe品位为56.40%,回收率为88.46%的指标.通过对原料和焙烧产品的XRD分析、铁的化学物相分析、SEM-EDS分析和VSM分析可知,赤泥中的弱磁性的赤铁矿在磁化焙烧过程中被还原成了强磁性的磁铁矿.

带式焙烧机生产磁-赤型球团矿焙烧试验研究

为扩大首钢京唐504 m2带式焙烧机的原料适应性,在原有配料结构(以磁铁精矿为主)的基础上配加部分赤铁矿粉进行了实验室焙烧试验,共设计了8组配矿方案用于生产磁-赤型球团矿。结果表明:8组方案的球团矿品位均超过65.71%,平均抗压强度均达到2 500N/P以上,还原膨胀率最低的达到17.43%。采用球团综合评价法得出:70%秘鲁磁铁矿粉+30%地方磁铁矿粉的配料方案为最优;当秘鲁磁铁矿配比不低于70%,地方磁铁矿配比不超过30%,两种赤铁矿配比总和不超过10%时,所生产的磁-赤型球团矿可满足超大型高炉的入炉标准,从而为大型带式焙烧机的生产配料提供了更多选择。

某难选铁矿石工艺矿物学研究

某铁矿为高效回收利用西部低品位难选矿石,对西部矿石进行了详细的工艺矿物学研究。研究结果表明:该矿石全铁品位为37.25%,有用矿物主要为磁铁矿和赤(褐)铁矿,分布率分别为90.85%和4.27%,主要杂质SiO2含量21.97%;该矿石主要具块状构造和层状结构。矿石中的磁铁矿主要呈细粒集合体嵌布,与脉石关系紧密,不易解离,磁铁矿在-0.07mm粒级的分布率为83.58%;赤铁矿主要为次生假象矿,原生矿较少,赤铁矿相对磁铁矿结晶粒度更为细小,全部分布在-0.07mm粒级;主要脉石矿物云母、碳酸盐矿物的嵌布粒度相对铁矿物较粗,云母在-0.07 mm粒级的分布率为61.38%,碳酸盐矿物粒度呈粗粒分布,在+0.07mm粒级的分布率为58.50%。

辽宁某磁赤混合铁矿选矿工艺优化研究

辽宁某磁赤混合铁矿选矿厂为了解决原矿中磁性铁含量急剧增加的问题,针对现有工艺流程已经很难适应新的矿石性质的问题,进行了磁、赤分选新工艺选别效果研究。研究结果表明:采用磨矿—阶段磁选—磁赤分离—赤铁矿反浮选的磁、赤分选新工艺选别,可获得全铁品位67.41%的铁精矿,磁、赤分选新工艺流程能实现铁矿物与脉石矿物的有效分离,获得理想的试验指标。

某闲置选矿系统处理某粉状赤铁矿石的可行性研究

毛里塔尼亚粉状(+5.0 mm 22.10%)酸性铁矿石铁品位58.65%,硫、磷含量极低,主要杂质成分为硅,铁在各粒级没有明显的富集现象。为确定该矿石的选矿工艺,进行了实验室试验和工业生产试验。结果表明,在磨矿细度-0.074 mm68.75%、强磁选磁感应强度为1.0 T的条件下,可获得铁品位64.09%、铁回收率92.18%的铁精矿;采用闭路磨矿—弱磁选—2次强磁粗选流程进行工业生产试验,可获得产率85.10%、铁品位63.54%、铁回收率92.68%的总精矿,铁品位28.68%的尾矿可作为铁质校正原料销售至周边水泥厂,实现资源的综合利用。

国外某高磷鲕状铁矿选矿试验研究

国外某高磷鲕状铁矿石主要铁矿物为磁铁矿和赤褐铁矿,有害杂质硫含量较低,伴生杂质硅、铝、磷含量较高。为降低该高磷鲕状铁矿石中的磷矿物含量,提前抛出部分含磷高的尾矿,进行了多粒级干式预选试验研究,探索预选抛废的可行性,同时对磨选工艺进行了阶段磨矿磨矿细度试验。试验确定了原矿阶段磨矿—弱磁选流程,最终获得了产率47.42%、铁品位64.45%、磷品位0.501%、铁回收率53.19%的铁精矿,有效降低了铁精矿中的磷含量,为合理开发利用该铁矿资源提供了参考依据。

梅山自产铁矿石矿物工艺学研究

为更好地开发利用梅山铁矿石资源,开展了工艺矿物学研究。结果表明:①半自熔性混合铁矿石中有回收价值的铁矿物磁铁矿、赤褐铁矿、假象赤铁矿中的铁总分布率达73.97%;磁铁矿多为粒状、不规则粒状、多孔不规则状,粒度悬殊,一般在0.03~0.6 mm,粗粒中常包裹有不等量的细小脉石颗粒,磁铁矿普遍发生了氧化蚀变,生成假象赤铁矿及赤铁矿,因而磁铁矿与赤铁矿共生关系紧密;假象赤铁矿部分与磁铁矿紧密交生产出,部分形成独立的矿粒,粒度一般在0.02~0.3 mm;赤铁矿多为不规则粒状、多孔状,粒度一般在0.015~0.4 mm,只有少部分赤铁矿呈单独矿物出现,与脉石矿物的嵌布关系较磁铁矿紧密。②不同种类的脉石矿物常构成脉石集合体,部分嵌布在不同种类铁矿物间隙,方解石、白云石结晶粒度较粗,与菱铁矿嵌布密切;石英晶粒较细小,部分聚集为集合体,分布较为分散,在脉石矿物及铁矿物间隙中均有嵌布;长石、云母等硅酸盐矿物分布较分散,多与细小石英混杂呈岩屑嵌布在不同矿物间。③在碎至-2 mm样品中,磁(赤)铁矿、菱铁矿单体较少,磁(赤)铁矿单体加富连生体合计占68.55%,这为在较粗粒度下进行预富集创造了条件,有利于减少后续磨选矿量,提高后续磨选给矿品位,减少细粒尾矿量,达到良好的节能减排、降本增效效果。