Research

14 pages, 1624 KiB

Open AccessArticle

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

by Nallely G. Picazo-Rodríguez, Ma. de Jesus Soria-Aguilar, Antonia Martínez-Luévanos, Isaias Almaguer-Guzmán, Josue Chaidez-Félix and Francisco Raul Carrillo-Pedroza

Minerals 2020, 10(4), 359; https://doi.org/10.3390/min10040359 - 17 Apr 2020

Cited by 13 | Viewed by 3362

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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21 pages, 2936 KiB

Open AccessArticle

The High Temperature Co-Processing of Nickel Sulfide and Nickel Laterite Sources

by Robbie G. McDonald and Jian Li

Minerals 2020, 10(4), 351; https://doi.org/10.3390/min10040351 - 14 Apr 2020

Cited by 9 | Viewed by 4831

Abstract

The pressure oxidation of low-grade nickel sulfide concentrate with high iron sulfides content generates significant amounts of sulfuric acid that must be neutralized. This acid can be utilized to leach metal values from ores such as nickel laterites. The present study demonstrates the [...] Read more.

The pressure oxidation of low-grade nickel sulfide concentrate with high iron sulfides content generates significant amounts of sulfuric acid that must be neutralized. This acid can be utilized to leach metal values from ores such as nickel laterites. The present study demonstrates the use of a low-grade nickel concentrate generated from Poseidon Nickel Mt Windarra ore to enable additional nickel and cobalt extraction from a Bulong Nickel Operation nickel laterite blend. The co-processing of these materials at 250 °C, with oxygen overpressure, using total pulp densities of 30% or 40% w/w, and a range of nickel concentrate to nickel laterite mass ratios between 0.30–0.53, yielded base metal extractions of 95% or greater. The final free acid range was between 21.5–58.5 g/L, which indicates that enough in situ sulfuric acid was generated during co-processing. The acid was shown from mineralogical analysis to be efficiently utilized to dissolve the laterite ore, which indicates that the primary iron hydrolysis product was hematite, while the aluminum-rich sodium alunite/jarosite phase that formed hosts approximately 5% of the hydrolyzed iron. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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12 pages, 4290 KiB

Open AccessArticle

Liberation of Gold Using Microwave-Nitric Acid Leaching and Separation-Recovery of Native Gold by Hydro-Separation

by Kang Hee Cho, Jong Ju Lee and Cheon Young Park

Minerals 2020, 10(4), 327; https://doi.org/10.3390/min10040327 - 06 Apr 2020

Cited by 6 | Viewed by 3942

Abstract

The purpose of this study was to liberate gold from sulfide minerals in a gold concentrate through microwave-nitric acid leaching and to separate the light minerals in an insoluble residue using a hydro-separation process. The representative sulfide minerals in the gold concentrate were [...] Read more.

The purpose of this study was to liberate gold from sulfide minerals in a gold concentrate through microwave-nitric acid leaching and to separate the light minerals in an insoluble residue using a hydro-separation process. The representative sulfide minerals in the gold concentrate were pyrite with minor galena. Mineralogical characterization was conducted on the gold concentrate using 1715.20 g/t based on lead-fire assays. During the leaching experiment, the effect of nitric acid concentration was studied. The results indicated that the metal leaching rate of the gold concentrate increased with increasing nitric acid concentration. After the microwave-nitric acid leaching, the resulting main feature was consistent with the increased exposure to reactive sulfide minerals and decrease in weight. Characterization techniques such as X-ray diffraction (XRD), scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and scanning electron microscope backscattered electron imaging (SEM-BSE) were performed to characterize the minerals in the insoluble residue using microwave-nitric acid leaching and the hydro-separation process. The XRD patterns of the insoluble residues were compared. The intensities of the pyrite peak decreased and disappeared under different nitric acid concentrations, whereas intensities of the quartz peak increased. The hydro-separation process focused on the separation of heavy (e.g., native gold) and light (e.g., quartz) minerals from the insoluble residues. After the hydro-separation treatment process, the heavy minerals exhibited typical diffraction lines of gold, as obtained using the XRD analysis. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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24 pages, 7470 KiB

Open AccessArticle

High Temperature Pressure Oxidation of a Low-Grade Nickel Sulfide Concentrate with Control of the Residue Composition

by Robbie G. McDonald, Jian Li and Peter J. Austin

Minerals 2020, 10(3), 249; https://doi.org/10.3390/min10030249 - 09 Mar 2020

Cited by 6 | Viewed by 5413

Abstract

High temperature pressure oxidation of a low-grade nickel concentrate was examined to demonstrate the potential benefits and shortcomings of this approach. The high iron sulfide content ensured that acid generation was much greater than for higher grade concentrates. This results in the formation [...] Read more.

High temperature pressure oxidation of a low-grade nickel concentrate was examined to demonstrate the potential benefits and shortcomings of this approach. The high iron sulfide content ensured that acid generation was much greater than for higher grade concentrates. This results in the formation of basic iron sulfate phases and a significant amount of sulfuric acid. Kinetic sampling during pressure oxidation tests also demonstrated the transformation of sulfide minerals, including the oxidative transformations of pentlandite to violarite and then to vaesite, the latter phase not previously noted in studies of this kind. Finally, addition of a divalent metal sulfate buffer, here magnesium sulfate, mitigates the formation of basic iron sulfates but with greater generation of sulfuric acid in the leach liquor. Under the conditions employed in this study, this acid could be employed to leach other nickel-containing materials such as nickel laterites. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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16 pages, 8058 KiB

Open AccessArticle

Research on Behavior of Iron in the Zinc Sulfide Pressure Leaching Process

by Shu-Chen Qin, Kai-Xi Jiang, Hai-Bei Wang, Bang-Sheng Zhang, Yu-Fang Wang and Xue-Dong Zhang

Minerals 2020, 10(3), 224; https://doi.org/10.3390/min10030224 - 29 Feb 2020

Cited by 19 | Viewed by 3492

Abstract

Dissolved iron exerts significant effects on mineral leaching, impurity removal, and solution purification in the zinc hydrometallurgy process. To date, iron oxidation and migration behaviors are yet to be fully understood and further research on effective regulation mechanisms of iron is required. In [...] Read more.

Dissolved iron exerts significant effects on mineral leaching, impurity removal, and solution purification in the zinc hydrometallurgy process. To date, iron oxidation and migration behaviors are yet to be fully understood and further research on effective regulation mechanisms of iron is required. In this paper, zinc sulfide concentrate was used as the research object. The behaviors of both Zn and Fe during pressure leaching were investigated for varying temperature, acid addition, and leaching time. At temperature of 100~160 °C, H₂SO₄/Zn ratio of 0.9:1–1.25:1, and leaching time of 0.5–2.5 h, the zinc extraction increased with temperature, acidity and leaching time. The iron extraction, however, varied differently with increasing temperature, acidity and leaching time: (A) it increased with temperature to 150 °C and then decreased at higher temperature, and (B) displayed an initial increase followed by a decrease with respect to the leaching time. Based on the characteristics of the residue phase, chemical phase analysis was used to analyze the residue in detail. The extent of dissolution of iron-containing minerals and the extent of precipitation of ferric ions during the leaching process were quantitatively calculated. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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13 pages, 6636 KiB

Open AccessArticle

Effect of a Small Amount of Iron Impurity in Sphalerite on Xanthate Adsorption and Flotation Behavior

by Jiang Yu, Xiqun Wu, Zhiqiang Zhao, Yangge Zhu and Sigang Luo

Minerals 2019, 9(11), 687; https://doi.org/10.3390/min9110687 - 06 Nov 2019

Cited by 5 | Viewed by 2460

Abstract

Through industrial testing at the Huize lead-zinc mine, it was found that the floatability of sphalerite varied greatly with the iron impurity content. Three kinds of Huize sphalerites with iron contents of 2.30 wt.%, 3.20 wt.% and 4.66 wt.%, were used to study [...] Read more.

Through industrial testing at the Huize lead-zinc mine, it was found that the floatability of sphalerite varied greatly with the iron impurity content. Three kinds of Huize sphalerites with iron contents of 2.30 wt.%, 3.20 wt.% and 4.66 wt.%, were used to study the influence of small amounts of iron impurity in the sphalerite on xanthate adsorption and flotation behavior. The flotation experiments showed that the flotation recovery increased with the increase in iron impurity content. Fourier Transform infrared spectroscopy (FTIR) and Ultraviolet–visible (UV-VIS) spectra showed that the adsorbed products of xanthate on the surface of three kinds of sphalerite were metal xanthate. The adsorption capacity measurements showed that the saturation absorption of xanthate on sphalerite increased with the increase in iron impurity content. The cyclic voltammetry curve and Tafel curve showed that with the increase in iron impurity content, sphalerite was more easily oxidized and the adsorption rate of xanthate on the surface of sphalerite increased obviously. To summarize, a small amount of iron impurity was beneficial to the recovery of sphalerite. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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15 pages, 2339 KiB

Open AccessArticle

Cupric and Chloride Ions: Leaching of Chalcopyrite Concentrate with Low Chloride Concentration Media

by Cynthia M. Torres, Yousef Ghorbani, Pía C. Hernández, Francisca J. Justel, Matías I. Aravena and Osvaldo O. Herreros

Minerals 2019, 9(10), 639; https://doi.org/10.3390/min9100639 - 18 Oct 2019

Cited by 12 | Viewed by 3906

Abstract

In this paper, the effect of the cupric and chloride ions concentrations on copper dissolution from chalcopyrite concentrate was studied in acidified media. Variables included three different concentrations of Cu²⁺ (0.5, 1.5, and 2.5 g L⁻¹), four different concentrations of [...] Read more.

In this paper, the effect of the cupric and chloride ions concentrations on copper dissolution from chalcopyrite concentrate was studied in acidified media. Variables included three different concentrations of Cu²⁺ (0.5, 1.5, and 2.5 g L⁻¹), four different concentrations of Cl⁻ (0, 5, 7, and 10 g L⁻¹), two different pH values of 1 and 2, and a constant temperature of 60 °C. Results indicated that addition of Cl⁻ to the system improves copper extractions, especially at higher concentrations of Cu²⁺. Initial copper concentrations in the leaching solution did not significantly affect the copper extraction when Cl⁻ was not present. Better copper extractions were obtained at pH 1 as compared with pH 2. As the Cu²⁺ and Cl⁻ concentrations were increased, higher values of redox potential were obtained. According to the formation constants of the chloro-complexes, the predominant species in the Cu²⁺/Cl⁻ system in the studied interval were CuCl⁺ and Cu²⁺. Using a model of copper speciation in the experimental range predicted for a single copper concentration with increasing Cl⁻ concentration, the Cu²⁺ concentration decreased significantly while the concentration of the chloro-complex species CuCl⁺ increased. In the leached residue, evidence of sulfur formation was found using SEM and corroborated by XRD analysis. When chloride is present in the medium, the amounts of copper and iron in the residue decrease, confirming a positive effect of chloride on the extraction of copper from concentrate for the studied conditions. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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12 pages, 1820 KiB

Open AccessArticle

Zeta Potential of Pyrite Particles in Concentrated Solutions of Monovalent Seawater Electrolytes and Amyl Xanthate

by Alvaro Paredes, Sergio M. Acuña, Leopoldo Gutiérrez and Pedro G. Toledo

Minerals 2019, 9(10), 584; https://doi.org/10.3390/min9100584 - 27 Sep 2019

Cited by 9 | Viewed by 5127

Abstract

Charge screening and adsorption capacity of monovalent ions onto pyrite (Py) in aqueous suspensions and the effect of potassium amyl xanthate (PAX) has been studied by measuring the changes in zeta potential (zp) versus pH with streaming potential. PAX addition in the absence [...] Read more.

Charge screening and adsorption capacity of monovalent ions onto pyrite (Py) in aqueous suspensions and the effect of potassium amyl xanthate (PAX) has been studied by measuring the changes in zeta potential (zp) versus pH with streaming potential. PAX addition in the absence of salts leads to an increase in |zp| suggesting dissolution of the surface ferric hydroxides and recovery of bare Py, corroborating existing theories. In the presence of salt, addition of PAX at pH > 6, for which hydroxides interference in not expected, has little effect over the zp, except when Li is present. The water network around the polar head of PAX is expected to be similar to that of hydrated Li⁺ facilitating the linkage between them and, thus, the formation of Li-mediated Py–PAX bridges. We speculate that these bridges lead to a xanthate shield around anionic sites on Py, decreasing |zp|. An increased PAX dose amplifies the effect of Li as a Py activator but only at low salt. At high salt concentrations, >0.01 M, PAX molecules do not find room to percolate to the surface of Py. Results for monovalent cations should improve our understanding of copper flotation processes in the presence of Py in saltwater. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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16 pages, 4431 KiB

Open AccessArticle

The Effect of Sodium Alginate on Chlorite and Serpentine in Chalcopyrite Flotation

by Guangjiu Pan, Guofan Zhang, Qing Shi and Wei Chen

Minerals 2019, 9(3), 196; https://doi.org/10.3390/min9030196 - 26 Mar 2019

Cited by 27 | Viewed by 5291

Abstract

Chlorite and serpentine are common magnesium-containing gangue minerals in copper sulfide flotation. In this study, sodium alginate, a natural hydrophilic polysaccharide, was introduced as a selective depressant for these gangue minerals. Micro-flotation tests were conducted on both single minerals and synthetic mixtures. The [...] Read more.

Chlorite and serpentine are common magnesium-containing gangue minerals in copper sulfide flotation. In this study, sodium alginate, a natural hydrophilic polysaccharide, was introduced as a selective depressant for these gangue minerals. Micro-flotation tests were conducted on both single minerals and synthetic mixtures. The flotation results showed that sodium alginate could simultaneously depress the flotation of chlorite and serpentine effectively, but seldom influenced the floatability of chalcopyrite at pH 9. In the ternary mixture flotation, a concentrate with a Cu grade of 31% could be achieved at Cu recovery of 90%. The selective depression of chlorite and serpentine was also validated by the real ore flotation experiments. The selective depression mechanism was investigated through adsorption tests, zeta potential measurements, and FTIR analyses. The adsorption density results implied that sodium alginate selectively adsorbed on the surface of phyllosilicates, but no adsorption on the chalcopyrite surface was observed. The zeta potential results showed that the sodium alginate could selectively decrease the surface charge of chlorite and serpentine. The FTIR results revealed the chemical adsorption of sodium alginate on the chlorite and serpentine surface and no form of adsorption on chalcopyrite, agreeing well with the adsorption density results. On the basis of these results, a selective adsorption model of sodium alginate on the mineral surface was proposed. Full article

(This article belongs to the Special Issue Hydrometallurgical Processing of Base Metal Sulphides)

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