Gold Ore Research Articles

Multiple laccase-mediator system treatments for carbonaceous matter degradation in double refractory gold ore

Double refractory gold ore contains a higher level of gold than general ore but has been ignored in industry due to economic reasons. To improve gold recovery from double refractory gold ore (DRGO), the sulfides must be oxidized to release gold grains and the carbonaceous matter must be degraded to minimize “preg-robbing” during cyanidation. Recently, the degradation of carbonaceous matter in DRGO by enzymatic reactions has gained extensive interest owing to its environmental friendliness. Reportedly, laccase using 1-hydroxybenzotriazole hydrate (HBT) as an electron mediator can improve gold extraction from DRGO. In the present study, multiple-divided additions of the laccase-mediator system (LMS) are performed to maintain the enzyme activity, thus resulting in an improvement of gold extraction to 86.1%, compared with performing single addition with the same final dose, which yields a gold extraction of only 67.0%. However, multiple-divided additions of a higher dose of LMS decrease the gold extraction. The total dose of laccase is optimized to 11.87 U/100 mL of 5.0 g pretreated DRGO with a C content of 5.2%. These interesting results are comprehensively interpreted by combining different characterization methods for natural carbonaceous matter, including thermogravimetry-differential thermal analysis, Raman spectroscopy, and three-dimensional fluorescence spectrometry. This LMS proposed represents a novel approach worthy of further attention, especially in understanding carbon science in hydrometallurgy.

Mass balance and techno-economic study of a complete treatment chain of bio-oxidation for the extraction and recovery of precious metals from gold ore

A techno-economic feasibility study of a complete chain of bio-oxidation treatment for the extraction of gold ore with refractory character was carried out. Several basic parameters were considered, including operating and technical parameters, capitalization parameters, direct and indirect costs of the operation, and basic market parameters. The data generated were used to develop a preliminary techno-economic model. SuperPro Designer software was used to identify the industrialization potential of the project. With an estimated total capital investment (TCI) of 220 M$ and an estimated operating cost of 58.27 M$/a, we estimate that a total revenue of 78.48 M$/a is achievable. Other economic data were also estimated such as a gross margin of 25.75 %, a return on investment (ROI) of 15.82 %, a payback period of 6.32 years, and an internal rate of return (IRR) of 9.55 %. All this project was shown to have a net present value (NPV) of 34.40 M$ and an interest rate of 7 % per year, which is considered a profit. The process was shown to be most sensitive to the change in gold price.

Financial Feasibility Study on Antam Pongkor Low-Grade Gold Ore Mine After Implementing Business-Level Strategy

The Pongkor Gold mine is under Production Operation Permit until 2031 while existing feasibility study stated that Pongkor gold Mine only have economical number until 2025 with ore volume in 1.5 million wmt and ore grades above 4 gpt. Pongkor Gold Mine has resources in low-grade gold ore (below 4 gpt) in 1.9 million wmt with the grades is 3.61 gpt. Having a gap period between mining permits (until 2031) and the latest feasibility study (until 2025) and abundant resources in low-grade gold ore, provides research opportunities to finding how to formulate business strategy level for Pongkor Gold Mine in order to maximize gap period by processing low-grade gold ore. This study started with business situation analysis, with VRIO and Internal Factor Evaluation (IFE) Matrix are conducted for internal analysis, while PESTLE (Political, Economic, Sociocultural, Technological, Legal, and Ecological) analysis, Porter’s Five Forces framework and External Factor Evaluation (EFE) matrix are conducted as external environment analysis. The result shown Pongkor Gold Mine in region V in internal-external (IE) matrix, the region indicated that hold and maintain strategies are suitable for Pongkor Gold Mine. Study continued with Porter generic competitive framework to define the strategy that most suitable with Pongkor Gold Mine condition. The result shown cost leadership strategy is the most suitable strategy with the detailed strategy are (i) implement a cost reduction program every year, (ii) substitute retired organic workers (permanent Employee) with outsourced or contracted workers, (iii) limiting investment only to things that have a direct impact on revenue and (iv) long-term contract in heavy equipment. The impact of these strategies will calculate in financial feasibility study. Financial feasibility study uses financial criteria of Net Present Value (NPV), Internal rate of return (IRR), and payback period (PBP). The results shown NPV in 25.33 million US$, IRR in 52.2% and payback period in 21 months, these number indicated the Pongkor project extension is feasible. This study also intended to determine the most affecting variable to the NPV by conducting sensitivity analysis. The results shown the extension project is feasible as long as the gold price not declined more than 18.4% from the base, production cost (COGS) not increased more than 22% and the productivity not decreased more than 16.94% from the base.

Stages of formation of gold mineralization and large gold ore deposits in Kyrgyzstan

There are about 100 gold deposits in Kyrgyzstan, including large and super large ones. According to the time of their formation, several stages are distinguished, the main of which are Paleozoic. A brief overview of these stages, the geodynamic setting, and examples of the gold deposits with description of several large objects are provided.

Research on gold leaching of carbonaceous pressure-oxidized gold ore via a highly effective, green and low toxic agent trichloroisocyanuric acid

In this work, trichloroisocynauric acid (TCCA) are used for gold leaching with the advantages of fast reaction rate, high leaching efficiency, low toxicity and environmentally friendly. In addition, an important feature is the continuous hydrolysis of TCCA in an aqueous solution to produce oxidants (HClO) while maintaining the effective chlorination concentration at a high level. The various factors affecting TCCA leaching carbonaceous pressure-oxidized gold ore were investigated and the leaching kinetics were established. According to the results of orthogonal experiments, the optimal conditions of TCCA concentration 0.25 mol L−1, NaCl concentration 50 g L−1, pH 5.5, leaching temperature 45 °C and solid-liquid ratio 1:6 could be obtained, and the gold leaching efficiency reached (88.64 ± 0.37) % within 3 h. After the three stages of TCCA leaching, a gold leaching efficiency was increased to 94.39%. Furthermore, TCCA leaching process could be divided into three steps, the findings of kinetic models revealed that in the early leaching step (0–2 h), TCCA leaching was controlled by solid products layer diffusion model, and yet shifted to be controlled by interfacial chemical reaction model in the final step. Importantly, TCCA leaching solution might be converted into a disinfectant with an effective chlorination concentration of 16.075% treated with resin adsorption and alum removal, enabling the secondary utilization of wastewater resources.

Geochronology, pyrite trace elements, and sulfur isotope geochemical characteristics of the Saibagou gold deposit in the eastern part of the northern Qaidam Basin

Introduction: The Saibagou gold deposit, located in the eastern part of the tectonic belt of the northern Qaidam Basin in western China, has its gold ore bodies strictly controlled by the regional fault system. Despite this understanding, there remain controversies surrounding the deposit’s metallogenic epochs, sources of ore-forming materials, and properties of ore-forming fluids. To address these controversy, the metallogenic process of the Saibagou gold deposit can be further determined by analyzing the U-Pb ages of hydrothermal zircons in the gold-bearing quartz veins and investigating the trace element and sulfur isotope compositions of pyrite in the gold deposit.Methods: This study does not focus on the mineral characteristics susceptible to interference by the metallogenic condition in gold ore bodies. Instead, it offers a detailed discussion on stable associated minerals and their indicative markers formed in the process of gold mineralization.Results: The results of this study showed that the metallogenic process of the gold deposit can be categorized into the following stages: 1) quartz–pyrite veins, 2) milky-white quartz—pyrite—native gold veins, 3) hoary quartz—native gold—polymetallic sulfide veins. As indicated by the U-Pb ages of hydrothermal zircons in the gold-bearing quartz veins, the Saibagou gold deposit has two metallogenic ages, namely, 423.91 ± 4.5 Ma (the Silurian) and 470.18 ± 4.92 Ma (the Ordovician).Discussion: The Silurian metallogenic age, predominates and nearly aligns with the expansion of the regional NWW-trending brittle-ductile shear zone, followed by the Ordovician metallogenic age. Data on the trace elements and sulfur isotopes of pyrite, show that the Saibagou gold deposit has similar pyrite compositions in the three metallogenic stages. Gold in the deposit primarily occurs as native gold or minor petzite inclusions and has a very low lattice gold concentration. As indicated by the concentrations of elements such as Co, Ni, and as in the pyrite, as well as the variation range of δ34S values, the ore-forming fluids were derived from low-temperature arsenic-bearing acidic magmas. In addition, the primary ore-forming materials appear to encompass mantle-derived materials from the deep earth.

Oxidative pretreatment of refractory gold ore using persulfate under ultrasound for efficient leaching of gold by a novel eco-friendly lixiviant: Demonstration of the effect of particle size and economic benefits

A novel pretreatment method for refractory gold ore using ultrasound-activated persulfate was developed to overcome the low extraction efficiency of gold in the leaching process. The feasibility of the pretreatment method was verified primarily by EPR (Electron paramagnetic resonance) and pre-oxidation tests. The free radicals generated by ultrasound-activated persulfate effectively promoted the oxidation of sulfide in the gold ore. The pretreatment efficiency of this process was higher than that of traditional heat activation, and the oxidation efficiency was two times higher. Furthermore, the gold leaching efficiency was higher under ultrasound activation conditions when using a novel eco-friendly lixiviant (Jinchan-its main effective component is Na3CN3C3H3N6O3, i.e., carbonized sodium cyanurate). Morphology analysis indicated that the synergistic effect of persulfate and ultrasound effectively reduced the particle size of the refractory gold ore, improved the specific surface area, and facilitated the oxidation of the enclosures, which benefited the subsequent leaching process. The maximum leaching efficiency of gold reached 86.9% after ultrasonic activated persulfate pretreatment for 3 h. This study provides a promising refractory gold ore pretreatment to improve gold leaching through persulfate oxidation using ultrasound activation.

Mineralogy and Р-T conditions for the formation of metasomatic rocks of the Voznesenskoye gold deposit (Southern Urals)

Research subject. Mineral associations, their chemical composition, and formation conditions of metasomatic rocks of the Voznesenskoye gold deposit located in the area of the Main Ural Fault in the Southern Urals.Methods. The chemical composition of minerals was studied using a Tescan Vega Compact scanning electron microscope equipped with an Oxford Instruments Xplorer 15 energy-dispersive analyzer. The formation P-T parameters were estimated using a chlorite geothermometer and a dolomite-calcite geothermobarometer.Results and conclusions. Two types of metasomatic rocks were identified: 1) propylites, which make up the outer zones of the metasomatic aureole, and 2) beresite-listvenites, common in its inner parts and hosting gold mineralization. The main propylite minerals were amphibole, orthoclase, albite, and ripidolite. Amphibole is represented by two generations, with the early generation comprising magnesian and actinolite hornblende and the late generation comprising actinolite. The crystallization temperature of ripidolite (307–313°С) corresponds to the temperature range of formation of propylites of the albite-actinolite facies. Beresite-listvenites (association: quartz, albite, chlorite, white mica, and carbonate) were formed at a temperature of 255–338°C and a pressure of 0.48–0.72 kbar. Gold ore mineralization was concentrated in the highest temperature zones of the halo of beresite-listvenite alterations. Such temperature conditions existed in dikes and their exocontact zones disturbed by ruptures. Light mica in beresite-listvenites is represented by sericite and phengite, and carbonate is a paragenesis of calcite and dolomite-ankerite. According to the composition and formation period, chlorite is differentiated into early ferruginous ripidolite and late pycnochlorite, depleted in Fe and enriched in Si, which is probably associated with a decrease in temperature during mineral formation and an increase in the activity of sulfide sulfur in the fluid. Along with an increase in the distance from the ore bodies, pycnochlorite exhibits greater contents of Si and lower contents of AlIV. The observed changes in the pycnochlorite composition are related to a decrease in temperature. The research results indicate the formation of the Voznesenskoye deposit under mesothermal conditions.

Improving xanthate flotation of fine pyrite using SPAM and the mechanism

ABSTRACT This paper focuses on the promotion mechanism of sulfonated polyacrylamide (SPAM) on SBX flotation performance on fine pyrite, and verifies the positive effect for a gold ore with pyrite as the main Au-bearing mineral. Micro flotation showed that fine pyrite (−26 + 15 μm) floated poorly compared with coarser ones (−74 + 38 μm), and this cannot be completely filled through increasing the SBX dosage; however, by adding moderate SPAM into the pulp after SBX the flotation of fine pyrite was obviously improved. The real ore flotation revealed that SPAM decreased total reagent dosage and improvement on the concentrate indexes. SBX/SPAM system enabled faster settlement of fine pyrite compared with only SBX or SPAM system, indicating that larger particle size was obtained through hydrophobic and bridging flocculation. Zeta potential results showed that the pre-adsorbed SBX had little effect on the further adsorption of SPAM. Contact angle measurements suggested that the addition of moderate SPAM (50 μg/L) had almost no effect on pyrite surface hydrophobicity, illustrating that SPAM just bridged different fine particles adsorbed SBX rather that covered them. FTIR results showed that the amount of SPAM participating in bridging action was few.

Non-dispersive solvent extraction as an alternative for sulfuric acid and copper recycling from membrane distillation concentrate of gold mining wastewater

The wastewater from the pressure oxidation process is a complex stream enriched in sulfuric acid and dissolved metallic species, conventionally treated by neutralization, a technique that does not allow for by-product recovery. Previous studies focused on water recovery from the wastewater by membrane distillation and the concern related to concentrate production after water is recovered is now addressed by using hollow-fiber membrane contactors in non-dispersive solvent extraction processes intended for sulfuric acid and copper recycling. Tris(2-ethylhexyl)amine (TEHA), Aliquat 336, and Lix 84-I were used as extractants, the first two for acid recovery and the latter for copper. It was investigated the contribution of different organic phases flow rate (4–12 cm3/s), organic phase composition (5–15 wt%), and temperature (30–60 °C) on the performance of hollow fiber membrane contactors, with an in-depth disclosure of mass transfer phenomena limiting the extraction efficiency. For both acid and copper recovery, a reduction in viscosity forces prevails over the decrease in inertial forces, improving the flow regime. Even so, the predominant mechanism was the diffusive transport of both solutes into the fluid, across the membrane pores, rather than being carried along by the aqueous phase flow. The acid and copper recovery from membrane distillation concentrate achieved values greater than 91%, which represents an acid stream containing 5.86 g-H2SO4/L and an aqueous copper solution with a concentration of 269.0 mg/L, both at high purity. It was discussed different opportunities for their reuse within the gold ore processing circuit and challenges related to their external commercialization. Preliminary economic analysis suggested that the mineral acid would present slightly higher costs than currently practiced (0.54 US$/kgH2SO4; market prices: 0.03–0.11 US$/kgH2SO4), although the operational costs related to copper were comparable with market prices (11.58 US$/kgCu; market prices: 10.31 US$/kgCu). In a broad context, the opportunity for acid and sulfuric acid recycling has the potential to extend sustainability in the mining sector.

A Statistical Theory for Sampling of Particulate Materials

The concepts currently applied to the sampling of broken minerals and particulate materials were recognised over 100 years ago. The first integrated theory of sampling for the mineral industries was proposed by Gy, who brought together means of estimation of the variance of sampling due to both the particulate nature of a broken ore and the time variation of composition of process streams. However, his theory deals only with sampling variance and cannot determine the full sampling distribution. The full distribution of the composition of potential samples arising from their particulate nature is developed in this paper based solely on the assumption that particle numbers in correct samples follow independent Poisson distributions. The enabling mathematical method is the use of the characteristic function of the sampling distribution. The practical means of calculating the full distribution completes the theory of sampling of particulate materials. The method is applied to a sample of gold ore to calculate the full sampling distribution and effectively clarifies several difficulties when sampling this material. The method has general applicability to all particulate materials, including foodstuffs.

Fluid evolution and metallogenesis of the Zhangjiapingzi gold deposit in mianning, Sichuan province: constraints from fluid inclusion studies

Introduction: The Zhangjiapingzi gold deposit, located at the western margin of the Yangtze Craton and controlled by the Jinhe-Chenghai deep fault, is a newly discovered super-large gold deposit in the Danba-Mianning metallogenic belt. The gold ore bodies are hosted in the Middle Triassic (T2) altered dolomite (Dm), and have two types of mineralization: altered rock type and quartz vein type. Previous studies on this deposit are rare, especially on the ore-fluid characteristics, which limit the understanding on the ore genesis.Methods: This study focused on fluid inclusions in quartz from altered rocks, and used microthermometry and laser Raman spectroscopy to investigate the properties and sources of ore-forming fluids, and to determine the ore genetic type.Results and discussion: The results show that the fluid inclusions are mainly CO2-H2O-NaCl inclusions, with medium temperature (220–300°C), low salinity (<10%), medium-low density (0.79–1.01 g/cm3) and high contents of CO2 and CH4, resembling typical orogenic gold ore fluids. We suggest that the Zhangjiapingzi is best classified as orogenic type, and our findings provide new insights into the fluid origin and metallogenesis of orogenic gold deposits in the Danba-Mianning metallogenic belt.

Process mineralogy characteristics of a very fine disseminated refractory gold deposit

The grade, recovery rate, or leaching rate of gold concentrate obtained by the flotation process or cyanide leaching process of gold ore is low, which is typical refractory gold ore. In order to fully understand the properties of the gold ore and optimize the gold recovery process and indicators, the process mineralogy of the ore was systematically studied by means of chemical multi-element analysis, optical microscope, scanning electron microscope (SEM), X-ray energy spectrometer, automatic mineral parameter analysis system (BPMA), and other test methods. The results show that the average grade of valuable element gold in the ore is 2.98g/t, and the contents of harmful elements mercury and carbon are 0.50% and 0.32% respectively; The main gold ore is natural gold, with a small amount of silver gold and tellurium gold; The main metal minerals are pyrite, pyrrhotite, magnetite, hematite, etc; The main gangue minerals include quartz, feldspar, kaolinite, mica, calcite, etc. Under the condition that the grinding fineness is -0.074mm, accounting for 90%, the distribution rates of single gold and bare gold in the ore are 3.15% and 57.66% respectively, and the distribution rates of gold with pyrite and quartz crystals are 5.77%, and the total distribution rates of the three are 66.58%, that is, the maximum theoretical flotation recovery rate of gold under the grinding fineness, but the particle size and fineness of gold minerals are both 5 μ Below m, the particle size of some gold ores is less than 0.5 μ m. It exists in the form of fine particles, micro gold, or ultra-micro gold, and it is difficult to recover gold by the flotation process, so it is recommended to adopt the whole slime cyanidation leaching process.

Mineralogical Characteristics and Refractory Properties of Arsenic-bearing Gold Concentrate

The arsenic-bearing gold ore in Anhui, China is an extremely refractory gold ore, and the cyanide leaching rate of gold concentrate is only 30%. The mineralogical factors of the low leaching rate were discussed by process mineralogical analysis. The results demonstrate that the gold concentrate contains 20.30 g/t gold, 3.39% arsenic, 29.80% sulfur, and 4.10% iron. Gold exists in the occurrence states of metallic mineral-wrapped gold, gangue mineral-wrapped gold, and fissure gold, which account for 64.90%, 8.31%, and 26.79% respectively. Pyrite, arsenopyrite, realgar, sphalerite, and pyrrhotite are the main metallic minerals in the gold concentrate. Among them, pyrite accounts for 51.20%, and arsenopyrite accounts for 24.30%. Gangue minerals include feldspar, sericite, quartz, calcite, and chlorite. Among them, feldspar, sericite, and quartz account for 30.30%, 22.70%, and 22.10% respectively. In addition, the grain size distribution and distribution characteristics of various minerals are obtained, and the texture and structure of the gold ore are analyzed. Pyrite and arsenic phase are the main factors causing the low gold leaching rate. The presence of carbonate minerals and clay minerals also has an effect on the rate of gold leaching. The oxidation pretreatment can increase the gold leaching rate to about 94%. The findings provide a theoretical foundation for the selection of manufacturing techniques in businesses and play an important guiding role in the development of similar ores.

Socio-economic baseline, economic feasibility study and processing activities ASGM in Obi Island, South Halmahera District, North Maluku Province, Indonesia

Artisanal and Small-Scale Gold Mining (ASGM) is mining of gold deposits with simple physical and chemical characteristics using simple equipment and technology. In 2005, total mercury release in the environment in ASGM was more than twice from this sector, around 35% of total mercury, with an annual estimate at 727 tons, becoming the largest global resource of anthropogenic mercury release. In Indonesia, total mercury released to the environment is estimated at 340 metric tons per year and also among the top 3 global emitters of mercury, with 57.5% from the ASGM sector, where 60% is being emitted to air, 20% to water, and the remaining 20% to land. The location of artisanal and small-scale gold mining (ASGM) in this study are in Anggai village and Air Mangga village in Obi sub-district, South Halmahera district, North Maluku Province. Amalgamation has been the preferred method for treating the gold ores in both Anggai and Air Mangga Villages. The methodology provides a suggested approach for collecting and analyzing data and guidance for analyzing policy, regulatory, and institutional aspects and health aspects in the ASGM sector, mainly covering the Socio Economy ASGM research methodology. An assessment of the practicality of a proposed plan or project is also called Feasibility Study. The objective of this research was to describe the socio-economic impact and feasibility of gold processing of ASGM in Obi Island, South Halmahera district, North Maluku Province.

Formation Model of the Gold-Sulfide Deposits of the Western Kalba and Its Main Forecast and Search Criteria

The West Kalba Gold ore Belt (WKB), located within the Greater Altai, is a unique gold ore province on a global scale. It contains about 500 known gold occurrences and deposits. The main industrial type for the WKGB are gold-bearing sulfide deposits. The article presents a model for the formation of gold sulfide deposits in West Kalba. The main predictive-search criteria are considered, which make it possible to assess the prospects of areas for the presence of potential gold-sulfide objects within the described territory. The aim of the work is to clarify the main predictive and prospecting criteria specific to the considered field model. The given data is highlighted using descriptive analytics methods.

Effect of ore heterogeneity on the ball mill wear rate during a grinding process at gold mines of Saudi Arabia (KSA)

Purpose. The current research aims to study the effect of gold ore grinding on the wear rate of grinding balls. Methods. Six boulder rock samples were selected from some KSA mines; five core samples were taken from each of them to identify the mechanical properties (compressive strength, Young’s modulus, and Poisson’s ratio). These mechanical properties were applied to identify the hardness class of all 30 core samples. Five samples with different mechanical properties from the same boulder sample were milled to study the effect of the compressive strength difference and grinding time on wear rate. Then, six samples were taken from different regions with similar mechanical properties but different petrographic characteristics. They were also milled under the same grinding conditions to study the effect of the microscopic mineral composition on the wear rate. Findings. The results showed that the wear rate increased with the improving mechanical properties and with the increa-sing grinding time. On the other hand, the results based on different microscopic descriptions of the six samples showed that despite similar mechanical properties, the wear rates differed. Petrographic characteristics confirmed the presence of quartz in most of the samples as an associated mineral; it is likely that it has the greatest effect on the grinding ball wear. Originality. The paper proposes a method for investigating ore heterogeneity, which has a major impact on the wear rate during a grinding process, as well as on the reducing costs and improving efficiency of grinding media. Practical implications. The research emphasizes the importance of investigating variables (e.g. ore heterogeneity) other than ball size, grinding medium composition, and wet or dry grinding that have a substantial impact on grinding efficiency. The findings could be applied in feasibility studies to calculate and evaluate grinding costs versus grinding efficiency.

Харгинский золотороссыпной центр Приамурской золотоносной провинции

The article presents the geotectonic and metallogenic position of the Amur gold-bearing province in the Kharga gold placer centre, in which there are eight ore-placer nodes (RRU) - Unya-Bomsky, Dugdinsky, Malomyrsky, Verkhnestoybinsky, Tokursky, Kharginsky, Sofiysky, and Kerbinsky. The main placers, which yielded about 25 % of the province's placer gold, and the sources of their formation are described. Placer gold production has been analyzed for almost a century and a half. Conclusions are made on the immediate prospects of the Kharga center for the placer and ore gold extraction.

Selective alkaline leaching of antimony from Low-grade refractory gold ores and process optimization

To eliminate the adverse effect of antimony on extracting of gold in matte smelting process from Sb-bearing refractory gold ores, the sodium sulfide leaching method was proposed to selectively remove antimony in advance. On the basis of the analysis and characterization of raw materials (XRD, SEM-EDS, mineralogical phase analysis, etc.), it can be detected that the antimony in refractory gold ores is mainly in form of stibnite with small quantities of oxides, and the gold is mainly wrapped up in sulfides and silicates. The effects of sodium sulfide and sodium hydroxide concentration, temperature, leaching time and liquid–solid ratio on the extraction rate of antimony and gold were discussed. Furthermore, the response surface method was applied to distinguish the interaction influence of process parameters on the antimony and gold extraction rate. It is detected that the polysulfides and thiosulfates are the main cause of associated leaching of gold. Furthermore, the regression equation model is established adopting the antimony extraction rate as response value, and it can be deduced that the relevance degree is Na2S concentration > temperature > NaOH concentration. Accordingly, the optimized process results are determined as follows: the extraction rates of antimony and gold reach 94.15% and 3.37%, respectively, under Na2S concentration of 85.66 g/L, NaOH concentration of 45.5 g/L, liquid–solid ratio of 1.5, leaching at 90 °C for 5 min, which are very consistent with the predicted values of the regression equation, proving the feasibility of the proposed optimization model.

Overcoming stereological Bias: A workflow for 3D mineral characterization of particles using X-ray micro-computed tomography

Mineral separation processes operate on properties of individual particle, which can currently be quantified with 2D characterization techniques, namely 2D automated mineralogy. While 2D automated mineralogy data have driven significant developments in particle-based separation models, this data inherently correspond to 2D slices of 3D objects, which leads to stereological bias in the quantification of geometric particle properties. X-ray micro-computed tomography (µCT) is a 3D imaging technique that can quantify particle geometry. However, µCT only collects limited information regarding material composition, making mineral identification quantification a challenge. To overcome this challenge, we present a workflow that utilizes individual particle histograms and corrects image artefacts caused by µCT measurements, such as partial volume effect. We demonstrate the application of the workflow to perform 3D mineral characterisation of a sulfidic gold ore, where mineral phases that are commonly mistaken with µCT could be distinguished: pyrite and chalcopyrite, gold, and galena. Results were verified by comparison with inductively coupled plasma mass spectrometry and 2D automated mineralogy. As a result, the workflow provides the user with a detailed 3D particle dataset containing the modal mineralogy and surface compositions, size, and geometrical properties of each particle in a sample – essential data for modelling mineral separation processes.