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The recovery of gold from refractory ore could guarantee sustainable development in the gold industry. However, there are many challenges in the treatment of ore, such as environmental pollution and low recovery. In this regard, the current research focuses on the pretreatment of refractory gold ore and investigates the effect of microwave power, the role of additives, and water on the oxidation and decomposition of sulfide minerals. Pretreatment using microwave-assisted roasting with NaClO3 as an additive to the oxidizing agent is a new method of processing refractory gold ore. Oxidation was studied through sulfur and chlorine mass balance analysis and the degree of metal extraction from sulfide minerals. SEM analysis was carried out to complete the study of the phase change of compounds in the oxidation of mineral sulfides. Roasting of refractory gold ore with a composition of 180 kg NaClO3 and 180 kg water/ton ore reached a temperature of 470 °C at a microwave power of 400 watts for 30 minutes. Total oxidized sulfur reached 90.6%, while only 10.4 % of the sulfur was released, and chlorine release was 49.5%. In addition, water leaching was conducted to investigate the extraction rate of metals after roasting. The results showed that the water leaching extraction of Cu, Zn, Pb, and Fe reached 84.3%, 97.6%, 22.8%, and 8.4%, respectively. Applying microwaves with appropriate concentrations of additives and water resulted in high oxidation of sulfide minerals (>90%) and low sulfur emissions in roasting refractory gold ore with relatively low power, temperature, and time. Moreover, leaching this roasted gold ore resulted in gold extraction of 92.5%; however, leaching of refractory gold without pretreatment resulted in gold extraction of only 47.5%.

Acid mine drainage (AMD) is a serious problem in many coal and mineral mines. Over the past 50 years, many researchers have developed static tests that play an essential role in preventing AMD. In Indonesia, static tests are conducted using two methods: acid–base accounting (ABA) and net acid generation (NAG) tests. On an operational scale, mining companies commonly use the NAG test because it is simpler and faster than ABA. The NAG test is performed using hydrogen peroxide at a concentration of 15% as a strong oxidizing agent, according to the ARD Test Handbook and Indonesian National Standard (SNI). However, since 1990, an Indonesian coal mining company, PT Kaltim Prima Coal, is conducting NAG tests using 7.5% hydrogen peroxide. In the present dataset, we compared the results of NAG tests obtained using 7.5% and 15% hydrogen peroxide for 564 rock core samples. The dataset also shows the behavior of the NAG solution for each representative rock characteristic—including the concentrations of Fe, Mn, and SO4, oxidation reduction potential (ORP), conductivity, total dissolved solids (TDS), and temperature—during the test. This dataset can be useful for researchers to investigate the differences in the NAG test when 7.5% and 15% hydrogen peroxide are used, as well as to understand the oxidation behavior of sulfide minerals when hydrogen peroxide is used as a strong oxidizing agent for AMD.

BACKGROUND: Micro-geochemical information of sulfide minerals plays a crucial role in the field of geochemistry, allowing discovery of the formation mechanism and evolution process of sulfide minerals by analyzing their element composition characteristics. LA-ICP-MS is currently the most popular microanalysis technology used for sulfide analysis, having yielded successful results. Due to their unique physical and chemical properties, sulfide mineral samples show different laser ablation behavior to conventional geological samples. The most intuitive phenomenon is the melting of ablation carters caused by laser thermal effect and the deposition of a large number of material particles around the ablation carters, which is the main factor limiting the precision and accuracy of sulfide sample analysis. Walting et al found that direct quantitation of multi-elements in sulfide minerals by infrared laser (1064-nm Nd:YAG laser) was impossible, which was because the strong thermal effect generated by the infrared laser will lead to severe large particle aerosol redeposition. It is reported that ablation systems with shorter wavelengths, such as ultraviolet lasers, including the 266 and 213nm laser, can be used to obtain acceptable analytical accuracy by reducing the thermal effect and aerosol particle size, but a poor precision was still observed. Guillong et al conducted a comparative study of 266, 213 and 193nm lasers and found that there were finer particle sizes of the aerosols and the weaker thermal effect when using 193nm laser ablation, and the RSDs of all elements less than 20% were obtained. In other words, collisions between photons and matter intensify in deep ultraviolet laser ablation systems (193nm) with shorter wavelength and can help reduce the melt zone and aerosol particle size. However, there is still a slight thermal effect during 193nm UV laser ablation. Fernández et al found that there is still a melting layer during 193nm laser ablation, and it leads to the formation of large particle aerosols. Different methods have been proposed to improve the thermal effect during laser ablation of sulfide. Muller et al found that the precision of line scanning could be improved by 50% compared to spot ablation. Guillong’s results showed that adding a small amount of hydrogen to the analysis could increase the sensitivity of the 47 elements in the test by two to four times. Moreover, research has focused on improving the thermal effect of sulfide minerals from shorter pulse width lasers and aerosol particle transport . However, there are still some thermal effects in the process of deep ultraviolet and short wavelength laser ablation, and how to inhibit the thermal effect in the process of ablation to obtain effective analysis results is still a difficulty in the analysis of sulfide mineral elements. The LA-ICP-MS low temperature ablation cell is an ablation system developed in recent years, whose main function is to provide a low temperature ablation environment to realize the effective analysis of cells, blood and other samples. The low-temperature ablation cell may be a new approach to resolve the thermal effect during sulfide mineral ablation. OBJECTIVES: In order to establish a high precision and high accuracy multi-element analysis method for sulfide minerals. METHODS: The use of a designed cryogenic ablation cell suppressed the thermal effect and refined aerosol particle sizes, which improved analytical precision and accuracy significantly. To explore the mechanism of sulfide ablation at low temperature, the aerosols ablated at low temperature were collected using an aerosol collection setup consisting of a membrane with an aperture of 0.1μm, which was installed at the outlet of the ablation cell. According to the micro-analysis results, the laser ablation behavior under low temperature ablation environment was further discussed. RESULTS: A precision and accuracy method for multi-elements analysis of sulfide minerals using CLA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry with a cryogenic ablation cell) was described. Ablation craters were investigated via scanning electron microscope (SEM) images to compare the amounts of melt produced. SEM measurements showed significant differences in melting between the low temperature (−30℃) and room temperature (20℃). The diameters and size distribution of particles were measured from nanometer particle potentiometer images of the collected ablated aerosol. Particles ablated using cryogenic ablation cell were smaller in average diameter (190nm and 400nm) and shorter in distribution range (570nm). Compared to the precision of timeresolved signal during laser ablation processes between the two temperatures, the precision was significantly improved and the RSD was reduced from 20.1%-34.4% to 11.5%-15.8% with a cryogenic ablation cell. A designed cryogenic ablation cell in sulfide sample analysis was utilized to minimize the thermal effect and improve analytical precision and signal intensity. In this study, the CRM (MASS-1) sample was analyzed with spot ablation mode at low (−30℃) and room (20℃) temperatures, respectively, and the RSDs of three times parallel analysis at these two temperatures were compared. At room temperature, the RSDs of elemental signals ranged from 20.1% to 34.4%. In contrast, the RSD of elemental signals was less than 15.8% when the sample was ablated at low temperature (Fig.2a). The significant improvements may be attributed to low ablation temperature, which suppress the thermal effect. Moreover, the signal intensities of elements improved by approximately 11% to 52% with the decrease in temperature of the cryogenic ablation cell (Fig.2b). Fig.2c shows the time-resolved signals of the MASS-1 sample at room temperature, the significant fluctuations and spikes could be observed, and the RSDs of all elemental signals was more than 20.1%. Interestingly, the signals at low temperature exhibited ideal stability, and the RSDs of elemental signals were less than 15.8%, as shown in Fig.2d. In order to explore the reasons for improving the analytical performance of low temperature, the morphology of ablation under different temperature conditions of two standard sulfide samples were discussed. SEM images of four ablation craters on chalcopyrite and pyrite were taken to investigate the effect of temperature on the ablation process (Fig.3). The sulfide samples were ablated using a 193nm excimer laser with a spot size of 60nm and a fluence of 8J/cm² . The ablation craters on the chalcopyrite showed a two-layer cyclic structure, in which the inner layer was a light-colored melting zone, and the outer layer was a white aerosol vapor sediment. At low temperature, there were fewer melt layers and thinner grain sediment zone than those at room temperature (Fig.3a, Fig.3b). However, the melting zone around the ablation craters of pyrite were more irregular. More of the unwanted ablation was melted away at room temperature (Fig.3c, Fig.3d). The craters formed at room temperature (Fig.3a, Fig.3c) showed a more serious melting phenomenon than those formed at low temperature (Fig.3b, Fig.3d), as evidenced by the abundance of molten ejecta around the former, especially at high laser energy densities. In contrast, the low temperature craters showed no obvious melting phenomenon and had a flatter bottom with a reduced number of large molten spherical particles. The use of CLA-ICP-MS weakened the melting phenomenon, thereby generating smaller aerosol particles, which further improved the aerosol transport and ionization efficiency. A particle size collection experiment was conducted to explore the distribution of aerosol particles at different temperatures. SEM images were used to analyze the shapes and sizes of particles that were collected on a membrane with an aperture of 0.1μm at room temperature (20℃) and low temperature (−30℃). The same sample chamber and 1m of tubing were used to transport the particles, and the ablation pulses continuously for 2min. The SEM images showed that the particles produced at room temperature were larger and formed large agglomerates (Fig.4a), whereas the particles produced at −30℃ were smaller and there were fewer agglomerations (Fig.4c). The shape of the agglomerates and their connection by filaments suggested strong charge during particle formation, which was more prominent at room temperature. Additionally, there were more single large particles produced at room temperature (Fig.4b), while there were fewer particles at −30℃ ( Fig.4d). Comparative measurements were conducted using 193nm laser to investigate the influence of temperatures on particle size distribution. Fig.4 shows a typical size distribution for LA under He atmosphere. The left part of Fig.5 shows a distribution of aerosols produced by ablation of 2min pulses at room temperature. The peak heights of mean diameter in this distribution were determined to be approximately 300nm and 700nm, respectively. Similarly, particle size distribution at −30℃ also presented a bimodal pattern, which was consistent with previous studies. The average diameters were 190nm and 400nm, both smaller than at room temperature, while the peak width was shorter. The chemical composition of fine particles produced at low temperature is closer to the sample body, improving the transport and ionization of aerosol in ICP, reducing element fractionation, and enhancing the signal strength and stability, thereby improving the analytical performance of ICP-MS. CONCLUSIONS: A new high-precision and accuracy method for determination of trace elements in sulfide minerals has been developed using the CLA-ICP-MS system. This method reduces thermal effect and decreases particle size during the ablation process, improving precision by freezing sulfide samples with a designed cryogenic ablation cell. Low temperature results in better data because fewer large particles are produced; sedimentation around the ablation crater and during transport is reduced, while ionization efficiency in ICP is higher. The precision calculated for transient signals decreases obviously if the sample is kept at low temperature (−30℃) compared to room temperature (20℃), while the sensitivity improved slightly. The deviation of all elements between the test values and the standard values falls within 7% by CLA-ICP-MS. In future work, it will be necessary to investigate even lower temperatures, as low temperatures can increase aerosol viscosity and affect analysis results. It is also worth exploring whether the performance of a long pulse width laser can be improved by lowering the temperature to match that of a short pulse width laser. [ABSTRACT FROM AUTHOR]

Sulfide minerals hold significant importance in both fundamental science and industrial advancement. However, certain natural sulfide minerals, such as NaFe3S5·2H2O (NFS), pose great challenges for exploitation and synthesis due to their high susceptibility to oxidation. To date, no successful precedent exists for synthesizing NFS. Here, a novel approach to synthesizing low‐cost and pollution‐free NFS with high stability using the high‐pressure hydrothermal method based solely on knowledge of its chemical formula is presented. Moreover, an innovative strategy inspired by the cicada's molting process to develop unstable natural materials is proposed. The mechanical, thermal, optical, electrochemical, and magnetic properties of the NFS are thoroughly investigated. The storage of lithium, sodium, and potassium ions is primarily concentrated in the gap between (0 0 1) crystal planes. Additionally, as a catalyst for hydrogen evolution reaction (HER) at 10 mA cm−2, micron‐sized NFS exhibits an excellent overpotential of 6.5 mV at 90 °C, surpassing those of reported HER catalysts of similar size. This research bridges the gap in the sulfide mineral family, overcomes limitations of the high‐pressure hydrothermal method, and paves the way for future synthesis of natural minerals, lunar minerals, and Martian minerals. [ABSTRACT FROM AUTHOR]

Bioleaching has been regarded as a green alternative to chemical leaching in metal extraction processes. In this study, the bioleaching properties of indigenous acidophilic bacteria for various sulfide minerals were compared and evaluated in terms of pH reduction and metal leaching. The primary minerals in the samples were sphalerite (ZnS) (SP), galena (PbS) (GN1 and GN2), pyrite (FeS2) (PY), and chalcopyrite (CuFeS2) (CCP), and an indigenous acidophilic bacterium, Acidiphilium cryptum (99.56%), was applied for bioleaching experiments. The metal extraction in bioleaching differed according to the mineral content. The leached metal concentration of Zn was higher than that of Pb for the SP sample with a high ZnS content, whereas the concentration of Pb was higher than that of Zn for the GN1 and GN2 samples with a high PbS content. Meanwhile, the leaching rate of Zn was faster than that of Pb for all samples. Corrosion action was observed on the surface of bacterial residues in SP and GN1 samples. These results show that the bioleaching mechanism based on sulfide minerals proceeds through indirect biological oxidation, chemical oxidation, and direct bacterial oxidation. The results of this study can provide basic research data for process optimization when employing bioleaching to extract valuable metals. [ABSTRACT FROM AUTHOR]

Abstract Sulfide minerals hold significant importance in both fundamental science and industrial advancement. However, certain natural sulfide minerals, such as NaFe3S5·2H2O (NFS), pose great challenges for exploitation and synthesis due to their high susceptibility to oxidation. To date, no successful precedent exists for synthesizing NFS. Here, a novel approach to synthesizing low‐cost and pollution‐free NFS with high stability using the high‐pressure hydrothermal method based solely on knowledge of its chemical formula is presented. Moreover, an innovative strategy inspired by the cicada's molting process to develop unstable natural materials is proposed. The mechanical, thermal, optical, electrochemical, and magnetic properties of the NFS are thoroughly investigated. The storage of lithium, sodium, and potassium ions is primarily concentrated in the gap between (0 0 1) crystal planes. Additionally, as a catalyst for hydrogen evolution reaction (HER) at 10 mA cm−2, micron‐sized NFS exhibits an excellent overpotential of 6.5 mV at 90 °C, surpassing those of reported HER catalysts of similar size. This research bridges the gap in the sulfide mineral family, overcomes limitations of the high‐pressure hydrothermal method, and paves the way for future synthesis of natural minerals, lunar minerals, and Martian minerals.

In this study, chalcopyrite (CuFeS2), a natural mineral with a bimetallic structure, was used as the activator to generate radicals for removing organic pollutants from aqueous solutions via the activation of peroxymonosulfate (PMS). Sulfisoxazole (SIX), a sulfonamide antibiotic, was selected as the model pollutant. The results showed that chalcopyrite was highly reactive toward the activation of PMS; under the conditions of 50 µM PMS and 1 g/L chalcopyrite, approximately 95.7% of the SIX was degraded after reaction for only 5 min. An increase in the loading of chalcopyrite (0.25–2 g/L) promoted the degradation of SIX, while elevated levels of PMS (0.05–0.5 mM) slightly retarded the degradation kinetics. Although the best performance was observed under acidic conditions (pHs 3 and 4), near complete degradation of SIX was also achieved at pH 5.5. Identification of reactive species revealed that both a hydroxyl radical and a sulfate radical were formed in chalcopyrite–PMS oxidation, and they were responsible for the degradation of SIX. Trace amounts of copper and iron were leached out from chalcopyrite during the activation, and both the heterogeneous and homogeneous activation of PMS contributed to the generation of oxidizing radicals. Common water constituents including Cl−, HCO 3 − , and natural organic matter at their environmentally relevant levels showed a limited effect on the degradation of SIX, which suggests that chalcopyrite–PMS oxidation has high reactivity and stability in the degradation of organic pollutants and shows great practical application potential. [ABSTRACT FROM AUTHOR]

Background. Almalyk MMC JSC processes molybdenum middling cinder by leaching. The role of metal ion ligands in the leaching of valuable components from Mo-cinder has not been sufficiently studied. Purpose: comparative characteristics of the processes of soda and ammonia leaching of molybdenum middling cinder with depressants of dissolved gold: D1 and zinc. Methodology. The composition of the cinder samples and the solutions and cakes formed during leaching was controlled spectrometrically (ААС Perkin-Elmer 3030В, ICP-Agilent 7500 IСP). The leaching of the cinder was carried out according to soda and ammonia schemes. Originality. According to the analysis of samples of a batch of molybdenite concentrate, a balance of the distribution of metals was compiled in a step-by-step scheme of the processing process. In order to identify losses of Au, Ag, a pilot laboratory test of the process of soda leaching of raw materials was carried out. Findings. The comparative characteristics of PPM cinder leaching in soda and ammonia schemes with D1 depressant and zinc were studied. Leaching products have been studied. [ABSTRACT FROM AUTHOR]

Bioleaching has been regarded as a green alternative to chemical leaching in metal extraction processes. In this study, the bioleaching properties of indigenous acidophilic bacteria for various sulfide minerals were compared and evaluated in terms of pH reduction and metal leaching. The primary minerals in the samples were sphalerite (ZnS) (SP), galena (PbS) (GN1 and GN2), pyrite (FeS2) (PY), and chalcopyrite (CuFeS2) (CCP), and an indigenous acidophilic bacterium, Acidiphilium cryptum (99.56%), was applied for bioleaching experiments. The metal extraction in bioleaching differed according to the mineral content. The leached metal concentration of Zn was higher than that of Pb for the SP sample with a high ZnS content, whereas the concentration of Pb was higher than that of Zn for the GN1 and GN2 samples with a high PbS content. Meanwhile, the leaching rate of Zn was faster than that of Pb for all samples. Corrosion action was observed on the surface of bacterial residues in SP and GN1 samples. These results show that the bioleaching mechanism based on sulfide minerals proceeds through indirect biological oxidation, chemical oxidation, and direct bacterial oxidation. The results of this study can provide basic research data for process optimization when employing bioleaching to extract valuable metals.

[Display omitted] • ML-based workflow that can generate prediction model for collector performance on sulfide minerals. • The ML model demonstrates robust predictive power for the collectors with diverse skeletons. • The ML model can reveal new structure-floatability relationships of new skeletons. • The method is critical to future high-throughput, virtual screening of flotation surfactants. Flotation, as one of the most important separation technologies in the 21st century, enables the large-scale utilization of mineral resources. The development of high-performance surfactants, especially collectors, is at the core of flotation separation. The evaluation and prediction of collector flotation performance on mineral recovery are prerequisites for its high-efficient development. In this work, we present a novel machine learning (ML) model that can evaluate and predict the recoveries of sulfide minerals (chalcopyrite, galena, pyrite and sphalerite) using the collectors under different flotation conditions (pulp pH, flotation time, collector concentration, etc.). In order to build the model, the features of 116 collectors (electrostatic properties, atomic charges, molecular orbitals, etc.) and 4 sulfide minerals (surface charges, band gap, adsorption energies, etc.) are characterized by quantum chemistry (QC) computation. The features, along with the flotation conditions reported in the literature, were used as input, and the experimental recoveries of four sulfide minerals are the output. Among 116 collectors, 10 randomly selected collectors were employed to refine the model until the mean absolute error (MAE) between the mineral recoveries from experiments and model prediction reaches a minimum of 10.0%. The optimized ML model was proved to successfully predict the flotation performance of 23 new collectors with MAE of 5.2%. We can conclude that this QC-ML model will offer great assistance in the future high-throughput screening and design of flotation reagents. [ABSTRACT FROM AUTHOR]

Background. At Almalyk MMC JSC molybdenum middling cinder is processed in soda medium by leaching. The role of metal ion ligands in the leaching of valuable components from Mo-cinder has not been adequately studied. Purpose: to obtain comparative characteristics of the processes of soda and ammonia leaching of molybdenum middling cinder. Methodology. The composition of the cinder samples and the solutions and cakes formed during leaching was controlled spectrometrically (ААС Perkin-Elmer 3030В, ICP-Agilent 7500 IСP). The leaching of the cinder was carried out according to soda and ammonia schemes. Originality. It is shown that the loss of Au, Ag from the leaching cakes of Mo-cinder is 20% and 34%, respectively, in the ammonia scheme, and 22% and 14%, respectively, in the soda scheme. The possibility of direct transfer of Au and Ag from PPM cinder into diphenylguanidine solution is shown. Findings. The leaching of molybdenum middling cinder in soda and ammonia schemes was studied. The composition of cakes and leaching solutions has been studied. [ABSTRACT FROM AUTHOR]

Sulfide-containing mine waste was oxidized to produce acid mine drainage, which lead to acidification of surrounding soil and downstream rivers and posed a threat to the surrounding environment. Quartz often coexists with sulfide minerals and affects the oxidation of sulfide minerals. In order to explore the role of quartz in the bio-oxidation of sulfide minerals in mine solid waste, the mixed minerals of quartz and sulfide minerals were bio-oxidized by Acidithiobacillus ferrooxidans. The results showed that quartz could improve the microbial activity and increase the acid production of sulfide minerals. The larger the proportion of quartz in bio-oxidation of sulfide minerals, the less the production of secondary minerals such as jarosite, and the larger the leaching amount of iron and sulfate. This research provides new ideas for speeding up the bio-oxidation of sulfide mineral to remove iron and sulfate. It provides a new way to solve acid pollution caused by oxidation of sulfide minerals. [ABSTRACT FROM AUTHOR]

Natural chalcocite (NCC) was chosen as a co-catalyst for activation of persulfate (PS) to degrade organic contaminants in this study. A synergistic effect between NCC and ferrous ions (Fe2+) was found in catalyzing PS for degradation of orange G (OG). The main role of NCC in the NCC/Fe2+/PS system was to facilitate Fe3+ reduction back to Fe2+ and thus improve the stoichiometric efficiency of PS. The results of scavenging experiments and electron paramagnetic resonance tests proved that both sulfate and hydroxyl radicals were the primary reactive oxidants in the NCC/Fe2+/PS system. Twelve potential intermediate products of OG were identified, and the degradation pathway was proposed. Experiment parameters, such as NCC dose, Fe2+ concentration, initial pH, and the presence of anions (H2PO4‒ and Cl‒), all had important impacts on OG degradation. NCC had good reusability in synergistic activation of PS with Fe2+ for OG degradation for five cycles. This study demonstrated a natural sulfide mineral as an efficient co-catalyst towards PS activation for destruction of organic contaminants in water.

[Display omitted] • Key properties are selected by ML to construct a collector property index (CPI). • Combining ML and QSAR, the theory-based prediction method is developed. • The method can predict collector flotation performance in galena-pyrite system accurately. • The methodology has the potential to be expanded to other mineral systems. The evaluation and prediction of flotation performance is a key step in the development of high-performance collectors for the efficient flotation separation of low-grade complex ores. In our previous work, we have created the flotation index (FI) for a comprehensive and standardized evaluation of collector flotation performance. However, as an experiment-based index, FI does not possess the quantitative predictive power that is fundamental to rational flotation reagent design. In this work, the collector properties were obtained by quantum chemistry (QC) calculation. By ranking the importance of the QC properties, machine learning (ML) aids the selection of key properties representing different aspects of a collector (polar, non-polar and overall polarity). The key properties were incorporated into a theory-based collector property index (CPI). Based on a quantitative structure–activity relationship (QSAR), the bridge between theory and experiment were established by searching for the relationship CPI and FI , enabling convenient evaluation and prediction of collector flotation performance. The accuracy of our QSAR model was verified using the galena-pyrite separation system. Our QSAR model demonstrates transferability in that it can predict collectors with diverse skeletons or types, pushing the limit of most conventional QSAR models, which only apply to collectors with similar skeletons or types. This work provides an alternative pathway for the rational design and performance prediction of flotation surfactants. [ABSTRACT FROM AUTHOR]

Microbe-sulfide mineral interactions (MSMI), often manifested as biofilm formation, are ubiquitous in natural and engineered environments. Such interactions were much dependent upon the evolution of chemical species of mineral surface and microbial extracellular polymeric substances (EPS), and in-situ characterization of which have been a demanding and crucial task. In this study, quartz crystal microbalance with dissipation (QCM-D) was used to real time characterize the adhesion of Acidithiobacillus ferrooxidans onto the pyrite surface after introducing L-cysteine (an important component of EPS). And by combining with monitoring the EPS composition in biofilm by confocal laser scanning microscopy (CLSM) and the surface sulfur species by SEM-EDS and X-ray-photoelectron spectroscopy (XPS) as well as the changes in pH, ORP, [Fe2+] and [Fe3+] in solution during A. ferrooxidans -pyrite interaction, the results show that L-cysteine can lead to the Cys-S-S 2 Fe complex formation on pyrite surface, and under the dosage of 0.02 to 0.1 g/L of L-cysteine, the Cys-S-S 2 Fe complex promoted the cell adhesion and biofilm formation of A. ferrooxidans with secretion of more EPS proteins but less EPS glycoconjugates, resulting in the promotion of sulfur biooxidation with inhibition of iron biooxidation, corresponding to no obvious formation of jarosites. The higher dosage of L-cysteine (e.g., 0.2 g/L) inhibited biofilm formation, reduced iron/sulfur oxidation. These results deepen the understanding of the roles of L-cysteine on MSMI. This study demonstrates the QCM-D-based method can be widely used for in situ characterization of MSMI, and opens an alternative pathway for revealing the micro-mechanism of MSMI correlated to the macroscopic effects. [Display omitted] • The cell adhesion and biofilm formation of A. ferrooxidans on pyrite was study real time by QCM-D. • L-cysteine modification led to the production of Cys-S-S 2 Fe complex on pyrite surface. • The surface Cys-S-S 2 Fe complex stimulated A. ferrooxidans to secret more proteins for promoting S oxidation. • L-cysteine modification significantly inhibited Jarosites formation with delaying iron oxidation. [ABSTRACT FROM AUTHOR]

The recovery of gold from refractory ore could guarantee sustainable development in the gold industry. However, there are many challenges in the treatment of ore, such as environmental pollution and low recovery. In this regard, the current research focuses on the pretreatment of refractory gold ore and investigates the effect of microwave power, the role of additives, and water on the oxidation and decomposition of sulfide minerals. Pretreatment using microwave-assisted roasting with NaClO 3 as an additive to the oxidizing agent is a new method of processing refractory gold ore. Oxidation was studied through sulfur and chlorine mass balance analysis and the degree of metal extraction from sulfide minerals. SEM analysis was carried out to complete the study of the phase change of compounds in the oxidation of mineral sulfides. Roasting of refractory gold ore with a composition of 180 kg NaClO 3 and 180 kg water/ton ore reached a temperature of 470 °C at a microwave power of 400 watts for 30 minutes. Total oxidized sulfur reached 90.6%, while only 10.4 % of the sulfur was released, and chlorine release was 49.5%. In addition, water leaching was conducted to investigate the extraction rate of metals after roasting. The results showed that the water leaching extraction of Cu, Zn, Pb, and Fe reached 84.3%, 97.6%, 22.8%, and 8.4%, respectively. Applying microwaves with appropriate concentrations of additives and water resulted in high oxidation of sulfide minerals (>90%) and low sulfur emissions in roasting refractory gold ore with relatively low power, temperature, and time. Moreover, leaching this roasted gold ore resulted in gold extraction of 92.5%; however, leaching of refractory gold without pretreatment resulted in gold extraction of only 47.5%. [ABSTRACT FROM AUTHOR]

Abstract Submarine hydrothermal deposits are one of the promising seafloor mineral resources, because they can store a large amount of metallic minerals as sulfides. The present study focuses on the electrical properties of active modern submarine hydrothermal deposits, in order to provide constraints on the interpretation of electrical structures obtained from marine electromagnetic surveys. Measurements of resistivity and spectral induced polarization (IP) were made using drillcore samples taken from the Iheya North Knoll and the Iheya Minor Ridge in Okinawa Trough, Japan. These hydrothermal sediments are dominantly composed of disseminated sulfides, with minor amounts of massive sulfide rocks. The depth profiles of resistivity and spectral IP properties were successfully revealed to correspond well to layer-by-layer lithological features. Comparison with other physical properties and occurrence of constituent minerals showed that resistivity is essentially sensitive to the connectivity of interstitial fluids, rather than by sulfide and clay content. This suggests that, in active modern submarine hydrothermal systems, not only typical massive sulfide rocks but also high-temperature hydrothermal fluids could be imaged as low-resistivity anomalies in seabed surveys. The spectral IP signature was shown to be sensitive to the presence or absence of sulfide minerals, and total chargeability is positively correlated with sulfide mineral abundance. In addition, the massive sulfide rock exhibits the distinctive IP feature that the phase steadily increases with a decrease of frequency. These results show the effective usage of IP for developing and improving marine IP exploration techniques. Graphical abstract .

Due to land uplift after the last ice age, previously stable Baltic Sea sulfidic sediments are becoming dry land. When these sediments are drained, the sulfide minerals are exposed to air and can release large amounts of metals and acid into the environment. This can cause severe ecological damage such as fish kills in rivers feeding the northern Baltic Sea. In this study, five sites were investigated for the occurrence of acid sulfate soils and their geochemistry and microbiology was identified. The pH and soil chemistry identified three of the areas as having classical acid sulfate soil characteristics and culture independent identification of 16S rRNA genes identified populations related to acidophilic bacteria capable of catalyzing sulfidic mineral dissolution, including species likely adapted to low temperature. These results were compared to an acid sulfate soil area that had been flooded for ten years and showed that the previously oxidized sulfidic materials had an increased pH compared to the unremediated oxidized layers. In addition, the microbiology of the flooded soil had changed such that alkalinity producing ferric and sulfate reducing reactions had likely occurred. This suggested that flooding of acid sulfate soils mitigates their environmental impact. [ABSTRACT FROM AUTHOR]

Abstract The effect of heavy metals-containing gold ore mineralogy on gold oxidation kinetics in solutions with various free cyanide (CN) and dissolved oxygen (DO) concentrations was studied by electrochemical tests. To effectively simulate the cyanide gold leaching conditions, the electrochemical experiments were carried out in the slurries of the ores. The results of the linear sweep voltammetry tests showed three significant gold oxidation peaks. The peak potentials and the corresponding current densities were dependent on the composition of the ores in the test slurries, and the CN and DO concentrations of the test solutions. The heavy metal concentration of the ores also effectively changed the electrochemical response of the tests. The highest gold oxidation kinetics were observed in a pyritic sample containing 1800 ppm Pb, 640 ppm Ag and 195 ppm Hg (sample 1). The fastest gold oxidation kinetics were registered at −0.2 V vs. Ag/AgCl when DO was 8.3 mg/L, and the corresponding Au oxidation peak current densities were 4.75 and 7.07 mA/cm2 at 600 and 900 mg/L free CN, respectively. The Au oxidation was assisted by cementation reaction between the aqueous Hg and/or Ag species, and metallic gold. The weak lead deposition was also observed. However, the positive effect of Hg on the gold oxidation kinetics was depressed at higher DO (37.0 mg/L) concentrations. Unlike Hg, the effect of Ag on increasing the gold oxidation kinetics was shown to be independent of the solution DO. The second sample of the study, sample 2, was a sulfidic gold ore with 0.25% galena (PbS). The results showed that the presence of galena in an electrochemical gold oxidation test could increase the gold oxidation kinetics. In tests with 8.3 mg/L DO, the current densities of 2.80 and 5.23 mA/cm2 at 600 and 900 mg/L CN solutions, respectively, were obtained at −0.4 V vs. Ag/AgCl. Increasing DO to 37.0 mg/L did not improve the gold oxidation kinetics. Based on the results of this study, the presence of the specified heavy metals is most effective in gold oxidation kinetics if the free CN concentration is high and the DO concentration is low. Besides, the electrochemical methodology introduced in this study could offer a solution for determining the leaching parameters. Highlights • Hg, Ag and Pb improve gold oxidation kinetics at low overpotential range at high CN and low DO concentrations. • At high DO condition, Hg and Pb are not very effective for gold oxidation. • Silver can enhance gold oxidation kinetics regardless of DO concentration. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) is a serious problem in many coal and mineral mines. Over the past 50 years, many researchers have developed static tests that play an essential role in preventing AMD. In Indonesia, static tests are conducted using two methods: acid-base accounting (ABA) and net acid generation (NAG) tests. On an operational scale, mining companies commonly use the NAG test because it is simpler and faster than ABA. The NAG test is performed using hydrogen peroxide at a concentration of 15% as a strong oxidizing agent, according to the ARD Test Handbook and Indonesian National Standard (SNI). However, since 1990, an Indonesian coal mining company, PT Kaltim Prima Coal, is conducting NAG tests using 7.5% hydrogen peroxide. In the present dataset, we compared the results of NAG tests obtained using 7.5% and 15% hydrogen peroxide for 564 rock core samples. The dataset also shows the behavior of the NAG solution for each representative rock characteristic-including the concentrations of Fe, Mn, and SO 4 , oxidation reduction potential (ORP), conductivity, total dissolved solids (TDS), and temperature-during the test. This dataset can be useful for researchers to investigate the differences in the NAG test when 7.5% and 15% hydrogen peroxide are used, as well as to understand the oxidation behavior of sulfide minerals when hydrogen peroxide is used as a strong oxidizing agent for AMD., (© 2023 The Author(s).)

This study examined the reaction mechanism of arsenite, As(III), and antimonite, Sb(III), with iron sulfide and compared their pH-dependent reaction behaviors under strictly anoxic environments. The comparison of Sb(III) with As(III), based on their chemical similarity, may provide useful insight into understanding the geochemical behavior of the less studied Sb(III). The pH-dependent batch sorption studies revealed that As(III) and Sb(III) displayed similar removal trends with pH in terms of the removal efficiency. However, the aqueous As(III) species transformed to thioarsenite species, while aqueous Sb(III) species remained inert under the highly sulfidic anoxic system. An X-ray absorption spectroscopy study demonstrated the reaction of As(III) and Sb(III) at acidic pH was closely related to the precipitation of sulfide minerals As 2 S 3 and Sb 2 S 3 , respectively, as a consequence of the reaction with sulfide produced through mackinawite dissolution. Meanwhile, the removal at basic pH was inferred as a surface reaction, possibly through surface complexation, surface-precipitation, or both. In this study, the pH-dependent Sb(III) uptake mechanisms proved to be similar to the corresponding mechanisms for As(III) uptake, with mackinawite demonstrating a superior capacity to scavenge Sb(III) in ferrous and sulfide-rich reducing environments. [ABSTRACT FROM AUTHOR]

Submarine hydrothermal deposits are one of the promising seafloor mineral resources, because they can store a large amount of metallic minerals as sulfides. The present study focuses on the electrical properties of active modern submarine hydrothermal deposits, in order to provide constraints on the interpretation of electrical structures obtained from marine electromagnetic surveys. Measurements of resistivity and spectral induced polarization (IP) were made using drillcore samples taken from the Iheya North Knoll and the Iheya Minor Ridge in Okinawa Trough, Japan. These hydrothermal sediments are dominantly composed of disseminated sulfides, with minor amounts of massive sulfide rocks. The depth profiles of resistivity and spectral IP properties were successfully revealed to correspond well to layer-by-layer lithological features. Comparison with other physical properties and occurrence of constituent minerals showed that resistivity is essentially sensitive to the connectivity of interstitial fluids, rather than by sulfide and clay content. This suggests that, in active modern submarine hydrothermal systems, not only typical massive sulfide rocks but also high-temperature hydrothermal fluids could be imaged as low-resistivity anomalies in seabed surveys. The spectral IP signature was shown to be sensitive to the presence or absence of sulfide minerals, and total chargeability is positively correlated with sulfide mineral abundance. In addition, the massive sulfide rock exhibits the distinctive IP feature that the phase steadily increases with a decrease of frequency. These results show the effective usage of IP for developing and improving marine IP exploration techniques. [ABSTRACT FROM AUTHOR]

The Duluth Complex in northeastern Minnesota hosts economically significant deposits of copper, nickel, and platinum group elements (PGEs). The primary sulfide mineralogy of these deposits includes the minerals pyrrhotite, chalcopyrite, pentlandite, and cubanite, and weathering experiments show that most sulfidebearing rock from the Duluth Complex generates moderately acidic leachate (pH 4 to 6). Microorganisms are important catalysts for metal sulfide oxidation and could influence the quality of water from mines in the Duluth Complex. Nevertheless, compared with that of extremely acidic environments, much less is known about the microbial ecology of moderately acidic sulfide-bearing mine waste, and so existing information may have little relevance to those microorganisms catalyzing oxidation reactions in the Duluth Complex. Here, we characterized the microbial communities in decade-long weathering experiments (kinetic tests) conducted on crushed rock and tailings from the Duluth Complex. Analyses of 16S rRNA genes and transcripts showed that differences among microbial communities correspond to pH, rock type, and experimental treatment. Moreover, microbial communities from the weathered Duluth Complex rock were dominated by taxa that are not typically associated with acidic mine waste. The most abundant operational taxonomic units (OTUs) were from the genera Meiothermus and Sulfuriferula, as well as from diverse clades of uncultivated Chloroflexi, Acidobacteria, and Betaproteobacteria. Specific taxa, including putative sulfur-oxidizing Sulfuriferula spp., appeared to be primarily associated with Duluth Complex rock, but not pyrite-bearing rocks subjected to the same experimental treatment. We discuss the implications of these results for the microbial ecology of moderately acidic mine waste with low sulfide content, as well as for kinetic testing of mine waste. IMPORTANCE Economic sulfide mineral deposits in the Duluth Complex may represent the largest undeveloped source of copper and nickel on Earth. Microorganisms are important catalysts for sulfide mineral oxidation, and research on extreme acidophiles has improved our ability to manage and remediate mine wastes. We found that the microbial assemblages associated with weathered rock from the Duluth Complex are dominated by organisms not widely associated with mine waste or mining-impacted environments, and we describe geochemical and experimental influences on community composition. This report will be a useful foundation for understanding the microbial biogeochemistry of moderately acidic mine waste from these and similar deposits. [ABSTRACT FROM AUTHOR]

Wastewaters generated during mining and processing of metal sulfide ores are often acidic (pH < 3) and can contain significant concentrations of nitrate, nitrite, and ammonium from nitrogen based explosives. In addition, wastewaters from sulfide ore treatment plants and tailings ponds typically contain large amounts of inorganic sulfur compounds, such as thiosulfate and tetrathionate. Release of these wastewaters can lead to environmental acidification as well as an increase in nutrients (eutrophication) and compounds that are potentially toxic to humans and animals. Waters from cyanidation plants for gold extraction will often conjointly include toxic, sulfur containing thiocyanate. More stringent regulatory limits on the release of mining wastes containing compounds such as inorganic sulfur compounds, nitrate, and thiocyanate, along the need to increase production from sulfide mineral mining calls for low cost techniques to remove these pollutants under ambient temperatures (approximately 8 °C). In this study, we used both aerobic and anaerobic continuous cultures to successfully couple inorganic sulfur compound (i.e. thiosulfate and thiocyanate) oxidation for the removal of nitrogenous compounds under neutral to acidic pH at the low temperatures typical for boreal climates. Furthermore, the development of the respective microbial communities was identified over time by DNA sequencing, and found to contain a consortium including populations aligning within Flavobacterium, Thiobacillus, and Comamonadaceae lineages. This is the first study to remediate mining waste waters by coupling autotrophic thiocyanate oxidation to nitrate reduction at low temperatures and acidic pH by means of an identified microbial community. [ABSTRACT FROM AUTHOR]

Sulfide minerals hold significant importance in both fundamental science and industrial advancement. However, certain natural sulfide minerals, such as NaFe 3 S 5 ·2H 2 O (NFS), pose great challenges for exploitation and synthesis due to their high susceptibility to oxidation. To date, no successful precedent exists for synthesizing NFS. Here, a novel approach to synthesizing low-cost and pollution-free NFS with high stability using the high-pressure hydrothermal method based solely on knowledge of its chemical formula is presented. Moreover, an innovative strategy inspired by the cicada's molting process to develop unstable natural materials is proposed. The mechanical, thermal, optical, electrochemical, and magnetic properties of the NFS are thoroughly investigated. The storage of lithium, sodium, and potassium ions is primarily concentrated in the gap between (0 0 1) crystal planes. Additionally, as a catalyst for hydrogen evolution reaction (HER) at 10 mA cm -2 , micron-sized NFS exhibits an excellent overpotential of 6.5 mV at 90 °C, surpassing those of reported HER catalysts of similar size. This research bridges the gap in the sulfide mineral family, overcomes limitations of the high-pressure hydrothermal method, and paves the way for future synthesis of natural minerals, lunar minerals, and Martian minerals., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

We characterized the adsorption of triglycine molecules on a pyrite surface under several simulated environmental conditions by X-ray photoemission spectroscopy. The triglycine molecular adsorption on a pyrite surface under vacuum conditions (absence of oxygen) shows the presence of two different states for the amine functional group (NH2 and NH3+), therefore two chemical species (anionic and zwitterionic). On the other hand, molecular adsorption from a solution discriminates the NH2 as a unique molecular adsorption form, however, the amount adsorbed in this case is higher than under vacuum conditions. Furthermore, molecular adsorption on the mineral surface is even favored if the pyrite surface has been irradiated before the molecular adsorption occurs. Pyrite surface chemistry is highly sensitive to the chemical changes induced by UV irradiation, as XPS analysis shows the presence of Fe2O3 and Fe2SO4—like environments on the surface. Surface chemical changes induced by UV help to increase the probability of adsorption of molecular species and their subsequent concentration on the pyrite surface.

In this study, effects of solid concentration, temperature, and initial Fe2+ concentration on bioleaching of sulfide mineral (chalcopyrite) obtained from Sarcheshmeh Copper Mine in the region of Kerman located in the south of Iran were investigated. A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans has been isolated from a typical chalcopyrite copper concentrate of the mentioned mine. Bioleaching experiments were carried out in two batch air-lift bioreactors with recycling stream. One reactor contained 2 liters of medium and 10% (v/v) inoculum while in the other reactor, control bioleaching tests were carried out with sterilized concentrate without inoculum by the addition of 40 ml of 0.5% (v/v) formaline in ethanol. The results indicate that the efficiency of copper extraction is dependent on all of the aforementioned variables. In addition, results show that the effects of solid concentration and temperature had more effect compared to the initial Fe2+ concentration. Maximum copper recovery was achieved 70% at pH=1.5, initial Fe2+ concentration=7g/L and pulp density = 10% (w/v) in bioreactor, after 10 days.