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A characteristic feature of serpentine oxidized nickel ores (ONO) of the Serov deposit (≈ 1 wt.% Ni) is the increased content of iron and magnesium. The main nickel-containing phases are lizardite, antigorite, clinochlore and iron oxides with the nickel content varying from 1.6 to 9.2 wt.%. Heap (percolation) leaching with aqueous H2SO4 solutions was used for processing. During a pilot study, 89% of nickel, 99% of cobalt, and 78.4% of iron were extracted from the oxidized nickel ores during 440 days of leaching at an acid consumption rate of 475.1 kg per ton of ore. The high iron content of the product solutions did not allow for high-quality extraction of nickel and cobalt. The dependences of the nickel, cobalt, and iron extraction on the irrigation pauses, initial size of the ore fragments, and specific consumption of the leaching solution were studied. A solution was found on how to reduce the sulfuric acid consumption and considerably decrease the iron content of the product solutions by increasing a pause between irrigations at the initial stage of or leaching and redirecting the leaching solutions to treat fresh ore. In this case, iron is hydrolyzed in the form of insoluble hydroxides within the ore body. The optimal process conditions of heap leaching of such ores are as follows: initial size of ore fragments – 50 mm; concentration of H2SO4 solutions – decreasing from 20 to 5 g/dm3 during the leaching process; irrigation density – 140 dm3 per ton of ore; combination of the irrigation pauses from 4 days during the initial stages to 1 day during the subsequent stages. Given the average rate of H2SO4 consumption of 221 kg per 1 ton of ore and leaching duration of 408 days, these conditions make it possible to extract up to 62% of nickel and 66.7% of cobalt, as well as significantly reduce the percentage of iron leached from the ore to obtain iron-free product solutions suitable for extraction of nickel and cobalt. [ABSTRACT FROM AUTHOR]

Purpose: Traditional measurement for soil properties is time-consuming and costly, while visible–near-infrared spectroscopy enables the rapid prediction of soil properties. In this study, visible–near-infrared spectroscopy was used to predict these four soil properties including OC (organic carbon) content, TN (total nitrogen) content, pH value, and clay content in rare earth mining areas based on different spectral transformation and calibration methods. Materials and methods: A total of 232 soil samples were collected from unexploited, in situ leaching, and heap leaching mining areas in southern Jiangxi Province, China. The chemical properties and reflectance spectra of air-dried samples were measured. Spectral transformations including first-order derivative (FOD), continuum removal (CR), and continuous wavelet transform (CWT) were selected to improve the prediction accuracy of the model. Partial least-squares regression (PLSR), the support vector machine (SVM), and extreme gradient boosting (XGBoost) were used to construct prediction models. Results and discussion: The highest prediction accuracies in terms of the coefficient of determination (R2), root mean square error (RMSE), and relative prediction deviation (RPD) were obtained using CWT spectra with XGBoost for organic carbon content (R2 = 0.89, RMSE = 0.24, RPIQ = 4.67), total nitrogen content (R2 = 0.86, RMSE = 0.01, RPIQ = 4.14), and pH value (R2 = 0.73, RMSE = 0.19, RPIQ = 1.66). The best prediction result for clay content was obtained using CWT spectra with the SVM (R2 = 0.67, RMSE = 6.45, RPIQ = 2.75). Conclusions: The CWT coupled with a non-linear model, such as XGBoost, is an effective method for the accurate prediction of soil properties in rare earth mining areas. [ABSTRACT FROM AUTHOR]

The article presents the results of experiments intended to leach copper from ore heaps of complex mineral composition biochemically. The processing of such heaps is complicated due to the presence of oxidized copper minerals among significant fragments of sulfide minerals and iron-calcium silicates. This factor does not allow to perform standard sulfuric acid leaching effectively without the use of additional oxidation catalysts, or to apply beneficiation methods for that kind of raw materials. Use of A. Ferrooxidans bacteria adapted to the composition of the copper dump, as a bio-catalytic agent, significantly accelerates the leaching process and increases the copper recovery degree into the productive solution. [ABSTRACT FROM AUTHOR]

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To better understand the current status of low-grade mineral and mine waste recovery, we collected 13 contributions in this Special Issue, whose topics can be divided into the following three main aspects: Section 1: Reaction mechanisms of chemical/bio-leaching - includes the leaching kinetics of copper sulfides, assisted leaching (chloride acidic leaching, iodide-assisted leaching, etc.), in situ leaching of uranium and salt deposits, etc. Mineral resources provide an important material foundation for industrial construction and are important for the economy, thus being closely integrated into our daily lives and near future [[1]]. [Extracted from the article]

[Display omitted] • Novel and efficient biogenic sulfuric acid production. • Up to 1.4 M biogenic acid generated by mixed acidophilic bacteria. • New application of biogenic acid production and heap-bioleaching. • Independent system for biogenic acid production and metal recovery. The biological leaching of metals from different waste streams by bacteria is intensively investigated to address metal recycling and circular economy goals. However, usually external addition of sulfuric acid is required to maintain the low pH optimum of the bacteria to ensure efficient leaching. Extremely acidophilic Acidithiobacillus spp. producing sulfuric acid and ferric iron have been investigated for several decades in the bioleaching of metal-containing ores. Their application has now been extended to the extraction of metals from artificial ores and other secondary sources. In this study, an optimized process for producing biogenic sulfuric acid from elemental sulfur by two sulfur-oxidizing species, A. thiooxidans and A. caldus and their combinations, was investigated in batch and stirred tank experiments. Using a combined culture of both species, 1.05 M and 1.4 M biogenic sulfuric acid was produced at 30 °C and 6% elemental sulfur in batch and semi continuous modes, respectively. The acid produced was then used to control the pH in a heap bioleaching system in which iron- and sulfur-oxidizing A. ferrooxidans was applied to biologically leach metals from waste incineration residuals. Metals like Cu, Ni, Al, Mn, and Zn were successfully recovered by 99, 93, 84, 77 and 68%, respectively within three weeks of heap bioleaching. Overall, a potential value recovery of incorporated metals >70% could be achieved. This highlights the potential and novelty of applying extremely acidophilic sulfur-oxidizing bacteria for cheap and efficient production of biogenic sulfuric acid and its use in pH control. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An attempt to evaluate potential hazard for quality of manufactured construction elements and concrete in case of use of leachate as technological water was made in this paper. This may lead to negative impact on strength parameters of the product made in the analysed company. Raw industrial leachate must not be discharged into sewerage system due to increased concentrations of some mineral components; it must be initially purified. Selected elements of multiple regression module and principal components analysis were used to describe the above phenomena. The model we have developed uses selected significant parameters of pollutants contained in leachate from a process industrial waste heap. The model takes into account leachate conductivity and sulphate ions, in which increased lead compounds concentration was determined. The model was verified during its use. The variables used in the model explain the significant percentage of variability noted for the dependent variable. [ABSTRACT FROM AUTHOR]

Rare-earth element (REE) mineralization in weathered granites of Primorye is localized in the basement rocks and rocks surrounding coal-bearing basins, which have been recently deformed and undergone argillic metasomatism. It was shown that the clay material from the zones of intense argillization can be a source of deficient REE and yttrium. The ion-sorbed and carbonate REE+Y species in them in combination with the clay composition of most of the ores make it possible to use inexpensive and low-toxicity salt and hydrochloric acid solutions during heap leaching. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article describes one of the solutions to the problem associated with the utilization of metallurgical wastes and presents a high-efficiency method for recycling a large amount of vanadium-containing BOF slag with heap leaching by sulfuric acid. The leaching degree of vanadium from vanadium-containing BOF slag was 98.5 pct by agitation leaching and 71 pct by leaching in a percolator column. The diffusion through the slag boundary layer is a limiting factor that determines the vanadium leaching efficiency. The authors carried out the experiment to determine the time required for the solution to diffuse into the vanadium-containing BOF slag. In this article, the authors determined the influence of the pause duration between irrigations of slag in the percolator column. The slag, both before leaching and after, was tested using the one-stage batch test and the standard toxicity characteristic leaching procedure extraction test to compare their leachate capacity in relation to vanadium. The composition and structural features of vanadium-containing BOF slag were investigated by X-ray diffraction, scanning electron microscopy, and an energy-dispersive x-ray analysis console. According to these data, vanadium is present in all phases of the slag in different concentrations. The process of heap leaching carried out in a percolation column in the laboratory-scale experiment can be considered selective, since the leaching degree of vanadium is higher than the leaching degree of other slag components, except for aluminum. [ABSTRACT FROM AUTHOR]

Purpose. To study gold-bearing ores subjected to heap leaching technology to identify both free gold particles, as well as gold in aggregates and adhesions, which makes it possible to obtain data on the distribution of gold by its occurrence forms. Methodolgy. Leaching process studies are conducted at the laboratory setup of the Institute of Metallurgy and Ore Beneficiation of the Ministry of Education and Science of the Republic of Kazakhstan. The gold particles are studied using an AxioScope A1 optical microscope on the polished thin section surface. The sample materials are taken from the heap leaching site of the Vasilkovsky gold ore deposit. Findings. As a result of a microscopic test of a sample taken from the heap leaching site, ultrafine-dispersed and finely-dispersed gold particles have been found both in free form and in aggregates with waste rock and arsenical pyrite, as well as the fact of Au particles – “adhesions”, accumulated on a grain of the host waste rock. The size class of detected Au particles varies from 0.35 to 9.5 μm. Originality. For the first time, according to the samples of gold-bearing ores of the Vasilkovsky gold ore deposit, a pattern of the gold distribution according to the forms of its occurrence has been revealed. Practical value. The data obtained as a result of the research make it possible to predict the distribution of the gold form occurrence in other areas of the deposit. This can greatly simplify the conditions for its development, as well as adjust the technological process of leaching the gold-bearing ores and the main technological parameters of the heap leaching process. [ABSTRACT FROM AUTHOR]

Due to the significant growth of the world population, the accelerated growth of economic industries in various countries, and improved living conditions, freshwater consumption has increased dramatically and is currently under critical pressure. Its good use and rationing are essential. Even though mining is an industry that consumes much less water than other industries, such as agriculture, surrounding communities are constantly questioned. This occurs mainly because mining deposits are generally found in arid areas where freshwater is scarce, forcing government authorities to regulate water use in mining processes more severely. Faced with this scenario, the mining industry has innovated the use of seawater and wastewater from processes for its production processes. In addition, various projects are under development to construct desalination plants and water impulsion systems of the sea; therefore, it is expected that seawater and/or wastewater in mining will continue to grow in the coming years. Among the main challenges faced in the use of these water resources in mining is: (i) the close relationship that exists between the use of seawater and energy consumption, transferring the problem of water scarcity to a problem of energy cost overruns; (ii) generation of greater integration between the use of water and sustainable energy; and (iii) brine management is economically expensive and technically challenging and, therefore, most desalination plants discharge untreated brine directly into the sea, causing an environmental impact. On the other hand, regarding the use of these water resources in leaching processes, there are very positive results for the dissolution of copper from sulfide minerals, where the wastewater from desalination plants presents better results than seawater due to its higher concentration of chloride ions, allowing it to work at higher redox potential values in order to increase copper dissolution. This manuscript is a bibliographic review in which finally, it is concluded that it is feasible to incorporate wastewater from water desalination plants in heap leaching processes for copper sulfide ores, as long as the cost of transfer from water desalination plants to mining sites can be supported. [ABSTRACT FROM AUTHOR]

The present study aims at assessing the potential application of CuPRO MEX-3302 in copper extraction from a heap leaching liquor. The role of influential significant parameters, including the leachate pH (0.1–2.7), CuPRO MEX-3302 concentration (5–15% (v/v)), temperature (25–70 °C), copper initial concentration (0.5 to 2.3 g/L) and extraction time (0–5 min), were investigated. The extraction efficiency at ambient temperature, 1:1 organic/aqueous phase ratio, 5% (v/v) extractant concentration, pH of about 2 and contact time of 30 min was found to be 95% with a value of Fe and Mn of less than 2%. Meanwhile, a two-step extraction process was dedicated on the basis of the McCabe-Thiele diagram to obtain an organic phase containing 2.9 g/L copper at pH of 2.1. Equilibrium analyses confirmed the association of 4 mol of CuPRO MEX-3302 per mole of extracted copper. The thermodynamic outcomes revealed a high affinity of the extractant together with an endothermic and spontaneous nature of copper extraction in the system studied. Moreover, the reaction kinetics showed that the reaction order of H+ and CuPRO MEX-3302 concentration was −0.54 and 0.50, respectively. Finally, a two-stage counter-current stripping simulation at Vo/Va = 1:1 with 180 g/L H2SO4 resulted in a copper stripping efficiency of 99.54%. [ABSTRACT FROM AUTHOR]

In cities, reinforced concrete pipes are often employed to construct storm sewer systems. Due to impervious base layers, stormwater runoff dominates rather than rainwater infiltration, leading to problems in aquatic ecosystems (e.g., degradation in urban watersheds, flood attenuation, and water quality). A thermoplastic perforated pipe can provide drainage channels in applications of solid waste landfills, mining heap leach pads, or irrigation systems. Inspired by these applications, perforation can be implemented in a reinforced concrete sewer to alter the moisture conditions in the ground under impervious base layers. Three-edge bearing tests and four-point flexural tests are conducted to investigate the structural integrity of perforated sewer pipes. A numerical model is also calibrated for use to optimize the layout design of drainage holes. It is found that perforation can result in strength degradation in concrete pipe, but the reduction in strength is not significant. A correlation between the ultimate load and opening ratio is established for the two testing conditions. The allowable opening ratio is determined as 0.2%, below which a perforated sewer can fulfill the requirements for both drainage and load resistance. [ABSTRACT FROM AUTHOR]

A series of large scale direct shear experiments is used to investigate the effect of the geomembrane (GMB) surface roughness, geotextile (GTX) properties, and GTX ageing, on the GMB-GTX interface shear behaviour. Interfaces involving smooth, coextruded textured, and structured surface GMBs underlying four different nonwoven needle-punched staple fibres (GTXs) with mass per unit areas between 200 and 2400 g/m2, and a geocomposite drain (GCD) are examined at normal stresses between 250 and 1000 kPa. The results showed that the interlocking between the GMB and GTX increased with increasing the GMB asperity height and/or decreasing the mass per unit area of the GTX. For the interfaces that involved GTXs preaged prior to the shear box experiments for up to 2 years at 85 °C, it was found that the 2400 g/m2 heat bonded two-layered GTX exhibited internal shear failure at low shear displacements. However, all the highly aged single layered GTXs showed an increase in the peak interface friction angles with the increase in their ageing. For these single layered GTX, the results suggest that assessing the interface friction angles using unaged GTXs for the stability analysis is conservative as long as the GTX remains intact in the field. • Under normal stresses up to 1000 kPa, no surface damage was observed in any of the geomembranes surface roughness. • Decreasing the geotextile mass per unit area, increased the friction angles for the geomembrane-geotextile interface. • Ageing of single-layer geotextiles resulted in an increase in peak interface friction angle. • Geotextile ageing resulted in higher post peak strength. • Preaged heat bonded two-layer geotextile exhibited internal failure at the interface between the two layers of the geotextile. [ABSTRACT FROM AUTHOR]

This article proposes a novel method termed HEAP for fast and reliably computing nose points, tracing the entire PV curve, and assessing static stability limits. Here, the prefix “HE” in HEAP refers to (fast and flexible) holomorphic embedding, and “AP” is short for arc-length parametrization. This novel method uses an arc-length parametrization and piecewise approximants that enable it to have the favorable feature of Continuation Power Flow that can pass through the nose point without numerical difficulties. Another outstanding feature of the proposed method HEAP is its computational efficiency by enabling the accurate approximation over a long interval of the parameter (i.e., a large step size). This is because of the large convergence region of HEAP. The existing methods for similar tasks usually suffer from several issues such as empirical criteria for detecting nose points, small convergence regions of correctors, numerous intermediate points, and large memory space consumption. These issues are well addressed by HEAP. To examine its numerical performance, HEAP is tested on various power system models with as many as 70,000 buses, and numerical results substantiate the outstanding features of HEAP. Depending on intended applications (e.g., only locating the nose point or fully tracking the curve), two tailored approaches are devised to effectively derive numerical solutions. In comparison with the continuation-based power flow method, HEAP attains speedups of 3x to 300x and notably attains speedups of at least 19x for all large test cases with 10,000 or more buses. The continuation-based power flow method fails in several large test cases, however, all of which are successfully solved by HEAP. After enforcing the generator reactive power limit, HEAP also produces the same accurate results as the continuation-based power flow method. [ABSTRACT FROM AUTHOR]

Recycled manure solids (RMS) bedding is an alternative bedding option that is growing in popularity on Canadian dairy farms. However, the microbiological characteristics and production of RMS bedding are poorly documented under on-farm conditions in eastern Canada. This bedding could support the presence of pathogens and could have an effect on cow and human health. The aim of this study was to describe the RMS microbiota when used under dairy cows and compare it with straw bedding. Unused and used bedding from 27 RMS and 61 straw-bedded dairy farms were collected and compared using 16S amplicon sequencing, bacterial counts, and Salmonella spp. and Listeria monocytogenes detection. Microbiota composition of unused RMS and unused straw were different. After use, both bedding microbiota were similar in their bacterial composition, structure, and diversity. Unused RMS generally contained higher bacterial counts than did unused straw, except for Klebsiella spp. counts. Salmonella spp. and L. monocytogenes were more frequently detected in unused RMS (Salmonella spp.: 11%; L. monocytogenes : 30%), than in unused straw (Salmonella spp.: 0%; L. monocytogenes : 11%). Finally, 2 RMS production systems (extraction of the liquid fraction followed by maturation in an opened or enclosed container vs. in a heap) did not influence the microbiota richness and bacteria distribution (α-diversity), but did influence the microbiota structure (β-diversity). In conclusion, animal and human pathogens were found in greater numbers and more frequently in unused RMS than unused straw, and this could eventually affect dairy cow or human health. [ABSTRACT FROM AUTHOR]

Purpose. Representation in a generalized form of the conducted research on the development of technology for heap leaching of gold-bearing tailings at the Vasilkovsky GOK (Altyntau Kokshetau), which can be used to recover gold from technogenic deposits in Kazakhstan. Methods. The research on the gold recovery from the ore beneficiation tailings at the Vasilkovsky deposit is conducted using direct cyanidation. Experiments are performed in open heat-resistant beakers equipped with a mechanical agitator. The preparation of the material for cyanidation consists of the following operations, such as grinding, water washing and alkaline treatment followed by cyanidation. The optimal cyanidation parameters are determined by performing a series of experiments with a change in one parameter at a constant value of others. After the optimal process duration is determined, a series of experiments are conducted with a change in the solids content in the pulp of 20, 25, 33, 50 and 100%. The concentration of cyanide in the solution is 0.1-1.0 g/dm3. The concentration of sodium thiosulphate in the cyanide solution is 0.5-5.0 g/dm3. The process temperature varies within 20, 30, and 40°С. The content of the nutrient medium is the sodium thiosulphate for the used culture T10. Findings. It has been determined that with an increase in the solids content in the pulp, the degree of gold recovery from tai-lings increases, reaching a maximum of 97.5%, with a ratio of (solid: liquid) S:L = 1:1. When the solids content in the pulp is below 50%, a longer agitation leaching of the pulp is required to achieve a recovery of at least 85-90%, which, in turn, leads to high operating costs. Originality. For the first time it has been found that the optimal solids content for maximum gold recovery in the pulp can be considered 50% (or S:L = 1:1). Practical implications. Increasing the solids content in the pulp contributes to the duration of the solvent contact with the ore mass, which allows the use of less concentrated solutions of the leaching agent. [ABSTRACT FROM AUTHOR]

Purpose. Substantiating the main explosive impulse parameters and determining the dependences of metal recovery during forced loosening and shaking of the ore mass by an electro-hydraulic blasting to intensify the heap leaching process. Methods. The experimental laboratory studies have revealed the dependences of the discharge energy influence on the blasting pressure at various parameters of the discharge capacity and inductance, as well as the change in the metal content in the productive solution when the ore mass is exposed to an electro-hydraulic blasting. Findings. A research methodology using the models of the electro-hydraulic blasting impact on the ore mass is proposed. In addition, the similarity criteria have been substantiated, which make it possible to study the nature of shaking and loosening under various loading parameters. It has been determined that using the method of influencing the ore mass with an electric discharge in a liquid increases the degree of metal recovery from the ore during heap leaching and increases the rate of the solution penetration into the depth of the ore mass. When using the method of loosening the ore mass by artificial shaking, the recovery of copper increases by 10-15% and the leaching time decreases by 1.5 times. Originality. It has been determined that due to the possibility of regulating the electric discharge capacity in the required range during blasting operations, loosening and additional crushing of the ore mass occurs; fractures are formed in lumpy ores, which contribute to an increase in the rate of leaching solution infiltration. Practical implications. The proposed technology makes it possible, without dismantling the equipment and irrigation communications, to perform additional loosening of the ore mass and increase the rate of the leaching process, as well as significantly reduce the time of the technological process. [ABSTRACT FROM AUTHOR]

The main objective of research was to assess the current level of bottom sediment and water pollution of the Olše River and its tributaries. The Olše River is an important stream in the Upper Silesian Basin which was significantly affected by coal mining and industrial activities in the past (Martinec et al. 2006). Monitoring of the area by the Povodí Odry State Enterprise (the Odra River management) has shown that the water quality in the river has significantly improved due to the development of municipal wastewater treatment plants. Currently, saline waters from coal mines in the Karviná sub-basin are considered to be the biggest threat to the river environment. A total of 19 river sediment and 9 surface water samples were collected (Fig. 1). The elemental content was determined using X-ray florescence spectroscopy (XRF); for selected river sediments, the organic carbon content was determined using the Elementar Vario TOC CUBE device. The loading of river sediments by elements was evaluated using Igeo Class. The content of major ions (HCO3-, K+, Ca2+, Na+, Mg2+, SO4 2- and Cl-) in the surface water samples was determined in the laboratory. The water in the Olše River belongs to the hydrochemical type of Ca-HCO3. The water in the Karvina Creek near the mining works is highly mineralised and represents a single case of the Na-Cl hydrochemical type. Despite the significant mineralisation level, the water from this creek does not significantly affect the quality of the water in the Olše River. The highest enrichment of river sediments compared to the natural background was found for Zn (Table 1) at all sites. Zinc is one of the elements with rather high mobility and tends to be bound to hydrated Fe and Mn oxides that occur in rather large quantities on adjacent spoil heaps in the area and can thus enter the system very quickly. The Mn (340 to 2,553 mg/kg) as well as Sr (71 to 1,836 mg/kg) concentrations are elevated compared to those in global shales (850 mg/kg and 300 mg/kg, respectively; Turekian - Wedepohl 1961). Their contents in the Upper Silesian Coal Basin river sediments should be systematically monitored. The Olše River sediments were slightly to moderately contaminated with Cr and Pb (Table 1). This is not considered to be related to mining but rather to road runoffs and the fact that the river flows through industrial areas. [ABSTRACT FROM AUTHOR]

The relationship between the density of seawater and acidified mixtures samples in the presence of up to a maximum concentrations of 0.18 m for Cu(II), 0.34 m for Mn(II) or 0.6 m for Al(III), in selected temperatures used in the copper leaching process (283.15 - 313.15 K), showed a positive linear behavior with salinity and cation concentration. The influence of temperature on the density rate changes was similar when comparing the three solutes in acidified solutions of different salinity. The effect of temperature on the change in density did not exceed 1% and by concentration, the greatest influence was due to Al(III) with 5.43%, in agreement with its greater relative quantity. The data obtained, using a vibrating tube density meter, were used to analyze and correlate to the Apelblat equation that was favorably applied to calculate the isobaric expansibility coefficient. The temperature had an influence on the isobaric expansibility coefficient values, suggesting a making interaction effect due to majority anions present in the seawater and mixture samples (Cl- > SO4-2), and a breaking interaction effect when the cations Cu(II), Mn(II) or Al(III) were added. [ABSTRACT FROM AUTHOR]

The cloud computing technique, which was initially used to mitigate the explosive growth of data, has been required to take both data privacy and users' query functionality into consideration. Searchable symmetric encryption (SSE) is a popular solution that can support efficient attribute queries over encrypted datasets in the cloud. In particular, some SSE schemes focus on the substring query, which deals with the situation that the user only remembers the substring of the queried attribute. However, all of them just consider substring queries on a single attribute, which cannot be used to achieve compound substring queries on multiple attributes. This paper aims to address this issue by proposing an efficient and privacy-preserving SSE scheme supporting compound substring queries. In specific, we first employ the position heap technique to design a novel tree-based index to support substring queries on a single attribute and employ pseudorandom function (PRF) and fully homomorphic encryption (FHE) techniques to protect its privacy. Then, based on the homomorphism of FHE, we design a filter algorithm to calculate the intersection of search results for different attributes, which can be used to support compound substring queries on multiple attributes. Detailed security analysis shows that our proposed scheme is privacy-preserving. In addition, extensive performance evaluations are also conducted, and the results demonstrate the efficiency of our proposed scheme. [ABSTRACT FROM AUTHOR]

In the traditional heap leaching of rare earth minerals, the top of the rare earth pile is covered with leaching liquid. This creates trouble for vegetation restoration carried out timely on the top of the pile. In order to solve this trouble, a novel pile structure into which leaching liquid is laterally injected is proposed for heap leaching of rare earth. In this study, a laboratory test is carried out to study the formation and distribution of preferential flow paths for the rare earth pile under a horizontal liquid injection condition. Furthermore, numerical simulations based on a dual-permeability model are conducted to investigate the influence of the preferential flow paths on the seepage characteristics in the rare earth pile. The results show that, under the horizontal liquid injection condition, the fine particles of the rare earth move away from the liquid injection end and also toward the lower part of the pile. The migration of the fine particles results in the formation and connection of macropore, thereby generating preferential flow paths in the rare earth pile. The preferential flow paths are mainly distributed in the lower part of the pile near the liquid injection end. This causes the fluid in the lower part of the pile to seep faster significantly than that in the upper part. Within the region where the preferential flow paths develop, the seepage in the early stage of the horizontal liquid injection is dominated by preferential flow. The preferential flow is more significant at the locations farther away from the liquid injection end. [ABSTRACT FROM AUTHOR]

This paper presents a novel suction-controlled chamber that permits the determination of the full water retention curves of geosynthetic clay liners (GCLs) under non-uniform temperature-stress paths. It investigates field conditions encountered in brine ponds (low confining stress settings) and heap leach pads (high confining stress settings) during construction and operation stages. Consequently, the analysis of the moisture dynamics in a GCL was defined under the wetting path (construction) and drying path (operation). High vertical stresses were found to facilitate a more rapid water uptake as capillarity is established faster than at low, confined stresses. In general, the drying curves increase the water desorption over the suction range investigated due to the low water viscosity caused by high temperatures. The wetting of the GCL at 20 °C and drying at 70 °C under either low, confined stress (2 kPa) or high confining stress (130 kPa) shows a reduction in the volumetric water contents. Furthermore, on the drying path, the coupled effect of elevated temperature and high confining stress accelerates water desorption leading possibly to potential desiccation. • A novel suction-controlled chamber (SSC) that permits the WRC determination over the full range of suctions under non-uniform temperature-stress paths is presented. • The unified SSC allows measurements of suctions sequentially on a single GCL specimen. • WRCs are presented for typical field conditions with particular emphasis on heap leach pads and brine ponds. • Paper provides a new and unique insight on the water retention properties of GCLs. [ABSTRACT FROM AUTHOR]

• The spatial and temporal heterogeneity of column leaching is often disregarded. • Surface-level techniques are not commonly applied to column leaching experiments. • Interest in non-destructive 3D imaging has surged over the last two decades. • Hydrodynamic studies consider gravimetric and residence time distribution methods. • Multimodal approaches are necessary to unlock the spatiotemporal heterogeneity. Column leaching experiments are an essential step in the upscaling process towards a heap leaching operation. However, these experiments are often restricted to the optimisation of a reduced set of parameters. In doing so, most column leaching experiments tend to be ore-specific and to neglect key aspects such as mineralogical or structural changes over time, surface-level processes, or hydrodynamic features. The omission of these factors results in the loss of information on the spatiotemporal heterogeneity of column leaching experiments, which could provide insights leading to more environmentally or economically sustainable operations. Certain studies have focused on accessing this spatiotemporal information by using 3D imaging techniques (such as Computed Tomography − CT or Magnetic Resonance Imaging − MRI) or hydrodynamic assessment procedures (residence time distribution − RTD analysis or gravimetric liquid holdup estimation methods) to study column leaching. These studies have demonstrated that there is more information in column leaching experiments than what is acquired during conventional optimisation tests. Despite this, two essential gaps have been identified in the literature: (1) surface-level processes have received very limited attention as part of column leaching experiments and (2) chemical characterisation of the leaching solution is restricted to collection points before and after the column, providing a very low spatial resolution for these measurements. Multimodal methodologies capable of assessing several aspects of the process need to be implemented to bridge these gaps and to unlock information on the spatiotemporal heterogeneity of column leaching experiments. [ABSTRACT FROM AUTHOR]

In this study, we propose a novel methodology for the automatic control of heap leaching by means of policies obtained using Reinforcement Learning (RL). This methodology models the leaching dynamics as a Markov Decision Process (MDP) whose reward function captures the economic profit of the heap leaching operation. As a case study, the leaching process of copper oxide heaps is simulated and controlled under various conditions. Results show that controlling this process using the proposed approach outperforms a heuristic control strategy that emulates real mining operations by increasing recovery rates by 2.25 times, reducing water consumption by 32.4% and acid consumption by 19.9%, and enhancing economic returns by 17.5%. This approach highlights the robustness of a Deep Reinforcement Learning (DRL) policy in heap leaching operations under significant out-of-distribution (OOD) conditions, demonstrating its adaptability and effectiveness under diverse and unpredictable conditions. Furthermore, this research highlights the potential for this methodology to be applied to other leachable ores, as it could reduce the overall environmental impact of this operation by using fewer resources. [Display omitted] • A novel methodology for heap leaching control using Reinforcement Learning is proposed. • The heap leaching control problem is formulated as an MDP whose reward is analogous to profitability. • The potential to increase productivity, efficiency, and profitability is empirically shown. [ABSTRACT FROM AUTHOR]

In order to solve the problem of vegetation restoration in the traditional heap leaching of rare earths, a novel heap leaching technology is proposed. In the novel technology, leaching liquid is laterally injected into the rare earth pile from the side end so that vegetation restoration can be carried out quickly on the top of the pile. In this study, a laboratory test was performed to investigate the permeability of the ion-adsorbed rare earth pile under lateral liquid injection conditions. Four rare earth samples with varied combinations of the mineral particles at different sizes were adopted in the test to emphatically discuss the influence of the particle composition on permeability. The experimental results show that the permeability of the rare earth pile under the lateral liquid injection conditions is governed by the migration of fine particles. As the hydraulic head of the leaching liquid increases, the fine particles undergo a motion process of stabilization, migration initiation, deposition, and remigration. Accordingly, the permeability coefficient of the rare earth pile exhibits a variation of stabilization, a gradual increase, a re-stabilization, and a re-increase. The fine particle migration and exudation causes the permeability of the rare earth pile to be non-uniform in space. The permeability coefficients near the liquid injection end and the liquid outlet end are much greater than those are at the middle positions of the pile. The particle composition of the rare earth has an important effect on the permeability of the pile. In the rare earth with a combination of coarse and fine particles, preferential flow paths are easy to develop as in this soil, the fine particles easily migrate and they cannot block the pore channels. By contrast, the fine particles find it difficult to migrate, and the permeability coefficient is relatively stable in the fine-medium particle rare earth. This particle composition is conducive to the heap leaching of the rare earth under lateral liquid injection conditions.

The percolation technique was used to examine the leachability of uranium from El-Sela uranium mineralization. The agglomeration effect, particle size, flow rates, free acidity, solid/liquid ratio, and the ratio of cobblestone effect were all studied in the kinetics of uranium leaching. At a height of 3.0 m within the column, the optimal ratio of cobblestone to ore was found to be 1:4, and the irrigation rate was reduced from 0.15 to 0.1L/m2/min, increasing the leachability of uranium from 47.5 to 79%. Finally, column leaching is confirmed by fitting data from an application first-order kinetic law with data collected. [ABSTRACT FROM AUTHOR]

Szklary Massif is situated about 60 km from Wrocław (southwestern Poland) and around 7 km from Ząbkowice Śląskie. The history of raw materials in this region started in the fifteenth century with the discovery of precious minerals like chrysoprase, chalcedony, and opal. The exploitation of nickel ore in this region started in the nineteenth century and was conducted with few stops until 1983. The remaining 17.21 mln mg of ore with 125,000 mg of nickel might be a chance to satisfy rising demand for raw materials used to develop electromobility. One of the crucial aspects regarding possible investment is the processing of ore. The pilot tests show the efficient use of heap leaching. The authors provide the future project in Szklary within the framework of circular economy. [ABSTRACT FROM AUTHOR]

The negative impacts of the overexploitation of resources on regional environments have become increasingly obvious. The contradiction between the environment and development and the management of the ecological environment in mining areas are urgent problems to be solved. This paper uses Landsat images from four temporal phases from 1991 to 2018 in the Lingbei mining area of Dingnan County, China, to construct a rare earth remote sensing-based ecological index (RE-RSEI) suitable for rare earth mining areas and to analyze the impacts of different rare earth mining methods, mining scales and environmental management measures on the mining area environment over the past 27 years. The results show that since 1991, due to the mining techniques of "pond leaching" and "heap leaching" and the soil condition, mining has caused severe damage to the land and vegetation, and the ecological environment quality of the entire mining area has been seriously reduced with its RE-RSEI value dropping from 0.744 to 0.675. After 2010, through the optimization of mining technology and the government's attention to ecological environmental governance, the quality of the ecological environment was slowly restored, and the recovery effect at some mine sites was remarkable. The RE-RSEI model has good applicability to rare earth mining areas, can intuitively reflect the destruction and restoration of the ecological environment of rare earth mining areas under different mining modes, and provides scientific guidance for promoting the coordination of the development and utilization of rare earth resources and mine ecological environmental protection and sustainable development. [ABSTRACT FROM AUTHOR]

Purpose. Increasing the efficiency of gold heap leaching by changing the solution rheological properties due to its mechanical activation. Semi-industrial tests were carried out to verify the results of laboratory work. Methodology. First, semi-industrial tests were carried out without activation of the solution (basic technology), and then the solution activation was applied. The ore amount in the stockpile was 600 kg; the gold content in the ore is 1.12 g/t. At the same time, the concentration of cyanide was 400 ppm. The activation degree was from 3 to 8 minutes, the leaching time was 2, 4, 6 hours, the solution temperature varied from 13 to 30 degrees. Findings. According to the results of semi-industrial tests, the dependence of gold content, pH value, and residual concentration of the reagent on the leaching time was obtained using both proposed technology and the basic one. Comparison of the semiindustrial test results related to the basic technology and proposed one (with the solution activation) showed that the maximum gold content in the productive solution with the basic technology is 1.83 mg/l, and with the activation of the solution it is 2.10 mg/l. Hence, there is an increase in the gold content by 14.7 % with the solution activation Originality. Dependence of gold content in productive solution, pH value, and residual concentration of the reagent in solution on the degree of its activation has been obtained. Practical value. The optimum degree of the treatment solution activation during gold heap leaching is determined, which is from 5 minutes to 7 minutes depending on the leaching time, which increases the gold content in the solution by 14.7 %. [ABSTRACT FROM AUTHOR]

Changshanhao open-pit gold mine in Inner Mongolia is the largest gold heap leach mine in North China. Recently, the mining depth and scale have increased, due to depletion of shallow resources. Since deep mining and steep slope mining have begun at Northeast stope of Changshanhao gold mine, landslides and instabilities of different scales occurred at many areas, constituting severe threat to both personnel and equipment. In order to comprehensively evaluate the slope stability of the Northeast stope and provide guidance for the division of dangerous areas in the stope, the 3D geological model of the Northeast stope of Changshanhao open-pit gold mine was established by using 3D digital modeling technology. Following, the rock quality designation (RQD) value of deep rock in the stope was estimated, based on RQD sample data of deep rock extracted from borehole and geostatistics method, while the distribution characteristics in three-dimensional space of rock mass quality of the open-pit slope were revealed. Ultimately, through the comparative analysis of the integrity investigation results outcrop rock mass and the prediction results of deep rock mass, the feasibility of three-dimensional geological modeling method and the reliability of the calculation results based on geostatistics method were verified, providing reference for safe mining of the high and steep slope within the open pit. The comparative analysis results indicated that: (1) the overall rock mass quality grade of current slope at the Northeast mining area was poor; (2) the rock mass at the north side of the upper part of the east U-shaped mouth was quite fractured, further reinforcement, monitoring and prevention are needed; (3) in the final state of design, the influence of mining disturbance will further degrade the quality of slope rock mass. [ABSTRACT FROM AUTHOR]