Minerals

2022

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11 pages, 13043 KiB

Open AccessArticle

Bioleaching of Enargite/Pyrite-rich “Dirty” Concentrate and Arsenic Immobilization

by Naoko Okibe, Kaito Hayashi, Keishi Oyama, Kazuhiko Shimada, Yuji Aoki, Takahiro Suwa and Tsuyoshi Hirajima

Minerals 2022, 12(4), 449; https://doi.org/10.3390/min12040449 - 6 Apr 2022

Cited by 2 | Viewed by 2233

Abstract

Bioleaching of arsenic (As)-rich, so-called “dirty” concentrates can produce additional Cu value from the flotation waste while simultaneously releasing toxic As. This study bioleached three such concentrates of varying pyrite/enargite ratios ([Py]/[Ena] = 0.7, 1.3 and 2.4) at a pulp density of 20%. [...] Read more.

Bioleaching of arsenic (As)-rich, so-called “dirty” concentrates can produce additional Cu value from the flotation waste while simultaneously releasing toxic As. This study bioleached three such concentrates of varying pyrite/enargite ratios ([Py]/[Ena] = 0.7, 1.3 and 2.4) at a pulp density of 20%. The dissolution behavior of Cu and As in relation to the solution redox potential (Eh) was studied with and without activated carbon (AC) as a potential Eh-controlling catalyst. At this high pulp density, Eh was naturally suppressed, without a need for AC dosing, to <700 mV (a rapid pyrite dissolution is prevented in this Eh range). The effect of AC dosing on Eh varied depending on the type of concentrate; Eh was further reduced only in the case of the most enargite-rich concentrate, DC-I. Among the three concentrates, the highest Cu dissolution (35%) was seen in DC-I (without AC dosing), which simultaneously achieved the lowest As solubilization. Arsenic was immobilized as amorphous precipitates, likely in a mixture of ferric arsenate, cupric arsenate, basic ferric sulfate and sulfur. Arsenic immobilization became increasingly ineffective as the pyrite content increased in the concentrate. Based on these results, setting a lower [Py]/[Ena] ratio prior to the dirty concentrate bioleaching could be a useful approach to promote Cu dissolution and As immobilization simultaneously. Full article

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2021

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14 pages, 23387 KiB

Open AccessFeature PaperArticle

Effects of Mechanical Activation on the Bioleaching of Sphalerite and Marmatite for Zn Extraction

by Shusheng Li, Yisheng Zhang, Luyuan Zhang, Anni Tang, Xin Lv, Yu Zhao, Li Shen, Hongbo Zhao and Guanzhou Qiu

Minerals 2021, 11(2), 111; https://doi.org/10.3390/min11020111 - 23 Jan 2021

Cited by 1 | Viewed by 2799

Abstract

Even though mechanical activation is a significant pretreatment technology for the efficient extraction of metals from mineral resources, its effects on the bioleaching of sphalerite and marmatite are rarely discussed. In this study, mechanical activation pretreatment using various grinding media and grinding times [...] Read more.

Even though mechanical activation is a significant pretreatment technology for the efficient extraction of metals from mineral resources, its effects on the bioleaching of sphalerite and marmatite are rarely discussed. In this study, mechanical activation pretreatment using various grinding media and grinding times was conducted, and particle size distribution, morphology, X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analyses, as well as batch bioleaching experiments, were carried out. The results suggest that #C conditions (corundum jar with zirconia balls) were more efficient than #S conditions (stainless steel jar with stainless steel balls) for the grinding of both sphalerite and marmatite. Mechanical activation significantly improved the bioleaching of sphalerite; however, it inhibited that of marmatite, possibly due to the formation of reactive oxygen species (ROS). The optimum grinding conditions for the bioleaching of sphalerite and marmatite are proposed. Full article

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2020

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16 pages, 3421 KiB

Open AccessArticle

Contributions of Microbial “Contact Leaching” to Pyrite Oxidation under Different Controlled Redox Potentials

by Bingxu Dong, Yan Jia, Qiaoyi Tan, Heyun Sun and Renman Ruan

Minerals 2020, 10(10), 856; https://doi.org/10.3390/min10100856 - 29 Sep 2020

Cited by 11 | Viewed by 4035

Abstract

The function of microbial contact leaching to pyrite oxidation was investigated by analyzing the differences of residue morphologies, leaching rates, surface products, and microbial consortia under different conditions in this study. This was achieved by novel equipment that can control the redox potential [...] Read more.

The function of microbial contact leaching to pyrite oxidation was investigated by analyzing the differences of residue morphologies, leaching rates, surface products, and microbial consortia under different conditions in this study. This was achieved by novel equipment that can control the redox potential of the solution and isolate pyrite from microbial contact oxidation. The morphology of residues showed that the corrosions were a little bit severer in the presence of attached microbes under 750 mV and 850 mV (vs. SHE). At 650 mV, the oxidation of pyrite was undetectable even in the presence of attached microbes. The pyrite dissolution rate was higher with attached microbes than that without attached microbes at 750 mV and 850 mV. The elemental sulfur on the surface of pyrite residues with sessile microorganisms was much less than that without attached microbes at 750 mV and 850 mV, showing that sessile acidophiles may accelerate pyrite leaching by reducing the elemental sulfur inhibition. Many more sulfur-oxidizers were found in the sessile microbial consortium which also supported the idea. The results suggest that the microbial “contact leaching” to pyrite oxidation is limited and relies on the elimination of elemental sulfur passivation by attached sulfur-oxidizing microbes rather than the contact oxidation by EPS-Fe. Full article

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15 pages, 5811 KiB

Open AccessArticle

Mechanical Activation on Bioleaching of Chalcopyrite: A New Insight

by Si-Ting Cao, Xing-Fu Zheng, Zhen-Yuan Nie, Yu-Hang Zhou, Hong-Chang Liu, Jian-Hua Chen, Hong-Ying Yang and Jin-Lan Xia

Minerals 2020, 10(9), 788; https://doi.org/10.3390/min10090788 - 7 Sep 2020

Cited by 11 | Viewed by 3189

Abstract

Mechanical activation as a means of accelerating the mineral dissolution may play an important role in chalcopyrite bioleaching. In the present work, the mechanical activation by ball-milling with 10 min, 30 min, 60 min, 90 min, 120 min and 180 min time periods [...] Read more.

Mechanical activation as a means of accelerating the mineral dissolution may play an important role in chalcopyrite bioleaching. In the present work, the mechanical activation by ball-milling with 10 min, 30 min, 60 min, 90 min, 120 min and 180 min time periods of bioleaching of chalcopyrite was studied, and then evaluated by a Density Functional Theory (DFT) calculation. The results showed that the specific surface area increased sharply in the very beginning of mechanical activation and then increased slowly until the agglomeration of the particles occurred, while the chalcopyrite lattices increased with the mechanical activation. The reaction activity analyzed by cyclic voltammetry (CV) increased slowly in 30 min, increased quickly in the following 90 min, and then decreased, while the hydrophobicity analyzed by contact angles of the chalcopyrite after activation showed less of a change. The results showed that after 15 days of bioleaching, the Cu leaching by Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans) increased from 9.39% in the 0 min of mechanical activation to 87.41% in the 120 min of mechanical activation, and the copper leaching rate increased by about 78%. The DFT results provide solid proof that the activated chalcopyrite can be adsorbed more easily by cells with higher adsorption energies and stronger bonds. Full article

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10 pages, 1949 KiB

Open AccessArticle

Kinetic Study in Atmospheric Pressure Organic Acid Leaching: Shrinking Core Model versus Lump Model

by Kevin Cleary Wanta, Widi Astuti, Indra Perdana and Himawan Tri Bayu Murti Petrus

Minerals 2020, 10(7), 613; https://doi.org/10.3390/min10070613 - 9 Jul 2020

Cited by 21 | Viewed by 4308

Abstract

The kinetics study has an essential role in the scale-up process because it illustrates the real phenomena of a process. This study aims to develop a mathematical model that can explain the mechanism of the leaching process of laterite ore using a low [...] Read more.

The kinetics study has an essential role in the scale-up process because it illustrates the real phenomena of a process. This study aims to develop a mathematical model that can explain the mechanism of the leaching process of laterite ore using a low concentration of the citric acid solution and evaluate that model using the experimental data. As a raw material, this process used powder-shaped limonite laterite ores with a size of 125–150 µm. The leaching process is carried out using 0.1 M citric acid solution, F:S ratio of 1:20, and a leaching time of 2 h. The temperature parameter was varied at 303, 333, and 358 K. The experimental results showed that the higher the operating temperature, the higher the extracted nickel. The results of this experiment were used to evaluate the shrinking core kinetics model and the lumped model. The simulation results for both models show that the lumped model can provide better simulation results. Quantitatively, the percentage of errors from the shrinking core model is around 3.5 times greater than the percentage of errors from using the lumped model. This result shows that in this leaching process, the process mechanism that occurs involves the reactant diffusion step and the chemical reactions step; those steps run simultaneously. Full article

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2019

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11 pages, 3206 KiB

Open AccessArticle

Bioleaching of Au-Containing Ore Slates and Pyrite Wastes

by Elena B. Daibova, Inna V. Lushchaeva, Victor I. Sachkov, Natalia I. Karakchieva, Vladislav V. Orlov, Rodion O. Medvedev, Roman A. Nefedov, Olga N. Shplis and Natalya I. Sodnam

Minerals 2019, 9(10), 643; https://doi.org/10.3390/min9100643 - 20 Oct 2019

Cited by 10 | Viewed by 5324

Abstract

The influence of the environment and bacterial cultures on the degree of gold leaching from Au-containing raw materials of different compositions, origins, and with different contents of gold, selected in the Ural Federal District (Russia), was determined. The leaching degree was determined according [...] Read more.

The influence of the environment and bacterial cultures on the degree of gold leaching from Au-containing raw materials of different compositions, origins, and with different contents of gold, selected in the Ural Federal District (Russia), was determined. The leaching degree was determined according to the change of the gold concentration in the ore by means of mass-spectrometry with inductively-coupled plasma. It was demonstrated that the degree of Au bioleaching from carbonaceous-argillaceous slates, containing 2.17 g/t of gold, and from pyritic technogenic raw materials, containing 1.15 g/t, when holding them in peptone water and Leten medium reached 92.17% and 87.83%, respectively. Full article

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10 pages, 1980 KiB

Open AccessArticle

Dissolution and Passivation of Chalcopyrite during Bioleaching by Acidithiobacillus ferrivorans at Low Temperature

by Tangjian Peng, Lei Chen, Jingshu Wang, Jie Miao, Li Shen, Runlan Yu, Guohua Gu, Guanzhou Qiu and Weimin Zeng

Minerals 2019, 9(6), 332; https://doi.org/10.3390/min9060332 - 28 May 2019

Cited by 18 | Viewed by 4277

Abstract

Our knowledge on the dissolution and passivation mechanisms of chalcopyrite during bioleaching at low temperature has been limited to date. In this study, an Acidithiobacillus ferrivorans strain with high tolerance to heavy metals and UV radiation was used for chalcopyrite bioleaching. At 6 [...] Read more.

Our knowledge on the dissolution and passivation mechanisms of chalcopyrite during bioleaching at low temperature has been limited to date. In this study, an Acidithiobacillus ferrivorans strain with high tolerance to heavy metals and UV radiation was used for chalcopyrite bioleaching. At 6 °C, no apparent precipitate was detected on the mineral surface after bioleaching using a scanning electron microscope (SEM). X-ray diffraction (XRD) revealed that the ore residue contained only chalcopyrite and quartz. X-ray photoelectron spectroscopy (XPS) analysis revealed that the content of S⁰ on the mineral surface remained low and the ratio of SO₄²⁻ decreased from 46.7% to 20.9%, but the amount of S_n²⁻ increased from 10.4% to 21.4% after bioleaching. Expression of five critical iron- and sulfur-oxidation genes during bioleaching was analyzed using quantitative real-time PCR. The gene rusA had higher expression in the mid-log phase than in the stationary phase but hdrA and cyoC1 showed an opposite trend. All genes had higher expression at 6 °C than at 28 °C, so as to compensate for the decline in the enzyme activities. The study revealed that polysulfide was the most plausible passivating substance at 6 °C, and the strain can maintain the iron- and sulfur-oxidation activities during low-temperature bioleaching. Full article

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14 pages, 4338 KiB

Open AccessArticle

Intermediates Transformation of Bornite Bioleaching by Leptospirillum ferriphilum and Acidithiobacillus caldus

by Maoxin Hong, Xingxing Wang, Lingbo Wu, Chaojun Fang, Xiaotao Huang, Rui Liao, Hongbo Zhao, Guanzhou Qiu and Jun Wang

Minerals 2019, 9(3), 159; https://doi.org/10.3390/min9030159 - 7 Mar 2019

Cited by 21 | Viewed by 4545

Abstract

Bioleaching experiments, electrochemical tests, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were conducted to investigate the intermediates transformation of bornite by Leptospirillum ferriphilum and Acidithiobacillus caldus. The bioleaching experimental results showed that the presence of L. ferriphilum and A. caldus significantly [...] Read more.

Bioleaching experiments, electrochemical tests, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were conducted to investigate the intermediates transformation of bornite by Leptospirillum ferriphilum and Acidithiobacillus caldus. The bioleaching experimental results showed that the presence of L. ferriphilum and A. caldus significantly accelerated the bornite bioleaching. In addition, the intermediate species of bornite bioleaching with these two kinds of bacteria were similar. Electrochemical analysis indicated that the dissolution of bornite was an acid-consuming process. The results of XRD showed that intermediate species, namely covellite (CuS), mooihoekit (Cu₉Fe₉S₁₆) and isocubanite (CuFe₂S₃), were formed during bornite bioleaching, and a mass of elemental sulfur was formed in the late stage of bioleaching. The Cu 2p photoelectron spectrum revealed that Cu was present in the form of Cu (I) during the bornite bioleaching. Additionally, the S 2p_3/2 photoelectron spectrum suggested that S²⁻ and S₂²⁻ were gradually converted to S_n²⁻/S⁰, and the formation of elemental sulfur hindered the further dissolution of the bornite. Full article

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13 pages, 1749 KiB

Open AccessArticle

Bioleaching of Major, Rare Earth, and Radioactive Elements from Red Mud by using Indigenous Chemoheterotrophic Bacterium Acetobacter sp.

by Yang Qu, Hui Li, Xiaoqing Wang, Wenjie Tian, Ben Shi, Minjie Yao and Ying Zhang

Minerals 2019, 9(2), 67; https://doi.org/10.3390/min9020067 - 22 Jan 2019

Cited by 67 | Viewed by 6330

Abstract

The aim was to study the bioleaching performance of chemoheterotrophic bacterium involved in leaching of major, rare earth, and radioactive elements from red mud (RM), and to explore the underlying mechanism. An acid-producing bacterium, identified as Acetobacter sp., was isolated from RM impoundment [...] Read more.

The aim was to study the bioleaching performance of chemoheterotrophic bacterium involved in leaching of major, rare earth, and radioactive elements from red mud (RM), and to explore the underlying mechanism. An acid-producing bacterium, identified as Acetobacter sp., was isolated from RM impoundment and used in the bioleaching experiments under one-step, two-step and spent medium process at up to 10% pulp density. The results showed that the leaching ratios of Al, Lu, Y, Sc, and Th were 55%, 53%, 61%, 52%, and 53% respectively under one-step process at 2% pulp density. Under both one- and two-step processes at 2% pulp density, the radioactivity of bioleached RM can meet the relevant regulation in China. The total amount of organic acids excreted by Acetobacter sp. increased with an increase of RM pulp density. After bioleaching, contents of hematite and gibbsite decreased but perovskite increased in RM. Micromorphology analysis indicated that the cells of Acetobacter sp. adhered to RM particles and formed large-size aggregates, and a new crystal of weddellite emerged. In view of the shorter lag phase and smaller biomass comparing to fungi even under direct contact with RM, bacterium Acetobacter sp. is supposed to apply to in situ heap or dump bioleaching of RM. Full article

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2018

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20 pages, 3615 KiB

Open AccessReview

Assessment of Bioleaching Microbial Community Structure and Function Based on Next-Generation Sequencing Technologies

by Shuang Zhou, Min Gan, Jianyu Zhu, Xinxing Liu and Guanzhou Qiu

Minerals 2018, 8(12), 596; https://doi.org/10.3390/min8120596 - 17 Dec 2018

Cited by 11 | Viewed by 6012

Abstract

It is widely known that bioleaching microorganisms have to cope with the complex extreme environment in which microbial ecology relating to community structure and function varies across environmental types. However, analyses of microbial ecology of bioleaching bacteria is still a challenge. To address [...] Read more.

It is widely known that bioleaching microorganisms have to cope with the complex extreme environment in which microbial ecology relating to community structure and function varies across environmental types. However, analyses of microbial ecology of bioleaching bacteria is still a challenge. To address this challenge, numerous technologies have been developed. In recent years, high-throughput sequencing technologies enabling comprehensive sequencing analysis of cellular RNA and DNA within the reach of most laboratories have been added to the toolbox of microbial ecology. The next-generation sequencing technology allowing processing DNA sequences can produce available draft genomic sequences of more bioleaching bacteria, which provides the opportunity to predict models of genetic and metabolic potential of bioleaching bacteria and ultimately deepens our understanding of bioleaching microorganism. High-throughput sequencing that focuses on targeted phylogenetic marker 16S rRNA has been effectively applied to characterize the community diversity in an ore leaching environment. RNA-seq, another application of high-throughput sequencing to profile RNA, can be for both mapping and quantifying transcriptome and has demonstrated a high efficiency in quantifying the changing expression level of each transcript under different conditions. It has been demonstrated as a powerful tool for dissecting the relationship between genotype and phenotype, leading to interpreting functional elements of the genome and revealing molecular mechanisms of adaption. This review aims to describe the high-throughput sequencing approach for bioleaching environmental microorganisms, particularly focusing on its application associated with challenges. Full article

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16 pages, 3266 KiB

Open AccessArticle

Synchrotron Radiation Based Study of the Catalytic Mechanism of Ag⁺ to Chalcopyrite Bioleaching by Mesophilic and Thermophilic Cultures

by Zhenyuan Nie, Weiwei Zhang, Hongchang Liu, Jinlan Xia, Wei Zhu, Duorui Zhang, Lei Zheng, Chenyan Ma, Yidong Zhao and Wen Wen

Minerals 2018, 8(9), 382; https://doi.org/10.3390/min8090382 - 3 Sep 2018

Cited by 4 | Viewed by 3751

Abstract

The catalytic mechanism of Ag⁺ for chalcopyrite bioleaching by mesophilic culture (at 30 °C) and thermophilic culture (at 48 °C) was investigated using synchrotron radiation-based X-ray diffraction (SR-XRD) and S K-edge and Fe L-edge X-ray absorption near edge structure (XANES) spectroscopy. Bioleaching [...] Read more.

The catalytic mechanism of Ag⁺ for chalcopyrite bioleaching by mesophilic culture (at 30 °C) and thermophilic culture (at 48 °C) was investigated using synchrotron radiation-based X-ray diffraction (SR-XRD) and S K-edge and Fe L-edge X-ray absorption near edge structure (XANES) spectroscopy. Bioleaching experiments showed that copper extraction from chalcopyrite bioleaching by both cultures was promoted significantly by Ag⁺, with more serious corrosion occurring on the minerals surface. SR-XRD and XANES analyses showed that the intermediates S⁰, jarosite and secondary minerals (bornite, chalcocite and covellite) formed for all bioleaching experiments. For these secondary minerals, the formation of bornite and covellite was promoted significantly in the presence of Ag⁺ for both cultures, while Ag⁺ has almost no effect on the formation of chalcocite. These results provided insight into the catalytic mechanisms of Ag⁺ to chalcopyrite bioleaching by the mesophilic and thermophilic cultures, which are both probably due to the rapid formation of bornite by Ag⁺ and the conversion of bornite to covellite. Full article

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23 pages, 5044 KiB

Open AccessArticle

(Bio)leaching Behavior of Chromite Tailings

by Viviana Bolaños-Benítez, Eric D. Van Hullebusch, Piet N.L. Lens, Cécile Quantin, Jack Van de Vossenberg, Sankaran Subramanian and Yann Sivry

Minerals 2018, 8(6), 261; https://doi.org/10.3390/min8060261 - 20 Jun 2018

Cited by 17 | Viewed by 7331

Abstract

Chromite beneficiation operations in Sukinda valley (India) produce large amounts of tailings, which are stored in open air. In this study, bioleaching experiments were carried out in batch reactors with Acidithiobacillus thiooxidans or Pseudomonas putida in order to determine the potential leachability of [...] Read more.

Chromite beneficiation operations in Sukinda valley (India) produce large amounts of tailings, which are stored in open air. In this study, bioleaching experiments were carried out in batch reactors with Acidithiobacillus thiooxidans or Pseudomonas putida in order to determine the potential leachability of metals contained in these tailings due to biological activity. Acidic and alkaline pH resulted from the incubation of tailings with A. thiooxidans and P. putida, respectively. Tailings were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM), and chemical extraction of Cr(VI) with KH₂PO₄ was performed. Mineralogical investigations showed that tailings are mainly composed of chromite, hematite, lizardite, chlorite, and goethite, which are all known as Cr-bearing phases. During the leaching with A. thiooxidans and P. putida, total Cr was initially extracted as Cr(VI) due to the presence of phosphates in the medium, and subsequently decreased because of Cr(VI) adsorption and reduction to Cr(III). Reduction was associated with bacterial activity, but also with the presence of ferrous iron. Despite the occurrence of siderophores in the tailings after incubation with P. putida, under acidic conditions, Fe extracted remained higher. Extracted Ni, Mn, and Al concentrations also increased over time. Given the significant amount of chromite tailings produced every year, this study shows that tailings storage and leachability represent a potential source of chromium. However, our findings suggest that the presence of bacterial communities, as well as physicochemical processes, favor Cr(VI) reduction. Full article

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11 pages, 1046 KiB

Open AccessArticle

Comparison of Heterotrophic Bioleaching and Ammonium Sulfate Ion Exchange Leaching of Rare Earth Elements from a Madagascan Ion-Adsorption Clay

by Megan J. Barnett, Barbara Palumbo-Roe and Simon P. Gregory

Minerals 2018, 8(6), 236; https://doi.org/10.3390/min8060236 - 30 May 2018

Cited by 38 | Viewed by 7876

Abstract

Rare earth elements (REE) are considered to be a critical resource, because of their importance in green energy applications and the overdependence on Chinese imports. REE rich ion-adsorption deposits (IAD) result from tropical weathering of REE enriched igneous rocks. Commercial REE leaching from [...] Read more.

Rare earth elements (REE) are considered to be a critical resource, because of their importance in green energy applications and the overdependence on Chinese imports. REE rich ion-adsorption deposits (IAD) result from tropical weathering of REE enriched igneous rocks. Commercial REE leaching from IAD, using salt solutions occurs via an ion-exchange mechanism. Bioleaching of IAD by Aspergillus or Bacillus, was compared to Uninoculated Control and Salt leaching (0.5 M ammonium sulfate) over 60 days. Salt leaching was most effective, followed by Aspergillus, Bacillus then Uninoculated Control. Most of the REE and major elements released by Salt leaching occurred before day 3. With bioleaching, REE and major elements release increased with time and had a greater heavy to light REE ratio. Similar total heavy REE release was observed in Salt leaching and Aspergillus (73.1% and 70.7% Lu respectively). In bioleaching experiments, pH was inversely correlated with REE release (R² = 0.947 for Lu) indicating leaching by microbially produced acids. These experiments show the potential for bioleaching of REE from IAD, but dissolution of undesirable elements could cause problems in downstream processing. Further understanding of the bioleaching mechanisms could lead to optimization of REE recovery. Full article

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19 pages, 1876 KiB

Open AccessReview

Bioleaching of Arsenic-Bearing Copper Ores

by José Antonio Díaz, Jennyfer Serrano and Eduardo Leiva

Minerals 2018, 8(5), 215; https://doi.org/10.3390/min8050215 - 17 May 2018

Cited by 26 | Viewed by 13753

Abstract

World copper (Cu) production has been strongly affected by arsenic (As) content, because As-rich Cu concentrates are not desirable in the metal foundries. When As-rich Cu concentrates are processed by smelting they release As as volatile compounds into the atmosphere and inside furnaces, [...] Read more.

World copper (Cu) production has been strongly affected by arsenic (As) content, because As-rich Cu concentrates are not desirable in the metal foundries. When As-rich Cu concentrates are processed by smelting they release As as volatile compounds into the atmosphere and inside furnaces, generating serious risks to human health. In recent years, exports of Cu concentrates are being penalized for the increasingly high As content of the ores, causing economies that depend on the Cu market to be seriously harmed by this impurity. In the last few decades, biohydrometallurgy has begun to replace the traditional Cu sulfide processing, however bioleaching processes for As-bearing Cu ores which contain enargite are still in the development stage. Researchers have not yet made successful progress in enargite bioleaching using typical mesophilic and thermophilic bacteria that oxidize sulfide. New approaches based on direct oxidative/reductive dissolution of As from enargite could result in significant contributions to Cu biohydrometallurgy. Thus, As-rich Cu concentrates could be pre-treated by bioleaching, replacing current technologies like roasting, pressure leaching and alkaline leaching by selective biological arsenite oxidation or arsenate reduction. In this article, we review the As problem in Cu mining, conventional technologies, the biohydrometallurgy approach, and As bioleaching as a treatment alternative. Full article

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14 pages, 14366 KiB

Open AccessArticle

The Evidence of Decisive Effect of Both Surface Microstructure and Speciation of Chalcopyrite on Attachment Behaviors of Extreme Thermoacidophile Sulfolobus metallicus

by Weibo Ling, Lei Wang, Hongchang Liu, Zhenyuan Nie, Yun Yang, Yi Yang, Chenyan Ma, Lei Zheng, Yidong Zhao and Jinlan Xia

Minerals 2018, 8(4), 159; https://doi.org/10.3390/min8040159 - 13 Apr 2018

Cited by 7 | Viewed by 4428

Abstract

The effect of the surface microstructure and chemical speciation of chalcopyrite on the attachment behaviors of thermoacidophilic archaeon Sulfolobus metallicus was evaluated for the first time by using integrated techniques including epifluorescence microscopy (EFM) and sulfur K-edge X-ray absorption near edge structure (S [...] Read more.

The effect of the surface microstructure and chemical speciation of chalcopyrite on the attachment behaviors of thermoacidophilic archaeon Sulfolobus metallicus was evaluated for the first time by using integrated techniques including epifluorescence microscopy (EFM) and sulfur K-edge X-ray absorption near edge structure (S K-edge XANES) spectroscopy, as well as scanning electron microscopy with energy dispersive spectrometry (SEM/EDS) and Fourier transform infrared (FT-IR) spectroscopy. In order to obtain the specific surface, the chalcopyrite slices were electrochemically oxidized at 0.87 V and reduced at −0.54 V, respectively. The EFM analysis showed that the quantity of cells attaching on the mineral surface increased with time, and the biofilm formed faster on the electrochemically treated slices than on the untreated ones. The SEM-EDS analysis indicated that the deficiency in energy substrate elemental sulfur (S⁰) in the specific microsize of local defect sites was disadvantageous to the initial attachment of cells. The XANES and FT-IR data suggested that the elemental sulfur (S⁰) could be in favor of initial attachment, and surface jarosites inhibited the adsorption and growth of S. metallicus. These results demonstrated that not only the surface microstructure but also the chemical speciation defined the initial attachment behaviors and biofilm growth of the extreme thermophilic archaeon S. metallicus. Full article

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26 pages, 5766 KiB

Open AccessReview

Copper Bioleaching in China: Review and Prospect

by Shenghua Yin, Leiming Wang, Eugie Kabwe, Xun Chen, Rongfu Yan, Kai An, Lei Zhang and Aixiang Wu

Minerals 2018, 8(2), 32; https://doi.org/10.3390/min8020032 - 23 Jan 2018

Cited by 101 | Viewed by 25271

Abstract

The commercial application of copper bioleaching, an environmentally-friendly approach for low-grade and secondary mineral resources recycling, has increased worldwide since the 2000s. As the world’s second-largest economic entity and the largest developing country, China has the largest demand for metal resources, significantly advancing [...] Read more.

The commercial application of copper bioleaching, an environmentally-friendly approach for low-grade and secondary mineral resources recycling, has increased worldwide since the 2000s. As the world’s second-largest economic entity and the largest developing country, China has the largest demand for metal resources, significantly advancing the theory and industrial technology of copper bioleaching. This paper reviews the exploration and application of copper bioleaching in China. Two typical bioleaching applications and technological processes, bioheap leaching at the Zijinshan Copper Mine and bioheap leaching at the Dexing Copper Mine, are introduced. The considerable research completed by researchers is summarized, especially focusing on the isolation and identification of leaching bacteria, the bioleaching mechanism and interface reactions, multistage percolation behavior, bioleaching system reconstruction, the multiphysics coupled model, and enhanced copper bioleaching from waste printed circuit boards (WPCBs). Based on this investigation in China, key trends and prospects in copper bioleaching—such as efficiency improvement, environmental protection, and improved technology applications—are proposed. Full article

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12 pages, 11684 KiB

Open AccessArticle

Vanadium Bioleaching Behavior by Acidithiobacillus ferrooxidans from a Vanadium-Bearing Shale

by Dunpei Wei, Tao Liu, Yimin Zhang, Zhenlei Cai, Jingtao He and Chengbao Xu

Minerals 2018, 8(1), 24; https://doi.org/10.3390/min8010024 - 15 Jan 2018

Cited by 20 | Viewed by 5618

Abstract

This study investigated bioleaching behavior of vanadium from a vanadium-bearing shale using Acidithiobacillus ferrooxidans (A. ferrooxidans). Results showed a maximum recovery of 62% vanadium in 1.2-day bioleaching, which was 22.45% higher than the controls. Then, the vanadium leaching efficiency decreased significantly, [...] Read more.

This study investigated bioleaching behavior of vanadium from a vanadium-bearing shale using Acidithiobacillus ferrooxidans (A. ferrooxidans). Results showed a maximum recovery of 62% vanadium in 1.2-day bioleaching, which was 22.45% higher than the controls. Then, the vanadium leaching efficiency decreased significantly, only 24% of that was obtained on the tenth day. The vanadium extraction in 1.2 days was mainly attributed to the dissolution of vanadium in free oxides of shale. Fe³⁺ produced by A. ferrooxidans promoted the dissolution process. X-ray diffraction (XRD) patterns of the leached residues confirmed the generation of jarosite. SEM-EDS analysis of the residues indicated that jarosite adsorbed on the shale and inhibited the further dissolution of vanadium. The relevance of V, Fe, S, O was quite good in the energy disperse X-ray spectrometry (EDS) element mapping of jarosite, and acid-washing of the jarosite resulted in 31.6% of the vanadium in the precipitates desorption, indicating that the decrease of vanadium leaching efficiency in bioleaching process was caused by both adsorption and co-precipitation with jarosite. Full article

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Co-Bioleaching of Chalcopyrite and Silver-Bearing Bornite in a Mixed Moderately Thermophilic Culture

by Congren Yang, Fen Jiao and Wenqing Qin

Minerals 2018, 8(1), 4; https://doi.org/10.3390/min8010004 - 26 Dec 2017

Cited by 19 | Viewed by 5910

Abstract

Chalcopyrite and bornite are two important copper minerals, and they often coexist. In this study, the co-bioleaching of chalcopyrite and silver-bearing bornite by mixed moderately thermophilic culture at 50 °C was investigated. The bioleaching results show that the extraction percentage of Cu for [...] Read more.

Chalcopyrite and bornite are two important copper minerals, and they often coexist. In this study, the co-bioleaching of chalcopyrite and silver-bearing bornite by mixed moderately thermophilic culture at 50 °C was investigated. The bioleaching results show that the extraction percentage of Cu for co-bioleaching of chalcopyrite (Ccp) and silver-bearing bornite (Bn) (Ccp/Bn = 3:1) was 94.6%. Compared to bioleaching of chalcopyrite or silver-bearing bornite alone, the Cu extraction percentage was greatly enhanced when they were bioleached together. The leaching residues were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Silver-bearing bornite dissolved preferentially compared to chalcopyrite, due to galvanic interactions. Simultaneously, Ag⁺ was released from the silver-bearing bornite into solution. Ag₂S formed on the surface because Cu and Fe in the chalcopyrite were replaced by Ag⁺, accelerating chalcopyrite dissolution and enrichment of Ag on the surface of the chalcopyrite. Full article

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