Low-grade Ore Research Articles

Phase transformation assisted reduction roasting of low-grade iron ore via industrial biomass as a reductant

Phase transformation assisted reduction roasting of low-grade iron ore via industrial biomass as a reductant

An environmentally friendly depressant for magnesite and calcite flotation separation: Selective depression and adsorption mechanism

The similar crystal structures and chemical properties of magnesite and calcite make their effective separation through flotation challenging. This study explores the use of Glutamic acid diacetic acid tetrasodium salt (GLDA), a novel environmentally friendly chelating reagent, to enhance the flotation separation of magnesite and calcite. Flotation test results indicate that in a sodium oleate (NaOL) system, GLDA selectively inhibits the flotation of calcite. Under optimal conditions (slurry pH=9.20, GLDA 15 mg/L, and NaOL 140 mg/L), a flotation concentrate with an MgO grade of 46.21 %, CaO grade of 1.39 %, and an MgO recovery rate of 73.17 % was achieved. GLDA minimally affects the hydrophobicity of magnesite but significantly reduces the hydrophobicity of calcite. The selective inhibition mechanism of GLDA was investigated using zeta potential measurements, FTIR, and XPS analyses. Results show that GLDA selectively reacts with Ca sites on the calcite surface, adsorbing and covering it, thereby preventing NaOL from adsorbing on the calcite. Conversely, GLDA has a minor impact on the Mg sites on the magnesite surface, resulting in a negligible effect on NaOL adsorption by magnesite. Consequently, GLDA enhances the flotation separation efficiency of magnesite and calcite. The research results have potential for application in the purification of low-grade magnesite ore.

Application of various methods of benefication to low-grade hematite ore

Application of various methods of benefication to low-grade hematite ore

Ore Characterization and Quality Control Aspects of Gold Cyanidation: The CIL Plant as a Case Study in Sudan

Mineralogical and chemical studies are key to mineral processing because they present the problem of low-grade ores to the metallurgist or mineral processing engineer. Quality control operations are also significant in obtaining good products by flowing the sequences of processes. In this study, the ore was characterized, and quality control issues were discussed. Results showed that the gold grade is 9.7 g/ton, the minerals are mainly silicates, and the pH of the ore is high, which means that without pre-treatment, i.e., roasting, oxidation, etc., it can be cyanided directly. Therefore, the CIL plant could recover more than 90% gold. In quality control of the plant, from each unit at a different time, a representative sample and an accumulative sample were collected and then subjected to analysis like fineness and solid percentage, moisture, and conditions of cyanidation. The results showed steady operation conditions for each unit.

Dissolution Kinetics of Carbonates in Low-Grade Microgranular Phosphate Ore Using Organic Acids as Leaching Agents

Dissolution Kinetics of Carbonates in Low-Grade Microgranular Phosphate Ore Using Organic Acids as Leaching Agents

A comparison of ore pre-concentration efficiency between two high voltage pulse generator systems

High Voltage Pulse (HVP) enabled ore pre-concentration can potentially provide large energy savings and the ability to upgrade low-grade ores for the mining industry. Two types of pulse generator systems commonly used in HVP breakage are Marx generators and pulse transformers. This initial assessment compares the pre-concentration performance of a SelFrag Lab Unit (utilising a Marx generator) and a custom-built HVP machine (employing a pulse transformer) from Huazhong University of Science and Technology (HUST). Eight sets of experimental results using the two generator systems were collected. Two approaches were taken to analyse the data; a trendline approach using all eight sets of data, and a single-point comparison approach with matched specific energy inputs. The results show that there are significant differences in pre-concentration efficiencies with the HUST machine performing better. To elucidate the potential causes, the degree of size reduction (t10), breakage probability, and selective breakage were investigated for the two generator systems. It is likely that the efficiency of selective breakage is one of the major causes, with the HUST machine presenting better results at selectively breaking high-grade particles and consuming less energy. Additionally, the two generator systems have different energy per discharge levels; the effect of this difference should be investigated in future work.

Sintering enhancement process based on fluidity and bonding phase strength

The sintering process is influenced by complex low-grade ores. This study used seven types of imported iron ore, A–F and domestically produced iron ore, G, as raw materials to study their chemical composition, as well as the liquid fluidity and bonding strength of the mixed ore after single and optimised ore blending. The high-temperature characteristic test values of mixed ores are positively correlated with the weighted calculated values of individual ores. Under the sintering cup conditions, the optimal ore mixing includes a 9% increase in liquid fluidity and a 6% increase in bonding strength. The latter significantly improved the sintering yield and drum strength, reaching 75.89% and 65.67%, respectively. In addition, the consumption of solid fuel has slightly decreased by 0.06 kg·t−1, and the utilisation coefficient has slightly increased. In addition, the sintering yield and quality indicators of the scheme have been comprehensively improved. Compared with the benchmark scheme, through liquid fluidity optimisation, an increase in magnetite phase, a decrease in haematite, and a significant decrease in acicular calcium ferrite were observed, interwoven with magnetite. The silicate-bounding iron oxide also showed an increase in this optimisation. In the optimisation of bonding strength, the corrosive structure interwoven with magnetite and needle shaped ferrite significantly increases, while the iron oxide bound with silicate decreases. The improvement effect of liquid phase fluidity and bonding phase strength optimisation on sintering process and mineralisation behaviour was verified through sintering cup test and mineral phase analysis.

Leaching Thermodynamics of Low-Grade Copper Oxide Ore from [(NH4)2SO4]-NH3-H2O Solution.

This paper describes a highly alkaline low-grade copper oxide ore. Copper can be selectively leached out while other metals are retained. A thermodynamic model of the CuO-(NH4)2SO4-NH3-H2O system was established for the leaching of tenorite (CuO) under conditions of mass and charge conservation. MATLAB's fitting functions, along with the diff and solve functions, were used to calculate the optimal ammonia concentration and total copper ion concentration of tenorite under different ammonium sulfate concentrations. The effects of various ammonia-ammonium salt solutions (ammonium sulfate, ammonium carbonate, ammonium chloride) on the copper leaching rate were investigated. Results show that under the conditions of an ammonia concentration of 1.2 mol/L, an ammonia-ammonium ratio of 2:1, a liquid-solid ratio of 3:1, a temperature of 25 °C, and a leaching time of 4 h, the copper leaching rate from the ammonium sulfate and ammonium chloride solutions reaches 70%, which is slightly higher than that of ammonium carbonate. Therefore, an ammonia-ammonium sulfate system is selected for leaching low-grade copper oxide due to its lower corrosion to equipment compared to the chlorination system. The impact of this study on industrial applications includes the potential to find more sustainable and cost-effective methods for resource recovery. The industry can reduce its dependence on resources and mitigate its environmental impact. Readers engaged in low-grade oxidized copper research will benefit from this study.

Laboratory Comparison of Dense Medium Separation and Acid Leaching for Preconcentration of Coarse Rejects from Phosphate Washing Plant

Reverse flotation is a commonly used method for separating carbonate minerals from apatite, but its application to phosphate beneficiation coarse rejects, which are low in P2O5, is often costly due to the high collector dosages used. This study aimed to explore alternative techniques for preconcentration before flotation to improve recovery rates and reduce costs. Our investigation focused on dense medium separation and acid leaching. Dense medium separation, conducted at a cut-off density of 2.76, yielded a preconcentrate with 27% P2O5 and a recovery rate of 90%. The feed material had an initial P2O5 content of 20.52% and a particle size range of +40 µm to −4 mm. In contrast, acid leaching, employing an 8% acetic acid solution over 35 min, yielded a concentrate with 29.11% P2O5, an LOI of 8.99%, and a recovery rate of 100% from an ore fraction [400–200 µm] with an initial P2O5 content of 22.82% and an LOI of 15.78%. Furthermore, integrating flotation and leaching resulted in a concentrate with 32.27% P2O5 and a recovery rate of 98.38%. These findings suggest that combining acid leaching with flotation can enhance P2O5 recovery and reduce processing costs for low-grade phosphate ores.

Sintering Mechanism and Leaching Kinetics of Low-Grade Mixed Lithium Ore and Limestone

With the rapid development of new energy fields and the current shortage of lithium supply, an efficient, clean, and stable lithium resource extraction process is urgently necessary. In this paper, various advanced detection methods were utilized to conduct a mineralogical analysis of the raw ore and systematically study the occurrence state of lithium; the limestone sintering process was strengthened and optimized, elucidating the sintering mechanism and analyzing the leaching process kinetics. Under an ingredient ratio of 1:3, a sample particle size of 300 mesh, a sintering temperature of 1100 °C, a sintering time of 3 h, a liquid–solid ratio of 2:1, a leaching temperature of 95 °C, and a leaching time of 1 h, the leaching rate of Li reached 90.04%. The highly active Ca–O combined with Si–O on the surface of β–spodumene to CaSiO4, and Al–O was isolated and combined with Li to LiAlO2, which was beneficial for the leaching process. The leaching process was controlled by both surface chemical reactions and diffusion processes, and Ea was 27.18 kJ/mol. These studies provide theoretical guidance for the subsequent re-optimization of the process.

A strategy for treatment of low-grade ore: Efficient separation and purification of iron

The gradual depletion of mineral resources has led to the emergence of a new engineering challenge in the field of mineral processing: the effective treatment of low-grade ores. In this study, the low-grade titanium ore leaching solution was employed as the raw material. The extraction ability of a series of hydroxyl extractants for the most common metal iron in minerals was investigated. As a result, a new high-quality processing system for low-grade ore with branched-chain octanol as the core component was constructed. In the treatment of mineral leaching solution, branched-chain octanol has high selectivity and large capacity (111.7 g/L) for iron. It was capable of efficiently removing a significant quantity of iron ions in low-grade ores that were not anticipated to be present. By employing quantum chemical (QC) methodologies, the mechanism for the high selectivity of branched-chain octanol for Fe(Ⅲ) has been elucidated by analyzing the frontier molecular orbital (FMO) energy of acid salts of common metals in minerals. Combined with spectral analysis and slope method, the structure of the extracted complex was confirmed to be [n-R8-OH]2·H·FeCl4. On the basis of system optimization, a three-stage countercurrent extraction and three-stage countercurrent stripping was employed to remove all the Fe(Ⅲ) in the mineral leaching solution. And after detecting, the purity of the obtained Fe(III) solution was greater than 99.5 %. In the treatment of low-grade minerals, especially those containing key metals, the branched-chain octanol extraction system demonstrates high selectivity and reliability, which is a effective means to improve the quality of mineral leaching solution.

A kinetic comparison between in situ hybrid microwave and conventional magnetising roasting of low-grade iron ore composite pellet

This article aims to comprehensively summarise the essential aspects of reduction kinetics in magnetising roasting of low-grade iron ore–coal composite pellets in the hybrid microwave and conventional furnace. The influence of crucial process parameters like temperature, time, and heating methods, including traditional and hybrid microwave heating, is explored. Investigating the impact of low-grade iron ore and coal quality on reduction kinetics is conducted to identify optimal heating methods for upgrading low-grade iron ore to blast furnace grade through magnetising roasting. The study uses diverse gas–solid reaction models to assess the reduction mechanism (Fe2O3 to Fe3O4). Results indicate the success of the contracting volume model for microwave heating, while conventional heating transitions from phase-boundary chemical control to diffusion control. XRD confirms magnetite dominance post-reduction, while scanning electron microscopy analysis establishes microwave crack-assisted efficiency over conventional heating for ease of reduction. A comparative study of apparent activation energy reveals the hybrid microwave method's four-fold lower (36.71 kJ/mol) than conventional resistance heating (156.19 kJ/mol). This underscores the potential of microwave heating for enhanced reduction kinetics and low-grade iron ore material processing applications.

Process Optimization for Gangue Removal from Low-Grade Iron Ore by a Flow-Type Reactor with a NaOH Solution

Process Optimization for Gangue Removal from Low-Grade Iron Ore by a Flow-Type Reactor with a NaOH Solution

Preparation of Nickel–Iron Concentrate from Low-Grade Laterite Nickel Ore by Solid-State Metalized Reduction and Magnetic Separation

Preparation of Nickel–Iron Concentrate from Low-Grade Laterite Nickel Ore by Solid-State Metalized Reduction and Magnetic Separation

Recovery of niobium and titanium from low-grade niobium ores and the evaluation of Fe5Si3 alloy by-product as oxygen evolution reaction electrocatalysts

A low-grade ore containing 4 % niobium and 7 % titanium has been extracted from Bayan Obo tailing, but its potential has not been fully utilized. This study aims to recover the niobium and titanium elements from this low-grade ores in the form of their carbides. The process involves reducing niobium and titanium to (Nb,Ti)C through a carbothermal process. During this process, iron and silicon are also reduced to Fe-Si intermetallic compounds, allowing (Nb,Ti)C to diffuse into them. Subsequently, selective electrochemical oxidation is used to separate (Nb,Ti)C from the Fe-Si intermetallic compounds in an aqueous ferrous sulfate solution. The Fe-Si intermetallic compounds are first oxidized to the Fe3Si phase, and then to the Fe5Si3 phase in the solution with pH 0.35. The (Nb,Ti)C/matrix interfaces are identified as the preferred site of electrochemical pitting corrosion. By exploiting the electrochemical oxidation reaction of iron in the matrix, (Nb,Ti)C powders are separated along these interfaces. The by-products of this process are FeSi alloys, which are evaluated for their electrocatalytic properties in oxygen evolution reactions. It is found that the Fe5Si3 alloy by-product exhibits good electrocatalytic activity and kinetics in the oxygen evolution reaction, demonstrating its potential for practical applications.

Anoxic Manganese Bioleaching – Investigation of Scale-up Parameters in a Stirred Bioreactor

Presently huge operation costs arising from aeration and high electron donor requirements accompanied by low metal recovery rates are some impediments to the large-scale application of bioleaching for low-grade ores. The current study investigates key parameters for scaling up anoxic bioleaching, which overcomes some of the above shortcomings, on polymetallic manganese nodules using soil-based manganese-reducing bacterial consortia in a stirred bioreactor. Operating conditions such as carbon source concentration and pulp density were optimized. Parameters like pH, oxidation–reduction potential (ORP), and microbial growth were monitored in the bioreactor in both stirred and non-stirred conditions. The Mn(IV) reduction and dissolution in the bioreactor was 27 (±2.8)% over 30 days, which significantly enhanced to 43 (±1.5)% and 42 (±0.35)% in the presence of humic acid and anthraquinone sulfonic acid, respectively, in 15 days. A maximum dissolution of 21 (±4.1)% Cu, 10 (±3.0)% Ni, 18 (±4.7)% Co and 7 (±3.9)% Fe were also obtained with 100 µM humic acid from the agitated bioreactor in 15 days. The corresponding specific glucose consumption rate per unit mass of ore was found to be 27 mg g−1 day−1, which is 10 times lower than the rates reported previously for aerobic bioleaching methods. The investigation shows that mild agitation can significantly improve the anoxic bioleaching, especially with added electron shuttles, to enable better ore-bacteria interaction and prevent ore compaction during scale-up. The pH and ORP of the system point toward a reductive dissolution of Mn by the organisms.

A New Approach of Pelletizing: Use of Low-Grade Ore as a Potential Raw Material

A New Approach of Pelletizing: Use of Low-Grade Ore as a Potential Raw Material

Investigating a siderophore-based approach for the recovery of critical metals from waste streams and leach solutions using microorganisms

As technological advancements progress and unsustainable consumerism of electrical devices rapidly increases, the demand for critical metals continues to rise. The limited supply of these metals, driven by the depletion of non-renewable natural resources, calls for the recycling of waste materials and the development of sustainable and cost-effective extraction methods. Conventional methods of leaching such as pyrometallurgy pose threats to the environment by creating slags and releasing toxic secondary materials. Biohydrometallurgy emerges as an environmentally friendly method to extract metals from low-grade ores and waste material. Siderophores are secondary metabolites secreted by microorganisms that have the ability to selectively chelate certain metals. By immobilizing these siderophores for subsequent bioleaching, target metals can be extracted from multielement solutions. This research focuses on optimizing the immobilization efficiency of the siderophore desferrioxamine B (DFOB) in sodium alginate using physical entrapment for the removal of gallium. Four parameters were varied to find optimal conditions: sodium alginate concentration (1 – 4 % w/v), calcium chloride concentration (1 – 10% w/v), agitation time (0.25 – 10 hours), and DFOB concentration (1 – 4 mM). Using UV-Vis spectroscopy, free siderophore concentration could be determined. After 30 runs, the highest immobilization yield of 80.05% was determined at 2.5% sodium alginate, 10% calcium chloride—the highest concentration tested—after 5.13 hours with a concentration of 2.25 mM DFOB. Design Expert-13 software was used to analyze all experimental results. 2D graphs support that DFOB immobilization depends on responsive parameters, CaCl2 demonstrating the largest impact.

High efficiency filtration and optimization of pelletizing performance of fine hematite concentrate using sulfuric acid filter aid: Behavior and mechanism

Following the application of anionic reverse flotation to fine low-grade hematite ore, a significant challenge emerges with elevated slurry viscosity and heightened moisture content in the resulting filter cakes. To address the challenge of dewatering during the filtration process of fine hematite concentrate, the impact of sulfuric acid filter aid dosage and filtration temperature on the filtration performance of hematite concentrate was systematically investigated in this study. In addition, the effect of sulfuric acid filter aid on the preparation of hematite pellets was also studied. The results revealed a significant decrease from 1.10 × 1010 1/m2 to 5.7 × 109 1/m2 in the specific resistance of the hematite filter cake when the sulfuric acid dosage was 1.2 g/kg and the filtration temperature was 20 °C. The mechanism underlying the enhancement of filtration performance of fine hematite concentrate by sulfuric acid was summarized. Sulfuric acid compressed the double electric layer on the surface of hematite concentrate particles, reducing the surface zeta potential and causing the aggregation of fine particles into larger ones. This led to an increase in filter cake porosity and compression of the hydration film thickness on particle surfaces, facilitating easier removal of filtrate from the filter cake. The appropriate dosage of bentonite for pelletizing was not significantly affected by sulfuric acid filter aid. Sulfuric acid improved the porosity, drying rate, and burst temperature of hematite green pellets. While the compressive strength of preheated pellets from sulfuric acid-assisted filtration of hematite concentrate showed a slight decrease, the compressive strength of roasted pellets was significantly increased.

Microwave-assisted alkaline fusion followed by water-leaching for the selective extraction of the refractory metals tungsten, niobium and tantalum from low-grade ores and tailings

The refractory metals tungsten, tantalum and niobium are considered critical raw materials in Europe. Diversifying the supply of such materials, for instance by recovering refractory metals from local low-grade ore materials could reduce their supply risks. However, the extraction processes require to be efficient with a low energy and material consumption and a minimal environmental impact. In this work, microwave (MW) assisted alkaline fusion was explored to extract tungsten from scheelite containing ore materials with different grades (high to very low) and tantalum and niobium from a columbite-tantalite [(Fe,Mn)(Nb,Ta)2O6] concentrate. During the fusion process scheelite was converted into soluble alkali tungstate salts [Na2WO4, K2WO4 and/or K3Na(WO4)2] and the reaction temperature could be lowered to 150–200 °C by fusion with a low-melting eutectic alkali salt system of an 1:1 (m/m) NaOH:KOH mixture. The application of MW-assisted heating allowed for fast and volumetric heating, thereby lowering reaction times to 10 min – 30 min. After fusion, tungsten was extracted by a simple water leaching step leading to extraction efficiencies ranging from 77 % to 97 %. Noteworthily, also P, S and As, which all form soluble oxyanions were extracted from the studied materials. Extraction of niobium and tantalum was also achieved though MW-assisted alkaline fusion as an alternative to acidic fluorine-based hydrometallurgical processes. MW-assisted heating allowed for a fast conversion of the (Fe,Mn)(Nb,Ta)2O6 into alkali tantalate and niobate salts. Under optimal conditions, MW-assisted fusion with KOH (salt:sample = 3:1 (m/m)) at 400 °C for 10 min leached ca. 74 %–88 % of tantalum and 77 %–86 % of niobium into water (L/S=10) at 40 °C for 120 min, while the main matrix elements Mn and Fe displayed limited dissolution (<4%). Due to the low solubility of sodium tantalate and niobate salts in water, MW-assisted alkaline fusion in an eutectic NaOH:KOH mixture followed by water leaching was not efficient.