Iron Ore Samples Research Articles

CARACTERIZAÇÃO DOS PARÂMETROS DE POROSIDADE DE CONCENTRADOS DE MINÉRIOS DE FERRO PELO MÉTODO DE ADSORÇÃO DE NITROGÊNIO

Nitrogen adsorption analysis using B.E.T. model has been widely used for the characterization of surface area and pore volume of porous and/or microporous materials such as ceramics, soils, clays, coals, non ferrous oxides, but has had little application in iron ore. In this work the main parameters of the B.E.T. method have been used in order to evaluate the iron ore fines characteristics. Some samples of fine-grained iron ore concentrate samples from Quadrilatero Ferrifero were used. The shape of the adsorption – desorption isotherm were used to indicate the geometric form of the porous, and pointed the presence of slit-shaped pores or parallel plates. The mineralogical characterization of pellet feed was determined using reflected light optical microscopy.

Effective Beneficiation of Low Grade Iron Ore Through Jigging Operation

The effectiveness of jigging operation for the beneficiation of low-grade iron ore deposits of Orissa, India has been investigated. Iron ore sample obtained from Barbil region of Orissa containing very high amount of silica and alumina was crushed using the laboratory jaw crusher and roll crusher to prepare different particle sizes. The sink and float tests were carried out to evaluate the possible response of the sample by gravity concentration technique. The samples were subjected to jigging in a laboratory Denver mineral jig and Harz jig. The operating variables used to determine the effectiveness of jigging include, particle size, velocity of water and amplitude. Recovery of iron values and the separation efficiency were assessed by determining mineralogy and the percentages of Fe in the jig concentrate and tailings by wet chemical and X-ray floroscence (XRF) techniques. Optimum iron ore recovery of 78.6% was achieved with 63.7% Fe in concentrate when the jig was operated at medium stroke, with an average water velocity and at a particle size of below 5 mm. The results are very close to theoretical results obtained by sink and float studies.

Utilization of optical image analysis and automatic texture classification for iron ore particle characterisation

Optical image analysis is a very convenient tool for obtaining comprehensive information about fine iron ore size fractions. Data can be obtained on mineral abundances, porosity, particle shape and ore textures with a high level of accuracy. A range of techniques has been used to characterise iron ore samples on a particle-by-particle basis. Automatic textural classification of iron ore particles was used to establish classes containing particles with very similar mineral composition and texture. Image analysis coupled with probe analysis and mineral density measurements provided information about the chemical composition and density of each particle class. The combination of these results enabled a “virtual feed” to be created, which can be a key input into a beneficiation unit model for predicting its performance. Identification and classification of the textural type of each particle was performed according to the CSIRO-Hamersley Iron Ore Group Classification Scheme. If more detailed classification is needed, further classification can be performed based on dimensional, chemical or mineral criteria, such as the presence of certain minerals in particles or total iron content. Some deficiencies of the current image analysis procedures and their further improvement and automation are also discussed.

Concentração de itabirito silicoso da Mina do Sapecado/Complexo Pico - MBR, empregando o classificador hidráulico de fluxo transversal "crossflow"

Nesse trabalho, foi efetuada a concentração da fração granulométrica compreendida entre 0,15 e 1 mm do minério itabirito silicoso da mina do Sapecado do Complexo Pico/MBR, usando o classificador hidráulico de fluxo transversal "crossflow" em duas rotas distintas, efetuando a etapa de concentração "rougher" e a etapa de limpeza dos concentrados de espirais de Humphreys. Para uma alimentação constituída por 60,19% de Fe e 11,81% de sílica, foram obtidos concentrados, de ambas as rotas testadas, com teores de impurezas dentro ou muito próximos aos teores de mercado para os produtos comercializados pela empresa.

Iron isotope fractionation during hydrothermal ore deposition and alteration

Iron isotopes fractionate during hydrothermal processes. Therefore, the Fe isotope composition of ore-forming minerals characterizes either iron sources or fluid histories. The former potentially serves to distinguish between sedimentary, magmatic or metamorphic iron sources, and the latter allows the reconstruction of precipitation and redox processes. These processes take place during ore formation or alteration. The aim of this contribution is to investigate the suitability of this new isotope method as a probe of ore-related processes. For this purpose 51 samples of iron ores and iron mineral separates from the Schwarzwald region, southwest Germany, were analyzed for their iron isotope composition using multicollector ICP-MS. Further, the ore-forming and ore-altering processes were quantitatively modeled using reaction path calculations. The Schwarzwald mining district hosts mineralizations that formed discontinuously over almost 300 Ma of hydrothermal activity. Primary hematite, siderite and sulfides formed from mixing of meteoric fluids with deeper crustal brines. Later, these minerals were partly dissolved and oxidized, and secondary hematite, goethite and iron arsenates were precipitated. Two types of alteration products formed: (1) primary and high-temperature secondary Fe minerals formed between 120 and 300 °C, and (2) low-temperature secondary Fe minerals formed under supergene conditions (<100 °C). Measured iron isotope compositions are variable and cover a range in δ 56Fe between −2.3‰ and +1.3‰. Primary hematite ( δ 56Fe: −0.5‰ to +0.5‰) precipitated by mixing oxidizing surface waters with a hydrothermal fluid that contained moderately light Fe ( δ 56Fe: −0.5‰) leached from the crystalline basement. Occasional input of CO 2-rich waters resulted in precipitation of isotopically light siderite ( δ 56Fe: −1.4 to −0.7‰). The difference between hematite and siderite is compatible with published Fe isotope fractionation factors. The observed range in isotopic compositions can be accounted for by variable fractions of Fe precipitating from the fluid. Therefore, both fluid processes and mass balance can be inferred from Fe isotopes. Supergene weathering of siderite by oxidizing surface waters led to replacement of isotopically light primary siderite by similarly light secondary hematite and goethite, respectively. Because this replacement entails quantitative transfer of iron from precursor mineral to product, no significant isotope fractionation is produced. Hence, Fe isotopes potentially serve to identify precursors in ore alteration products. Goethites from oolitic sedimentary iron ores were also analyzed. Their compositional range appears to indicate oxidative precipitation from relatively uniform Fe dissolved in coastal water. This comprehensive iron isotope study illustrates the potential of the new technique in deciphering ore formation and alteration processes. Isotope ratios are strongly dependent on and highly characteristic of fluid and precipitation histories. Therefore, they are less suitable to provide information on Fe sources. However, it will be possible to unravel the physico-chemical processes leading to the formation, dissolution and redeposition of ores in great detail.

Neutron radiography of porous rocks and iron ore

Neutron radiography can provide images of the internal structure of rocks, through virtue of the differing neutron attenuation characteristics of hydrogen versus other elements commonly found in nature. Thus, pores filled with water, or oil, will attenuate neutrons to a greater extent than the surrounding rock matrix. Similarly, the internal structure of iron ore, which contains mixtures of limonite and goethite, which contain hydrogen in their crystalline lattice, and magnetite (no hydrogen), can also be imaged using neutrons. The ability of the technique to distinguish “effective porosity” versus “total porosity” is derived from the neutron radiographs. Images of two iron ore samples have also been analyzed to demonstrate how both different mineral assemblages and porosity can be determined.

Iron Ore Characterisation during High Temperature Thermal Processing

AbstractIronmaking essentially involves different ways of combining iron ores and energy sources to produce metallic iron. The thermal properties of the iron ores determine the amount of energy required for processing. Investigating and understanding these thermal properties is thus extremely important with respect to controlling the ironmaking processes.Using experimental and mathematical techniques, six iron ores from different origins were thermally characterised in this study. Chemical and structural changes in the iron ore during heating were investigated using SEM, EDS, and XRD analysis. Throughout the process, a number of transformations and reactions were apparent, and these have been quantified for each ore.Goethite was found to decompose between 250‐350 d̀C. This endothermic reaction was found to be the most important stage with the energy requirement to heat iron ore samples dependent upon the amount of goethite in the iron ore. The endothermic kaolinite decomposition occurred at 600 d̀C while the exothermic partial reduction of hematite to magnetite occurred at 850 d̀C. Differences between the raw and sintered iron ores were investigated.

Selective separation of gold from iron ore samples using ion exchange resin

Gold in iron ore samples is separated from iron (major matrix cation), antimony and vanadium using anion exchange resin in (0.2 M) HBr, potassium peroxodisulfate and acetone:water:nitric acid media. The exchangeable anion Cl − of the ion exchanger Dowex 1X 4 is replaced by Br − using (6 M) HBr solution. Certified reference material DGP-M1, spiked ferric magnetic oxide, gold radioactive tracer 198Au and gold standard solutions are used to study the adsorption efficiency and the yield recovery of tetrabromoaurate AuBr 4 − from the resin. Ten eluents have been tried to elute gold from the column, and it has been found that a 10 ml potassium peroxodisulfate and 240 ml acetone:water:nitric acid [125:5:5] solution fulfills the objective. The set up of the separation procedure allows quantitative adsorption of gold by the resin, while the major matrix cation (Fe) and others (Cd, Ag, Cu, V, Sb, Ti) have been passed through the column with the feeding solution (0.2 M) HBr. The resin selectivity coefficient ( K) of separating Au from Fe has been found to be K Fe Au≈6.4×10 11. The eluted Au is treated with K 2S 2O 8 and H 2O 2 for spectrophotometric determination as rhodamine-B complex at 555.6 nm. The linearity, detection limit, precision, and accuracy of the determination method have been found to be up to 2.0 μg g −1, 0.018 μg g −1, 0.009 μg g −1 and 3%, respectively.

Calibration by the gradient ratio-standard addition method in flow injection flame atomic absorption spectrometry

A calibration method has been developed which is realised in the flow injection analysis (FIA) by the gradient technique. According to this method two transient peaks, one for a sample and the other for a sample with standard addition, are recorded and compared point by point in the entire defined time range. The analytical result is estimated on the basis of information gained about the local analyte concentrations in the sample zone. The method allows the results to be reliable when both the non-linear calibration dependence and the interference effect occur. As an example, calcium in synthetic samples containing silicon, phosphate, aluminium, vanadium and titanium, and also in iron ore sample, were determined by flame atomic absorption spectrometry (FAAS). It has been proved, that the method can be effective in overcoming even extremely strong interferences, providing analytical results with average accuracy equal to ca. 5% and with precision 2–3 times inferior to that obtained by conventional FI calibration.

Statistical validation of standardless and standard-based analysis by X-ray fluorescence spectrometry in iron ores characterisation

An X-ray fluorescence (XRF) study comparing the performances of standardless or semiquantitative analysis in relation to the traditional standard-based or quantitative analysis technique is presented. This comparison using precision lines and simultaneous confidence intervals provides reliable information about the precision and trueness that each technique can achieve. This study enables the comparison of the results obtained with two different analytical approaches for iron ore samples in terms of precision and accuracy of results, sample preparation and availability of standards. A new technique for assessing the accuracy of an analytical method using linear regression is presented, wherein the results of both analyses are regressed against certified reference materials. The statistical test performed is based on the joint confidence interval for the slope and the intercept of the regression line calculated considering the uncertainties in both axes or in both analytical methods. The slope, intercept and variances associated with the regression coefficients are calculated with bivariate least-squares regression. Some chosen standard-samples were analysed for statistical validation of the methods. These samples had sufficient replicates to perform the calculations and later statistical comparison between the accuracy (precision and trueness) of each analytical method and evaluation of its precision lines.

Isotachophoretic separation behavior of rare-earth EDTA chelates and analysis of minor rare-earth elements in an iron ore by bidirectional isotachophoresis–particle-induced X-ray emission

Mobilities of 16 anions of rare-earth–EDTA 1:1 chelate (RE–EDTAs) were isotachophoretically measured by using two leading electrolytes (pH 3.6 and 6.0) in order to assess their separation behavior. The leading electrolyte was 20 m M hydrochloric acid. The pH of the solution was adjusted to 3.6 by adding β-alanine and to 6.0 by adding histidine. The obtained mobilities were very close to each other in the range 20.1·10 −5–21.9·10 −5 cm 2 V −1 s −1 with the minimum mobilities for Pr–EDTA and Nd–EDTA for pH 3.6 and 6.0, respectively, and pH dependence was hardly observed. On the basis of the above knowledge, minor rare-earth elements in a standard iron ore sample were determined as RE–EDTAs by bidirectional isotachophoresis–particle-induced X-ray emission (PIXE), where the Fe(II) matrix digested by alkali fusion was separated as Fe(II)Phen 3 2+ (phen=1,10-phenanthroline). Since 5% of the total iron was still detected as Fe(III)EDTA − and might disturb PIXE analysis of RE–EDTA −, itaconic acid was used as the spacer for Fe(III)EDTA − and RE–EDTA −. The fractions of RE–EDTA − were successfully analyzed off-line by a multielemental analytical method, PIXE [analytical result (3.62% (w/w) as RE 2O 3]; the nominal value was 3.37% (w/w) as RE x O y .

Mineralogical And Chemical Investigations Of Bloomery Slags From Prehistoric (8th Century Bc To 4th Century Ad) Iron Production Sites In Upper And Lower Lusatia, Germany

More than 400 fayalitic bloomery slags from prehistoric iron production sites in Upper and Lower Lusatia, eastern Germany, as well as bog iron ore samples and intermediary samples of the smelting process, were analysed by chemical and mineralogical techniques. While the precursor bog iron ores exploited in the two regions under investigation were very similar in composition, consisting of low‐manganese/low‐barium as well as high‐manganese/high‐barium types of ore, pronounced differences in slag composition were detected. Slags from 17 investigated sites in Upper Lusatia showed average P2O5 contents between 1 and 3 mass%, whereas slags from 15 investigated sites in Lower Lusatia were generally much richer in phosphorus, reaching values as high as 7 mass% P2O5. Since a reasonable correlation exists between calcium and phosphorus contents in the slags of the latter sites, it is conjectured that deliberate addition of CaO to the ore/charcoal charge of the bloomery furnace may have taken place in order to fix the phosphorus in the slags effectively. In many samples, this conjecture is being supported by the detection of a slag mineral Ca–Fe phosphate Ca9−xFe1+x(PO4)7 that presumably crystallized from a residual phosphorus‐rich melt and shows a cotectic relationship to both Ca‐rich fayalite and wustite, as well as to members of the solid solution series magnetite–hercynite.

Teaching Sample Preparation in the Undergraduate Laboratory

Teaching sample preparation in an undergraduate analytical chemistry laboratory provides many challenges. For example, the time required to properly digest a sample means that sample preparation and method development are often deliberately overlooked in the undergraduate laboratory. To teach sample preparation, we have developed an experiment for the acid digestion of an iron ore sample in a microwave oven. From a pedagogical perspective, the microwave oven has the advantage of allowing easy control of experimental parameters such as heating power and time. This experiment requires two 3-hour lab periods. One lab period is required for determining the optimum conditions to achieve maximum extraction of Fe from an iron ore sample. The digestion parameters used for this experiment are choice of acid, digestion time at a fixed microwave power, and microwave power at a fixed time. A second lab period is required for the preparation of calibration standards and the analysis of the ore samples for Fe using flame atomic absorption spectroscopy. Using the optimum digestion parameters, Fe was measured in a known ore sample and was within 2% of the expected concentration.

Behaviour of manganese oxides during magnetising reduction of Baharia iron ore by CO–CO2 gas mixture

High manganese containing iron ore samples were isothermally reduced with a CO–CO2 gas mixture at 600–1000°C. The course of reduction was followed by a weight loss technique. The influence of reducing gas composition and temperature on the reduction kinetics was investigated. The different phases formed during reduction were identified by X-ray phase analysis, while their structures were microscopically examined. The reduced samples were magnetically tested by means of a Davis tube tester. The effect of grain size, drum speed, and cleaning conditions on the efficiency of magnetic separation was studied using a Box-Mag wet low intensity magnetic separator. The separation efficiency was determined by analysing total iron, manganese, and acid insoluble contents in both magnetic and non-magnetic fractions. Best testing results were obtained on separation of the sample reduced with 80CO–20CO2 (vol.-%) at 800°C. The optimum grain size for magnetic separation is below 0·15 mm while that of the drum speed is 100 rev min-1 . The cleaning of the magnetic fraction increases the iron content and decreases the manganese and acid insoluble contents.

Significance of Pressure, Temperature and Reaction Rate Events in a Blast Furnace Simulation Test.

The condition of iron ore samples in blast furnace simulation tests according to the REAS procedure was determined by interrupting the test at different stages close to the maximum in the pressure drop across the sample bed. While the onset of the pressure increase does agree with liquid formation (melting of fayalite), the increase in the pressure drop appears to be related to sample compaction (softening). Elimination of pores formed by reduction (rather than lubrication by liquid) appears to be the main factor affecting compaction. The first strong temperature arrest is not associated with melting of the slag phase, but rather with the onset of (endothermic) direct reduction.

Dephosphorisation of western australian iron ore by hydrometallurgical process

More than 80% of Western Australian iron ore contains an average of 0.15% phosphorus, and attracts a penalty due to its high level of phosphorus when it is exported. At the current rate of mining, identified premium grade iron ore with low phosphorus content (<0.05%) will be depleted in 30 years. The development of an economical dephosphorisation process is critical for the future success of the Western Australian iron ore industry. In the current work, effective dephosphorisation of Western Australian iron has been demonstrated. Sulphuric acid was chosen as the leachant on the basis of its availability and low cost. The iron ore sample used in this study typically contained 0.126% phosphorus, was from the Pilbara region of Western Australia. After roasting at 1250°C lump ore P 80 5.6 mm), pellet 1 (grinding to 100% −1.5 mm before pelletisation) and pellet 2 (grinding to 100% −0.15 mm before pelletisation) were leached in solutions with different sulphuric acid concentrations. After leaching for 5 hours at 60°C in 0.1 M sulphuric acid solution, 67.2%, 69.0% and 68.7% of the phosphorus was leached from the above three samples, respectively. The phosphorus content was reduced from 0.126% to 0.044%, 0.055% and 0.042% respectively. The dissolution of iron during leaching was negligible. The optimum sulphuric acid concentration was 0.1 M in terms of acid cost and iron loss. The acid consumption cost is as low as $A 0.47/tonne. reserved.

Successive Potentiometric Titration of Iron(II) and Iron(III) with Cobalt(II) in the Presence of 1,10-Phenanthroline

A novel potentiometric titration of iron(II) and iron(III) is proposed. The method is based on the effect of 1,10-phenan-throline (phen) on the redox reactions of chromium(VI) and iron(III) with cobalt(II). In the presence of phen the conditional redox potential of the Co(III)/Co(II) system falls below those of the Cr(VI)/Cr(III) and Fe(III)/Fe(II) systems at pH around 1. Therefore, chromium(VI) and iron(III) can be titrated with cobalt(II) in the presence of phen, alternatively. Firstly, to a sample solution containing iron(II) and iron(III), a known amount of chromium(VI) is added in excess at pH around 1, so that iron(II) can be oxidized to iron(III) in the absence of phen. After the pretreatment, the sample solution containing the excess of chromium(VI) and iron(III) (total iron) is titrated with a standard cobalt(II) solution in the presence of phen. The concentrations of iron(II) and iron(III) can be calculated from the first and second potential breaks at the equivalence points for the titration. The relative standard deviations of this method were 0.66 and 0.81% for four determinations of 5 × 10–4 mol dm–3 iron(II) and 1 × 10–3 mol dm–3 iron(III), respectively. The proposed method was successfully applied to the determination of total iron in standard iron-ore samples (JSS No. 801–4, 814–1 and 850–4) and to the successive determination of iron(II) and iron(III) in a Mosan iron-ore sample (JSS No. 812–3).

Flow-injection/standard subtraction method for the determination of iron(III) based on its catalytic effect and inhibition of EDTA

A new approach for the flow-injection catalytic determination of 10 −6 M levels of iron(III) is proposed. This method is based on the catalytic effect of iron(III) on the oxidative coupling of p-anisidine with N,N-dimethylaniline to form a blue compound ( λ max=735 nm) in the presence of hydrogen peroxide and 1,10-phenanthroline as an activator, and the inhibitory effect of EDTA on the iron(III)-catalyzed reaction. The concentration of iron(III) can be determined from only two flow signals which are obtained by injecting the iron(III) and iron(III) plus EDTA solutions into the flow lines without a calibration graph for iron(III); this procedure may be called standard subtraction. The proposed method permits the analysis of 12 samples per hour (24 peaks per hour) and was successfully applied to the determination of iron in standard iron ore samples.

Calibration procedure for flow injection flame atomic absorption spectrometry with interferents as spectrochemical buffers

The flow injection calibration procedure has been developed to correct for interferences in flame atomic absorption spectrometry. For this purpose a sample and standard solutions were injected one after the other into the carrier stream containing some reagents known to usually produce strong interference effects. Affecting the analyte in both zones to the same extent they were able to act as spectrochemical buffers. As an example, calcium in synthetic samples containing aluminium, titanium and vanadium, and also in iron ore samples, was determined. The procedure appeared to be quite effective in overcoming interferences even as strong as nearly 90%, providing analytical results with average accuracy equal to ca. 5%. Precision attained was 2–3 times inferior than that obtained using conventional FI calibration.

Evidence for hibbingite–kempite solid solution

AbstractNew occurrences of hibbingite, γ-Fe2(OH)3Cl, have been found associated with platinum-group minerals in the Noril'sk Complex, and with the Korshunovskoye iron ores of the southern Siberian platform. The Norils'k grains, which are up to 0. 6 mm in diameter, are associated with the platinumgroup minerals froodite, cabriite, urvantsevite and with native silver in massive pentlandite–cubanite– chalcopyrite ore. The Korshunovskoye iron ore sample in which hibbingite was found is composed of fine-grained magnetite ore associated with halite. Hibbingite, hematite and silver grains are found in cavities in halite; the reddish-brown hibbingite grains usually occur as encrustations in the cavities. The size of hibbingite and hematite grains is up to 100 µm.Hibbingite from the Noril'sk Complex contains a significant kempite (Mn2(OH)3Cl) component; in some cases it contains over 50 mol. % Mn. These data suggest that at least a partial solid solution series exists between hibbingite and kempite. All known occurrences of hibbingite represent paragenetically late mineral assemblages. In the case of the Korshunovskoye deposits, the occurrences are associated with highly concentrated hydrothermal brines derived from the Lower Paleozoic saline sediments of the Siberian Platform cover.