Leaching Of Minerals Research Articles

Effect of Processing Methods on the Micronutrient Profile, Colour, and Anti-nutritive Components of Justicia heterocarpa (mwidu)

Justicia heterocarpa (mwidu) is a popular indigenous leafy vegetable picked wild in rural regions of Morogoro, Tanzania, during the wet seasons. This research examined the impact of processing on micronutrients, total phenols, and anti-nutrient content. The fresh leaves (FL) underwent direct shade drying (UBLDDR), blanched shade drying (BLDR), blanched oven drying (BLDO), fermentation (FFL), and gas and microwave cooking (FLCO5, FLCO10, and FLMCO2). Vitamins, chlorophyll, minerals, phenolic compounds, and anti-nutrients were analyzed. All laboratory experiments adhered to procedures and guidelines. The pH dropped more significantly to <3.5 in a 3% salt-3% sugar brine solution with 1.328 ± 0.006 mg/100 g of lactic acid compared to its counterpart. Blanched leaves dried in 5 days, but unblanched leaves took 15 days. Fermented samples demonstrated a notable reduction in total chlorophyll concentration (0.0964 ± 0.075 mg/g) compared to other processing techniques. The nutritional and anti-nutritional composition of Justicia heterocarpa showed significant change (P < 0.05) depending on processing methods. The results indicated a significant loss of vitamin C in the fermented and ten-minute cooked samples, at 74.57% and 61.64%, respectively.Cooked FLMCO2 (107.4%, 11.29 ± 0.03 mg/100g) and FLCO5 (86.26%, 10.51 ± 0.02 mg/100g) exhibited more than a two-fold increase in beta-carotene compared to fresh leaves (3.67 mg/100g). In comparison to alternative processing procedures, samples cooked for 10 minutes exhibited significant mineral leaching, whereas unblanched direct shade drying preserved the highest mineral concentration. Fermented samples (532.83 ± 14.91 GAE/100 g) exhibited a 64.19% increase in total Phenolic compounds compared to fresh leaves (190.83 ± 14.91 GAE/100 g). Nonetheless, tannins increased by 68.1% (254.44 ± 7.45 GAE/100g) in the fermented samples. Samples exposed to extended cooking (17.8 ± 3.17 mg/100 g) and fermentation (40.28 ± 3.34 mg/100 g) exhibited the lowest levels of phytates. The oxalate concentration was significantly decreased in the cooked samples. Justicia heterocarpa may serve as a sustainable food supply in areas of Tanzania experiencing nutritional deficits.

Effects of mineral leaching on combustion efficiency of coal gangue

Effects of mineral leaching on combustion efficiency of coal gangue

Seasonal and spatial contributions of sulfate and trace elements in river water in mining districts: Insights from hydrogeochemical and isotopic analysis based on statistical models.

Although sulfur-bearing minerals are valuable resources, they pose significant environmental risks to river ecosystems by releasing hazardous leachate. Accurately tracing these sources is crucial but challenging due to overlapping chemical signatures and pollutant transport dynamics in river systems. This study investigates seasonal and spatial variations in sulfate (SO42 -) and trace element contributions in mining districts of the upper Nakdong River basin, South Korea. Sulfate isotopes (δ34SSO4 and δ18OSO4) and Monte Carlo simulations enhanced the precision of source estimation. Bayesian stable isotope mixing models revealed acid mine drainage (55.3 %) dominated during the wet season, while smelter tailings and mine leachate dominated during the dry season (43.8 %). Model uncertainty was addressed through probabilistic approaches, with Monte Carlo simulations, ensuring robustness in δ18OSO4 predictions. Additionally, the Positive Matrix Factorization (PMF) model identified dominant emission sources and impact ranges for hazardous elements, mostly validated by high correlation coefficients (r > 0.8). Notably, the contribution of Cd-dominated emissions from smelters increased from 13 % in the wet season to 51.5 % in the dry season, while the contribution of As-dominated emissions from mining increased from 30.3 % to 40.7 %. Despite sorption and coprecipitation processes, As contamination migrated ∼ 50 km downstream during the dry season. Statistical correlation and cluster analyses further confirmed consistency between observed and modeled geochemical patterns. This study underscores the reliability of integrating Bayesian and PMF models with isotopic and hydrogeochemical data, offering valuable insights for tracing anthropogenic sources in complex mining environments.

Analysis of the Effects of Different Spectral Transformation Methods on the Estimation of Chlorophyll Content of Reclaimed Vegetation in Rare Earth Mining Areas

Ion adsorption rare earths are an important strategic resource, but their leach mining causes post-mining wastelands and tailings to suffer from soil sanding, acidification, and heavy metal contamination. This makes natural vegetation recovery difficult, relying mainly on artificial reclamation; however, the reclaimed vegetation grows poorly due to environmental stress. Hyperspectral remote sensing technology, with its high efficiency, non-destructive nature, and wide-range monitoring capability, can accurately estimate the physiological parameters of reclaimed vegetation. This provides support for environmental regulation in mining areas. In this study, three typical types of reclaimed vegetation in the Lingbei Rare Earth Mining Area, Dingnan County, Ganzhou City, were analyzed. Hyperspectral data and the corresponding chlorophyll content were collected to compare the spectral differences between reclaimed and normal vegetation. The spectral data were processed using mathematical transformation, fractional order differentiation, discrete wavelet transform, and continuous wavelet transform. Sensitive bands were extracted, and multispectral transformed feature bands were integrated. Linear and machine learning regression models were used to estimate chlorophyll content. The effects of different spectral processing methods on chlorophyll estimation were then analyzed. The results showed that reclaimed vegetation had higher spectral reflectance than normal vegetation, with the red valley shifting towards the long-wave direction and a steeper red edge slope. Different spectral transformation methods impact the accuracy of chlorophyll content estimation. Using appropriate methods can improve estimation accuracy. Fusing multi-spectral transformation features can achieve relatively good results. Among the models, the random forest regression model provides the best performance in estimating the chlorophyll content of reclaimed vegetation. This study provides a scientific basis for rapid and accurate monitoring of reclaimed vegetation growth in rare earth mining areas, supporting environmental management and decision-making and contributing to ecological restoration.

A Time Series Proposal Model to Define the Speed of Carbon Steel Corrosion in an Extreme Acid Environment.

This article shows the behavior of the corrosive effect of acid mine water on carbon steel metal alloys. Mining equipment, composed of various steel alloys, is particularly prone to damage from highly acidic water. This corrosion results in material thinning, brittle fractures, fatigue cracks, and ultimately, equipment failure. For this purpose, a set of carbon steel metal plates similar to those found in mine facilities were immersed into mine leachates of an AMD (Acid Mine Drainage) polluted river from the Tharsis Mine (Huelva, Spain). In these leachates, physicochemical variations occur, directly correlated with the alterations produced in the metal plates, manifested with the appearance of dissolved materials and particulate matter. Weight loss of up to 37 g in 30 weeks for plates of about 140 grs occurred and an increase in EC up to 45.64 mS/cm from 5.40 mS/cm and an increase in TDS from 2600 mg/L to 17,100 mg/L. STATGRAPHICS Centurion, a powerful data analysis tool was used for performing the time series analysis that was used for the first time to statistically define the corrosion effects on metal alloys. As a result, a significant variability in the physical and chemical factors of the leachates was observed due to the redox and precipitation-dissolution processes occurring within the system: an increase in total dissolved solids (TDS), electrical conductivity (EC) and temperature (T) (the corrosion process is an exothermic reaction) and a decrease in pH. It was also demonstrated that the longer the exposure time, the plates noticeably lost more material and became further weakened. Finally, these results allowed the formulation of a simple algorithm to define weight loss as a function of exposure time to acidic water.

In Situ Uranium Extraction through the Synthesis of the Uranyl Peroxide Studtite Using a Nonthermal Plasma.

Extraction of uranium from water is an essential step in in situ leach (ISL) mining and environmental decontamination. This is often done by precipitating uranium in solution as the uranyl peroxide studtite, [(UO2)(O2)(H2O)2](H2O)2, by adding hydrogen peroxide, which is energy-intensive to produce and hazardous to transport. Here, we present a method for synthesizing studtite, by generating reactive oxygen species in solution using a nonthermal plasma. Precipitation of studtite is observed within 5 min of the onset of plasma treatment as confirmed by X-ray diffraction and Raman spectral analysis. The faradaic efficiency of studtite formation is analyzed to estimate the values of hydrogen peroxide yield, 1.23 molecules per incident ion, and the rate constant of the studtite-forming reaction, 4.44 × 107 M-1 s-1. This work is a proof of concept and identifies significant parameters for the future development of a larger scale, higher throughput system.

Unravelling the Seasonal Dynamics of Limnological Parameters and Assessment of Ecological Health: A Case Study of Lingadheeranahalli Lake in Bangalore North, Karnataka, India

ABSTRACT: The present study investigates the seasonal dynamics of limnological variables and the developmental response of D. rerio in the wetland ecosystem of Lingadheeranahalli in the northern clutches of Bangalore in Karnataka. Once a vital water source for agriculture and replenishing groundwater, the lake faces degradation due to anthropogenic activities and the need for more awareness. A yearlong analysis was conducted with five sampling seasons and three sampling stations identified within the wetland. Parameters viz. physical, chemical, and biological were analyzed following American Public Health Association (APHA) guidelines. Somite development was studied using embryos while the heart rate was counted during the torpedo stage of D. rerio. The results of this comprehensive study revealed unique and significant seasonal variations over limnological parameters, providing novel insights into the dynamics of the wetland ecosystem. pH values are slightly acidic and influenced by precipitation and terrestrial vegetation. Turbidity spiked during winter due to colloidal dispersions, while conductivity peaked in spring due to sewage disposal. Reduced dissolved oxygen, high biochemical and chemical oxygen demand indicated organic pollution and microbial activity, particularly affecting the inlet station. Elevated phosphate and nitrate levels in spring indicated eutrophication potential. The influence of rains and mineral leaching during monsoons affected parameters such as alkalinity, total dissolved solids, total hardness, and Magnesium. Analysis of D. rerio demonstrated delayed development and decreased heart rates in the inlet and deposit stations, indicative of potent stressors in the wetland ecosystem. All-inclusive Lingadheeranahalli Lake exhibited poor water quality, focusing on the need for adaptive management strategies to mitigate pollution and safeguard wetland ecosystems. Continued wetland research gives more insights into water quality and seasonal dynamics, paving the way for its conservation.

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.

Advanced Sorbents for Separation of Metal Ions

Effective, sustainable, and selective methods for recovering or removing metals from various media, such as mining leachates, recycling waste, industrial effluents, and natural water, are necessary due to the increasing demand for metals and stringent environmental constraints [...]

Industry relevant microfluidic platforms for mineral leaching experiments

Microfluidic and lab-on-a-chip devices offer exquisite temporal and spatial control over chemical and physical processes that are important in mineral exploration and mining. These include mineral-water interfacial reactions, dissolution, and adsorption/desorption in pores, fractures, or other micro/nanostructures. Microfluidic mineral studies offer advantages of small sample and reagent volumes, high throughout, and short analytical cycles that may enable in-field mining decisions. However, not many microfluidic studies have targeted these mining sector challenges for mineral leaching. In this review, special attention is given to microscale experimental platforms for predicting extraction and leaching of industrially-relevant samples (real ore samples). Advantages and challenges of these platforms are given. The review concludes that there are significant opportunities for microfluidics in mineral analysis, screening, process intensification, and process control in the resource and minerals sector.

Assessment of groundwater fluoride and human health effects in a hard rock province of south India: Implications from Pollution Index Model (PIM) and GeographicalInformationSystem (GIS) techniques.

This research examines whetherthe groundwater in the Sivakasi Region of South India is suitable for consumption, and assesses the possible health hazards for various age demographics including infants, children, teenagers, and adults. A totalof 77 groundwater samples were gathered, covering a total area of 580km2 and analyzed for major and minor ions. The hydrogen ion concentration (pH) of the samples indicates neutral to marginally alkaline. The total dissolved solids (TDS) fluctuate from 255 to 2701mg/l and electrical conductivity varies from 364 to 3540µS/cm. A wide range of fluoride concentration was detected (0.1 to 3.2mg/l) with nearly 38% groundwater samples surpassing the proposed limit (1.5 mg/l) suggestedby the World Health Organization in 2017. Gibbs plot analysis suggested that most of thesamples were influenced by geogenic factors, primarily rock weathering in this region. Correlation analysis showed that most of the samples were impacted by both natural and human sources. The pollution index of groundwater (PIG) fluctuated from 0.67 to 2.60 with approximately 30% and 53% of samples falling into insignificant and low pollution categories, respectively. Furthermore, 10% and 5% of total samples were characterized as moderate and high pollution levels, and 2% asvery high pollution category. Spatial analysis using GIS revealed that 440.63km2 were within safe fluoride levels according to theWHO standards, while 139.32km2 were identified as risk zone. The principal component analysis (PCA1) showedstrong positive loadings on EC (0.994), TDS (0.905), Mg2+ (0.910), Cl- (0.903) and HCO3- (0.923) indicating rock water interaction. PCA2 accounts the high positive factor loading on HCO3- (0.864) indicating ion exchange and mineral leaching. The PCA1 and PCA2 indicated that variables such as mineral leaching and rock water interaction are themajor mechanisms contributing to the chemical signatures in groundwater, which may support for theelevated fluoride levels in certain areas. Risk assessments, including Hazard Quotient results showed that 71%, 61% 38%, and 34% of groundwater samples exceededthe permissible THI limit (THI > 1) for infants, children, teenagers, and adults, respectively. The study recommends implementing measures such as denitrification, defluorination, rainwater harvesting, and improved sanitation infrastructure to enhance the health conditions in the study region. Additionally, it suggests introducing educational programs in rural areas to create awarenessabout the health dangers due to consumptionof water with high fluoride levels.

Synergistic enzymatic mechanism of lepidolite leaching enhanced by a mixture of Bacillus mucilaginosus and Bacillus circulans

Numerous studies have demonstrated that the co-leaching of ores by different silicate bacteria significantly improves the performance of bioleaching systems. Nevertheless, the mechanism of different silicate bacteria synergistically or complementarily enhanced the leaching process of lithium-containing silicate remains unclear. This study discussed the leaching impact of the combined presence of two metabolically distinct silicate bacteria on lepidolite, with the aim of comprehending the synergistic effect resulting from the presence of Bacillus mucilaginosus and Bacillus circulans in the leaching process. The results indicated that the polysaccharides and proteins secreted by bacteria-containing functional groups such as -OH and -COOH, which played an important role in the complex decomposition of ores. Organic acids played the role of acid etching and complexation. Bacillus mucilaginosus and Bacillus circulans exhibited low individual leaching efficiency, primarily due to their weak organic acid secretion. Moreover, the prolific polysaccharide production by Bacillus mucilaginosus led to bacterial aggregation, diminishing contact capability with minerals. Bacillus circulans decomposed the excessive polysaccharides produced by Bacillus mucilaginosus through enzymatic hydrolysis in the co-bioleaching process, providing later nutrient supply for both strains. The symbiosis of the two strains enhanced the synthesis and metabolic capabilities of both strains, resulting in increased organic acid secretion. In addition, protein and humic acid production by Bacillus mucilaginosus intensified, collectively enhancing the leaching efficiency. These findings suggested that the primary metabolic products secreted by different bacterial strains in the leaching process differ. The improvement in bioleaching efficiency during co-leaching was attributed to their effective synergistic metabolism. This work contributes to the construction of an efficient engineering microbial community to improve the efficiency of silicate mineral leaching, and reveals the feasibility of microbial co-culture to improve bioleaching.

Rare earth elements redistribution in mine tailings soil: A comparative study of sunlit and shady slopes after in-situ leaching

The in-situ leaching of rare earth minerals results in ecological differences between sunlit and shady slopes, which may be related to differences in the distribution REEs in the associated soil matrices. Studies of REEs mine tailings in Southern China indicated higher total concentrations of REEs on sunlit slopes compared to shady ones. Specifically, the exchangeable REEs fraction (F1-REEs) was higher on the shady slopes, whereas the Fe/Mn oxides bound REEs fraction (F3-REEs) was higher on the sunlit slopes. In addition, light REE (LREE) concentrations were lower at lower elevations. With the exception of the Ce fraction which remained stable, this indicated a change in all REEs distributions, moving from F1-REEs towards the residual fraction. Hierarchical cluster and principal component analysis revealed a strong correlation between F3-REEs, organic matter bound REEs (F4-REEs), and LREEs, and a positive association of F3-REEs with sunlight exposure. Partial Least Squares Path Modeling analysis suggested that OM promoted the conversion of LREEs to F3 and F4-REEs in soil driven by sunlight exposure. Additionally, as the Feo/Fed ratio decreased, more LREEs were converted to F3. This study suggests that sunlight and elevation both play a critical role in the geochemical dynamics of REEs in in-situ tailings, advocating for environmental evaluations to be undertaken in order to accurately understand the ecological impacts of rare earth mining.

The behavior of pyrite during in-situ leaching of uranium by CO2 + O2: A case study of the Qianjiadian uranium deposit in the Songliao Basin, northeastern China

Oxidative weathering of pyrite, a widespread iron sulfide mineral, is crucial for the uranium mineralization in sandstone-hosted uranium deposits and the ore utilization leaching under manual intervention. To understand the behavior of pyrite under CO2 + O2 leaching conditions in sandstone-hosted uranium deposits, samples of uranium ore from the mineralized zone of the Qianjiadian IV uranium deposit located in the lower section of the Yaojia Formation were collected for this study. The stirring leaching experiment was carried out through the processes of the pyrite-bearing uranium ore samples thinned before and after the reaction, followed by an optical microscopic study and the TESCAN Integrated Mineral Analyzer analysis, and finally, the thermodynamic simulation by making use of PHREEQC3.0.The results revealed the following: (1) The dissolution particles of pyrite become smaller, which may increase the porosity of the ore layer and the exposure ratio of uranium minerals. And more soluble pyrite with a high free surface will be more competitive with uranium minerals for the consumption of O2. (2) The ion (Fe2+) produced by the dissolution of pyrite will be oxidized to Fe3+ by excess O2 (4 mol), which provides an oxidant for the oxidation of uranium minerals, and the generated SO42- will combine with the Ca2+ released from calcite to form a permanent precipitate of gypsum, which may block pores and cover the uranium ore. (3) Pyrite and calcite will consume O2 and CO2 in the injection system, thus jointly inhibiting the leaching of uranium minerals. After the injection of excessive CO2 and O2, the concentration of Ca2+, SO42-, Fe3+, UO22+, and HCO3– in the system will continue to accumulate, resulting in the secondary precipitation of calcite, co-precipitation of gypsum, iron minerals, colloids, and hexavalent uranium minerals, resulting in plugging pores and seriously affecting the effective leaching of uranium.This study contributes to the understanding of the behavior of pyrite during uranium recovery through CO2 + O2 leaching. It also contributes to the understanding of quantitative uranium mineralization in sandstone-hosted uranium deposits and process parameters in in-situ leaching (ISL) of uranium.

Ecological and Geochemical Characteristics of Potassium Industry Waste

The analysis of the ecological and geochemical characteristics of waste from the extraction and processing of potash salts, which determine the ecological state of the areas of development of these deposits, is carried out. Objects are salt dumps, sludge storages, drainage waters formed on the territory of the Verkhnekamskoye potassium-magnesium salt deposit. Under research of chemical composition of waste and the drainage waters of the sludge storage it was determine that high concentrations of mobile forms of chemical elements in drainage sodium chloride waters of waste storage facilities, an increase in the concentration of nitrogen compounds in filtration waters have been established. The active role of salt solutions in the leaching of clay minerals of salt dumps and sludge dumps, clay protective screens is determined, which leads to active filtration of salt solutions through the bed of the sludge dump, salt dump, migration of microelements in a readily soluble form into the environment.

Pb isotopic fingerprinting of uranium pollution: New insight on uranium transport in stream-river sediments

Uranium mill tailings (UMT) present a significant environmental concern due to high levels of radioactive and toxic elements, including uranium (U), thorium (Th), and lead (Pb), which can pose serious health risks to aquatic ecosystems. While Pb isotopic tracers have been widely utilized in environmental studies to identify elemental sources and geological processes, their application in U geochemistry remains relatively limited. In this study, we investigate the distribution and migration of U in stream-river sediments surrounding a decommissioned U hydrometallurgical area, employing Pb isotopes as tracers. Our findings reveal significant enrichment and ecological risk of U, Pb, and Th in the sediments. Uranium predominantly associates with quartz and silicate minerals, and its dispersion process is influenced by continuous leaching and precipitation cycles of typical U-bearing minerals. Furthermore, we establish a compelling positive relationship (r2 = 0.97) between 208Pb/207Pb and 206Pb/207Pb in the stream-river sediments and sediment derived from UMT. Application of a binary Pb mixing model indicates that anthropogenic hydrometallurgical activities contribute to 2.5–62.7% of the stream-river sediments. Notably, these values are lower than the 6.6–89.6% recorded about 10 years ago, prior to the decommissioning of the U hydrometallurgical activity. Our results underscore the continued risk of U pollution dispersion even after decommission, highlighting the long-term environmental impact of UMT.

Laboratory weathering studies to evaluate the water quality impact of a lithium mining in Portugal

Lithium mining driven by the growing demand for lithium-ion batteries, has environmental consequences linked to soil and water pollution. Nevertheless, research on the environmental impacts of lithium extraction still needs to be improved, highlighting the imperative for additional research. The article addresses the potential impact of the C57 lithiniferous feldspar mine on water quality, specifically focusing on surface, groundwater and spring water samples collected at the mining site and surrounding area in Gonçalo (Guarda, Portugal). The objective is to evaluate the environmental consequences of mining activities, with particular emphasis on mineral leaching. This study aims to evaluate the water quality around the C57 mine and the potential environmental impacts of mining operations. Water samples were collected from different sources, such as surface, underground, and spring waters, and chemical analyses were carried out to determine concentrations of different parameters, which were later compared with national and international reference guidelines. In addition to analysing the water samples, weathering tests were carried out using the Soxhlet extractor method to simulate the leaching of minerals over a shorter period (about 125 days). The concentrations of the analysed elements by atomic absorption spectroscopy (Al, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb and Zn) in the weathering solutions were generally low and decreased throughout the testing period, with significant concentrations of aluminium and chromium exceed Canadian environmental quality guidelines for surface waters. The detected lithium concentrations are quite different, ranging from 8.7 to 19.8 μg/L in surface waters, from 6.9 to 74.1 μg/L in groundwater, and from 25.6 to 35.4 μg/L in spring waters, but are all below the US EPA (2021) recommendations threshold of 0.7 mg/L. Based on the findings, the article concludes that there is currently no clear evidence to indicate the environmental impact of mining activities on water quality in the analysed samples. However, weathering tests suggest potential long-term implications regarding the leaching of specific chemical elements, particularly aluminium and chromium.

Study on the leaching behavior differences of rare earth elements from coal gangue through calcination-acid leaching

Critical metals in coal-based byproducts have been gradually regarded as one of the most important alternative resources due to the market parameters, strategic perspective, and advanced technology. In this study, the mechanism of calcination-acid leaching for rare earth elements (REY) recovery from coal gangue of Jungar coalfield was proposed based on the results of sample characteristics, extraction law, kinetic analysis, and typical mineral leaching. The micro-particles of bastnaesite and monazite were found and embedded in the kaolinite via micro-observation with SEM-EDS. Kaolinite in coal gangue calcined at 600 ℃ was transformed into highly positively reactive metakaolinite, enhancing the dissolution of aluminum (Al) and exposing the rare earth minerals encapsulated within the particles. Meanwhile, bastnaesite was thermally decomposed into rare earth oxides and rare earth fluorides. Rare earth oxides are more easily dissolved by acid, and the fluoride ions and the aluminum ions form a stable complex ion [AlF6]3-, which promotes the dissolution of rare earth fluoride. In addition, a high REY and Al recovery (78.8% of REY, and 88.5% of Al) came true from calcined coal gangue at optimal conditions. The leaching kinetics showed that REY leaching followed the hybrid control model of interfacial transfer and diffusion through solid layer, while Al leaching is controlled by chemical reaction. The leaching test of monazite shows that the leaching efficiency of LREY is higher than that of HREY indicating the leaching difference of LREY (82.3%) and HREY (61.3%) in coal gangue is mainly influenced by monazite. This may be related to the crystal structure and the radius of trivalent rare earth ions. This study provides a useful reference for the extraction of REY from coal gangue.

An electrochemical method for the regeneration of trivalent iron to increase the efficiency of in-situ leaching of uranium

Due to the increasing demand for electricity with the development of production and general infrastructure, increasing the production of uranium as an economically and environmentally efficient source of energy is an urgent problem. The purpose of this study is to develop an electrochemical method for the regeneration of iron (III) ions used as a uranium oxidizer in the process of in-situ leaching of uranium minerals with sulfuric acid solutions. Methods. The mechanism of reactions in the iron (II)-iron (III) redox system was studied by recording potentiodynamic polarization curves and conducting electrolysis of the oxidation of divalent iron ions under galvanostatic conditions. Results and discussion. Cathode-anodic and anodic-cathode cyclic polarization curves taken on platinum electrodes showed that the redox reactions of iron ions are reversible and these reactions occur at a slight overvoltage. The influence of the main electrochemical parameters (current density, concentrations of iron (II) ions and sulfuric acid) on the oxidation of divalent iron ions was studied for the first time using granular anode electrodes, the electrode spaces of which are separated by an anionite membrane. It has been found that the use of granular graphite electrodes in the oxidation divalent iron ions increases the current output by more than 2 times compared to a plate graphite electrode. Conclusion. According to the results of the study, it was noted that under optimal conditions, the current output of the oxidation of divalent iron ions exceeds 90%. Extensive research has shown that trivalent iron ions, widely used in the in-situ leaching process for uranium production, can be regenerated by electrochemical methods.

Technological and environmental features of the well construction cycle in mineral leaching methods

Technological and environmental features of the well construction cycle in mineral leaching methods