Dissolution Of Galena Research Articles

Effect of galena during the electro-assisted reductive leaching of a chalcopyrite concentrate in HCl solutions

This research presents a systematic study of the effect of galena (PbS) on the electro-assisted reductive leaching of chalcopyrite in HCl solutions. The electro-assisted reduction of chalcopyrite and current efficiency were assessed varying the pulp density of chalcopyrite concentrate in the presence of different amounts of galena. The dissolution of galena and continuous electrodeposition of lead was evaluated during the electro-assisted reduction tests. The effect of lead on the kinetics of hydrogen evolution reaction (HER) was studied using electrochemical techniques. The results revealed that galena is susceptible to be partially dissolved in HCl media, then metallic lead can be continuously electrodeposited during the electro-assisted reduction of chalcopyrite. The HER tests showed that the presence of metallic lead on the cathode modified the kinetics of HER, i.e., monoatomic hydrogen generation was affected due to a decrease in the exchange current density, this phenomenon decreased considerably the kinetics and extent of the chalcopyrite reduction. The results also showed that the continuous electrodeposition of lead decreased the HER kinetics and the current efficiency of the system.

Influence of Temperature and Potential on the Electrochemical Dissolution of Galena in HNO3 at pH 2.0

Influence of Temperature and Potential on the Electrochemical Dissolution of Galena in HNO3 at pH 2.0

Application of inverse modelling for prediction of the surface water chemistry of the ekulu river in enugu, southeastern nigeria

Surface water chemistry evolution of Ekulu River was conducted by inverse geochemical modelling using the PHREEQC computer program. In this study, samples were collected from the Ekulu river at 100m intervals, and were taken to the laboratory for major anions and cations, heavy metal and bacterial content analyses. Inverse geochemical modelling results reveal that the river evolved as a result of dissolution of siderite, quartz, gypsum, galena, sphalerite, pyrolusite and precipitation of goethite and pyrite. The Piper diagram indicates Calcium-Chloride water type, with high Ca2+ + Mg+ and Cl- + SO42 contents, which is typical of water originated from gypsum dissolution and mine drainage. The results of the analyses show that the water cannot be recommended for drinking because the E. coli and coliform contents are higher than the permissible limits. The water chemistry of Ekulu river is as a result of secondary minerals dissolution and mine drainage from Onyeama coal mine whereas the microbial content resulted from pollution from recent faeces.
 

The Effect of Macroscopic Particle Features on Mineral Dissolution

Mineral dissolution is a dynamic process in which kinetics depend on the reactive surface area, orientation, and geometry of the dissolving mineral grain. Dissolution rate is, thus, not represented by a single value, but rather, by a spectrum that is affected by the reactivity of different types of surface features. Such dissolution rate spectra are usually obtained by very detailed studies of perfectly cleaved surfaces by atomic force microscopy or in situ studies, such as flow-through experiments. This study visualizes dissolution progress by repeated X-ray computed tomography scans of a single particle. This allows studying the influence of larger particle features, such as corners and edges, at the interception of macroscopic faces of particles, as well as the influence of those macroscopic features on the dissolution rate spectra. As a suitable case study, the dissolution of a monomineralic galena (PbS) particle in ethaline is studied. The observed changes in particle geometry are evaluated using a newly developed empirical model in order to break down the rate spectra as a function of the particle geometry. Results illustrate that dissolution rates are exponentially correlated with the distance to crystal corners and edges. The reactivity map generated from these exponential relations shows a linear trendline with the dissolution rates over the entire surface of the studied galena particle. The empirical reactivity map developed here opens the possibility of predicting the dissolution rate of particulate materials based on computed tomography and the optimal geometrical properties of the particles that maximize the dissolution, e.g., size and shape.

Kinetic investigation of galvanic dissolution of ZnS and PbS with FeS2 from hydrothermal sulfides in seawater

Sulfide mineral dissolution is an important reaction controlling geochemical and environmental chemical processes in aqueous environments. In this study, we quantitatively evaluated the kinetic influence of galvanic interactions between different sulfide minerals on their dissolution in seawater. Four hydrothermal sulfides with different amounts of Fe disulfide minerals (pyrite) were reacted with artificial seawater for 144 h, and the dissolution rates of Zn and Pb were determined by an extraction method. The Zn dissolution rates from samples with high Fe/Zn molar ratios (>0.26) were 1.3–1.5 × 10−10 mol m−2 s−1; approximately one order of magnitude higher than those of samples with low Fe/Zn molar ratios (<0.002; 1.6–1.8 × 10−11 mol m−2 s−1). The Pb dissolution rates from a sample with high Fe disulfide were approximately nine orders of magnitude higher (8.4× 10−10 mol m−2 s−1) than reference data of the single galena dissolution rate (8.9 × 10−19 mol m−2 s−1). The higher solubility of PbSO4 than PbS and PbCO3 could explain the intense release of Pb from the other samples. These results and mineralogical observations with X-ray diffraction, X-ray photoelectron spectroscopy, and electron probe micro-analysis of sulfide mineral particulates provide evidence for the selective dissolution of anodic sulfide minerals (e.g., sphalerite and galena) at a higher reaction rate than cathodic sulfide minerals of Fe disulfide (e.g., pyrite).

Ozonation of recalcitrant O-isopropyl-N-ethylthionocarbamate catalyzed by galena in flotation effluents and its dissolution behaviors

Little attention has been paid to the catalytic effects of sulfide minerals and their dissolution behaviors in treating flotation effluents by advanced oxidation processes (AOPs). In this work, the improved ozonation of recalcitrant O-isopropyl-N-ethylthionocarbamate (IPETC) collector by adding galena was investigated with the disclosure of galena dissolution. The removal efficiency of IPETC and its mineralization was compared by sole ozonation and galena catalytic ozonation. The galena dissolution process was examined by determining Pb(II) concentrations and analyzing galena surface with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The galena had remarkably increased the IPETC removal and promoted its mineralization by the ozonation. Simultaneously, the ozone consumption could be significantly reduced. The catalytic decomposition of ozone on galena surface resulted in the yield of more hydroxyl radicals, leading to the enhanced removal of IPETC. The released Pb(II) concentrations were as high as 14.9–23.2 mg/L after the ozonation, indicating the significant dissolution of galena. The XPS and FTIR analysis confirmed the formation of lead oxides with high solubility after the oxidation of galena. The negative impacts of releasing toxic heavy metals from sulfide minerals were discussed while the flotation effluents were treated by the AOPs.

A cross scale investigation of galena oxidation and controls on mobilization of lead in mine waste rock

Galena and Pb-bearing secondary phases are the main sources of Pb in the terrestrial environment. Oxidative dissolution of galena releases aqueous Pb and SO4 to the surficial environment and commonly causes the formation of anglesite (in acidic environments) or cerussite (in alkaline environments). However, conditions prevalent in weathering environments are diverse and different reaction mechanisms reflect this variability at various scales. Here we applied complementary techniques across a range of scales, from nanometers to 10 s of meters, to study the oxidation of galena and accumulation of secondary phases that influence the release and mobilization of Pb within a sulfide-bearing waste-rock pile. Within the neutral-pH pore-water environment, the oxidation of galena releases Pb ions resulting in the formation of secondary Pb-bearing carbonate precipitates. Cerussite is the dominant phase and shannonite is a possible minor phase. Dissolved Cu from the pore water reacts at the surface of galena, forming covellite at the interface. Nanometer scale characterization suggests that secondary covellite is intergrown with secondary Pb-bearing carbonates at the interface. A small amount of the S derived from galena is sequestered with the secondary covellite, but the majority of the S is oxidized to sulfate and released to the pore water.

Geochemistry, risk assessment, and Pb isotopic evidence for sources of heavy metals in stream sediments around the Ulukışla Basin, Niğde, southern Turkey

Concentrations of selected elements (Al, Fe, Mn, Mo, As, Cd, Cu, Cr, Ni, Co, Pb, Sb, and Zn) and Pb isotope ratios were determined in 53 sediments from Alihoca, Gümüş, Horoz, and Çakıt streams around the south-central Taurides (Ulukışla Basin), Niğde, which is a known mining province in Turkey. Several pollution and risk assessment indices were used to assess possible heavy metal pollution in the stream sediments and the associated potential ecological risks. Concentrations of As, Cd, Cu, Cr, Ni, Co, Pb, Sb, and Zn were elevated in the streams located near ancient mines, active mines, and slag piles in the area, suggesting an influence from mining activities. The pollution assessment indices indicated that the sediments were significantly polluted by As, Cd, Sb, Zn, and Pb and moderately polluted by Cu, Ni, Cr, and Co. The sediments show very high potential ecological risk with As, Cd, Sb, and Pb as the principal contributors. Ni, Cr, As, Pb, Zn, and Cd exceeded the probable effect concentrations in most of the samples implying that their concentrations may frequently affect sediment-dwelling organisms. Multivariate statistical analyses indicate that the accumulation of heavy metals in the stream sediments is due to an interplay of anthropogenic activities (mining and agrochemical application) and geogenic processes (weathering of bedrocks and supergene alteration of base metal-rich mineralization). Pb isotopic tracing indicates that total Pb in the sediments (206Pb/207Pb = 1.09–1.29) is primarily from weathering and dissolution of ultrapotassic rocks (206Pb/207Pb up to 1.20) and galena (206Pb/207Pb up to 1.21) from the Pb-Zn-Au deposits in the area with some anthropogenic input from mine slag piles (206Pb/207Pb = 1.10).

A Flow-Through Reaction Cell for Studying Minerals Leaching by In-Situ Synchrotron Powder X-ray Diffraction

A flow-through reaction cell has been developed for studying minerals leaching by in-situ time-resolved powder X-ray diffraction, allowing for a better understanding of the leaching mechanisms and kinetics. The cell has the capability of independent control of temperature (up to 95 °C) and flow rate (&gt;0.5 mL min−1) for atmospheric pressure leaching. It was successfully tested at the powder diffraction beamline at the Australian Synchrotron. Galena powder was leached in a citrate solution under flow-through condition at a flow rate of 0.5 mL min−1, while diffraction patterns were collected during the entire leaching process, showing rapid galena dissolution without the formation of secondary mineral phases. The flow-through cell can be used to study leaching processes of other ore minerals.

The influence of galvanic interaction on the dissolution and surface composition of galena and pyrite in flotation system

The dissolution behavior and surface composition of galena and pyrite in their coexisting flotation system were studied by metal ion releasing experiment and XPS analysis, to reveal the influence of galvanic interaction on their flotation. The results indicated that the dissolution of lead ions from galena surface was strongly enhanced in the presence of pyrite, significantly depending on the pyrite content. The dissolution of iron ions from pyrite surface was also enhanced in the presence of galena, but the effect of galena content was small. XPS analysis verified that the galvanic interaction enhanced the galena oxidation, leading to an increase in oxysulfide/hydroxide components on its surface. However, the galvanic interaction only had little impact on the pyrite oxidation, other than the migration and adsorption of lead ions. This work demonstrated that the galvanic interaction between galena and pyrite altered their surface components and increased the difficulty in flotation separation process.

Electrochemical Study of Galena Weathering in NaCl Solution: Kinetics and Environmental Implications

Exploitation of seafloor massive sulfide deposits exposes galena and other metal sulfides to weathering factors. Galena weathering process leads to release of toxic metals into the water column. Although galena weathering has an impact on the environment, the mechanisms and kinetics of galena oxidation under seawater conditions are rarely studied. In this work, several electrochemical experimental methods were combined to examine the kinetics of galena weathering in NaCl solution to simulate the effects of Cl− in seawater, and the effects of sodium chloride concentration and pH on it were studied. The results show that galena weathering can lead to mineral surface passivation. More chloride ions can accelerate the dissolution of galena. Higher acidity and alkalinity promote the dissolution of galena in NaCl solution. Galena will release Pb2+ at a rate of 2.849 × 10−2 g m−2 d−1 in the near neutral NaCl mediums, and the amount increases to 5.705 × 10−2 g m−2 d−1 at pH 1.0 and even up to 7.569 × 10−1 g m−2 d−1 at pH 13.0. The results of polarization curves are consistent with the impedance spectrum data. Based on the dissolution kinetics of galena, the environmental significance of galena weathering is proposed.

Using ToF-SIMS to study metal ions transfer between chalcopyrite and galena during grinding

Grinding has an important effect on the chemical composition of the mineral surface. In this study, the interaction of galena and chalcopyrite during grinding was studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS), principal component analysis (PCA), and inductively coupled plasma optical emission spectrometry (ICP-OES). Results showed that during mixed grinding, the surface compositions of chalcopyrite and galena became more similar, and the dissolution of chalcopyrite and galena was promoted. Grinding not only results in the adsorption of lead ions released from galena to the chalcopyrite surface, but also results in the adsorption of copper and iron ions released from chalcopyrite to the galena surface. The Cu, Fe, and Pb atoms on the surface of chalcopyrite and galena may be bonded in the form of PbOCu, PbOFe, and PbSCu. This study can provide a surface chemical basis for controlling the grinding process of copper-lead sulfide ore.

Modeling and optimization of galena dissolution in a binary solution of nitric acid and ferric chloride using artificial neural network coupled with genetic algorithm and response surface methodology

In this research, the optimization of lead recovery from galena with a binary solution of nitric acid and ferric chloride using response surface methodology (RSM), artificial neural network (ANN) and genetic algorithm (GA) was carried out. The galena mineral was examined for mineralogical properties with X-ray diffraction spectroscopic system while the elemental composition was analyzed with X-ray fluorescence (XRF). The results revealed that the galena mineral exists as lead sulphide (PbS). The central composite design was employed for RSM modeling while back propagation (BP) coupled with the Levenberg-Marquardt (LM) algorithm was used to construct a feed-forward neural network (FFNN). The leaching temperature, acid concentration, stirring rate, leaching time and ferric chloride concentration were chosen as input factors, while the percentage yield of lead was the response. The multilayer perceptron with design of 5-9-1 gave the best performance. Comparison of the RSM and ANN model indicated satisfactory prediction of the response, with AAD of 0.887% and 0.377%, R2 of 0.9910 and 0.9989, and RMSE of 0.815 and 0.290, respectively. The process parameters were optimized via GA and RSM optimization tools. An optimum lead yield of 90.33% was obtained with a leaching temperature of 80.2°C, HNO3 concentration of 3.55 M, stirring rate of 498.88 rpm, leaching time of 86.91 minutes and ferric chloride concentration of 0.35 M using RSM while a yield of 87.11% was achieved via GA.

The kinetics of Indonesian galena concentrate leaching in fluorosilicic acid and hydrogen peroxide as its oxidants

Lead smelting is known as a lead extraction technique which has negative impact to environment because it produces emissions of dust, SO 2 gas and lead. The leaching is conducted to reduce the smelting’s weaknesses by extracting the lead without damaging the environment. This technique, often called hydrometallurgical lead extraction, uses liquid media to extract the lead and separate it from the elemental sulphur (S 0 ) by filtration. Particle size, slurry density (solid percentage) and acid concentration affect the dissolution of Indonesian galena concentrate with fluorosilicic acid and hydrogen peroxide as oxidants. By means of these reagents, it is expected that the Pb extraction process from galena concentrate resulted from flotation of sulfide ore can be carried out at low temperatures and lead recovery can be accomplished from the leach solution by electrowining. Studying galena leaching kinetics is required to perform galena leaching with high Pb extraction percentages. Two kinetics models are commonly used to study leaching kinetics, namely shrinking core model (SCM) and shrinking particle model (SPM). These models are used to determine the mechanism which controls leach reaction and reaction rate constant or diffusion constant of the reacting species. Total plotting of sulfide fraction dissolves with time adjusted to the existing mathematical model, and fitting the curve from the dummy model to the experimental data, are two techniques that are utilized to obtain the best kinetics model which important in controlling the leaching reaction rate. Applying the Arrhenius equation, the relation of the reaction rate constant or the diffusion constant and the temperature is determined to calculate the leaching activation energy. The result from kinetics analysis showed that the leaching of Indonesian galena concentrate in fluorosilicic acid with hydrogen peroxide as oxidants followed the shrinking core model with diffusion through porous solid product layer as the reaction controller with activation energy of 45.81 kJ/mol or 10.91 kcal/mol.

The Combined Effects of Galvanic Interaction and Silicate Addition on the Oxidative Dissolution of Pyrite: Implications for Acid and Metalliferous Drainage Control.

The aim of this study was to determine the combined effect of galvanic interaction and silicate addition on the dissolution of pyrite, the major contributor to acid and metalliferous drainage (AMD). Single (pyrite, sphalerite, and galena)- and bi-sulfide (pyrite-sphalerite and pyrite-galena) batch dissolution experiments were carried out with addition of 0.8 mM dissolved silicate for comparison to previously published data. The pyrite dissolution rate was reduced by 98% upon silicate addition at pH 7.4 with little effect at pH 3.0 and 5.0. The effect of galvanic interaction on reducing pyrite dissolution decreased with increasing pH and was greater in the presence of sphalerite than galena. In contrast, the effect of silicate addition increased with increasing pH and was greater in the presence of galena than sphalerite. The greatest combined effect was at pH 7.4, with <0.1% of pyrite leached in both bi-sulfide systems. Silicate addition also significantly reduced the dissolution of sphalerite or galena (by 10-44%, except at pH 3 for the pyrite-sphalerite system). These results suggest that silicate addition, for reducing both pyrite dissolution and metalliferous drainage, may be applicable at a broad pH in mixed sulfide systems.

Parameters that affect the dissolution of Indonesian galena concentrate in fluorosilicic acid and hydrogen peroxide

Pyrometallurgical process still dominates the extraction of galena concentrates. The process used to extract the lead includes reduction smelting in a blast furnace, air flash smelting (Boliden process), oxygen flash smelting (Kivcet, Boliden Kaldo, Outokumpu), air-slag bath smelting (Isasmelt) and oxygen-slag bath smelting (QSL). However, those generate dust, SO 2 gas and volatile Pb liquid. As a result, such processes are ineffective to treat the complex sulfides and low-grade flotation con concentrates. Referring to the lack of high-grade lead ore the lead pyrometallurgical is a problem in the future. In addition, the environmental regulation becomes very strict lately. Those pushes the metallurgist to seek the alternative process that are environmentally friendly and able to treat the low-grade concentrates. Lead extraction through hydrometallurgical process is considered to be safer as the process do not produce dust, SO 2 gas and lead vapor.Researches for lead extraction through hydrometallurgical routes have been performed using various leaching agents such as acetic acid, ferric methanesulfonate, ferric chloride, ferric fluorosilicate and nitric acid with hydrogen peroxide and ferric ion as the oxidants. So far, no lead plant operates hydrometallurgically in an industrial scale. Fluorosilicic acid has a potential to be used as the leaching reagent for concentrating the lead because of high lead solubility in this solution and cheaper price of the reagent in compared to sulfamate and fluoroborate solutions. This research used galena concentrates from a mining area in Bogor, Indonesia, fluorosilicic acid and hydrogen peroxide as the oxidants. The highest Pb extraction percentage of 99.26% was achieved from the leaching experiment using 3.44 M of H 2 SiF 6 and 9.79 M of H 2 O 2 , at 97 o C and concentrate particle size distribution of -100+150 mesh after 135 minutes. The XRD analysis of the leaching residue with no oxidant showed the presence of galena, sphalerite and chalcopyrite, while the residue of the leaching with oxidant showed anglesite (PbSO 4 ), galena, sphalerite, sulphur and pyrite. Lead extractions were increased by the increase of temperature and concentration of fluorosilicic acid. The best solid percentage that gave the highest lead extraction percentage was 12%. Variations of rotation speeds at the range of 300-700 rpm did not significantly influence lead extraction percentage. However, the particle size distribution that resulted in the best extraction percentage of lead is 100+150#, at which the finer particle size of the concentrate give a lower extraction percentage of the lead due to PbSO 4 precipitation.

Galena Non-oxidative Dissolution Kinetics in Seawater

The rate of non-oxidative galena dissolution in seawater compositions over the pH range of 2–4.5 was determined from batch reactor experiments. The derivative at zero time of a polynomial fit of the Pb concentration versus time data for the first 30 min was used to determine the rate. A plot of RGn (rate of galena dissolution) versus pH for data from six experiments is linear (R2 = 0.96), with a slope of 0.5. The rate equation describing the rate of galena dissolution as a function of hydrogen ion activity is $$R_{\text{Gn}} = - \,10^{ - 10.72} \left( {a_{{{\text{H}}^{ + } }} } \right)^{0.50}$$ Varying the concentration of dissolved oxygen produced no significant effect on the measured rates. The activation energy, based on four experiments carried out over the temperature range of 7–30 °C, is 61.1 kJ/mol.

Hydrometallurgical Processing of a Nigerian Galena Ore in Nitric Acid: Characterization and Dissolution Kinetics

The physico-chemical characterization and dissolution kinetics study of a Nigerian galena ore in nitric acid has been undertaken. The effects of acid concentration, temperature, particle size, stirring speed and solid/liquid ratio on the leaching of galena were investigated. The X-ray fluorescence data showed that the galena ore used in the study exists mainly as PbS. Lead (Pb) was detected as the major metal for galena with metals such as Na, Ca, Fe, Zn, Al and Mg occurring as minor elements. The XRD analysis also confirmed the originality of the galena ore as it revealed that galena exists mainly as lead sulphide (PbS). The Fourier transform infrared (FTIR) analysis also supported the XRF and XRD analysis by revealing the presence of sulphur in the ore. The scanning electron micrograph (SEM) analysis revealed a high level of crystallinity of the ore. Results of the leaching studies showed that galena dissolution in nitric acid (HNO3) increases with increasing concentration of nitric acid, temperature and stirring rate, and decreases with increasing particle diameter and solid/liquid ratio. In 10 M HNO3 at a temperature of 90°C using 75 μm particle diameter with solid/liquid ratio of 20 g/L and stirring speed of 540 rpm, about 84.5% of galena was dissolved in 150 minutes. The values of activation energy, order of reaction and Arrhenius constant calculated at the conditions above for galena were 27.01 KJ/mol, 0.93, 26.71 s-1 respectively. The mechanism of dissolution of galena was established to follow the shrinking core model for the diffusion controlled mechanism, with surface chemical reaction as the rate controlling step for the leaching process. Finally, the XRD analysis of the post-leaching residue revealed the presence of gahnite and anglesite.

Modeling and Optimization of Galena Dissolution in Hydrochloric Acid: Comparison of Central Composite Design and Artificial Neural Network

Response surface methodology (RSM) and Artificial neural network (ANN) were used for the simulation and optimization of galena dissolution in hydrochloric acid. The galena ore was characterized for structure elucidation using FTIR, SEM and X-ray diffraction spectroscopic techniques and the results indicate that the galena ore exists mainly as lead sulphide (PbS). A feed-forward neural network model with Leverberg-Marquardt back propagating training algorithm was used to predict the response (lead yield). The leaching temperature, acid concentration, solid/liquid ratio, stirring rate and leaching time were defined as input variables, while the percentage yield of lead was labelled as output variable. The multilayer perceptron with architecture of 5-9-1 provided the best performance. All the process variables were found to have significant impact on the response with p-values of 2 of 0.991 and 1.00, respectively. A non-dominated optimal response of 85.25% yield of lead at 343.96 K leaching temperature, 3.11 M hydrochloric acid concentration, 0.021 g/ml solid/liquid ratio, 362.27 rpm stirring speed and 87.37 min leaching time was established as a viable route for reduced material and operating cost using RSM.

Influence of pH, Pb2+, and temperature on the electrochemical dissolution of galena: environmental implications

We investigated the influence of pH, Pb2+, and temperature on the electrochemical dissolution of galena. The experimental results showed the following: (1) Acidic or alkaline conditions stimulate galena electrochemical dissolution. The galena electrode corrosion current density (j corr) increased from 0.072 to 0.143 μA·cm−2 as the pH decreased from 6.0 to 2.0 (promotion efficiency of 98.61 %) and from 0.066 to 0.132 μA·cm−2 as the pH increased from 8.0 to 12.0 (promotion efficiency of 100 %). (2) Pb(NO3)2 promotes galena electrochemical dissolution at low concentrations ( 0.10 mol·L−1) because Pb2+ has two different functions during galena electrochemical dissolution. (3) Higher temperatures are favorable for galena electrochemical dissolution. The galena j corr increased from 0.143 to 0.226 μA·cm−2 as the temperature increased from 25 to 55 °C. These experimental results are of direct significance for the control of environmental pollution during galena weathering and mining activities.