Raw Ore Research Articles

Occurrence and transformation of mercury in formerly contaminated soils due to operation of amalgamation techniques and assessment of consequences

Soils formerly contaminated with mercury due to the implementation of amalgamation processes at two localities in the Czech Republic were analyzed to assess the impact of such contamination on both the environment and human health. One site is an abandoned gold mine at Libčice, where, in the past, gold was extracted from the raw ore by the mercury amalgamation technique. The second site is the environs of a small building in Prague where dental surgery was formerly undertaken. Soils were tested for total mercury (T-Hg), elemental mercury (Hg0), methylmercury (MeHg+), phenylmercury (PhHg+), and gaseous elemental mercury (GEM). The T-Hg concentrations in both localities exceeded many times the maximum permissible limit for soils in the Czech Republic. The most contaminated soils were found around the dental surgery releasing GEM at concentrations of up to 1308 ng m−3, which can represent a danger mainly for people through inhalation. Soils near the abandoned gold mine release GEM at concentrations of up to 26 ng m−3, which indicates a long-term burden on the environment and a danger for surrounding farmland.

Effects of energy source on bioleaching of vanadium-bearing shale by Acidithiobacillus ferrooxidans

The effects of energy source (ferrous iron, elemental sulfur and its mixture) on bioleaching of differently pretreated vanadium-bearing shale by Acidithiobacillus ferrooxidans (A. ferrooxidans) were investigated in this paper. The results in the absence of energy source indicated that bioleaching efficiencies of vanadium from raw ore and decarbonized sample were 25.32% and 30.11%, respectively. The positive effects of sulfur as a sole energy source were observed on two types of samples, with vanadium leaching efficiency values of up to 47.86% and 63.32%. However, the bioleaching efficiencies of Fe2+ as a sole energy source were only 36.22% and 25.94%, respectively. Decarbonization promoted the vanadium leaching efficiency of other groups, but growth on only Fe2+ immensely reduced vanadium bioleaching efficiency. The changes of pH, Eh and cell density indicated the relatively higher activities of A. ferrooxidans cultures containing iron in comparison to cultures grown on sulfur as the sole energy source soon after inoculation. A bioleaching mechanism model of differently pretreated vanadium-shale with the culture of Fe2+ as sole energy source was projected. Compared with Fe-containing culture, the addition of sulfur avoided the formation of jarosite, which was more propitious to vanadium extraction. Meanwhile, the sulfur amended cultures achieved higher acidity, which reduced the acid consumption.

Leaching Process and Mechanism of Weathered Crust Elution-Deposited Rare Earth Ore

The leaching processes and mechanisms of weathered crust elution-deposited rare earth (RE) ores with ammonium sulfate were investigated for their high efficiency and low consumption exploitation. The leaching process is a typical reversible heterogeneous ion exchange reaction in liquid–solid systems. The raw ore and leached tailings were analyzed by SEM and FTIR. Results indicated that no dissolution or structural changes of the ores occurred during the leaching process. The migrations of RE3+, Al3+, and $$ {\mathrm{NH}}_4^{+} $$ in the leaching process were studied under various liquid–solid ratios. With increasing liquid–solid ratio, the content of $$ {\mathrm{NH}}_4^{+} $$ adsorbed on clay mineral by physical effect decreased, $$ {\mathrm{NH}}_4^{+} $$ adsorbed by ion-exchange increased, and the content of exchanged RE and Al increased until reaching equilibrium. The adsorption capacity of the RE ores for $$ {\mathrm{NH}}_4^{+} $$ remained about 0.61–0.63 mg/g. It was difficult to desorb $$ {\mathrm{NH}}_4^{+} $$ from RE ores with washing water alone. The leaching mechanism of Al was the same as RE, but the leaching of Al slightly lagged behind RE. At the optimal liquid–solid ratio of 0.4:1, the leaching efficiencies of RE and Al were 95.51% and 90.99%, respectively, and 56.65% of $$ {\mathrm{NH}}_4^{+} $$ remained in the leachate. After impurity removal and RE precipitation, the leachate can be reused by replenishing fresh leaching agent. The aim of this study is to enhance the leaching process of RE, restrain the leaching of impurities, and decrease the consumption of leaching agents.

Dissolution Kinetics of Ilmenite Ore in A Binary Solution

Leaching of iron from ilmenite ore using a binary solution (HCl-NaNO3) was investigated. The raw ilmenite ore sample was characterized using Scanning Electron Microscopy (SEM), X-ray diffraction spectroscopy (XRD) and X-ray Flourescence (XRF) techniques. The influence of acid concentration, oxidant concentration, particle size, solution temperature, stirring speed and liquid-to-solid ratios on the extent of dissolution was examined. The experimental data obtained at various process parameter conditions were tested in six kinetics models: shrinking core model’s diffusion through liquid film model(DTLF), diffusion through product layer model (DTPL), surface chemical reaction model (SCR)); mixed kinetics model (MKM), Jander (three dimensional) model and Kröger and Ziegler model. The crystalline morphology of the sample was displayed by the SEM micrograph. XRF result revealed the dominance of titanium and iron in ilmenite while XRD confirmed that ilmenite exist mainly as FeTiO2. The results of the leaching studies showed that ilmenite dissolution in the binary solution increases with increasing acid concentration, oxidant concentration, reaction temperature, stirring speed and liquid-to-solid ratio; while it decreases with particle size. The study showed that 94.77% iron was dissolved by 1MHCl-0.6M NaNO3 at 75μm particle size, 75˚C reaction temperature, 300rpm stirring speed and 30L/g liquid-to-solid ratio. The kinetics of the leaching process was best described by Kröger and Ziegler model with diffusion through the product layer as rate controlling step. The activation energy, Ea, was calculated to be 6.42kJ/mol. The results indicate that HCl-NaNO3 binary solution can be used as an effective lixiviant for extracting iron from ilmenite ores.

Dissolution Kinetics of Ilmenite Ore in A Binary Solution

Leaching of iron from ilmenite ore using a binary solution (HCl-NaNO3) was investigated. The raw ilmenite ore sample was characterized using Scanning Electron Microscopy (SEM), X-ray diffraction spectroscopy (XRD) and X-ray Flourescence (XRF) techniques. The influence of acid concentration, oxidant concentration, particle size, solution temperature, stirring speed and liquid-to-solid ratios on the extent of dissolution was examined. The experimental data obtained at various process parameter conditions were tested in six kinetics models: shrinking core model’s diffusion through liquid film model(DTLF), diffusion through product layer model (DTPL), surface chemical reaction model (SCR)); mixed kinetics model (MKM), Jander (three dimensional) model and Kröger and Ziegler model. The crystalline morphology of the sample was displayed by the SEM micrograph. XRF result revealed the dominance of titanium and iron in ilmenite while XRD confirmed that ilmenite exist mainly as FeTiO2. The results of the leaching studies showed that ilmenite dissolution in the binary solution increases with increasing acid concentration, oxidant concentration, reaction temperature, stirring speed and liquid-to-solid ratio; while it decreases with particle size. The study showed that 94.77% iron was dissolved by 1MHCl-0.6M NaNO3 at 75?m particle size, 75?C reaction temperature, 300rpm stirring speed and 30L/g liquid-to-solid ratio. The kinetics of the leaching process was best described by Kröger and Ziegler model with diffusion through the product layer as rate controlling step. The activation energy, Ea, was calculated to be 6.42kJ/mol. The results indicate that HCl-NaNO3 binary solution can be used as an effective lixiviant for extracting iron from ilmenite ores.

Harnessing Native Iron Ore as an Efficient Electrocatalyst for Overall Water Splitting

AbstractElectrochemical water splitting is a widely accepted approach to generate hydrogen at a scale that is suitable for storing renewable energy. Therefore, the choice of catalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical in terms of cost when scaling up this technology. Thus, earth abundant transition metals oxides and sulfides have received significant attention as catalysts for the OER and HER, respectively. However, very few examples of actual Earth abundant materials mined from the Earth's crust have been used as electrocatalysts for these reactions. Here, we demonstrate that a raw iron ore is active for both the HER and OER under alkaline conditions, which is due to the natural abundance of the key elements of iron, nickel, and sulfur. The catalyst is stable for both reactions and can operate at 100 mA cm−2, which is comparable to many chemically synthesised nanomaterials based on these elements. This approach may be attractive for adding value to iron ore while minimising the cost of catalyst production.

A method to evaluate the overall breakage degree of pre-weakening processing and its applications

The product fineness indicator t10 and the pre-weakening degree indicator percentage change of A * b value (CAb) were used to described the two aspects of the breakage result of processing with pre-weakening effect. However, there lacks a method to evaluate the ‘overall’ breakage degree with a single index. It was observed that when the high voltage pulse breakage (HVP breakage or HVPB) induced cracks inside pre-weakened particles were consumed during impact breakage, the breakage characteristics of the progeny particles are the same to raw ore particles. Based on this phenomenon, the concepts of equivalent size Sie and equivalent size reduction t10e are proposed. Raw ore particles of size Sie is ‘equivalent’ to pre-weakened particles of size Si in terms of their impact breakage product size distribution. Therefore the value of Si and the consequently derived t10e can be used to evaluate the overall breakage degree of pre-weakened particles. The calculation procedure of Sie and t10e is demonstrated in the context of HVP breakage. It is found that the impact breakage product of pre-weakened particles can be well predicted from Sie. In addition to the evaluation of overall breakage degree of pre-weakening processing, this method also has potential to apply in the simulation of comminution circuits with pre-weakening processing and the development of breakage model for processing with pre-weakening effect.

Impact analysis of carbon prices on metal mining projects by block-based estimation model: Implications for cleaner production

Carbon dioxide emissions pricing is employed as an approach to mitigate climate change. To analyze the impact of carbon prices on the metal mining industry, this paper presents a new block-based carbon dioxide emissions estimation model to assess the carbon dioxide emissions and carbon intensity in varying carbon prices, by employing the engineering-based inputs from life cycle of mineral production. Such engineering-based data of an iron case is provided to test the impact of carbon prices on mining projects. The results indicate that the negative impact of carbon prices on the profit of mining projects is more sensitive in low minerals prices, especially for underground method. On the other hand, carbon price rising facilitates the mitigation of carbon dioxide emissions, by lowering the ratio of excavated waste rocks to mined-out raw ore, which varies linearly with the emissions. The carbon dioxide emissions in the studied case decrease from 39.92 kg carbon dioxide eq per ton to 21.50 kg carbon dioxide eq per ton, and from 51.02 kg carbon dioxide eq per ton to 42.80 kg carbon dioxide eq per ton, for surface and underground method, respectively. The results of carbon intensity show that it keeps increasing due to carbon price rising, until the mining boundaries are optimized based on the increased carbon price.

Collecting performance of vegetable oils in scheelite flotation and differential analysis

The composition of a collector directly affects its collecting performance in mineral flotation. In this study, three vegetable oils were used as the collectors, the flotation performance of scheelite and the differential analysis were studied through flotation experiments, zeta potential, contact angle measurement and Fourier transform infrared spectrum (FTIR) analysis. Flotation results show that the recovery of scheelite increases in the order of oleic acid<rapeseed oil<rice bran oil<soybean oil, especially in the pH range of 5–8. The distinction in the scheelite recovery is due to the different compositions of these collectors. The addition of LA, LNA and PA (<5%) can increase the recovery of scheelite with OA, but the addition of SA deteriorates the scheelite flotation. Results of zeta potential, contact angle measurement and FTIR analysis indicate that the collector adsorption on scheelite surface is enhanced when using the three vegetable oils. For the raw ore with 0.086% WO3, a rough concentrate containing 1.423% WO3 with the recovery of 84.22% is obtained using soybean oil as the collector.

Selective vanadium extraction from vanadium bearing ferro-phosphorus via roasting and pressure hydrogen reduction

A novel process involving roasting with additives, water leaching, and vanadium precipitation by high-pressure hydrogen reduction is proposed to selectively extract vanadium from vanadium-bearing ferro-phosphorus. The optimum conditions of roasting and leaching are obtained as follows: roasting temperature of 850 °C, Na2CO3 dosage of 30 wt%, CaCO3 dosage of 30 wt%, roasting time of 1 h, leaching time of 2 h and a leaching liquid–solid ratio of 1 mL/g. A V2O3 product having a purity of 99.92% is precipitated from the leaching solution by a high-pressure hydrogen reduction. The total recovered vanadium is up to 92.3%. X-ray diffraction (XRD) analysis of the raw ore, roasted ore, and leaching residue shows that the additive of Na2CO3 during roasting can react with the vanadium-bearing compounds and transform it into water-soluble NaVO3, while the additive of CaCO3 can solidify phosphorus-bearing and chromium-bearing compounds into non-water-soluble phosphates of Ca3(PO4)2 and Cr3(PO4)2. Moreover, the iron-bearing compounds are converted into non-water-soluble Fe2O3 and Na3Fe2(PO4)3. Thus, vanadium can be selectively extracted through the subsequent water leaching and high pressure hydrogen reduction process. Compared with the traditional process, this process is more efficient and environmentally friendly owing to the high recovery of vanadium, the non-used roasting additive of sodium chloride and the adopted eco-friendly vanadium precipitation method.

Extraction of gold from refractory gold ore using bromate and ferric chloride solution

During gold extraction by cyanidation, fine gold particles encapsulated in sulfidic minerals are not readily extracted and carbonaceous matter can absorb aurocyanide complexes from the leaching solution. Therefore, high-sulfur and high-arsenic carbonaceous refractory gold ore cannot be treated effectively using cyanidation alone. In this study, an efficient and low-toxicity method for extracting gold from a high-sulfur and high-arsenic carbonaceous refractory gold ore was developed using a solution of bromate and ferric chloride. The gold extraction rate for raw gold ore under optimum conditions (0.25 M potassium bromate, 0.08 M ferric chloride, 0.4 M hydrochloric acid, extraction time of 5 min, stirring speed of 250 rpm, and liquid-to-solid ratio of 5) was 94.5%. For a gold flotation concentrate, the gold extraction rate was as high as 91.8%. Characterization of the leached residues by scanning electron microscopy-energy-dispersive X-ray spectroscopy and X-ray powder diffraction showed that most of the sulfidic minerals were decomposed after leaching. In addition to being efficient and low in toxicity, the proposed leaching method can realize a high gold extraction rate in a very short time without any pretreatment when leaching gold from high-sulfur and high-arsenic carbonaceous refractory ores.

Utilization of high-gradient magnetic separation–secondary grinding–leaching to improve the copper recovery from refractory copper oxide ores

Copper-oxide raw ore has a complex composition and cannot be processed effectively by conventional, single-stage sorting methods. Based on the characteristics of copper-oxide ore, a new combined grinding–flotation–high-gradient magnetic separation–secondary grinding–leaching process has been proposed to recover copper. Test results show that the new process is very effective. Sodium sulfide was used as a vulcanizing agent in the flotation process, and butyl xanthate was used as a collector to obtain a qualified copper concentrate with a copper grade of 29.37% and a recovery rate of 32.22%. The flotation tailings were subjected to high-gradient magnetic separation to obtain magnetic concentrates and magnetic tailings, and copper was recovered by leaching from the magnetic concentrates and tailings. After secondary grinding of the magnetic concentrates, the leaching rates of copper from the magnetic concentrates and magnetic tailings were 26.85% and 26.95%, respectively. The total copper recovery was 86.02%. The new process introduces high-gradient magnetic separation, enriches refractory chrysocolla, leaches chrysocolla at 65 °C, leaches malachite from the magnetic tailings at 40 °C, and saves heating costs. Secondary grinding can reduce the leaching temperature, shorten the leaching time, and achieve a low energy consumption and effective extraction of refractory copper-oxide ore.

Steel Micro-alloying with Boron: A Perspective Direction to Reduce the Consumption of Manganese Ferroalloys

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Intensification of waste gangue removal from 6–1 mm fine-sized iron ores based on density-based dry vibrated separation and upgrading

Density-based dry separation with a vibrated fluidized bed was performed to investigate the segregation and separation of 6–1 mm fine-sized iron ore through the removal intensification of waste gangue. The 6–3 mm and 3–1 mm iron ore samples were a typical hematite with total Fe-grades of 46.5% and 46.2%, respectively. The effects of static bed height (Hs), vibration amplitude (A), and frequency (f) on the fluidization characteristics of the fine-sized iron ore were experimentally studied. Fluidization tests indicated that the appropriate operational factors of Hs = 80–110 mm, A = 1.5–2.5 mm, and f = 13–17 Hz should be adjusted to ensure fluidization stability. The separation performance of the fine-sized iron ore was studied under various operational conditions. The highest concentrate recoveries were 74.2% and 69.1% under the optimal operational factors for the 6–3 and 3–1 mm iron ore samples, respectively. The actual segregation processes of the iron ore particles obtained using a high-speed dynamic camera validated the separation results. This work aims to provide laboratory-scale experimental results for the discharging intensification of waste gangue from raw fine-sized iron ores using an efficient dry-based separation technology.

Reduction Roasting of Titaniferous Ores

Questions regarding the oxidizing roasting of raw iron ore materials (agglomerate and pellets) are studied. Features of the phase structure of raw iron ore materials containing titanium and vanadium are discussed. Reducibility, durability, and temperatures of the softening and melting of metallurgical raw iron ore materials are studied in vitro. Object of research – titaniferous ores with various titanium dioxide content. The behavior of agglomerate and pellets in a blast furnace are studied, as well as the influence of their physical and chemical properties on heat and mass transfer processes using a mathematical model of the blast furnace process [1].

Experimental research on mineral processing for a stibnite ore in Shaanxi

The refractory stibnite used in this research is from Shan yang, Shaanxi. The ore characteristics are coarser grain size of the stibnite, which is favorable for flotation. But the clay minerals (kaolinite and illite), pyrite and arsenopyrite in the ore will bring some difficulties to flotation. Through on the research of the slurry regulator, stibnite collector and gangue mineral inhibitor, better flotation index was obtained. Under the condition of the Sb raw ore grade 2.25%, the flotation index of the concentrate contains Sb 65.12% with the recovery of 91.56%, and the arsenic content of 0.20 was obtained.

Influence of microwave treatment on grinding and dissociation characteristics of vanadium titano-magnetite

The effect of microwave treatment on the grinding and dissociation characteristics of vanadium titano-magnetite (VTM) ore were investigated using scanning electron microscopy (SEM), nitrogen absorption measurements, particle size distribution measurements, X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopic analysis, and magnetic separation. SEM analysis showed that microfractures appeared in the microwave-treated VTM, which is attributed to the microwaves’ selective heating characteristic and the differential expansion between minerals and gangues. Nitrogen absorption showed that the microfractures were more pronounced when the microwave heating time was increased. Particle size distribution analysis showed that microwave treatment could improve the grindability of the VTM, thus increasing the weight percent of the fine-ground product. The increase in grindability was more significant with prolonged heating time. Moreover, the particle size distribution of the fine-ground product changed only slightly after the microwave treatment. XRD analysis showed that the crystallinity of the microwave-treated VTM increased with increasing microwave heating time. The magnetic separation tests revealed that the separation efficiency increased as a result of the intergranular fractures generated by microwave treatment. The Fe grade of the magnetic fraction of microwave-treated VTM was 1.72% higher than that of the raw ore. We concluded that the microwave treatment was beneficial, especially for the mineral processing characteristics.

Denitrification performance of rare earth tailings-based catalysts

Abstract Rare earth tailings from the Bayan Obo mine are rich in rare earth, iron, and other catalytically active substances. In this study, Na2CO3 and Ca(OH)2 were mixed with rare earth tailings, roasted, and the tailings modified by HCl-citric acid leaching and pickling to prepare high-performance rare earth tailings-based denitrification catalysts. Denitrification performance tests show that, in the temperature range 700°C~900°C, the alkali and acid co-processed modified tailings sample gave the best catalytic denitrification performance. XRD, SEM, and H2-TPR analyses show that, compared with raw ore samples, Fe activity sites increased after alkali and acid co-treatment. Cracks and holes appeared on the surface of the sample, and the reduction temperature range was broadened. XPS analysis showed that Fe coexisted in the forms Fe2+ and Fe3+, and Ce in the forms Ce3+ and Ce4+. At a rare earth tailings microwave roasting temperature of 500°C, NO concentration of 500 ppm, CO/NO ratio 4:1, and reaction temperature of 900°C, the denitrification efficiency of the catalyst was optimal, at up to 96.2%. In this study, a relatively green and pollution-free method was used to prepare catalysts, which can provide reference for solving the problem of rare earth tailings accumulation.

Формування сепараційної характеристики процесу згущення рудної сировини на основі методу модельного прогнозуючого керування

Формування сепараційної характеристики процесу згущення рудної сировини на основі методу модельного прогнозуючого керування

Quantitative analysis of stibnite content in raw ore by Raman spectroscopy and chemometric tools

AbstractThis paper presents a non‐destructive and fast methodology to quantify the stibnite content in raw ore samples using Raman spectroscopy. A total of 120 raw ore reference samples were obtained from a froth flotation process, and multipoint collection and averaging were used to obtain Raman spectra from the raw ore samples. Our aim was to create the best multivariate calibration model for the quantitative analysis of stibnite contents in the raw ore samples. Several strategies were evaluated to generate a robust model; these strategies included preprocessing methods (de‐nosing, baseline correction, and vector normalization), selecting the key wavenumbers for the quantitative analysis of stibnite, and building a multivariate calibration model. Synergy interval partial least squares (PLS), backward interval PLS, stability competitive adaptive reweighted sampling, and PLS with a genetic algorithm (GA) were investigated to build the linear multivariable models, whereas artificial neural network (ANN) and support vector regression (SVR) preceded by GAs (GA‐ANN and GA‐SVR) were implemented to build the non‐linear multivariable models. Experimental results showed that the best multivariable calibration model for stibnite was obtained by a combination of an ANN and GA (GA‐ANN). In contrast to the PLS model based on the full spectrum, the root mean square error of calibration and root mean square error of prediction of the GA‐ANN method for the calibration and validation sets were reduced to 0.2038 from 0.3552 and to 0.2196 from 0.3927, respectively, and the squares of the correlation coefficients of the calibration and validation sets were increased to 0.9369 from 0.8053 and 0.9219 from 0.7561, respectively. The above results indicate that the multivariable calibration model for stibnite is stable. Furthermore, this method could be used in the froth flotation process to precisely determine the stibnite content in raw ore samples.