Leaching Of Sphalerite Research Articles

Experimental and dynamic molecular study of zinc extraction from sphalerite concentrate in ternary deep eutectic solvent

The utilization of deep eutectic solvents (DESs) as a novel class of solvents in metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20–1440 min, 40–100 °C, and 0–24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to improve efficiency substantially. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced zinc efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The sphalerite leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data were in the range of 0.87–0.97 for temperature of 40–100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.

Oxidative Dissolution Process of Sphalerite in Fe2(SO4)3-O3 System: Implications for Heavy Metals Removal and Recovery.

Metal sulfides in waste rocks and tailings are susceptible to serious soil and water contamination due to the generation of acid mine drainage (AMD) during stockpiling. The hydrometallurgical process is one of the most essential heavy metal remediation technologies through harmless disposal and resource utilization of the waste sulfides. However, atmospheric hydrometallurgy of sulfides still faces great challenges due to low leaching efficiency and high cost. In this work, we proposed a cooperative leaching system (Fe2(SO4)3-O3) and investigated the oxidative dissolution process of sphalerite (ZnS). Under the optimal conditions, the extracted zinc reached 97.8%. Reactive oxygen species (ROS) (·OH, 1O2 and ·O2-) were identified in the radical quenching experiments. The dissolution of sphalerite did not show passivation due to the ozone's capability to oxidize the sulfur in sphalerite to sulfate. In addition, stirring rate, O3 inlet concentration, and Fe2(SO4)3 concentration had a significant effect on the dissolution of sphalerite. Meanwhile, the apparent activation energy was 24.11 kJ/mol based on kinetic fitting, which indicated that the controlling step of the reaction was mainly a diffusion process. This work demonstrated the cooperative effect of sphalerite leaching in the O3-Fe2(SO4)3 system and provided a theoretical reference for efficient and atmospheric dissolution of sphalerite.

Sphalerite Leaching in Acid Media: a Review

The reserves of rich ores, from which the production of zinc by the existing conventional roasting-leaching-electrowinning process is technologically possible and economically justified, are decreasing year by year. For this reason, increasing attention has been directed towards researching the possibility of obtaining zinc from complex polymetallic ores with a low metal content, adhering to sustainable development goals following strict environmental regulations. Leaching procedures are commonly utilized for the processing of such mineral raw materials.As sphalerite is the widespread and most significant mineral of zinc sulfide, a large part of the research focuses on studying the behavior of sphalerite in the leaching process. This paper reviews the existing knowledge about the leaching of sphalerite in acidic solutions as well as the phenomena accompanying the dissolution process. Special attention is given to research related to the kinetics and mechanism of sphalerite oxidation in an acidic medium influenced by various oxidants, such as hydrogen peroxide, oxygen, dichromate ions, nitrate and nitrite ions, ferric and cupric ions, and others. All these results enable the development of new technological procedures to produce zinc from low-grade and complex ores while meeting increasingly rigorous environmental requirements.

Optimization of Pyrite Bio-Oxidation to Produce Ferric Reagent for Sphalerite Leaching

Leaching of zinc from sulfide minerals is a subject of considerable interest over the last few years. Ferric solutions were commonly reported to leach base metals sulfide concentrates. The current study investigates the potential of biological ferric solutions for Zn and Pb extractions from a sphalerite concentrate at 65°C. Comparative leaching experiments with ferric sulfate and ferric chloride are also performed. Actually, biological ferric ions have resulted from pyrite bio-oxidation. The aim of this work is to introduce a potential application of this metabolite as a mineral oxidizing agent to recover zinc from the sphalerite concentrate. To produce a biogenic reagent with the highest ferric, the bio-oxidation process is optimized by investigating the effects of different factors including pH, pulp density, and inoculum percent. At the optimum conditions, a metabolite with 7.87 g/L of ferric ions and a pH = 0.98 is produced. The results indicate that pyrite bio-oxidation includes three phases: chemical dissolution, lag phase, and biological dissolution. The scanning electron microscope (SEM) images showed that a layer of crystals was present on the surface of pyrite. Based on energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, this layer is related to the presence of potassium jarosite. The metabolite was then used for ZnS direct leaching and results were compared with sulfide and chloride leaching. The final zinc recoveries with biological ferric ions, ferric sulfate, and ferric chloride were 78.0%, 88.9%, and 85.4%, respectively.

The impact of light on understanding the mechanism of dissolution and leaching of sphalerite (ZnS), pyrite (FeS2) and chalcopyrite (CuFeS2)

A theoretical framework is presented for understanding the interaction of light with the electronic structure of sphalerite, pyrite and chalcopyrite and how these factors affect their rate of dissolution. Their electronic structure gives rise to the colour of these minerals, primarily because of their semiconducting properties. An advanced theory of dissolution is presented that describes how the electronic structure of these minerals also impacts their mechanism of dissolution. This theory is based on the requirement that in order to dissolve these minerals under oxidative conditions, electrons must be removed from bonding orbitals. Since the electrons with the highest energy are in the upper valence band, the bonding character of the upper valence band plays a crucial role in determining the relative rate of dissolution of different minerals. These ideas are used to interpret the effect of light on the rate of dissolution of these minerals. The implications of this analysis for the order of the relative rates of dissolution of sulphide minerals is discussed.

Controlling a continuous stirred tank reactor for zinc leaching

This work focuses on the open-loop and closed-loop analysis of a continuous stirred tank reactor for zinc leaching from sphalerite (ZnS) via modeling and simulation approaches. The corresponding process analysis is based on a multi-input multi-output, approach by considering the inlet flows of minerals, acid solution, and aeration as process inputs and dissolved oxygen, ZnS concentrations, and pH as process outputs. An analysis of the relative gain array matrix was performed to determine the best control input pairs. In addition, a bifurcation analysis was carried out considering the process inputs as bifurcation parameters to show adequate operating regions. A local stability analysis of the selected equilibrium points in the chemical reactor under the previously selected operating conditions is presented, employing an eigenvalue analysis. Finally, a class of smooth super twisting sliding-mode controller is proposed to regulate the corresponding dissolved oxygen and pH in the reactor, which leads to increased sphalerite leaching; its performance was compared with a standard super twisting sliding-mode controller. The controllability of the reactor was analyzed via the dynamic behavior of the uncontrolled variables (zero dynamics). Numerical experiments show the satisfactory performance of the proposed controller under the selected operating conditions.

Cu2+-catalyzed mechanism in oxygen-pressure acid leaching of artificial sphalerite

The potential autoclave was used to study the catalytic mechanism of Cu2+ during the oxygen pressure leaching process of artificial sphalerite. By studying the potential change of the system at different temperatures and the SEM-EDS difference of the leaching residues, it was found that in the temperature range of 363–423 K, the internal Cu2+ formed a CuS deposit on the surface of sphalerite, which hindered the leaching reaction, resulting in a zinc leaching rate of only 51.04%. When the temperature exceeds 463 K, the system potential increases steadily. The increase in temperature leads to the dissolution of the CuS, which is beneficial to the circulation catalysis of Cu2+. At this time, the leaching rate of Zn exceeds 95%. In addition, the leaching kinetics equations at 363–423 and 423–483 K were established. The activation energy of zinc leaching at 363–423 and 423–483 K is 38.66 and 36.25 kJ/mol, respectively, and the leaching process is controlled by surface chemical reactions.

Kinetic models of zinc dissolution from artificial sphalerite with different iron contents in oxygen pressure leaching

ABSTRACT The oxygen pressure leaching of sphalerite in sulphuric acid solutions is a slow process in the absence of iron because of the limitations of the oxygen delivery carrier (redox couple: Fe3+/Fe2+). Herein, the artificial sphalerite with 25.70%, 15.20%, 5.75% iron contents and non-iron was prepared via the sintering of ZnS and FeS and used in the kinetic oxygen pressure leaching experiment. The results indicated that the zinc leaching rate of non-iron sphalerite was significantly lower than those of sphalerite with 25.70%, 15.20%, and 5.75% iron contents. This ratio decreased from 90 to 98% to approximately 65% at a temperature of 403 K, sulphuric acid concentration of 110 g L−1, oxygen partial pressure of 0.8 MPa, and leaching time of 70 min. Furthermore, when compared to the artificial sphalerite with 25.70%, 15.20%, 5.75% iron contents, the activation energy decreased from 32.31 kJ mol−1 for non-iron sphalerite to 29.02, 26.30, and 21.60 kJ mol−1, respectively. The leaching reaction process followed a shrinking unreacted core model that gradually shifted from surface reaction control to diffusion control. The orders of reaction for the sulphuric acid concentration and oxygen partial pressure were also obtained. Finally, artificial sphalerite leaching kinetics model equations with different iron contents were established.

Oxygen pressure acid leaching of artificial sphalerite catalyzed by Fe3+/Fe2+ self-precipitation

The mechanism of oxygen pressure acid leaching of sphalerite catalyzed by Fe3+/Fe2+ self-precipitation was investigated in this study. Artificial sphalerite was fabricated with varying amounts of iron content via the sintering of ZnS and FeS and used for the pressure acid leaching experiment. The variations in the potential of the pressure leaching system were investigated by using a self-designed potential autoclave. The results showed that compared to the non-iron sphalerite, there was a violent redox reaction between the 25.70% Fe-artificial sphalerite and dissolved oxygen during the process of pressure leaching; and the catalytic mechanism was attributed to the redox couple Fe3+/Fe2+, where Fe3+oxidizes the H2S gas film and the reduced Fe2+ state is subsequently oxidized by the dissolved oxygen. Furthermore, the effect of temperature, H2SO4 concentration, and oxygen partial pressure on the artificial sphalerite with different iron contents was studied. The sphalerite samples with iron content were observed to dissolve more easily in sulfuric acid compared to the non-iron samples. Moreover, the activation energy of artificial sphalerite was observed to be lower in the sample with 25.70% iron content (22.26 kJ/mol) compared to that with no iron (32.31 kJ/mol); and the apparent reaction orders were obtained with respect to H2SO4 concentration (1.10 and 1.36) and oxygen partial pressure (1.29 and 1.41), respectively. A comprehensive kinetic model was developed on the basis of the experimental data and the fitted leaching ratio plot; and the kinetic equations for the leaching of sphalerite catalyzed by Fe3+/Fe2+ self-precipitation were determined.

Direct Acid Leaching of Sphalerite: An Approach Comparative and Kinetics Analysis

The present work reports the direct leaching of zinc from a sphalerite concentrate in acid media. Lab-scale and pilot-scale experiments were conducted in atmospheric-pressure and low-pressure reactors, respectively. Leaching of zinc and precipitation of iron was achieved in the same stage using different reagents like Fe3+, O2, O3, and Fe2+ (which is continuously oxidized in the leaching solution by H2O2 and O2). The highest percentage of zinc extraction (96%) was obtained in pilot-scale experiments using H2SO4, Fe2+, and O2. Experimental results were compared with those of other researchers to provide a better understanding of the factors influencing the dissolution of zinc. In the first instance, it was determined from analysis of variance that leaching time and the use of an oxidant agent (O2 or O3) were the most influential factors during the direct leaching of zinc from the sphalerite concentrate. Kinetic models were also evaluated to determine the rate-limiting step of the sphalerite leaching; it was concluded that the type of the sulfur layer formed in the residue (porous or non-porous) depends on the type of the oxidant used in the leaching media, which determines the dissolution kinetics of zinc.

Modelling and optimization of zinc recovery from Enyigba sphalerite in a binary solution of hydrochloric acid and hydrogen peroxide

SYNOPSIS This work focused on the prediction of optimal conditions for zinc recovery from sphalerite in a binary solution of hydrochloric acid and hydrogen peroxide. The sphalerite sample was characterized with X-ray fluorescence spectrometry (XRF), X-ray diffractometry, and Fourier transform infrared analysis (FTIR). The central composite design of response surface methodology (RSM) developed in Design Expert software and the genetic algorithm (GA) tool in matlab, were deployed for the optimization exercise. The leaching temperature, acid concentration, stirring rate, leaching time, and hydrogen peroxide concentration were defined as input variables, while zinc yield was the response. An ideal zinc yield of 90.89% could be obtained with a leaching temperature of 84.17°C, HCl concentration of 3.14 M, stirring rate of 453.08 r/min, leaching time of 107.55 minutes, and hydrogen peroxide concentration of 3.93 M using RSM; while a yield of 87.73% was obtained using GA. Analysis of the post-leaching residue revealed the presence of sulphur, zircon, fluorite, gahnite, anatase, and sylvite. Keywords: sphalerite leaching, genetic algorithm, optimization, response surface methodology.

Color of Oxidative Pressure Leaching Liquor: A Case of Sphalerite

In lab-scale experiments of oxidative pressure leaching of sphalerite, an interesting phenomenon is that the leaching liquor looks three main colors: black, red and green. In on-going work, semi-quantitative study is carried out to investigate such phenomenon, including drawing of predominance area color diagram, effect of sulfur surfactant on color of leaching liquor, color and stability of oxidation of leaching liquor. Experimental results show that color of the leaching liquor depends on leaching condition mainly including temperature, dissolved oxygen concentration, that experimental results show sulfur surfactant has no effect on the color of leaching liquor, that, with increased molar ratio of elemental sulfur and sodium sulfide, , x = 1 ∼ 8 is more stable, and that in oxidation of aqueous sulfide anion, to achieve reasonable fast oxidation kinetic, temperature of 150 °C and oxygen pressure of 2 × 105 Pa is the minimum required conditions, which is coincide with such conditions to achieve reasonable fast oxidation kinetic in oxidation of aqueous ferrous iron. In this paper, different reaction mechanisms in given leaching condition were discussed.

Variable surface passivation during direct leaching of sphalerite by ferric sulfate, ferric chloride, and ferric nitrate in a citrate medium

Direct leaching of sphalerite has been considered as a cost effective and an environmentally benign alternative to the traditional two-step roasting-leaching approach. Yet the slow leaching rate due to the formation of surface passivating phases remains the main challenge. Here, we studied the mechanism and kinetics of sphalerite leaching in the temperature range of 35–130 °C using three oxidants, Fe2(SO4)3, FeCl3, and Fe(NO3)3, and observed distinctly different surface passivation and significantly different leaching rate. Leaching using Fe2(SO4)3 was the slowest, due to the formation of passivating surface layers of sulfur at the early stage and hydrated (Fe,Zn)-sulfates at the later stage. The formation of hydrated (Fe,Zn)-sulfates reduced Zn extraction by up to 20%, leading to incomplete Zn extraction. Using FeCl3, leaching was faster than in Fe2(SO4)3. However, the formation of surface sulfur also caused passivation. Leaching in Fe(NO3)3 was the fastest, as the initially formed surface sulfur was quickly oxidized to sulfuric acid and hence passivation was negligible. Using Fe(NO3)3, complete Zn extraction from 106 to 150 μm sphalerite particles took 7 days at 35 °C, 2 days at 70 °C, 5 h at 90 °C, and 1 h at 130 °C. This is about one order of magnitude and two orders of magnitude faster than leaching in FeCl3 and Fe2(SO4)3, respectively. The observed leaching behaviors were in agreement with changing activation energy as a function of leaching extent, analyzed by the modified ‘time-to-a-given-fraction’ method. In the case of Fe2(SO4)3 and FeCl3, leaching was controlled by phase-boundary reactions at the early-to-middle stages, but changed to diffusion control at the later stage after the formation of passivating surface layers; in the case of Fe(NO3)3, leaching was controlled by phase boundary reactions over the entire leaching process. This work demonstrates that Fe(NO3)3 is the more efficient oxidant than FeCl3 and Fe2(SO4)3 for fast leaching of sphalerite at low temperatures with minimum surface passivation.

Influence of Zinc Sulfide Wetting in Surfactants Presence on Leaching Parameters

This paper is describing an investigation of surfactants influence on zinc sulfide wetting by non-polar liquids and sphalerite concentrates pressure leaching parameters. Zinc sulfide preferential wettability by oil was tested in presence anionic surfactants with different chemical structures. Interfacial tension was determinated by the maximum liquid drop volume method. It allows to determine surfactant potential effectivity on pressure leaching of sphalerite concentrate. It is found that SDBS decreases zinc sulfide wettability by non-polar liquids in a greater degree than SDS and Ls. Combined addition of Ls and SDBS allowed to receive residues with optimal coarseness, eliminate pellet formation and increase zinc extraction.

Kinetics Etude of the Experimental Leaching ofSphalerite Using Acidic Lixiviant

Kinetics Etude of the Experimental Leaching ofSphalerite Using Acidic Lixiviant

Oxidative acid leaching of mechanically activated sphalerite

ABSTRACTThe pressure leaching kinetics of mechanically activated sphalerite was investigated in this work. X-ray diffraction and scanning electron microscopy were used to characterise the influences of crystalline structure and morphology, respectively. A laser particle size analyser and specific surface area tester were used to determine the particle size and specific surface area, respectively. Compared to the non-activated sample, the activated samples demonstrated distinct physicochemical properties with higher reaction efficiencies and increased Zn recovery ratios. The activation energy of sphalerite decreased from 69.96 to 45.91, 45.11, and 44.44 kJ mol−1 as the activation time increased from 0 to 30, 60, and 120 min, respectively. The reaction orders for the H2SO4 solutions of the sphalerite samples activated for 0, 30, 60, and 120 min were 1.832, 1.247, 1.214, and 1.085, respectively, which indicated that the dependency of the sphalerite leaching process on H2SO4 could be reduced by means of mechanical activation.

Parameters optimization and kinetics of direct atmospheric leaching of Angouran sphalerite

In this research, a zinc sulfide (sphalerite) concentrate of Angouran mine was studied by direct atmospheric leaching process. This process is an alternative to the conventional method of roast-leach-electrowinning (RLE) for zinc production by assisting ferric ions as powerful oxidant. The independent sphalerite leaching parameters investigated were ferric ions concentration (0.4–1.2M), temperature (40–80°C), particle size (21–53μm), sulfuric acid concentration (0.5–1.5M) and time (2–6h). Response surface methodology (RSM) was used to optimize the process parameters. The most influencing parameter was found to be temperature and the less effective was acid concentration. Based on the results, ferric ions illustrate a complex effect on the recovery of zinc; In this regard, interaction of ferric ions with operational parameters was proposed. The optimum recovery for leaching of the zinc sulfide concentrate (e.g., 84.72%) was obtained at ferric ions concentration of 1.2 M, temperature of 80°C, mean particle size of 21μm and leaching time of 6h. The predicted percentage recovery of zinc at the optimum condition was found to be 84.96% which was very close to the experimental value of 84.72%. Kinetic investigation was carried out in the optimum condition that obtained by RSM. Kinetic results showed that there were two stages in the sphalerite leaching. At the beginning of the leaching process, kinetics of sphalerite leaching is fast, while after about an hour the overall rate of leaching has decreased. The kinetic of leaching in the first stage is affected by both rate of chemical reaction and rate of diffusion through the sulfur layer. In this stage, the contribution of chemical reaction gradually decreases by increasing the temperature. In the second stage, the leaching rate of sphalerite is controlled only by diffusion through the product layer.

A mechanistic kinetic model for direct pressure leaching of iron containing sphalerite concentrate

In the current study, a numerical mechanistic kinetic model for direct leaching of zinc from iron containing sphalerite concentrate is presented. The model is based on the well-known shrinking-core model approach. However, in order to consider possible chemical changes that might take place in the liquid phase the model is solved numerically. This also makes it possible to separate and quantify different factors that might limit the leaching process. It is suggested that the most probable leaching mechanism is a combination of the acid attack and electrochemical reaction mechanisms. At first, zinc sulphide reacts with hydrogen ions at the surface of particles liberating zinc ions and forming hydrogen sulphide. Then in the next step, hydrogen sulphide is oxidized by ferric ions or molecular oxygen according to an electrochemical reaction mechanism. The estimated reaction orders for the oxidants are close to 0.5 which supports the electrochemical mechanism. The mechanism of sphalerite leaching also involves simultaneous surface reactions and internal diffusion of oxidants. The obtained results show that the rate of the leaching process is mainly limited by the surface reactions. However, internal diffusion might decrease the leaching rate in some cases up to 50% at higher sphalerite conversions. It is also demonstrated in the study that by using advanced statistical mathematical methods, such as the Markov chain Monte Carlo method, new information can be obtained about the kinetics of sphalerite leaching, the parameters affecting the leaching rate and the uncertainties involved in the model predictions.

Catalytic and galvanic effects of pyrite on ferric leaching of sphalerite

The catalytic and galvanic effects of pyrite on the dissolution kinetics of a zinc sulfide concentrate in an acidified ferric sulfate medium were assessed. The effects of particle size, oxidant concentration (ferric ion), and amount of pyrite added with respect to the original amount of zinc concentrate was explored, while temperature (70°C), hydrogen potential (pH=1.0) and agitation speed (600rpm) of the leach solution were held constant. A process based on the galvanic coupling between pyrite and sphalerite at solution potentials above 500mV to ensure rapid and complete sphalerite dissolution in a ferric sulfate medium is proposed. As a result, the highest zinc extraction in the shortest possible time was obtained through minimizing the formation of a passivating film, which inhibits further reaction, and by a synergetic effect between pyrite and sphalerite. The rate of zinc leaching was considerably improved by doping with pyrite in the presence of Fe3+. The results have demonstrated that it was possible to achieve 98.9% zinc extraction with doping pyrite in 6h and 85% zinc extraction without pyrite in 7h, both results being for a fine grain size. Ferric leaching reached 75% Zn extraction with doped pyrite and 70% without it, both in 7h using a coarse grain size. Scanning electron microscopy (SEM) images show a passivating layer on the sphalerite surface after ferric leaching without pyrite, while in presence of pyrite this layer was not observed and the pyrite surface was not attacked. The galvanic interaction between pyrite and sphalerite particles can be explained by the difference between their Fermi energies and the electrochemical potential of the solution. During this process pyrite remains mostly unleached, acting as a redox catalyst (electron-accepting) for sphalerite (electron-donating) dissolution. This diminishes the typical passive behavior of sphalerite in a ferric solution enhancing considerably the kinetics of sphalerite. This confirms that the difference between the rest potentials of pyrite and sphalerite is the driving force that improves zinc dissolution. For an industrial hydrometallurgical operation, using an appropriate sphalerite-pyrite concentrate does not necessarily represent a significant cost because the ore contains both sulfides.

Kinetics and Modeling of Chemical Leaching of Sphalerite Concentrate Using Ferric Iron in a Redox-controlled Reactor

This work presents a study for chemical leaching of sphalerite concentrate under various constant Fe3+ concentrations and redox potential conditions. The effects of Fe3+ concentration and redox potential on chemical leaching of sphalerite were investigated. The shrinking core model was applied to analyze the experimental results. It was found that both the Fe3+ concentration and the redox potential controlled the chemical leaching rate of sphalerite. A new kinetic model was developed, in which the chemical leaching rate of sphalerite was proportional to Fe3+ concentration and Fe3+/Fe2+ ratio. All the model parameters were evaluated from the experimental data. The model predictions fit well with the experimental observed values.