Sulfide Minerals Research Articles

Efficient activation of persulfate by metallic sulfide mineral for the efficient removal of pesticides: Performance, radical generation and mechanism

In current years, the harm of pesticide residual pollution to environmental ecology and human health has obtained increasing attention. Hydroxylamine (HA) promoted activation of persulfate (PS) by the natural metallic sulfide mineral chalcopyrite (CuFeS2) for the removal of pesticide chlorpyrifos (CPF) and imidacloprid (IMP) in water had been systematically investigated in this study. Experimental results showed that HA could greatly accelerate the regeneration of Cu2+ and Fe3+ in solutions for PS decomposition. Nearly 99% of CPF removal by CuFeS2/PS/HA process was achieved within 80 min under optimal conditions. The decomposition of PS in the CuFeS2/PS/HA process was higher than that in the CuFeS2/PS process. Several coexisting cations (ie., Ca2+, Mg2+ and Al3+) and anions (ie., HCO3− and HPO42−) presented different levels of negative effects on CPF removal. Both HO• and SO4•− were generated in the CuFeS2/PS/HA process, and HO• might be the main reactive species responsible for the removal of CPF. The synchronized removal of CPF and IMP by CuFeS2/PS/HA process had been successfully achieved under certain conditions. The possible pathways of CPF degradation and enhanced mechanism for both CPF and IMP removal by CuFeS2/PS/HA process were thereby proposed. This study highlights the applications of CuFeS2/PS/HA process for the remediation of multiple pesticides-polluted wastewaters.

Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure–Activity Relationship

Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure–Activity Relationship

Vanished evaporites, halokinetic structure, and Zn-Pb mineralization in the world-class Angouran deposit, northwestern Iran

The Angouran deposit (19.3 Mt at 23.4% Zn and 4% Pb) is the second-largest Zn-Pb deposit in Iran. The deposit is hosted in a Neoproterozoic−Cambrian marble-schist sequence within a breccia pipe in a domal structure, with sulfide mineralization under low-temperature hydrothermal conditions (<200 ºC). The features of the ore-hosting breccias are similar to known halokinetic diapir breccias in the world but evaporite minerals are subtle. The common types of breccia clasts in the Angouran breccia pipe include a matrix-supported angular clast (float breccia) with highly variable sizes and orientations and exotic volcanic clasts. The volcanic clasts were derived from the underlying Miocene volcanic rocks, evidenced by the consistent petrography and zircon U-Pb ages dated at 20−19 Ma. Abundant smithsonite pseudomorphs after anhydrite and anhydrite inclusions within sphalerite and pre-ore marcasite in the breccia matrix indicate that the breccia pipe contains abundant anhydrite prior to the Zn-Pb mineralization. The enrichment of evaporite is also supported by the occurrence of considerable double-terminated quartz crystals that contain spherical and tabular carbonate inclusions and anomalously high Li, Na, and K concentrations, relatively high B concentration, and high δ18O values (up to 28.3‰). These observations suggest the Angouran deposit formed in a former halokinetic diapir breccia pipe. The halokinetic diapirism was possibly triggered by thrust loading of the marble-schist sequence over the Miocene evaporite beds during the Arabia-Eurasia continental collision. Halokinetic structures elsewhere in the Angouran region warrant this consideration. Most of the evaporite minerals in the breccia pipe were dissolved and replaced before and/or during subsequent Zn-Pb sulfide and smithsonite mineralization events. This study provides a good example for the identification of vanished evaporites, halokinetic structure, and associated Mississippi Valley-type mineralization.

Random forest classification for volcanogenic massive sulfide mineralization in the Rouyn-Noranda Area, Quebec

Random forest (RF) classification was applied to 37 predictor maps (vectors to mineralization) producing a Mineral Prospectivity Map (MPM) for volcanogenic massive sulfide (VMS) mineralization in the Noranda District, Abitibi subprovince, which is host to ∼ 20 VMS deposits and numerous subeconomic occurrences. The predictor maps were created using geological, geochemical, and geophysical data, and the known VMS deposits were used to train the RF classifier. The RF model was applied on two regions of interest (ROI) to investigate the effect of different sized ROIs on the results. Five sets of balanced and unbalanced training data were used in the experiments to examine the sensitivity of RF to different sets of training data. The probability/prospectivity maps showed very high success rate of classification with regard to training data particularly for the training sets with higher ratio of non-deposits/deposits. Accuracy assessment of classification maps using cross-validation also showed very high accuracy when assessed by the training data in all experiments again giving a higher accuracy for the training sets with higher ratios of non-deposits/deposits, however the later showed very low accuracy when applying k-fold cross-validation or when assessed by 15 VMS showings used as the test data indicating an overfitting problem with the unbalanced data. In most of the experiments, principal component 4 (PC4) of geochemical analysis, proximity to synvolcanic tonalite-trondhjemite-granodiorite (TTG) intrusions, lithology, and sericite alteration maps showed higher predictive power. The importance of individual variables changed when the ROI was changed to a smaller area suggesting that RF is sensitive to the study area.

Column Bioleaching of Nickel from Sulfidic Samples with Different Nickel and Magnesium Content

Nickel is a valuable metal that is becoming more prevalent in the industry. Column bioleaching was used in this study to extract nickel from magnesium-bearing sulfide minerals. Two different sulfidic samples with different nickel and magnesium content were utilized to investigate the performance of column bioleaching. It was discovered that mesophilic cultures’ adaptation is delayed by increasing magnesium contents. Bioleaching outperformed leaching in terms of recovery by 80% compared to 50% in sample 1 and 70% compared to 40% in sample 2. Jarosite is precipitated in samples with a high magnesium content due to the high pH and oxidation level, which lowers bioleaching effectiveness. The pretreatment method using acid washing before the start of bioleaching treatment can reduce the amount of magnesium in samples, which increases the Ni recovery in both samples. SEM analysis was performed on each bioleaching residue. The result showed that high amounts of magnesium in the second sample could be a factor in the precipitation of jarosite. Finally, it can be concluded that the pretreatment method is a feasible Bio-heap operation.

The Mineral Chemistry of Magnetite and Its Constraints on Ore-Forming Mechanism in the Sandaozhuang Skarn-Type W-Mo Deposit in East Qinling, China

The Sandaozhuang super-large W-Mo deposit is located in the southern margin of the North China Craton, within the well-known East Qinling Mo mineralization belt, and is one of the typical skarn-type W-Mo deposits in China. Based on EMPA and LA-ICP-MS analyses, major and trace elements were presented, and the mineral chemistry of magnetite at various mineralization stages was discussed. Combining field observations, petrography, and geochemical characteristics, the magnetite at the Sandaozhuang deposit can be classified into three types, namely early-magmatic-stage high-temperature magnetite (Mag1), potassic-alteration-stage magnetite (Mag2), and retrograde-alteration-stage magnetite (Mag3). The Mag1 and Mag2 magnetites primarily occurred in granites in association with potassium (K) feldspar and biotite, whereas Mag3 is associated with metallic sulfide minerals that occurred mainly in vein-like structures in skarn. The three magnetites Mag1, Mag2, and Mag3 can be distinguished as having magmatic, magmatic–hydrothermal transition, and hydrothermal origins, respectively. All three types of magnetite exhibit a depletion of high-field-strength elements (HFSEs) such as Zr, Hf, Nb, Ta, and Ti, and large-ion lithophile elements (LILEs) including Rb, K, Ba, and Sr, compared to the mean continental crust composition. Conversely, they are enriched in elements such as Sn, Mo, V, Cr, Zn, and Ga. Mag3 showed no significant depletion of Co, Ni, Cu, and Bi, indicating that the influence of coexisting sulfides on the composition of magnetite at the Sandaozhuang deposit is limited. There are systematic variations in major and trace elements from Mag1 to Mag3, which exhibited similar patterns in trace element spider and rare earth element diagrams, and Y/Ho ratio, indicating a consistent source for the three types of magnetite. The changes in V and Cr contents and (Ti + V) vs. (Al + Mn) diagram of magnetite at the Sandaozhuang deposit reflected the evolution of ore-forming fluids with an initial increase in oxygen fugacity and a subsequent decrease, as well as a gradual decrease in temperature during skarn mineralization. The early high-temperature and high-oxygen-fugacity magmatic fluids became W and Mo enriched by hydrothermal fluid interaction. The rapid change in fluid properties during the retrograde alteration stage led to the precipitation of scheelite and molybdenite.

Expression, Purification and Characterization of a Novel Rusticyanin from the Psychrotolerant Acidithiobacillus ferrivorans

Rusticyanin plays a crucial role in ferrous oxidation of sulfide minerals during bioleaching for industrial metal extraction. Diverse isoforms of rusticyanin have been found, but until now, except for type-A rusticyanin, other isoforms or sources of rusticyanin have been scarcely investigated. Here, a rusticyanin (gene locus 0470) from the psychrophilic Acidithiobacillus ferrivorans was gene-cloned, expressed, purified, and assembled in vitro. All forms of the protein exhibit extreme acid stability, even at pH 0.3. The stability of the protein is obviously enhanced after binding of the copper cofactor; the oxidation state is more stable than the reduced state. The protein has characteristic UV-vis peaks and EPR signals similar to type-A or type-B rusticyanin but is different with a small position shift and an obvious intensity change. The vibrational spectrum of the apoprotein was more different than these between the oxidation and reduced states of the protein. The ferrous oxidation kinetic rate constant of the protein is obviously faster than that of both the type-A and type-B rusticyanins previously reported. Further bioinformatics analysis reveal their changes in sequence and molecule: the mutations related to the peculiar shield belt mostly account for the variation in the properties of the protein, and the classification of the protein as a new isoform, type-C rusticyanin, is proposed.

Sulfidic schist release of As, Cu, and Pb in laboratory experiments and across eleven watersheds in central Massachusetts, USA.

Sulfidic schists are important rock formations due to their trace metal and metalloid (TMM) content and carry the potential for pyrite and pyrrhotite to hydrate and oxidize leading to acid-enhanced chemical weathering. The objectives of this study were to compare TMMs in sulfidic schists to other co-occurring bedrock, evaluate conditions that optimize TMM rock weathering, and examine streamwater TMMs in relation to bedrock lithology and human development in eleven streams across central Massachusetts. Sulfidic schists samples had the highest As (72 ± 46mgkg-1), Cu (63 ± 21mgkg-1), and Pb (63 ± 33mgkg-1) concentrations. Electron Probe Microanalysis (EPMA) images show As and Pb were widely distributed across silicate and sulfide minerals in both the mica schist and sulfidic schists, not exclusively hosted in sulfide minerals as hypothesized. Batch reactors had TMM dissolution rates an order of magnitude higher for sulfidic schists than granite and mica schists. Furthermore, TMM dissolution was greatest under pH 9 than pH 7 or pH 5 and dissolution rates were two times greater under anoxic conditions compared to oxic conditions. Streamwater concentrations of As (0.01 to 10.3μg L-1), Cu (0.2 to 206μg L-1), and Pb (0.001 to 8.3μg L-1) were below Massachusetts Surface Water Quality Standards. Across the eleven watersheds, % sulfidic schists were positively correlated with mean streamwater S and Cu concentrations and area-normalized annual export. Streamwater As and Pb concentrations were significantly correlated with %Developed land and %Mica schist, which strongly covaried. Our study confirmed the elevated abundance of TMMs in sulfidic schists but laboratory experiments suggest the precipitation of amorphous Fe oxyhydroxide phases decreased dissolved TMMs during oxic weathering. Future work will need to incorporate groundwater and stable isotope systems to separate anthropogenic and geogenic analyses.

A nanoparticle cationic polystyrene-co-poly(n-butylacrylate) collector to eliminate the negative effect of lizardite slimes in pyrite flotation

Lizardite slime coating is one of significant factors in the deterioration of the floatability of sulphide minerals. In this study, a nanoparticle cationic polystyrene-co-poly(n-butylacrylate)(PS-PBNH) collector was introduced to eliminate the negative impact of lizardite slimes in pyrite flotation. Microflotation results demonstrated that lizardite slims did not affect the recovery of pyrite in the presence of PS-PBNH. Good flotation separation of pyrite from lizardite was achieved when the nanoparticle PS-PBNH collector was used. The results from adsorption study indicated that PS-PBNH exhibited a significant adsorption on the pyrite surface in the presence of lizardite slimes. Sedimentation tests showed that hetero-aggregation occurred between lizardite slimes and pyrite, whereas the introduction of PS-PBNH collector resulted in a heterogeneous dispersion between them. Zeta potential measurements suggested that PS-PBNH collector interacted with pyrite surface, and the PS-PBNH adsorption changed the surface charge of pyrite from negative to be positive. As a result, the interaction of pyrite with lizardite shifted from electrostatic attraction to electrostatic repulsion, as supported by the DLVO calculations. These results indicated PS-PBNH can be used as a potential collector for pyrite flotation in pyrite/lizardite slimes system without the need for a depressant.

Genetic Engineering of Acidithiobacillus ferridurans Using CRISPR Systems To Mitigate Toxic Release in Biomining.

Biomining processes utilize microorganisms, such as Acidithiobacillus, to extract valuable metals by producing sulfuric acid and ferric ions that dissolve sulfidic minerals. However, excessive production of these compounds can result in metal structure corrosion and groundwater contamination. Synthetic biology offers a promising solution to improve Acidithiobacillus strains for sustainable, eco-friendly, and cost-effective biomining, but genetic engineering of these slow-growing microorganisms is challenging with current inefficient and time-consuming methods. To address this, we established a CRISPR-dCas9 system for gene knockdown in A. ferridurans JAGS, successfully downregulating the transcriptional levels of two genes involved in sulfur oxidation. More importantly, we constructed an all-in-one CRISPR-Cas9 system for fast and efficient genome editing in A. ferridurans JAGS, achieving seamless gene deletion (HdrB3), promoter substitution (Prus to Ptac), and exogenous gene insertion (GFP). Additionally, we created a HdrB-Rus double-edited strain and performed biomining experiments to extract Ni from pyrrhotite tailings. The engineered strain demonstrated a similar Ni recovery rate to wild-type A. ferridurans JAGS but with significantly lower production of iron ions and sulfuric acid in leachate. These high-efficient CRISPR systems provide a powerful tool for studying gene functions and creating useful recombinants for synthetic biology-assisted biomining applications in the future.

3D Inversion of Gravity and Aeromagnetic Data over the Western North Singhbhum Mobile Belt, Eastern Indian Shield, for Delineating Prospective Sulfide (Au) Mineralization Zones

3D Inversion of Gravity and Aeromagnetic Data over the Western North Singhbhum Mobile Belt, Eastern Indian Shield, for Delineating Prospective Sulfide (Au) Mineralization Zones

A study on the desulfurization of sulfidic mine tailings for the production of a sulfur-poor residue

The mining industry generates large amounts of tailings every year. The most common destination for the tailings is deposition in tailings storage facilities (TSFs), which can have enormous dimensions. The management and storage of such large volumes of material pose many challenges in terms of dam stability and immobilization of hazardous contaminants that represent human-health and environmental risks, particularly for sulfide-containing materials. In addition, considerable amounts of precious and base metals can be lost in the tailings. Due to the economic value and growing industrial demand for precious and base metals, tailings may therefore be potential sources of secondary raw materials. This contribution investigates the flotation of pyrite-rich tailings, containing residual chalcopyrite, galena, and sphalerite, and high amounts of ultrafine particles. Flotation was used to recover the sulfide minerals and generate tailings with low sulfur content. The Cu-Pb-Zn-rich product could go to further treatment (e.g. (bio)hydrometallurgy) to recover the metals, while the low sulfur fraction could be used in the civil construction industry. Automated mineralogy (MLA) was used to provide quantitative mineralogical and textural data. Bench-scale experiments were performed by combining classic flotation and floc flotation (flotation of flocs of targeted minerals). Flotation of the material as received, as well as after classification into two fractions was performed. The samples as received and the coarser fraction (+37 µm) underwent classic flotation, while the finer fraction (−37 µm) was processed either by using the classic or the floc flotation approach. The flotation of the coarser particles provided higher sulfide recoveries, higher combined Cu-Pb-Zn grades in the concentrate (3.66%), cleaner residues (1.6% S), faster flotation rates, and reduced reagent consumption. Likewise, the results from the fine particle flotation allowed lower S content in the residues (3.4% S) as compared to the flotation of the original material. The results of the use of floc flotation for the finer fraction show an increase in the mass pull with a slight increase in the recovery of sulfides. Overall, the development of a route to process the tailings proved to be promising and the use of a two-route approach indicates advantages as compared to a single route.

Bioleaching of polymetallic sulphidic mining residues: influence of increasing solid concentration on microbial community dynamics and metal dissolution

Within the European research project NEMO, a bioleaching strategy was developed for efficient metal extraction from bioleach residue currently heap-leached at Sotkamo (Finland) that still contains sulphidic minerals and valuable metals (Ni, Zn, Co, Cu). The strategy of gradually increasing the solid content with 5% steps allowed the adaptation of the consortium up to 20% (w/w) solid content, with efficient metal dissolution and same dominant bacteria. Largest proportions of Sulfobacillusthermosulfidooxidans while Eh increased suggested it to be most involved in iron oxidation. Acidithiobacilluscaldus was rather found when pH stabilized, in line with a production of protons from sulphur oxidation that maintained low pH. ‘Acidithiomicrobium’ P2 was favoured towards the end of the runs and at 20% (w/w) solids possibly due to its tolerance to Ni. The use of gene abundance to evaluate biomass in the pulp provided complementary results to classical cell counts in the liquid phase, and suggested a key role of bacteria associated to mineral particles in iron oxidation. Scaling-up in 21-L stirred-tank reactor at 20% (w/w) solids had no detrimental effect on bioleaching and confirmed metal extraction rates. ‘Acidithiomicrobium’ P2 and Sb. thermosulfidooxidans remained main actors. However, the biological activity was considerably reduced at 30% (w/w) solid concentration, which may be due to a too drastic environmental change for the bacteria to adapt to higher solid concentration. Efficient bioleaching of Sotkamo bioleaching residue at high solid concentration was demonstrated, as well as the robustness of the selected moderately thermophilic consortium, at laboratory and pilot scales.

Geochemistry of Cryogenian Datangpo manganese deposits in the southeastern Yangtze Platform of South China: implications for the origin of metallogenesis and depositional environment

ABSTRACT Sedimentary manganese (Mn) deposits in the southeastern Yangtze Platform of China have been newly discovered with considerable potential for resource exploration. Such deposits formed due to dynamic changes in the global environment, including the break-up of the supercontinent Rodinia, Snowball Earth glaciation, and the Neoproterozoic Oxygenation Event. The Mn-bearing sequences are hosted in the basal Datangpo Formation and are interbedded with black carbonaceous shale in a series of graben sub-basins in the Nanhua Rift Basin. We investigated the origin of these Mn deposits by analysing the major and trace elements, total organic carbon, and stable carbon and oxygen isotopes. Positive Eu anomalies were observed, indicating that the Mn was derived from a hydrothermal system. Redox-related elements, including Ce, Mo, U, V, S, and P, indicated that the depositional environment of the Mn layers was oxidative and that Mn2+ was initially oxidized to Mn oxides. However, the host rock (i.e. black carbonaceous shale) was deposited under dysoxic – anoxic and even sulfidic water conditions. The alternating distribution of Mn ore and host rock suggested alternating redox conditions in the sub-basins. A negative correlation between the Mn content and δ 13Ccarb values (−10‰–−7‰) and a deficiency of sulphide minerals indicate that the diagenetic degradation of organic matter (δ 13Corg from − 34‰ to − 31.9‰) took place through Mn oxide reduction rather than microbial sulphate reduction and can contribute to a considerable source of bicarbonates. The approximately homogeneous δ 13Ccarb depletion and their apparent discrepancy with δ 13Corg indicate that the post-depositional genesis of the Mn carbonate ore occurred in a relatively open early diagenetic pore water system with a considerable contribution from seawater-derived carbon sources.

Spatial distribution of rock uplift in the Bongarà district (Peruvian Andes) and implications for the genesis of supergene ore deposits

Topography and river landscape morphometry of two hydrographic basins, the Utcubamba River and the Chiriaco River basins (Bongará district, Amazonas region) allowed to determine the relationship between the irregular distribution of vertical motions (e.g., rock uplift) and the genesis of supergene Zn deposits. The latter derives from variable weathering of pre-existing carbonate-hosted Zn sulfides orebodies, in three distinct localities: Florida Canyon, Mina Grande and Cristal. The research was carried out through the evaluation of the parameters such as elevation, local relief, swath profile, river longitudinal profiles and transformed river profiles (χ-long profiles), and slope/area analysis to derive the normalized channel steepness index (ksn). The NE-ward sharp increase in mean and minimum elevation coupled with a jump in the mean ksn values, suggests that the Chiriaco River basin has experienced more recent rock uplift than the Utcubamba River basin. In fact, the Utcubamba River experienced a long-lasting uplift, resulting in a rugged local relief and lowering the mean and minimum elevations, and exhumation and weathering of the Triassic-hosted sulfide mineral deposits at Florida Canyon. In the Chiriaco River basin, the younger uplift has promoted the weathering of the more surficial Jurassic-hosted Mina Grande and Cristal mineral deposits. The morphometric approach proved to be effective in recognizing fertile areas with near-surface orebodies also in regions characterized by distinct types of ore deposits.

Biostratigraphic and structural research in the Guedelhinha–Lançadoiras–Algaré sector in the context of the geology of the Neves–Corvo mine region, Iberian Pyrite Belt

Based on drill hole sampling and sedimentary rock dating by palynology, the present research focuses on the palynostratigraphic events established in the key geological section of Guedelhinha–Lançadoiras–Algaré located in the Portuguese Neves–Corvo mine region, Iberian Pyrite Belt. The age data allow detailing the lithostratigraphic sequence and further understanding the complex structural setting, representing an important contribution to the geological knowledge of this sector located to the immediate WNW of the Neves–Corvo VMS deposit. The combination of the studied events allows the reconstruction of the Devonian-Carboniferous sedimentation and paleoenvironments along the Iberian Pyrite Belt. Several stratigraphic hiatuses identified in the Neves–Corvo region by the palynological record are confirmed, mainly occurring from the mid Frasnian to mid Famennian, from the early and mid Strunian, and from the early to late Tournaisian, which were mainly coincident with the worldwide extinction events, in particular during Frasnian–Famennian and Late Devonian times. Extensional tectonics and related gravitational faults, local uplift mechanisms and intense volcanic activity could also explain the lack of palynological data and sedimentary hiatus. In this research, the importance of the late Strunian times in the Iberian Pyrite Belt (Miospore Biozone LN of the Neves Formation) is highlighted, confirming the contemporaneity of felsic volcanism, hydrothermalism, sulphide mineralization precipitation and black shale anoxic sedimentation.

Geochemical and mineralogical evaluations of coal, shale, and mine waste overburden from Makum coalfield of the Northeast India

The Cenozoic-age Makum coal from northeastern India offers numerous research opportunities because of its diverse geochemical and geological characteristics. Due to its high sulfur content, the coal has been found to be less useful for industrial purposes. It can, however, serve as a hub for ongoing research on coal-based derivative products. The aim of this research work is to investigate the mineralogical and geochemical compositions of the coal, mine overburden (MOB) and shale samples taken from the Makum coal field and also on establishing a mutual relationship between them. To characterize the geochemical controlling factors of the Makum coal field, the study employs coal petrography, FTIR, mineralogical, and geochemical analysis. According to X-ray diffraction analysis, the major minerals like quartz, kaolinite, haematite, illite, pyrite, and calcite are present in coal and MOB. Pyrite is observed by SEM–EDS analysis as cubic-shaped particles that are smaller than a few µm in size. The presence of sulfide minerals represents a phase of pyrite mineralization. The petrography study was used to better understand the environment that existed during the formation of the plant material, which aids us in determining the quantity of detrital mineral sediment contained in the coal. According to the ICP-MS analysis, the samples indicate significant levels of rare earth elements including yttrium. The present study reveals higher concentrations of potential hazardous elements in the coal samples, with V, Cr, Ni, Cu, and Zn content in coal being considerably enriched compared to world-average concentrations. The correlation analysis reveals that the potential hazardous elements like Co, Ni, As, and Cu are associated with pyrite as they have strong affinity towards pyrite. Thus, numerous minerals and rare earth elements (REEs) exist, opening up a fresh avenue for more research in the area. This study also assists researchers in understanding the significance of Makum coal and provides numerous ideas for coal characterization.

Pathfinder elements and indicator minerals of Au from the Kubi Gold ore deposits in Ghana

The Au mineralization in the Kubi Gold Mining Area in the Birimian of Ghana is associated with garnet (about 85 vol.%), magnetite, pyrrhotite, arsenopyrite, and sulfide minerals, as well as quartz with gold and calcite. These minerals and the included elements can act as indicator minerals or pathfinder elements. For the present work, we collected samples from drill holes at different depths, from the alluvial zone (0–45 m) to the ore zone (75–100 m). The distributions of minerals and elements in the rocks that act as indicator minerals and pathfinder elements in the concession area were investigated along the drill hole cross sections. X-ray diffraction shows that the samples contain garnet, pyrite, periclase, and quartz as the main indicator minerals. By energy-dispersive X-ray spectroscopy, Fe, Mg, Al, S, O, Mn, Na, Cu, Si, and K are identified as corresponding pathfinder elements. The results indicate that the Au mineralization in the Kubi Mine area correlates mostly with the occurrence of garnet, pyrite, goethite, and kaolinite in the host rocks, which show towards the surface increasingly hematitic and limonitic alteration in form of Fe(oxy-)hydroxides.

Selective depression of pyrite with a novel thiocarbonate in a pyrite-galena flotation system

Eco-friendly depressants suitable for industrial applications are required for the mineral processing industry to achieve sustainable production and environmental protection. Herein, a novel micromolecular organic reagent, sodium O-(2,3,4,5,6-pentahydroxyhexyl) carbonodithioate (SPHC), was synthesised and employed as a selective depressant for pyrite in the flotation separation of bulk galena/pyrite concentrate. Micro-flotation tests demonstrate that SPHC exhibits superior selectivity and depressing ability on pyrite. The adsorption amount of SPHC on the pyrite surface is significantly higher than that on galena in a wide pH range of 4–12, indicating the greater affinity of SPHC on pyrite than on galena. Cyclic voltammetry measurements reveal that SPHC can selectively adhere to the pyrite surface to form hydrophilic products and thereby decrease its floatability. By contrast, the adsorption of SPHC on the galena surface is low and hence its surface hydrophobicity is not altered noticeably. Even in the presence of pre-adsorbed xanthate molecules, the adsorption behaviour of SPHC on both mineral surfaces is hardly affected. Thus, the studied organic depressant not only is an effective depressant for the separation of galena and pyrite but also a promising candidate reagent for the flotation separation of pyrite from other sulphide minerals.

Simultaneous extraction of copper and iron from chalcopyrite concentrate via surfactant-assisted chlorination leaching

Among several non-ferrous metals, copper is a vital metal having wide industrial applications and is mainly found to be associated with sulfides. Numerous pyro- and hydro-metallurgical processes were developed to extract copper from such sulfide minerals. However, due to dwindling grades of copper ore, hydrometallurgical methods are being increasingly used and gaining popularity. High temperature-based oxidation-leaching techniques are usually adopted, while higher recovery of copper at ambient temperature is still challenging. In this regard, an attempt has been made to develop a low-temperature chlorine gas leaching process to maximize copper dissolution from sulfides ores. In this work, chalcopyrite leaching was carried out in the presence of gaseous chlorine in an aqueous solution within the temperature range of 278 K to 293 K and atmospheric pressure. Low-temperature leaching with chlorine gas is found to be more efficient as compared to oxidative leaching processes. However, the challenge is to overcome the slow leaching kinetic caused by passivation. An attempt has been made to address this problem by using a strong oxidizing agent (Cl2 gas) in this study. Surfactant-mediated-chlorine leaching further improves the recovery as it helps to overcome the passivation issue by dispersing the elemental Sulphur. Tri-chloro-ethylene (C2HCl3) (TCE) has been used as an ‘S’ dispersant. Various process parameters, such as solid-to-liquid ratio, gas flow rate, and leaching temperature, were studied and optimized. The recovery of copper was found to be only 70% at 285 K without any surfactant addition, whereas it will increase to 94.8% after the addition of only 2% (v/v) tri-chloro-ethylene (TCE).