Search

A series of large-scale direct shear tests was carried out to examine the effectiveness of smooth, textured and structured surface geomembranes (GMBs) with different soil subgrades for heap leach p...

In this study, the reject fraction of the jaw crusher, located in the first part of the crushing circuit, is used as a considerable stock in copper tank-leaching plant. High market value of copper and ease of practice were the motivating forces on studying the leaching kinetics under controlled conditions. In this regard, first, the influencing parameters such as the acid concentration, solid-to-liquid ratio, agitation speed, particle size, and temperature were assessed on the leaching fraction of copper. The findings showed that the leaching rate is nearly independent of the agitation rate at the high values of 300 rpm. The recovery of copper strongly promoted from 2 to 90% by increasing sulfuric acid concentration from 0.3 to 1.8 M. The increase in the solid-to-liquid ratio and temperature were found to be beneficial as well. Additionally, it was found that above 71% copper could be leached from the reject samples in the size range of 0–2 mm by 0.9 M sulfuric acid after 30 min contact time at 25 °C temperature. In the second stage, the leaching kinetics was studied by shrinking core models to gain a better description of the dissolution process of copper from crushing circuit reject. The results indicated that the dissolution rate could be controlled by both chemical reaction and diffusion process. However, diffusion process was the dominant mechanism in the system investigated. Ultimately, a mixed kinetic model with an activation energy of 11.72 kJ/mol was proposed as the leaching rate-controlling step.

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 leach...

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.

Over the past century, many problems have been focused on the problems of low leaching rate of gold and methods have been developed to intensify the leaching of gold. Among these methods, the use of hydrogen peroxide to accelerate the leaching of gold is known. In order to intensify the leaching process, the indicators of cyanide leaching of gold from ore using hydrogen peroxide were studied. This article presents the results of assay-gravimetric, chemical, and mineralogical analyses of gold-bearing ore from the Sari Gunay Deposit (Iran). The content of sulfide sulfur ore belongs to the category of low-sulphide, by oxidation of sulphur (50.70%) to the category of oxidized ores. Thermodynamic analysis of possible reactions of ore components with hydrogen peroxide is carried out. Laboratory studies on cyanide leaching of gold have shown that the maximum recovery of gold is 52.92% at a concentration of hydrogen peroxide of 0.5%, the recovery of gold without ore treatment is 52.03%. The results of laboratory and column tests with and without treatment with hydrogen peroxide (H2O2–0.5%) were compared. Treatment of gold-bearing ore with hydrogen peroxide during heap leaching of gold increases gold recovery by 1.2% and amounts to 55.89%, without treatment - 54.69%. This increases the consumption of sodium cyanide by 0.04 kg/t.

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.

The widespread introduction of physical and chemical geotechnologies in the production of mineral raw materials makes it possible to involve ores that are poor in the content of the useful component, which are unprofitable to work out using traditional physical and technical methods. One of these new geotechnologies is the heap leaching of rocky uranium ores. When planning the volume of output of finished products, it is necessary to have an analytical apparatus that would make it possible, using the acquired knowledge, to calculate the required volume of mineral raw material production and its varietal composition. Based on their task, studies were conducted on the qualitative and quantitative characteristics of ores that affect the indicators of extraction of useful components from them. As a result of the research, the dependence of the index of uranium extraction into a productive solution during infiltration of sulfuric acid leaching on the material composition of ores was established. Ores localized in various lithological differences of acidic, medium and basic rocks were tested: granites, felsites, trachydacites, andesites and conglomerates. The ores were classified according to the size of the piece with the allocation of fineness classes +200 mm, -200 +150 mm, -150 + 100 mm, -100+70 mm, -70+ 30 mm, -30 mm. The tests were carried out in laboratory and semi-industrial conditions. The maximum extraction was obtained for the class – 30 mm in columns. When leaching in stacks, the maximum extraction of uranium into the solution was obtained for the size class -70+30 mm. The reason for the lower extraction from the -30 mm class during leaching in semi-industrial conditions was the processes of mechanical colmatation, due to the large number of fine fractions. The criterion characterizing the material composition of ores is the content of silica (SiO2). During the tests, the dependence of the uranium extraction coefficient in the productive solution on the content of silica in the ores was established. The higher the concentration of silica, the more uranium passes into the productive solution during leaching with a stable composition of uranium mineralization. The dependence is described by a mathematical formula, which allows us to use it to calculate the extraction of uranium into a productive solution, knowing the material composition of ores

The success of the physico-chemical technologies’ application in the development of ore deposits, such as underground and heap leaching, depends on the petrographic and mineral composition of the ores and their host rocks, type of reagents leaching the useful component, technology of ore preparation and irrigation modes of lumpy ores. The efficiency of leaching of uranium-ore minerals is determined by the physico-chemical laws of the interaction of reagents with the ore material. In the course of the research, the relationship between the silica content in the rocks containing mineralization and their physical and mechanical properties was established. This makes it possible, knowing the type of rocks, to predict the conditions of ore preparation by drilling and blasting to obtain the optimal piece size for leaching. In addition, the influence of the ore texture on the leaching efficiency was proved experimentally. Previous researchers found that the rate of conversion of uranium to the mobile state during leaching depends on the rate of penetration of the leaching reagent into the piece, displayed by the effective diffusion coefficient (Kef). The analysis of mining and geological information made it possible to establish the relationship between the Kef and the type of host rocks through the SiO2 content and the type of uranium minerals through the uranium content. The obtained knowledge makes it possible to predict favorable conditions for the use of physico-chemical geotechnologies in the development of rock-poor uranium deposits

The experience of heap leaching (HL) was analyzed in the following cold climate regions: Alaska, Western regions of the United States, Canada, Kazakhstan, and Russia. The disadvantages of the developed domestic mobile units were uncovered, and the potential for creating HL mobile units was assessed to enable a year-round use of the technology, including in the cryolithozone. The results are presented, which were obtained during investigation of the material composition of the study object, i.e., technogenic gold-containing deposits of the Transbaikal region. The main element content of the mineral raw materials of the technogenic deposits was as follows: Au — 0.35 g/m3, Ag — 3.9 g/m3, SiO2 — 69.3 %, Al2O3 — 15.4 %, Fe2O3 — 5.9 %, CaO — 0.21 %, and MgO — 1.15 %. The phase forms of gold included: cyanidable (intergrown) — 2.3 %, “sealed in quartz” — 13.5 %, “enveloped” — 28.6 %, in magnetite — 55.6 %. A continuous process line was developed, which included the following four unit modules: gravity concentration, first stage of leaching (tank leaching), second stage of leaching (heap leaching), and sorption. The layout of the continuous process line (HL option during the period of subzero temperatures) is provided. The optimal values of the main process parameters of gravity concentration, as well as the first and second stages of leaching have been established experimentally. Prior to tank leaching, an active multiple-reagent solution based on sodium chloride, water and ozone compounds was prepared in a sealed electrochemical reactor. The tank was partitioned into three sections, in which the following operations were carried out in series: chemical opening of the gold-containing minerals; chlorine removal from the geomaterial; and tank leaching of gold. The total duration of heap leaching was 365 days, which was achieved by using two technological options: option 1 (195 days) — classic HL method (from early April to mid-October), option 2 (170 days) — heap leaching in stationary concrete cuvettes using engineering solutions during the period of subzero temperatures (from mid-October to the end of March). A schematic layout of the stationary concrete cuvette constructed in a special way and buried within a 5 to 8 m layer of soil above the ground level with shielding of the upper surface of the stack (heat-insulating covering, clay, large pieces of ore, sulfide rocks) is provided. Product solution drainage was used at various heights, and perforated rigid PVC pipes were used for supplying warm air deep inside the material. The recovery of gold from the technogenic raw materials was increased on average by 27.1 % due to a year-round heap leaching with the use of two technological options: 1 — by 28.7 % (from 58.1 to 86.8 %) using a classic HL method, and 2 — by 27.4 % (from 58.1 to 85.5 %) by using HL in stationary concrete cuvettes. It is proposed to utilize the secondary waste of the HL field (total of five types) in the road-building and construction industries.

The features of the technology of heap leaching with floating gold are disclosed. It was found that significant technological losses of gold in the processes of enrichment of gold-bearing ores, as a rule, are associated with its natural fine mineralization or technogenic transformation to such a state. It has been shown that flat gold flakes (even with a gold grain size of more than 1 mm) are quite well retained on the surface of technological solutions, i.e., have a certain buoyancy. The wettability of gold particles is explained by the manifestation of the surface tension forces of aqueous solutions, the mechanisms of which are determined by the van der Waals interaction. In addition, the wettability of gold grains is affected by their electric charge, which, accumulating on a convex surface, creates a negative charge that prevents the formation of a double electric field around the gold particle, which is an additional reason for the non-wettability of gold. The mechanism of the formation of gold films, which are formed at a high value of surface tension, with the formation of floating "islands" covered with a hydrophilic shell, is explained. It was revealed that the energy of interaction of a gold nanoparticle with water can serve as a quantitative indicator of the buoyancy of gold grains and "islands" of nanogold, at a value of which of 0.05427 eV, clearly pronounced hydrophilic properties appear. The theoretical substantiation of the buoyancy of gold grains and "islands" of nanogold is the van der Waals interaction. On this basis, heap leaching technology was developed, with the targeted deposition of floating gold in the most suitable places. As a result of a decrease in the surface tension of leaching solutions, nanogold loses their initial buoyancy and sink from them to the bottom, where they will be subjected to the processes of their disembarkation (collection and extraction).

Detailed studies of uranium heap leaching from different uranium mineralization resources situated in Eastern Desert of Egypt were investigated using sulfuric acid via batch experiments, followed by using the obtained optimum condition on bench scale leaching tests using small column. The previous optimum parameters were implemented on another large scale column in order to make more condition control and evaluate the time and reagents needed while transferring from small to large scale. The obtained data shows that leaching efficiency of GII mineralization attained about 78.3% with consumed acid amount about 34 kg/ton in a 44 days as leaching time, on the other hand, leaching efficiency of uranium from El-Missikat mineralization higher than GII mineralization and attained about 86.6% and the consumed as lower than G-II about 28kg/ton in a 40 days leaching time. Kinetics reaction models of column tests have been investigated to optimize the column leaching behavior. Based on the leaching results of the two mineralized occurrences, the rate of the uranium dissolution is controlled by both the chemical reaction and the diffusion reaction but diffusion reaction control was more predominate than a chemical reaction.

One of the cheapest methods of extracting gold is heap leaching. However, the recovery of gold by this method is relatively low, compared with cyanidation of the crushed material, so the search for the ways to intensify leaching and increase gold recovery is an urgent task. Investigations on heap leaching of gold from the gold-bearing ore of the Sari Gunay deposit were conducted using a promising reagent sodium acetate to intensify the heap leaching process. The results of assay-gravimetric, chemical, mineralogical and granulometric analyses of oxidized ore are presented. The average gold content in the ore was 2.90 g/t. According to the electron probe analysis, gold in the ore is present in the form of fine (micron) inclusions in minerals and ore rocks. Comparative studies on heap leaching of gold from the crushed ore with a grain size of –20 + 0 mm with the addition of sodium acetate and without that were carried out. The degree of gold recovery with sodium acetate at a flow rate of 0.5 kg/t was 58.74%, that without sodium acetate was 54.69%, i.e. the addition of the reagent provides an increase in recovery of more than 4%. Leaching with the addition of the reagent also reduces sodium cyanide consumption from 0.65 to 0.59 kg/t. The research results have shown that sodium acetate can be used to intensify the process of heap leaching of gold when the ore size is –20+0 mm.

The paper provides a theoretical justification of the key chemical aspects of enhancing the process of heap leaching (HL) of gold by using a reagent complex containing hydrogen peroxide. A schematic illustration of heterogeneous catalytic reactions, which occur during metal leaching, as well as examples of the geometry and dissociation energy of a number of gold clusters are presented. The paper provides the results of studying the mineral composition of various types of waste produced by the Darasun mine, including cut-off grade ores of the Talatuy deposits (gold content — 0.7 g/t), mature tailings of the Darasun gold-processing plant (GPP) (gold content — 1.45 g/t), and flotation tailings of the current ore processing at the Darasun GPP (gold content — 0.3 g/t). A process flow diagram is presented to describe the conducted experimental studies of heap leaching of gold from the pelletized granules of technogenic minerals obtained from various types of mining waste. The process of leaching was performed using a reagent complex containing sodium cyanide solution and hydrogen peroxide, which served as a catalyst of the chemical reactions. The conditions that must be met by the geomaterial to be pelletized in order to obtain strong granules and enable gold leaching have been identified. The optimal values of the following key process parameters were determined: grain size of the crushed cut-off grade ore; waste fraction of the pelletized geomaterial (cut-off grade ore : mature tailings : current processing tailings = 1:0.5:0.5); amounts of sodium cyanide and hydrogen peroxide in the leaching solution, which are introduced into the process in stages at a ratio of H2O2 :NaCN = 10:1. An enhancement of the process of geomaterial heap leaching using hydrogen peroxide enables a higher concentration of oxygen in the lower parts of the pile, which results in an increase in gold recovery by 7.6 % (from 79.5 % to 87.1 %) in comparison with the conventional process. The proposed method utilizing physico-chemical geotechnology of gold recovery ensures a sustainable use of the natural mineral resources, as well as a closed cycle of mining production.

An understanding of the spatial and temporal variations of surface moisture content over a heap leach pad (HLP) is essential for leaching production and to achieve a high ore recovery. The current practice of leach pad monitoring and data collection remains highly manual and labor-intensive, and exposes technical staff to hazardous material (i.e., cyanide solution). To address these challenges, we propose using unmanned aerial vehicles (UAVs) equipped with thermal imaging sensors to remotely obtain high temporal and spatial resolution image data for monitoring the surface moisture distribution over HLPs. A field study was conducted over a sprinkler-irrigated HLP at El Gallo gold mine in Sinaloa State, Mexico, and the acquired data were used to derive an empirical relationship between the surface moisture content and the remotely sensed surface temperature using linear regression. Moreover, the data were used to generate moisture distribution maps of the entire HLP surface. In situ samples were taken manually during the field experiments to measure the ground-truth material moisture at selected sampling locations. The results show a good agreement between the remote sensing method and the measured ground-truth samples.

Organic solutions are promising lixiviants for fast and environmentally sustainable Pb extraction from ore minerals at low temperatures. However, engineering of novel leaching flowsheets has been h...

Metallurgical & materials engineering 26(2), 199-208 (2020). doi:10.30544/513 special issue: "Hydrometallurgical operations and processes", Published by [Verlag nicht ermittelbar], Belgrade

Hydro-Jex® is a new enhanced method for heap leach treatment with significantly higher mineral recovery. In this case study at the Los Filos Mine in Mexico, the Hydro-Jex operation is evaluated for heap leach stability. This is pursued by numerical modeling of the heap leach pad stability and well monitoring of the phreatic surface before and after the Hydro-Jex operation. Experimental and numerical results both indicate an improvement in mineral processing under the influence of Hydro-Jex. Numerical results show an insignificant decrease and a significant increase in stability during and after Hydro-Jex injection application, respectively. The integrity of the liner is maintained in both cases. The zonal injection pressure, operationally below the overburden pressure, is found to be negligible compared with the dimensionality of the heap, and stability of the structure is not exposed to any significant risk, even up to 25% above overburden pressure. Furthermore, heap leach factor of safety increases after Hydro-Jex application. This is attributed to breakdown of the water solution build-up and thus a decrease in the phreatic surface depth below the top of the pad. It is suggested that injection wells be drilled, based on thorough geophysical data, in locations where overcompaction of heap material results in water solution build-up and pore pressure enhancement. Compared with traditional heap leaching, the Hydro-Jex technique not only expedites mineral processing by increasing chemical kinetics extraction but also increases the stability of the heap by unclogging drains.

The heap leaching process has been widely used for recovering different metals since its first application at the end of the 1960s. In Chile, copper production via heap leaching has accounted for between 30 and 40% of annual copper production over the past 10 years. This level of production has been achieved through and supported by the use of a mathematical relation, known as the leaching ratio (LR) or irrigation ratio (IR), which relates operational parameters with metal extraction in a heap leaching operation. This ratio has been used to develop leaching column tests, to scale up results from the laboratory to industrial operations, to design new heap leaching plants, and in metallurgical control and production estimation. In spite of the widespread industrial use of this relation, few scientific studies mention it. This is due to its simplicity and basic theoretical foundations. This disparity between industrial practice and scientific research could lead to operational decisions which lack substantial theoretical support, and to scientific studies which have limited industrial impact. Against this background, several questions arise about the use of the LR: What are the constraints on the use of the LR? Are there practical advantages with respect to reported kinetic models? What is the main reason that industry prefers the use of the LR over kinetic models, which enjoy greater theoretical support? In order to guide its future use, this paper describes the leaching ratio and its current uses and limitations, through a literature review and case studies.

The effect of high-pressure grinding roll (HPGR) comminution on the physical properties of ore particles and heap leaching of gold was investigated compared with that of conventional jaw crusher co...

Heavy metal-containing waste has become one of heavy environmental problems. Processing of such waste accumulated at waste dumps to extract valuable components is commercially beneficial activity and, in addition, decreases environmental impact. In this study, Lewatit MonoPlus TP 207 (TP 207) ion exchange resin was evaluated for its suitability for selective removal of cobalt (Co) and copper (Cu) from mine waste waters, generated by heap leaching waste materials at a Chilean copper mine. In series of laboratory scale fixed-bed ion exchange column tests, the effects of process parameters, such as waste water flow rate and regenerant (sulfuric acid) concentration, were studied in both waste water treatment by the ion exchange resin process and the resin regeneration (metals eluting) process. The regeneration process tests were performed using 1 % and 10 % sulfuric acid. The best separation of the metals (in the eluting process) was achieved with regeneration of TP 207 resin using 1 % sulfuric acid at flow rate of 1 bed volume per hour (BV/h).

В настоящей время мировые запасы месторождений с высоким исходным содержанием и легко извлекаемыми рудами в настоящее время практически истощены. В процессе добычи и переработки золотосодержащих руд были образованы многочисленные техногенные отходы: отвалы золотосодержащих бедных и забалансовых руд, хвостохранилища переработанной руды (в виде пульпы), а также отработанные штабеля кучного выщелачивания. Это обусловливает уменьшение объёмов переработки кондиционных руд и вовлечение в разработку техногенных отходов, труднообогатимых руд и забалансовых и низкосортных отвалов., At present, the world's reserves of deposits with a high initial grade and easily extractable ores are practically depleted. In the process of mining and processing of gold-bearing ores, numerous technogenic wastes were generated: dumps of gold-bearing poor and off-balance ores, tailings of processed ore (in the form of pulp), as well as spent piles of heap leaching. This causes a decrease in the volume of processing of conditioned ores and the involvement in the development of man-made waste, refractory ores and off-balance and low-grade dumps.

The quantitative effect of particle shape, porosity, wettability, particle size, and solution viscosity on the residence time distribution (RTD) profiles of non-reactive, steady-state, drip-irrigated ore beds characteristic of heap leaching systems is presented. Results were obtained using step-up tracer tests and allowed for the analysis of preferential flow behaviour within the systems. The key findings were as follows. Increased particle sphericity enhanced channelling in beds of smaller particles, but not for larger particle sizes. Higher particle wettability caused greater liquid dispersion during both initial wetting studies and at steady-state fluid flux. Higher porosity levels and the inclusion of fines in mixed sized beds resulted in longer average solute residence times, higher liquid hold-up, longer solution and tracer breakthrough times, and increases in drain-down moisture percentages. Increasing the irrigation fluid’s viscosity, reflective of the increase in ionic concentrations in leach solutions, reduced both the solution and tracer breakthrough times and increased dispersion with signs of more discontinuous or isolated fluid volumes at steady-state. These results highlighted the importance of the inclusion of fines in agglomerated beds to improve uniform wetting especially those with low to moderate particle porosities (

The volatility of the price of commodities generates the need for copper mining to control costs and make production processes more efficient. In this context, it is not possible to have real control over the productive indicators if it does not know the logistics of the processes, or you do not have a clear idea of the impacts of the variables or operational parameters on the dependent variables or responses. The present work aims to describe the production process for the leaching of secondary copper sulphides by means of heap leaching. This study focused on the search for theoretical relationships that define the behavior of copper recovery and the derivation of an analytical model that explains the response, developing a model capable of assertively representing the reality of the extractive process.

Accelerated carbonation of ultramafic mine tailings has the potential to offset CO2 emissions produced by mining ores from Cu-Ni-platinum group element, podiform chromite, diamondiferous kimberlite, and historical chrysotile deposits. Treatments such as acid leaching, reaction of tailings with elevated concentrations of gaseous CO2, and optimization of tailings pore water saturation have been shown to enhance CO2 sequestration rates in laboratory settings. The next challenge is to deploy treatment technologies on the pilot and field scale while minimizing cost, energy input, and adverse environmental impacts. Implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore-processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures. Here, we describe column experiments designed to trial two geochemical treatments that address these criteria: (1) direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation (10% CO2 in N2) and (2) repeated heap leaching of ultramafic tailings with dilute sulfuric acid. In the first experiment, we report rapid carbonation of brucite [Mg(OH)2] in the presence of 10% CO2 gas within tailings sampled from the Woodsreef chrysotile mine, New South Wales, Australia. Within four weeks, we observe a doubling of the amount of CO2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field. Our simulated heap leaching experiments, treated daily with 0.08 M H2SO4, produce high-Mg leachates that have the potential to sequester 21.2 kg CO2 m–2 y–1, which is approximately one to two orders of magnitude higher than the rate of passive carbonation of the Woodsreef mine tailings. Although some nesquehonite (MgCO3 · 3H2O) forms from these leachates, most of the Mg is precipitated as Mg sulfate minerals instead. Therefore, an acid other than H2SO4 could be used; otherwise, sulfate removal would be required to maximize CO2 sequestration potential from acid heap leaching treatments. Reactive transport modeling (MIN3P) is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years. Finally, our synchrotron X-ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals (Fe, Ni, Mn, Co, Cr) become highly concentrated within secondary Fe (hydr)oxide minerals at the pH neutralization horizon within our column experiments. This discrete horizon migrates downward, and our reactive transport models indicate it will become increasingly enriched in first-row transition metals in response to continued acid leaching. Acid-leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings, waste rock, or low-grade ores.

Since the cost of gold has increased by an order of magnitude over the past 20 years, gold mining began to be carried out from ores that are not previously acceptable for heap leaching (HL) technology – these are refractory ores with thin and ultrafine inclusions of precious metals, ore with an increased silver content. In the Russian Federation, classical representations in the field of gold and silver HL prevail in design solutions. At the same time, the problem of silver leaching is considered in terms of the associated extraction of the main component. This approach is determined by a limited set of technological measures that have become an integral part of the classic technological regulation: ore crushing to the class –200–40 mm, sodium cyanide consumption at the level of 0,5 kg/t; pH value – 10,5; cycle duration 65 days or more; gold concentration in production solutions – fractions, mg/l; using activated carbon for sorption of noble metals. Processing ores with silver contents of 30 g/t and a more classical approach to gold HL does not allow to increase the degree of extraction. There is a need to modernize the circuit or change the parameters of the technological regulations. The object of the study was a sample of poor quartz ore provided by the customer developing one of the gold and silver deposits of the Far Eastern Federal District, the object was to increase the degree of leaching of silver from poor gold-bearing ores without changing the technological scheme and without attracting additional mining equipment. Critical analysis of literary data was carried out and the main directions of gold production from poor gold-bearing ores were identified. Chemical and mineralogical compositions of silver-containing minerals and ore rocks were investigated. Forms of association of silver with ore minerals and rocks have been established. The option of physical and chemical activation of increase of reactivity of cyanide solutions during heap leaching of silver from poor gold-bearing ores is chosen. In laboratory conditions, it was found that an increase in the concentration of sodium cyanide by 6 times or more contributes to a satisfactory extraction of gold both in agitation and percolation leaching of silver. However, in the latter case, the positive result was obtained only with the use of solutions with increased reactivity

Modern methods of heap leaching process intensification, which make it possible to increase efficiency of metal conversion into productive solution by means of mechanical activation, which will ensure metal extraction increase without additional leaching costs considered and analyzed. Mechanical activation of leaching solution - leads to increase of solution chemical activity after its treatment in activation plant. Leaching solution activation increases conversion of commercial component into liquid phase with simultaneous reduction of leaching time.

Compared with the traditional pyrometallurgical process, copper bioleaching has distinctive advantages of high efficiency and lower cost, enabling efficiently extracts of valuable metal resources from copper sulfides. Moreover, during long-term industrial applications of bioleaching, many regulatory enhancements and technological methods are used to accelerate the interfacial reactions. With advances in microbial genetic and sequencing technologies, bacterial communities and their mechanisms in bioleaching systems have been revealed gradually. The bacterial proliferation and dissolution of sulfide ores by a bacterial community depends on the pH, temperature, oxygen, reaction product regulation, additives, and passivation substances, among other factors. The internal relationship among the influencing factors and the succession of microorganism diversity are discussed and reviewed in this paper. This paper is intended to provide a good reference for studies related to enhanced bioleaching.

A variety of modeling techniques can be utilized to forecast metal production at heap leaching operations. These approaches reflect a wide range of complexity, flexibility, time to implement, cost, and accuracy. For many operators, a spreadsheet-based modeling technique is attractive since the calculations are directly accessible, models can often be developed by site staff, and the results are generally easy to extract and interpret. The authors have developed a spreadsheet-based modeling technique that provides a high degree of flexibility, while still considering detailed operating information for ore properties, leach kinetics, scale-up factors, lift height, and in-heap metal inventories. The technique involves establishing kinetic leach curves for each ore type to characterize metal extractions, followed by application of separate metal recovery curves to define the rate at which leached metals exit the heap in pregnant solution, taking into account delays due to the in-heap solution inventory. At any point in time, the difference between total metal extracted and total metal recovered is equal to the in-heap inventory of the leached metal. This modeling technique is particularly useful for larger multi-lift heaps where delays in metal recovery are appreciable due to in-heap solution holdup. The technique is also applicable to sites with multiple heaps, leach cycles, and/or metal recovery plants (e.g., carbon columns for gold; solvent extraction for copper). This paper describes the modeling technique, including input data required and methods for defining kinetic leach curves and metal recovery curves. The technique is compared against an alternative spreadsheet technique using a simplified in-heap solution inventory calculation to forecast metal production, which has proven to be effective at a number of sites.

Despite lots of techniques in improving the heap leaching performance, many constraints on the industrial applications remain. We proposed a correspondingly effective and new idea of introducing forced aeration to improve the bad permeability and leaching effect of Yangla Copper Mine (YCM) during heap leaching. The dual-media theory was employed to study the impact mechanism of forced aeration on the variations of porous and fractured media during the column leaching experiments. An X-Ray Computed Tomography (CT) set was utilized to perform the pore imaging of the specimens and the fracture morphology of the particles within the columns was analyzed by Scanning Electron Microscope (SEM) as aeration rate (AR) changed. The results show that there exists copious fine particles within the heap of YCM, the particle size distribution of which is not reasonable. The forced aeration can not only promote the development of the porous and fractured structures but effectively break the blocked seepage paths. Then the leaching degree is improved and the seepage performance of the solute within the solution is enhanced. Therefore, the forced aeration is probable of making the leaching performance greatly improved.

Heap leaching is a hydrometallurgical processing technique where the effective mass transfer between the multiple phases dictates the process efficiency. It is employed to process low grade mineral deposits, which cannot be treated economically by conventional mineral processing techniques, such as flotation followed by smelting. While the noteworthy merits of heap leaching are low capital and operational costs, a significant shortcoming is the low recovery efficiencies. Heap hydrodynamics is a vital contributor to the overall recovery as it facilitates the transport of both the chemical reagents and the dissolved metal species. Although a uniform liquid distribution is a requisite for an improved metal recovery, often an anomalous liquid distribution (liquid channelling) is observed in industrial heaps. This study explores the effect of the heap packing structure on heap hydrodynamics by introducing non-ore particles as a packed bed modification strategy, which is analogous to novel heap construction methods. It was studied by introducing planar printed circuit board (PCB) pieces (25*25 mm2 and 50*50 mm2) and those were used to form the layered and mixed packed beds. Out-flow liquid distribution, ultraviolet (UV) fluorescence based flow paths visualisation, liquid holdup measurements, and liquid mal-distribution factors were determined and the results were compared again with the same given by the two control packed beds, namely, the ore bed and the PCB bed. The out-flow liquid distributions and liquid holdup profiles were combined to asses heap hydrodynamics and mass transport mechanisms. The layered beds and the mixed bed with larger PCB pieces contributed to a widely distributed out-flow profile by creating more liquid flow paths and thus the channelling effect was alleviated. The result of this work could be used to develop novel heap construction techniques with further studies on introducing non-ore particles into ore systems.

The decreasing grades of some gold deposits combined with the increasing depths, difficult surface topography, socioeconomic and geopolitical pressures often make the processing of such deposits infeasible by conventional mining, comminution and leaching technologies. To overcome these problems, the application of in-place, in-situ, and heap leaching often represent an optimal solution that minimises the capital and operating costs associated with mining and processing operations. Non-toxic, low cost lixiviants that are stable over an extended range of pH and Eh are required to provide any practical solution to in-situ leaching (ISL). Since ISL has the inherent benefit of increased natural rock temperature and pressure, glycine-based systems can be considered to extract valuable metals. Based on earlier studies on glycine leaching of pure gold foil, this research shows that Western Australian paleochannel ores are amenable to glycine-based ISL, at elevated alkalinity. The effects of pH, temperature, free glycine, ferric ions, sodium chloride and solids percentages on the kinetics of gold extraction were assessed. More than 85% of the gold can be extracted from ore with solutions containing 15 g/L glycine at pH 12.5 in 336 h. The presence of ferric ions did not improve the gold extraction, and most of the ferric has been precipitated from the leach solutions, implying that the chosen ferric complex was not sufficiently stable at the operating pH. The impurities dissolution during glycine leach was very low and highly selective leaching of gold over gangue was observed.

The semiconductor properties of chalcopyrite during leaching in sulfate solutions in the presence of silver have been investigated. A combination of Mott-Schottky plots and potentiodynamic polarisation was used to determine the transformations of the chalcopyrite surface as the potential was changed between +200 mV (SHE) and 1200 mV (SHE). The tests were carried out at 25 °C and 50 °C. The solutions used were 0.2 M and 0.5 M H2SO4 in the presence of 100 ppm Ag+ and then in the absence of Ag+. The semiconductor behaviour of chalcopyrite was different depending on the presence or absence of Ag. At 25 °C, two surface layers formed between 500 mV (SHE) and 1000 mV (SHE) in both the 0.2 M and 0.5 M acid solutions. The presence of Ag in both these solutions shifted the potentials at which the surface phases formed to more positive potentials. In the presence of Ag at 50 °C, there was formation of successive surface layers at potentials between 850 mV (SHE) and 1000 mV (SHE). It was concluded that Ag had a significant influence on the semiconductor properties of the chalcopyrite surface. The Ag present on the surface as metallic Ag acts as surface states and provides a path for electrons to tunnel or hop from the valence band to the conduction band.

Processing oxidized nickel ores (ONO) by shaft smelting is unprofitable. Introduction of hydrometallurgical methods will resolve this problem. In this work, according to X-ray phase (X-ray diffraction) and X-ray spectral microanalysis (XMA), the main sources of nickel and cobalt in the ONO are minerals of the serpentine group, primarily lizardite and antigorite. Heap leaching of nickel from ONO is studied and dependences are established for nickel extraction from acid solutions, acid consumption, and leaching duration. Parameters for leaching for the pause between irrigation, acid concentration, and the number of solution circulations at stages up to 10%, 20%, and ≥ 50% nickel extraction are proposed.

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.