Formation Of Elemental Sulfur Research Articles

The Dissolution Behavior of Pyrite and Chalcopyrite During Low-Temperature Pressure Oxidation: Chalcopyrite Influence on Pyrite Oxidation

The research of this paper was carried out on the low-temperature (100 ± 2 °C) pressure (0.2–0.8 MPa) leaching of pyrite, chalcopyrite and their mixture. According to experiments on chalcopyrite dissolution, increasing the oxygen pressure from 0.2 up to 0.8 MPa had a slight effect on chalcopyrite dissolution. Oxygen pressure and initial sulfuric acid concentration in the range of 10–50 g/L had the greatest positive effect on the pyrite oxidation. The SEM and EDX mappings indicate the chalcopyrite and pyrite surfaces to be passivated by elemental sulfur. The oxidation degree of pyrite in its mixture with chalcopyrite increased significantly from 54.5 up to 80.3% in 0–240 min. The reaction time is relative to the dissolution of the individual mineral, while the dissolution of chalcopyrite remained virtually unchanged. The addition of Cu (II) and Fe (III) ions does not influence pyrite dissolution when chalcopyrite is added in a leaching process, which can be explained by the formation of an electrochemical link between the minerals. The positive effect of chalcopyrite addition is associated with a decreased formation of elemental sulfur on the surface of pyrite. The described method can be used for the hydrometallurgical processing of copper raw materials with increased pyrite content, as well as for the pretreatment of copper concentrates with gold-rich pyrite concentrates to increase the recovery of gold and silver.

Photocatalytic Generation of Carbocation from Thiols and Application to Cross-Nucleophile Coupling.

Represented herein is a simple thiol identified as an effective precursor to photochemically form a carbocation. Thanks to the thiyl radical rapid transformation to disulfide, which serves not only to stabilize the generated thiyl radical but also to allow the second electron transfer to form a carbocation. The resulting carbocations, including primary benzylic, secondary, and tertiary carbocations, can smoothly couple with nitrogen, oxygen, and carbon nucleophilic coupling partners as well as complex drug molecules, accompanied by elemental sulfur formation in air.

Authigenic carbonate and native sulfur formation in Messinian (upper Miocene) marine sediments: Sedimentological, petrographical and geochemical constraints

Carbonate concretions accompanied by elemental sulfur were found in an early Messinian (Late Miocene) marine succession of NW Italy. The rocks were studied with an integrated approach including sedimentological, petrographical, stable isotope (carbon, oxygen, and multiple sulfur isotopes), and lipid biomarker analyses. Unlike other examples from Messinian strata of the Mediterranean area, the studied carbonate and sulfur concretions did not derive from the diagenetic replacement of sulfate minerals. Three lithofacies were distinguished: a) laminated lithofacies representing aphotic carbonate stromatolites enclosing fossils of filamentous sulfide-oxidizing bacteria; b) brecciated lithofacies deriving from the brecciation of carbonate stromatolites by mud injections; c) sulfur-bearing lithofacies deriving from the precipitation of thin laminae of elemental sulfur at or close to the sediment-water interface. The carbon and oxygen stable isotope composition of authigenic carbonate minerals and lipid biomarkers indicate that the initial formation of the laminated lithofacies was favored by organoclastic sulfate reduction in the shallow subsurface close to the sediment-water interface, producing sulfide that sustained dense microbial mats of sulfide-oxidizing bacteria at the seafloor. Calcification of the mats and consequent formation of stromatolites were possibly favored by nitrate-driven sulfide oxidation at the seafloor. The subsequent brecciation of the stromatolites was apparently the consequence of sulfate-driven anaerobic oxidation of methane (SD-AOM) in an underlying sulfate-methane transition zone (SMTZ). Focused fluid flow from below, possibly resulting from destabilization of gas hydrates, was not only responsible for the brecciation of the stromatolites, but also for the delivery of bicarbonate ions and the consequent precipitation of additional, 13C-depleted calcite (δ13C values as low as −52‰). Along with bicarbonate, also hydrogen sulfide was produced by SD-AOM at the SMTZ and was transported upwards. The oxidation of hydrogen sulfide at or close to the seafloor promoted the formation of elemental sulfur characterized by δ34S values and Δ33S values close to coeval seawater sulfate.

Cu-MOF-derived Cu nanoparticles decorated porous N-doped biochar for low-temperature H2S desulfurization

Hydrogen sulfide (H2S) is a highly toxic and corrosive gas that poses significant risks to human health and the environment. Therefore, the development of an adsorbent capable of efficiently purifying H2S at room temperature remains a challenging task. In this study, a novel composite adsorbent with a specific surface area of 434 m2·g−1 was fabricated by modifying porous N-doped biochar with Cu nanoparticles (Cu/NBC) derived from Cu-MOFs for low-temperature desulfurization of H2S. The effect of pyrolysis temperature and the doping ratio of Cu-MOFs to biochar on the desulfurization performance of H2S for the as-prepared Cu/NBC was comprehensively investigated. Experimental results indicated that the desulfurization capability of the optimized Cu/NBC-600-1 adsorbent (synthesized at a pyrolysis temperature of 600 °C and a doping ratio of 1:1) was significantly affected by the desulfurization conditions, and the optimal conditions were determined to be at 25 °C, with 20 % oxygen content and 70 % relative humidity. Under the optimized conditions, the Cu/NBC-600-1 adsorbent exhibited a high H2S removal capacity of 158.28 mg·g−1, which was about 3.8 times higher than that of the pristine N-doped biochar. The desulfurization mechanism of the Cu/NBC composite was demonstrated to involve reactive adsorption and catalytic oxidation, resulting in the formation of elemental sulfur and copper sulfides as the main products. This study not only provides a promising approach to modify porous biochar with MOF derivatives, but also offers an effective strategy to remove low concentration H2S at room temperature.

New insight and countermeasure for sulfur poisoning on nickel-based catalysts during dry reforming of methane

Dry reforming of methane (DRM) is the method to convert two greenhouse gases to synthesis gas. The nickel-based catalysts used in the DRM are extremely easily poisoned by H2S in the feed gas, however, the associated poisoning process is not clear. In this work, a mechanism for poisoning the Ni/Al2O3 catalyst by elemental sulfur migration was proposed, and silica was added to the catalyst to prolong the sulfur tolerance of the catalyst. From the characterizations of the catalyst with different methods, it was noted that the main factor accelerating catalyst poisoning was the formation and migration of elemental sulfur. The catalyst Ni/Al2O3 with 1.0 % SiO2 exhibited improved sulfur tolerance. The addition of SiO2 inhibits the growth of Ni particles during the reduction process, and the smaller Ni particles lead to less coke and a longer period of sulfur tolerance.

Preparation of nitrogen-doped activated carbon used for catalytic oxidation removal of H2S

In this study, nitrogen-doped modified activated carbons were synthesized for H2S removal from Zhuxi activated carbon and 4,4′-bipyridine as raw material and nitrogen source, respectively. The synthesis strategy was hydrothermal treatment and subsequent NH3 annealing, and the formation and conversion patterns of the different N configurations were investigated. When the annealing temperatures were 500 °C and 600 °C, N-5 account for the majority. As the annealing temperature increased, the proportion of N-6 gradually increased. After the temperature increased to 1000 °C, N-5 and N-6 were converted to N-Q to a certain degree, while the amount of nitrogen doping decreased significantly. The sample H160-0.2-800 exhibited excellent H2S removal with a high sulfur capacity of up to 206.89 mg/g, significantly higher than that of the original activated carbon ZX1200 (67.56 mg/g). The reason for this is that the micropores (Vmic = 0.5155 cm3/g) and specific surface area (SBET = 1369.5 m2/g) of the modified activated carbon are more developed than those of the original activated carbon. A high nitrogen content (3.14 wt%) and N-6 configuration proportion (73.56 %) are significant reasons for the excellent adsorption properties. The mechanism of the catalytic oxidation was investigated. The introduction of surface nitrogen-containing functional groups alkalizes the activated carbon surface, enhancing the adsorption and dissociation of H2S and O2 and facilitating the formation of sulfur radicals and elemental sulfur.

Investigation of Sulfur Redox Chemistry in MoS2 Anodes for Potassium Ion Battery

Molybdenum disulfide (MoS2) with layered structure composed of molybdenum atoms coordinated with sulfur atoms makes it a suitable intercalation and conversion-based anode material for K-ion batteries (KIBs). But the electrochemical mechanism for K-ion storage in MoS2 remains unclear due to the probable occurrence of both conversion and polysulfide reactions. The formation of elemental sulfur (S0) due to irreversible conversion reaction of MoS2 is predicted to be a contributor for polysulfide reactions. Hence, in this study we utilised commercially available MoS2 as an anode for KIBs and studied the electrochemical performance by controlling the depth of discharge in the first cycle. It is identified that K-ion storage mechanism in MoS2 differs widely by operating at different discharge voltages. As a result, the characteristic voltage profile differs from the subsequent cycle, signifying dissimilar reaction pathways. Our results suggest that by controlling the depth of potassiation in MoS2, sulfur redox reactions co-exist along with conversion reaction. The existence of Mo metal and sulfur in the charge state is confirmed from various ex-situ spectroscopy studies. Moreover, formation of potassium polysulfides in the discharge state also strongly confirms the occurrence of sulfur redox reactions. Due to the dual reaction pathways, K-ion storage capacity is boosted up to 256 mAh g-1 and 93 mAh g-1 at 0.03 and 2 A g-1, respectively. The dual reaction also stabilizes the structure, which helps to attain a capacity retention of 84 % and 58 % after 500 and 1000 cycles, respectively. This study provides a mechanistic insight into the reaction pathway of K-ion storage in MoS2 when operating at various potential windows. Also, it may provide reference to utilising metal sulfides as a catalytic cathode in metal-sulfur batteries.

The Extraction of Copper from Chalcopyrite Concentrate with Hydrogen Peroxide in Sulfuric Acid Solution

Research on chalcopyrite leaching represents a great challenge, given its importance as one of the most abundant copper minerals and its significant role in global copper extraction. This study aimed to evaluate the effects of different parameters on chalcopyrite leaching by hydrogen peroxide as a strong oxidizing reagent in sulfuric acid solution. A series of leaching tests were carried out to investigate the effect of the solid/liquid ratio, stirring speed, temperature, oxidant and acid concentrations, and lixiviant dosing method on copper extraction from chalcopyrite concentrate. The catalytic decomposition of hydrogen peroxide occurred in the investigated leaching system, as reflected in the obtained metal extraction values. Copper extraction was increased in the first 60 min of the reaction, after which it essentially ceased. The maximum final copper extraction of 64.5% was attained with 3.0 mol/L H2O2 in 3.0 mol/L H2SO4 at a temperature of 40 °C after 120 min of reaction. Due to the catalytic decomposition of hydrogen peroxide in the examined leaching system, the leaching experiment was performed with the periodic addition of lixiviant at specific time intervals as well. The dissolution process was described by the first-order kinetics equation with an apparent activation energy of ~39 kJ/mol. Finally, XRD and SEM-EDS analyses were used to characterize the leached residue, and the results showed that the formation of elemental sulfur on the chalcopyrite surface affected the dissolution process.

(Electro)catalytic oxidation of sulfide and recovery of elemental sulfur from sulfide-laden streams

MnxOy coated over TiO2 nanotube array substrate was doped with Mo and polyaniline (PANI) and applied for electrochemical desulfurization of concentrated sulfide (HS−) solutions at basic pH, typical of biogas scrubbing solutions and industrial wastewater. Mo and PANI co-dopants significantly enhanced the anode activity towards sulfide oxidation and ensured its complete stability even in highly corrosive sulfide solutions (e.g., 200 mM HS−). This was due to the increased electrochemically active surface area, improved coating conductivity and reduced charge transfer resistance. The (electro)catalytic oxidation of HS− demonstrated robust performance with very limited impact of different operational parameters (e.g., dissolved oxygen, anode potential, HS− concentration). Due to the formation of elemental sulfur (S0) layer at the anode surface at basic pH, longer term anode usage requires its periodic removal. Chemical dissolution of S0 with toluene allows its rapid removal without affecting the anode activity, and easy recrystallization and recovery of pure sulfur.

Evaluation of the effects of L-cysteine addition on the bioleaching of zinc and cadmium from sphalerite flotation concentrate

The primary zinc ore in the world is sphalerite, and roasting-leaching-electrowinning (RLE) is the most typical method of processing. This method has different disadvantages, and bioleaching is an alternative and eco-friendly method for sphalerite treatment. The major drawback of bioleaching is its slow kinetics. In this study, an evaluation of the effects of L-cysteine addition on the bioleaching of zinc and cadmium from a concentrate of sphalerite was investigated in the presence of mixed cultures of mesophilic and moderately thermophilic microorganisms. The results showed that L-cysteine addition increased the dissolution rates of zinc and cadmium while reducing them at higher concentrations. The optimal conditions were achieved by using 0.1 g/L of L-cysteine in mesophilic cultures with zinc recovery of 73.92% and cadmium recovery of 81.45%, respectively. Similarly, zinc recovery was 92.54% in thermophilic cultures, while cadmium recovery was 88.66%. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analyses have detected the formation of jarosite and elemental sulfur on sphalerite surfaces in mesophilic conditions, as well as ammoniojarosite and elemental sulfur in moderately thermophilic conditions. Fourier transform infrared (FTIR) spectroscopy was employed to identify molecular structures and functional groups on the surface of bioleached residues in mesophilic and moderately thermophilic conditions. To assess the environmental risk of residues, a combination of synthetic precipitation leaching procedure (SPLP) and toxicology characteristic leaching procedure (TCLP) methods were used.

Biodesulfurizing Microbes in the Petroleum Refinery Areas of Saudi Arabia

Gordonia sp., Rhodococcus, Paenibaccilus, Mycobacterium and many other desulfurizing strains have shown good potential for dibenzothiophene (DBT), 4, 6-Dimethyldibenzothiophene (4-6-Dimethyl dibenzothiophene) and other organosulfur biodesulfurization. These are microbes which have 4S pathway to remove S from remaining calcitarant organosulfur compounds even after deep desulfurization. Sulfur compounds present in crude oils, diesel and petrol when combust in engines they emerge out in the form of elemental Sulfur, which causes environmental and health problems. Therefore, efforts are going to remove this Sulfur compounds by Hydrodesulfurization (HDS) treatment. Some organosulfur compounds remain there even after HDS, which can only remove by highly evolved microbes residing nearby petroleum-contaminated areas in refineries zone. Nature has such adopted and evolved microbes for the bioremediation of such toxic substances. Here we have isolated and characterized highly evolved and adopted Biodesulfurizing microbes present around oil refineries in Kingdom of Saudi Arabia and prepare the culture collection of such highly evolved and adopted biodesulfurization microorganisms for future application of applied Industrial petroleum refineries, which can reduce the Sulfur load in the petroleum products. The several (10 different types) microbes have been reported in these soils to grow in sulfur compounds. Out of these microbes one microbe desulfurizes by 4S pathway. It was identified to be Rhodococcus erythropolis type named as Rhodococcus erythroplis KAU10. They show good potential for various organosulfur compounds (DBT, 2,4,6-Trimethyl Benzothiophene, Benzothiophene, Dibenzyl sulfide, Benzonaphthothiophene, Dibenzothiophene sulfone, along with crude oil and Petrol and Diesel. Isolated strain Rhodococcus erythroplis KAU10 have good potential for Biodesulfurization.

Studying the Nature of Light Flashes in the Explosive Oxidation of Hydrogen with SO2

The reaction of hydrogen oxidation with sulfur dioxide in the region of self-ignition (T = 470–510°C and R 200 Torr) is accompanied by the formation of elemental sulfur in an explosive mode. Kinetic calculations made with the SENKIN:CHEMKIN II program are used to analyze observed flashes of light from the explosive process, based on a mathematical model describing the oxidation of hydrogen with sulfur dioxide. Characteristics of the oxidation of hydrogen with sulfur dioxide in the region of a low-temperature chain explosion are revealed.

Receiving of New Carbon-Sulfur-Containing Plastic Lubricants Based on Regenerated Products and Used Sorbents

The work is devoted to the solution of the actual problem of waste management and its use for obtaining useful technical products, in particular, special purpose plastic lubricants. The research has been conducted on the use of spent sorbents after complex adsorption purification of industrial wastewater from Cu2+, S2– and HS–-ions in the composition of plastic lubricants. The composition of the latter includes a solid modified surface of sorbents [(activated carbon + kieselguhr) + CuS + S] and regenerated industrial oil I-40A. High operational properties of plastic lubricants are provided by modification of the solid surface of the components, on which there are active centers for chemisorption. The surface modification of activated carbon has been carried out in order to obtain [Cu(µ-S5)]2 or CuS2 as possible equivalent substitutes for MoS2. It was established that the chemical interaction of the pentasulfide anion and the copper (II) cation ends with the formation of a planar six-coordinated chelate center CuS4(Н2О)2 on the surface, followed by its destruction and the formation of copper (II) sulfide and elemental sulfur. Activated carbon acts not only as a sorbent, but also as an active catalyst of topochemical reactions on a solid surface. Modification of the kieselguhr surface is caused by the presence of active centers on its surface – silanol groups –OH, which are subject to esterification. The developed plastic lubricants provide the necessary operational properties of heat-resistant industrial lubricants.

Research on the Selective Electrocatalytic Reduction of SO2 to Recover S0 by Pb Electrode

Resource utilization of SO2 from flue gas is a key challenge for the green development of the smelting industry. Recovery of sulfur resources in the form of elemental sulfur (S0), which has a high market demand and is a current focus in the field of SO2 treatment, can reduce the solid waste from desulfurization. In this study, it was found that Pb as a cathode material had good catalytic activity for the electrochemical reduction of SO2 and good selectivity towards elemental sulfur. However, the cathode suffers from sulfur poisoning. The problem was resolved by introducing surfactant, specifically sodium dodecyl benzene sulfonate (SDBS), which significantly lowered the sulfur content ratio on the surface of the electrode from 31.82% to 2.17%. Through the optimization of electrocatalytic parameters, this method enables efficient conversion of SO2 to S0, achieving a selectivity of 83% at pH = 0.25 and E = −0.8 V (vs. SCE).

Study of Microbial Sulfur Metabolism in a Near Real-Time Pathway through Confocal Raman Quantitative 3D Imaging.

As microbial sulfur metabolism significantly contributes to the formation and cycling of deep-sea sulfur, studying their sulfur metabolism is important for understanding the deep-sea sulfur cycle. However, conventional methods are limited in near real-time studies of bacterial metabolism. Recently, Raman spectroscopy has been widely used in studies on biological metabolism due to its low-cost, rapid, label-free, and nondestructive features, providing us with new approaches to solve the above limitation. Here, we used the confocal Raman quantitative 3D imaging method to nondestructively detect the growth and metabolism of Erythrobacter flavus 21-3 in the long term and near real time, which possessed a pathway mediating the formation of elemental sulfur in the deep sea, but the dynamic process was unknown. In this study, its dynamic sulfur metabolism was visualized and quantitatively assessed in near real time using 3D imaging and related calculations. Based on 3D imaging, the growth and metabolism of microbial colonies growing under both hyperoxic and hypoxic conditions were quantified by volume calculation and ratio analysis. Additionally, unprecedented details of growth and metabolism were uncovered by this method. Due to this successful application, this method is potentially significant for analyzing the in situ biological processes of microorganisms in the future. IMPORTANCE Microorganisms contribute significantly to the formation of deep-sea elemental sulfur, so studies on their growth and dynamic sulfur metabolism are important to understand the deep-sea sulfur cycle. However, near real-time in situ nondestructive metabolic studies of microorganisms remain a great challenge due to the limitations of existing methods. We thus used an imaging-related workflow by confocal Raman microscopy. More detailed descriptions of the sulfur metabolism of E. flavus 21-3 were disclosed, which perfectly complemented previous research results. Therefore, this method is potentially significant for analyzing the in-situ biological processes of microorganisms in the future. To our knowledge, this is the first label-free and nondestructive in situ technique that can provide temporally persistent 3D visualization and quantitative information about bacteria.

Effects of Nutrients on the Performance of the Biological Sulfur Recovery Unit for Sulfur Removal from Water

The Biological Sulfur Recovery Unit (BSRU) with Thiobacillus as biocatalysts is believed to be suitable for handling soluble sulfur in wastewater. The purpose of this study is to evaluate the effect of nutrient (SO42−, PO43−, and Fe2+) concentration on BSRU performance, particularly on the conversion of sulfide to elemental sulfur. This study shows that the variation of SO42− concentration does not significantly affect the conversion process, while a small increment of PO43− (KH2PO4 1.7 g/L and K2HPO4 1.36 g/L) results in a higher yield of elemental sulfur production. Fe2+ also significantly affected the formation and conversion rate of elemental sulfur.

Study on deposit formation model in sulfide-containing natural gas environment

The breathing pipe of a produced water storage tank in a sulfide-containing natural gas station is prone to deposit formation, which leads to pipeline blockage. In this study, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses of the deposit in breathing pipe show that the deposit is composed of elemental sulfur and corrosion scales of ferrous polysulfide and ferrous sulfate. Existing deposit formation prediction models cannot predict the formation of elemental sulfur and corrosion scales in sulfide-containing environments. Herein, based on thermodynamic models of elemental sulfur and corrosion scale formation, deposit formation models of elemental sulfur, ferrous polysulfide, and ferrous sulfate scale formation are established. It is found that deposition of elemental sulfur and ferrous polysulfide increases with decreasing temperature of the breathing tube. Corrosion of pipe in the precipitating corrosive water leads to higher activity of left[{mathrm{Fe}}^{2+}right] on the inner wall of the pipe carried by the sulfide-containing natural gas. Consequently, ferrous polysulfide and ferrous sulfate are easily deposited when the activity products of ferrous, sulfide, and sulfate ions are higher than the thermodynamic solubility product constant. The aforementioned prediction models are applied to predict the deposition of ferrous polysulfide, ferrous sulfate corrosion scale, and elemental sulfur using the chemical composition data of gas and precipitating water in the breathing pipe of the produced water tank of TB101-X1 well. The prediction results of the models are consistent with those of actual chemical composition analysis, which verifies the accuracy and reliability of the models.

Activating sulfur oxidation reaction via six-electron redox mesocrystal NiS2 for sulfur-based aqueous batteries.

Sulfur-based aqueous batteries (SABs) are deemed promising candidates for safe, low-cost, and high-capacity energy storage. However, despite their high theoretical capacity, achieving high reversible value remains a great challenge due to the thermodynamic and kinetics problems of elemental sulfur. Here, the reversible six-electron redox electrochemistry is constructed by activating the sulfur oxidation reaction (SOR) process of the elaborate mesocrystal NiS2 (M-NiS2). Through the unique 6e- solid-to-solid conversion mechanism, SOR efficiency can reach an unprecedented degree of ca. 96.0%. The SOR efficiency is further revealed to be closely associated with the kinetics feasibility and thermodynamic stability of the M-NiS2 intermedium in the formation of elemental sulfur. Benefiting from the boosted SOR, compared with the bulk electrode, the M-NiS2 electrode exhibits a high reversible capacity (1258mAhg-1), ultrafast reaction kinetics (932 mAh g-1 at 12 A g-1), and long-term cyclability (2000cycles at 20 A g-1). As a proof of concept, a new M-NiS2‖Zn hybrid aqueous battery exhibits an output voltage of 1.60V and an energy density of 722.4Wh kgcath-1, which opens a new opportunity for the development of high-energy aqueous batteries.

Easy Handling Preparation of Cubic Sulfur in Aqueous Extract of Sapindus rarak rinds


 
 
 The aqueous extract of Sapindus rarak (S. rarak) was produced by heating its rinds in demineralized water at 80 °C. The main experiment was conducted at room temperature by mixing a solution of sodium thiosulfate with the extract obtained previously. After adding dilute hydrochloric acid (10%), fine granules gradually formed in the solution and precipitated when the reaction was stopped and allowed to stand for 24 h. The analysis results showed the consistency of the X-ray diffraction (XRD) peak of the obtained material with sulfur standards. When looked at the surface using scanning electron microscopy (SEM), sulfur was found to be cube-shaped. The formation of cuboidal elemental sulfur possibly occurs due to the covering of thiosulfate ions and elemental sulfur during and after the reaction. Organic compounds were found covering sulfur through elemental and functional group analyses using energy-dispersive X-ray (EDX) and Fourier-transform infrared (FTIR) spectroscopy, respectively
 
 

Secondary phase formation during electrokinetic in situ leaching of intact copper sulphide ore

Electrokinetic in situ leaching (EK-ISL) of copper sulphides is a novel mining technology aimed at recovering copper from orebodies without physical excavation, thereby significantly reducing the environmental footprint of the mining operation. Its viability at larger scale is, however, highly dependent on developing a comprehensive understanding of the geochemical processes occurring inside the pore space of the intact rocks during leaching. One of the critical issues affecting the efficiency of copper sulphide leaching operations is the formation of secondary layers. So far, the details of their formation have only been studied under ex situ conditions and for ground samples. Therefore, this study was aimed at a detailed characterisation of the secondary leaching products under EK-ISL induced leaching conditions and how they evolved over time. We conducted time-dependant leaching tests on intact core samples with either ferric chloride or ferric sulphate as lixiviant. SEM-EDS and laser Raman microspectroscopy showed the formation of elemental sulphur as a result of the oxidation of longer-chain polysulphides. The neo-formed phases showed to slow down copper recovery, yet did not completely halt the leaching progress. Our conceptual model of the secondary layer formation suggests that the sustained dissolution of polysulphides during EK-ISL-induced leaching under the induced geochemical conditions exposes new mineral surfaces to attack. Importantly, this creates the opportunity for secondary phase re-solubilisation and therefore enhanced copper recovery.