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The current study presents the effect of process chemistry as well as climate conditions on the water balance of a heap leach operation for black-schist ore. The research is based on the actual water balance at the Terrafame (former Talvivaara) mine site in Finland during the years 2017 and 2018 (base case). In addition, scenarios with a deviation in climatic conditions (Antofagasta case), chemistry (non-heat generation case) and effects of climate change (RCP4.5 (representative concentration pathway) case and RCP8.5 case) were investigated. In the first case, the annual precipitation and evaporation were simulated for a highly arid climate such as in the Antofagasta Mountains, whereas in the second case, an assumption was made of no excess heat generation (exothermic reactions) in the heap reactions. The base case predicted a requirement of 9,000,000 m3 annual discharge of water from the site with the heaviest annual rainfall. The discharge requirement and therefore the water footprint of the plant was shown to be highly dependent on the climatic conditions, as the Antofagasta case predicted a discharge of water from the site as low as zero. Heat generation, typical of the reactions dominating in a boreal black-schist heap leach operation, was shown to be vital for water management operations and therefore discharge management in Nordic climatic conditions (the non-heat generation case), where the discharge requirement was shown to be nearly threefold compared to the base case (2018). If the black-schist ore body resided in Antofagasta, the freshwater consumption would be over eight times the current consumption in the base case in Finland. Climate change scenarios show that the changing climate would increase the range of variation but only increase the need for water discharge from the site by 5% in the wettest years, while raw water utilization would increase by 46 to 83% during the driest years. In general, the results highlight the issues related to the mass and energy balance of a heap leach nickel process, and therefore feasibility—showing that although the heat generation is ore- and process-specific, the water consumption as well as discharge to the surrounding environment is highly dependent on the climatic conditions (precipitation, temperature) in the geographical location. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Numerous high-altitude copper mines occur in arid areas of northern Chile and Southern Peru in South America and other global regions. These mines require a water supply for on-site copper extraction, particularly those using the heap leach process. A common problem in determining the least costly option to obtain process water is a choice between pumping treated seawater or desalinated seawater (freshwater) from the coast to the mine site, commonly 600–4,900 m above sea level and 10–200 km inland from the shoreline. A detailed analysis of this problem was conducted to assess the key cost factors involved in water treatment, transport, and impacts on the heap leach process. The analysis showed that water treatment cost was 70% higher for desalted water, pump efficiency was 6.95% lower to transport seawater, in both cases, the transmission pipeline must be constructed with epoxy-coated steel, water reuse potential in the process was up to 70% greater using freshwater, the hydraulic conductivity of the heap material was 2.6% lower when using seawater, and the use of acid was more than 32 times greater when using seawater. Overall, the water type used showed little difference in cost when considering all factors. However, the use of seawater creates some additional operational factors in a greater volume of onsite salt and brine disposal and some potential environmental impacts. The use of freshwater may be preferred when considering the socio-political factor involving water supply to the local population and the residual value of the desalination facility. [ABSTRACT FROM AUTHOR]

Microorganisms capable of oxidizing sulfide minerals were isolated for the bioleaching experiments. Ore samples from the Allarechensk mining waste dump and low-grade ore samples from the deposit Nud II were studied. The samples have a similar ore mineral composition - pyrrhotite, pentlandite, chalcopyrite, and magnetite. In the study, the solution was recycled to make the process environmentally friendly. [ABSTRACT FROM AUTHOR]

ROM grade of certain Inner Mongolia Gold Mine is 1.64 g/t, and gold is the only valuable metal. The mine is featured with big reserve, diversified grades and different types of ores. Through analysis on ore properties and mineral processing test results, it was found that the processing and metallurgical indices vary in a great extent. To ensure the maximum economic benefit of the mime, a process to treat high-grade ores with all-slime cyanidation technique and treat low-grade ores with heap leaching technique was adopted. This paper provided a general illustration on crushing system, all-slime cyanidation system and heap leaching system of the mine, in addition, under the prerequisite to guarantee design indices and process parameters, also discussed selection of high-efficient and energy-conserving processing and metallurgical equipment as well as equipment configuration optimization as per site relief. [ABSTRACT FROM AUTHOR]

In a series of four extended industrial column leach experiments spanning 542 days, aimed at examining Cu-recovery from low-grade sulfide ores, all instances yielded suboptimal Cu recovery rates (<27%). Through a nuanced analysis integrating time-resolved chemical data on leachate with detailed mineralogical investigations, we highlight that the dissolution of aluminosilicate gangue minerals is a pivotal factor constraining Cu recovery. The source materials, extracted from a low-grade segment of a Cu–Au porphyry deposit (∼0.32–0.36 wt% Cu), underwent diverse leaching conditions employing various lixiviants, curing phases, redox conditions, and particle size distributions. Notably, poor Cu recovery is closely tied to gangue mineralogy. The ammonia leach column experienced limited Cu leaching due to an inert gangue shielding chalcopyrite from the lixiviant. In acid columns, swift precipitation of silica-rich phases impeded effective Cu leaching at multiple scales, from large-scale-column to molecular levels. Identifying gangue mineralogy and considering their impact during acid leaching are crucial for formulating effective lixiviant strategies for Cu recovery from low-grade primary sulfide ores. The curing phase, requiring high acid concentrations (∼50 g/L H2SO4), emerges as a critical aspect for promoting effective gangue dissolution while preventing refractory silica-rich phase precipitation. • Industrial column leach trials were analysed for the impact of gangue mineral reactions on Cu extraction. • The dissolution of the gangue minerals had a stronger buffering effect on redox potential than the addition of ferric iron. • Chlorite was the most soluble aluminosilicate gangue mineral in acid media. • Dissolution of aluminosilicates at pH 1.5–2 led to the precipitation of Si-gel which limited copper recovery. • SEM-BSE, FIB-SEM and XANES showed Cu (and Fe) is trapped in the Si-gel as small mineral grains and sorbed to silica gel. [ABSTRACT FROM AUTHOR]

[Display omitted] • High metal recovery yields were attained during bioleaching of low-grade Ni-Cu ore. • Rapid release of acid soluble metal with acid addition and irrigation at beginning. • Subsequent slow metal dissolution driven by microbial residual sulfide oxidation. • Recycling of leaching solution for irrigation negatively affected extraction rates. • Inoculation and nutrient addition did not give any advantages for metal recovery. Over the past several decades, extensive research has focused on improving bioleaching of different ores, and increasing research on applying bioleaching for the processing of tailings produced from mining operations around the world. As part of the research project Near-zero-waste recycling of low-grade sulfide mining waste for critical-metal, mineral and construction raw-material production in a circular economy (NEMO), we have studied the effect of nutrient availability, the effect of high concentration of dissolved salts (Al and Mg sulfates) on metal (Cu, Co, Mn, Ni, Zn) extraction rates by bioleaching in laboratory column tests at high temperature (48 °C and 60 °C), using secondary ore from the Sotkamo mine (Terrafame operation, Finland). Metal dissolution rates showed two stages: a rapid first stage, where acid addition and initial irrigation released acid-soluble metal species, and a second stage, with slower rates of metal dissolution by microbial oxidation of residual metal sulfides with Fe(III) as the oxidant. Experiments showed that adequate Fe(II) oxidation rates depended on the addition of salts but not so much as the addition of nutrients (P as phosphate, N as ammonium and K). High dissolved salt concentrations resulted in low redox potentials (745–760 mV vs standard hydrogen electrode), limiting Co dissolution rates. For example, Co extraction yield at 48 °C when added salts plus nutrients was 57 %, and without salts (with or without nutrients) ∼75 %. Other metal dissolution rates were not affected by the composition of the irrigation solution or temperature, e.g. Ni extraction rates were between 88 % and 92 % in all the experiments. This was mostly due to the high metal content as readily soluble phases formed during the first heap leaching as metal dissolution in mine waste (e.g. tailings) highly depends on the metal speciation. Recycling of the leaching solution for irrigation, a common practice in heap bioleaching, affects negatively metal extraction rates, the precise reason for this is still to be determined in further experiments, possible effects including changes in solution chemistry affecting mineral oxidation, precipitation of insoluble salts, or toxicity or inhibition of microbial growth rates limiting microbial activity and mineral leaching. [ABSTRACT FROM AUTHOR]

Omics technologies is the most powerful upcoming tool that can extend a great aid in understanding the genomic and proteomic complexities of bioleaching microorganisms leading to the discovery of novel genes, enzymes, metabolic pathways, and also novel species. Advances in bioleaching technology The advancement of bioleaching technology has been investigated for different applications including polluted wastewater, industrial effluents, end of life batteries, and many more through biological approaches and received significant consideration (Mishra and Das [24]). Currently, the world is plagued with the issue of enormous waste generation from various anthropogenic sources including mining and industrial activities (Ghosh and Das [14]a; Mishra et al. [30]; Singh et al. [40]). Through biomining process microorganisms are applied to recover precious minerals and metals of commercial significance from mining and industrial waste residues. [Extracted from the article]

The quantitative indices and structure of the microbial community in flotation samples of sulfide copper-nickel ores at concentration plant of Kola Mining and Metallurgical Company have been determined. The smallest number of saprotrophic and oligotrophic bacteria has been observed in samples of ore and recycled water, which can be explained by the low temperature of samples and the lack of nutrients. It has been found out that the bacteria contained in the ore and recycling water flowing from the tailings increased their number during the flotation process due to coming of the organic compounds with the flotation reagents, aeration and increased temperature. Dominating strains have been isolated from recycled water and basic flotation products and classified as Pseudomonas. It has been shown that with an increase in the number of bacteria, the flotation time of copper-nickel ores increases. There is also a tendency to change the extraction of copper and nickel, which can be caused by both the increase in the flotation time for operations and the change in the number of bacteria in the circulating water. The thionic bacteria have been distinguished from the flow tailings of the Allarechensk deposit. The heap leaching experiments have proved the bacterial leaching to give good results on the ore samples passed through magnetic separation, having shown high content of the nickel and copper in filters. When leaching low-grade ore of the Nude Terrasa, the advantage of bacterial leaching use in comparison with the sulphuric-acid leaching only to copper has been revealed. The nickel content in the filtrates for bacterial leaching is 275 mg/l, and for sulfuric acid – 310 mg/l. The average copper content in the filtrates is 19 and 15 mg/l.

The present paper gives the thus far unpublished results of a pilot-scale heap leaching test of a Greek low-grade nickel oxide ore, aiming at verifying, at a large scale, the amenability of Greek laterites to heap leaching by the HELLAS (Heap Leaching LAteriteS) process, developed at the National Technical University of Athens for the first time worldwide and patented by some of the authors as early as in 1991. The test was conducted at the site of Aghios Ioannis mine of G.M.M.S.A. LARCO in 2006–2008 and was financed and supervised by the Institute of Geology and Mineral Exploration (I.G.M.E). The ore sample, 800 t, was from the “Triada” deposit of LARCO, in Euboea, and contained 0.73% nickel, 0.06% cobalt, 35.6% iron and 15% silicon. The ore was ground to −18 mm and the leaching agent was 2N (100 g/L) sulphuric acid solution. The nickel and cobalt recoveries obtained at the time of termination but not completion of the test, after four leaching cycles and 114 days of irrigation, were 60 and 36%, respectively. The corresponding nickel and cobalt concentrations in the produced leach liquor were 3.4 and 0.17 g/L, respectively. The value of the ratio Fe/Ni in the leach liquor was 10/1, much lower than the value 45/1 in the ore, thus showing the selectivity of the leaching of nickel over iron in the Greek ores by the above method. The consumption of sulphuric acid was 66 kg H2SO4/kg Ni recovered. The preliminary feasibility study, that followed the test, confirmed the economic viability of the integrated HELLAS process for the low-grade nickel oxide ores of Greece.

This paper describes channeling of liquid flow in copper ore heaps used for chemical or bio- leaching. The size of packed beds utilized as heap is 5 by 5 meters and the height is 3.5 or 5 meters. Tracer tests with lithium as tracer were carried out to investigate the liquid flow within the heaps. The experimental results were analyzed by the advection diffusion model with multiple step-wise liquid flow pattern. As a result, the maximum liquid velocity was 3.8 times larger than the average velocity at the final stage of leaching while the maximum was 1.4 times larger than the average at the initial stage of leaching. These results indicate that the channeling is clear quantitatively and become larger with time.

Heap leaching is a firm extractive metallurgical technology facilitating the economical processing of different kinds of low-grade ores that are otherwise not exploited. Nevertheless, regardless of much development since it was first used, the process advantages are restricted by low recoveries and long extraction times. It is becoming progressively clear that the selection of heap leaching as an appropriate technology to process a specific mineral resource that is both environmentally sound and economically feasible very much relies on having an ample understanding of the essential underlying mechanisms of the processes and how they interrelate with the specific mineralogy of the ore body under concern. This paper provides a critical overview of the role of gangues and clays minerals as rate-limiting factors in copper heap leaching operations. We aim to assess and deliver detailed descriptions and discussions on the relations between different gangues and clays minerals and their impacts on the operational parameters and chemical dynamics in the copper heap leaching processes.

The article focuses on the potential for extracting critical minerals and metals from abandoned mines to support decarbonization efforts, addressing challenges of mine waste and contamination. Topics discussed include the significance of environmentally friendly technologies for a low-carbon future, the impacts of mining and extraction on the environment, and promising techniques such as heap leaching for resource recovery while considering environmental implications.

Crude uranium concentrate (30–35.8% U) from G. Gattar pilot plant, North Eastern Desert, Egypt, produced by acid heap percolation leaching, was upgraded by 1,5-diphenylthiocarbazone-modified Amberlite XAD-7 (H2Dz-XAD-7). The modified resin was characterized by EDAX, SEM, CHNSO analysis, and FTIR. The purified cake was characterized by XRD, EDAX, and ICP-OES techniques. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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Water level and wind speed have important influences on radon release in particle-packing emanation media. Based on radon migration theory in porous media under three water level conditions, an experimental setup was designed to measure the surface radon exhalation rate of uranium tailings from heap leaching uranium mine at different water levels and wind speeds. When the water level was at 0.3 m (overlying depth 0.05 m), radon transfer velocities at the gas–liquid interface were also measured at different wind speeds. Results show that when the water level was equal to or lower than the surface of the sample, the radon exhalation rate increased with increasing wind speed and decreased with increasing water level. When the water level was higher than the surface of the sample, radon exhalation rate of the water surface increased with increasing surface wind speed. The wind speed, however, was less influential on the radon exhalation rate as the depth of the overlying water increased, with a dramatic decrease in radon release. That said, at different wind speeds, radon transfer velocities at the gas–liquid interface were consistent with literature. On the other hand, changes in wind speed had significant influences on the radon transfer velocity at the gas–liquid interface, with the effect less pronounced at higher wind speeds. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of a study of the anodic characteristics of chalcopyrite in alkaline hydroxide and carbonate solutions. The cathodic reduction of oxygen, peroxide and hypochlorite have also been investigated as possible oxidants in a two-stage process for the heap leaching of chalcopyrite under alkaline conditions. Mixed potential measurements of chalcopyrite in alkaline solutions showed that the reactivity of the common oxidants is in decreasing order hypochlorite > peroxide > oxygen >> chlorate. Anodic oxidation of chalcopyrite involves active oxidation at low potentials followed by a passivation peak and transpassive oxidation at higher potentials. The kinetics of oxidation is favoured by increasing pH in both hydroxide and carbonate solutions. The formation of solid products of oxidation does not prevent continued oxidation for up to 18 h at potentials below the peak. Coulometric measurements suggest that both thiosulfate and sulfate ions are produced by oxidation in sodium hydroxide solutions while thiosulfate is the main product in carbonate and bicarbonate solutions. At potentials close to the mixed potentials, the rate of reduction of hypochlorite is approximately first-order in hypochlorite concentration and is greater at low hydroxide ion concentrations. The rate of the cathodic reduction of peroxide is also greater at lower pH values but is complicated by the surface catalysed disproportionation of peroxide to water and oxygen. Rates of oxidation of chalcopyrite by both hypochlorite and peroxide in sodium hydroxide solutions have been estimated. The rates in hypochlorite are an order of magnitude greater than those in peroxide solutions and are of the same order of magnitude as those previously measured for the dissolution of chalcopyrite in ammoniacal solutions with copper(II) ions as the oxidant. • Anodic oxidation of chalcopyrite involves active oxidation at low potentials followed by passivation and transpassive oxidation. • The kinetics of oxidation is favoured by increasing pH in both hydroxide and carbonate solutions. • Coulometric measurements suggest that both thiosulfate and sulfate ions are produced by oxidation • Rates of reduction of hypochlorite and peroxide are first-order and greater at low hydroxide ion concentrations. • Rates of oxidation by hypochlorite are an order of magnitude greater than those in peroxide solutions. [ABSTRACT FROM AUTHOR]

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. • Novel packed bed/heap modification strategies were carried out using coarse PCBs. • Channelling was alleviated in the ore beds that use PCBs as layers and mixtures. • Liquid spreading is improved and liquid holdup is comparable in modified ore beds. • Non-ore particles could be used in heaps to improve heap hydrodynamics. [ABSTRACT FROM AUTHOR]

In order to study the radon release behavior when heap leaching uranium ores with dilute sulfuric acid, unleached uranium ores from a uranium mine in southern China were selected as test samples. Adopting parameters from leaching processes commonly used in uranium mines, a laboratory experiment was carried out for 21 days with a one-dimensional acid heap leaching experimental column. The surface radon exhalation rate of uranium ore column was determined by static accumulation method while spraying with deionized water and dilute sulfuric acid. The uranium leaching rate and ore column height for all 21 days of the experiment were also measured. The results show that (1) when sprayed with a leaching agent, the surface radon exhalation rate of uranium ore column initially increased with time sharply. After a maximum value was reached, the rate gradually decreased and stabilized. When the spraying stopped, the surface radon exhalation rate of uranium ore column initially decreased, before increasing until it tended to stabilize. (2) During the entirety of the 21-day leaching experiment, the cumulative leaching rate of uranium increased gradually with time. On the other hand, the surface radon exhalation rate of uranium ore column fluctuated, but the leaching of uranium from uranium ores had almost no effect on the radon exhalation rate. (3) There was no linear correlation between the surface radon exhalation rate and the residual height of ore column during leaching, but the collapsing event of ore column was the direct inducing factor of the fluctuation of surface radon exhalation rate. [ABSTRACT FROM AUTHOR]

• Leaching gold oxide ores using glycine as a non-toxic lixiviant. • The leaching system is suitable for heap and in-situ applications. • Effects of glycine, temperature, pH and sodium chloride on gold extraction were evaluated. • More than 85% gold was extracted with solutions containing 15 g/L glycine at pH 12.5. • Selective leaching of gold over gangue minerals was achieved. 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 E h 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. [ABSTRACT FROM AUTHOR]

The availability and efficiency of water use is now a major concern for the global minerals industry. Seawater is a potential water source for mineral beneficiation and metal extraction processes. With a focus on using seawater for heap leaching, we investigated and modelled the kinetics of chalcocite leaching with ferric chloride. To this end, a series of leaching tests were carried out in jacketed reactors under fully controlled pH and solution potential at ambient temperature using pure chalcocite as the model mineral. The effects of key parameters, including chloride concentration, ferric concentration, ferrous concentration, ferric/ferrous ratio, temperature, and particle size, were determined on the first and second stages of chalcocite leaching. The first stage leaching rate was sensitive to ferric concentration, temperature, and particle size, whereas it was insensitive to ferrous and chloride concentration. The second stage leaching rate was independent of chloride concentration but sensitive to solution potential, temperature, and particle size. A distinct kinetic model was obtained for each stage of chalcocite leaching. Based on the kinetic models, it is concluded that the leaching rate of the first stage was controlled by the diffusion of ferric ions, while a mixed kinetics governed the second stage kinetics, i.e., a combination of mineral decomposition and ferric reduction. The findings of this research are important for prediction of copper extraction performance when seawater is being applied to heap leaching of chalcocite to replace fresh water. • Chalcocite leaching in chloride media occurred in two stages. • A distinct kinetics model was obtained for each stage of chalcocite leaching. • First stage leaching was controlled by ferric diffusion through product layer. • Second stage leaching was controlled by mineral decomposition and ferric reduction. • Second stage leaching was sensitive to temperature with high activation energy. [ABSTRACT FROM AUTHOR]

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 H 2 SO 4 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. • Mott-Schottky study of chalcopyrite semiconductor properties • Evolution of the surface with potential has been explained. • The presence of Ag in solution changes the semiconductor properties. • Ag0 on the surface behaves as surface states which improves charge transfer. [ABSTRACT FROM AUTHOR]

This investigation compares bacterial leaching to chemical leaching to solubilize copper from a copper containing ore of the new site Northern Qarashoshaq in Zhylandy (Kazakhstan) which is currently under commercial development. From ICP-OES analysis, the bulk ore sample contains 1.5% of Cu and a trace level at 0.0024% of Ag. Phase analysis shows the main copper containing minerals are covellite, chalcocite, malachite, chrysocolla and chalcopyrite. According to X-ray diffraction analysis, silver is mainly presented as jalpaite (Ag3CuS2) minerals. Copper leaching was carried out by acidophilic bioleaching for comparison with extraction by chemical methods involving the addition of sulfuric acid and Fe3+ or only sulfuric acid in flasks, as well as column leaching tests to simulate heap leaching. Ag was extracted by cyanidation methods again in flasks as well as column leaching tests. Results showed that copper extraction is up to 95% when using bioleaching in the flask, 83% in the case of Fe3+ with sulfuric acid and 76% for sulfuric acid. Furthermore, subsequent extraction of Ag reaches 97% for bioleaching and 92% for chemical leaching. Column bioleaching tests showed an 82.3% yield of copper after 70 days of the experiment and a 70% of silver, whereas for chemical leaching the yield of copper is 66.8% and silver is 51%. In conclusion, this investigation demonstrated higher extraction for both copper and silver from the primary ore in the bioleaching sample compared to the chemical leaching sample. More silver was extracted in the bioleaching case as there was less copper remaining to compete for the cyanide anions. [ABSTRACT FROM AUTHOR]

A large-scale investigation into the effect of increased aeration on heap leaching of a pyrrhotite-rich pentlandite ore was commenced at the Terrafame mine in Finland. The typical reference air feed amount in operation is approximately 0.05 m3/metric ton/h, fed from one direction of the 330 to 350 m wide heap. In the current study approximately 62% higher air feed vs. reference operation was trialed by installing another layer of aeration from the opposite direction of the heap. The hypothesis was that air distribution across the ore would be improved and that the increase in air feed would result in faster oxidation of pyrrhotite, leading ultimately to improved recovery of valuable metals. The heaps were observed for 150 days after stacking. The results revealed an increase in the leaching rates of several metals: manganese, magnesium, iron, nickel and zinc leached 14, 171, 142, 1932, and 1309% more in the presence of extra aeration during the observation period. In addition, applying the extra air showed a 324% increase in the generation of acid within the heap. • 60% higher aeration was tested for pyrrhotite-rich pentlandite ore heap leach • Mn, Mg, Fe, Ni and Zn leach rates increased 14, 171, 142, 1 932 and 1309% with higher aeration, respectively • Acid generation was increased within the extra aerated heap by 324% [ABSTRACT FROM AUTHOR]

Chilean mining is one of the main productive industries in the country. It plays a critical role in the development of Chile, so process planning is an essential task in achieving high performance. This task involves considering mineral resources and operating conditions to provide an optimal and realistic copper extraction and processing strategy. Performing planning modes of operation requires a significant effort in information generation, analysis, and design. Once the operating mode plans have been made, it is essential to select the most appropriate one. In this context, an intelligent system that supports the planning and decision-making of the operating mode has the potential to improve the copper industry’s performance. In this work, a knowledge-based decision support system for managing the operating mode of the copper heap leaching process is presented. The domain was modeled using an ontology. The interdependence between the variables was encapsulated using a set of operation rules defined by experts in the domain and the process dynamics was modeled utilizing an inference engine (adjusted with data of the mineral feeding and operation rules coded) used to predict (through phenomenological models) the possible consequences of variations in mineral feeding. The work shows an intelligent approach to integrate and process operational data in mining sites, being a novel way to contribute to the decision-making process in complex environments.