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Abstract

Chalcopyrite is the primary copper mineral used for production of copper metal. Today, as a result of rapid industrialization, there has been enormous demand to profitably process the low grade chalcopyrite and "dirty" concentrates through bioleaching. In the current scenario, heap bioleaching is the most advanced and preferred eco-friendly technology for processing of low grade, uneconomic/difficult-to-enrich ores for copper extraction. This paper reviews the current status of chalcopyrite bioleaching. Advanced information with the attempts made for understanding the diversity of bioleaching microorganisms; role of OMICs based research for future applications to industrial sectors and chemical/microbial aspects of chalcopyrite bioleaching is discussed. Additionally, the current progress made to overcome the problems of passivation as seen in chalcopyrite bioleaching systems have been conversed. Furthermore, advances in the designing of heap bioleaching plant along with microbial and environmental factors of importance have been reviewed with conclusions into the future prospects of chalcopyrite bioleaching. Copyright © 2015 Elsevier Ltd. All rights reserved.

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... These microorganisms are constituted of a variety of genus, e.g., Acidithiobacillus, Sulfolobus, Acidianus and Leptospirillum (Das, Ayyappan and Chaudhury 1999). A list of potential acidophilic microorganisms reported in bioleaching along with their characteristic features can be found elsewhere (Panda et al. 2015a;Schippers 2007;Schippers et al. 2014;Valdes et al. 2010). As bioleaching environment/condition determines the growth of microorganism; acidophilic microorganisms have been classified as mesophiles, moderate thermophiles and extreme thermophiles according to their ability to support a range of temperature. ...
... Among the acid-insoluble sulphide minerals, the thiosulfate pathway is mostly investigated for pyrite (FeS 2 ) (Rohwerder et al. 2003;Tao and Dongwei 2014). The following reactions (4, 5) illustrate the thiosulfate pathway (Panda et al. 2015a;Vera, Schippers and Sand 2013). ...
... In case of the polysuphide pathway, the dissolution of metal sulphides are ensured by a proton attack and electron extraction (by Fe 3+ ) leading to the release of elemental sufur. The overall reactions (6-8), are shown below (Panda et al. 2015a;Tao and Dongwei 2014): ...
Article
Mineral biotechnological applications e.g. bioleaching and bio-beneficiation, for waste treatment and resource recovery have invited due attention owing to their economic and eco-friendly benefits in comparison to the conventional methods. Although research has progressed well, there are several aspects that are still not well understood and require more attention in view of full scale industrial application of these processes. For example, microbe-mineral/galvanic interactions, passivation phenomenon, synergistic effects among the microbes, identification of novel and robust microbial strains etc., require more studies to explore the fundamental aspects. In addition, mode of treatment for a wide variety of ores and/or concentrates, advances in engineering applications and scaling-up of bio-processes to industrial level along with the assessment of techno-economic feasibility, life-cycle and environmental impact can provide numerous opportunities for the researchers to further explore the applied aspects. This paper presents comprehensive details, including the latest research, on the fundamentals and applications of bioleaching, bioflotation and bioflocculation for the readers. The key microorganisms and their mode of action, factors affecting each bio-processes and aspects related to their scale-up and industrial applications are reviewed, analyzed and compared. It is believed that the recent advances, emerging dimensions and future directions of research presented in this paper will serve as a guide for the researchers to further explore this exciting field of research.
... The pH level is also a key factor for microbial colonization and metabolism. According to [27], the growth of Leptospirillum ferriphilum is inhibited below pH 1.0 and above 3.0, with an optimum pH between 1.3 and 1.8 [30]; Sulfobacillus thermosulfidooxidans and Acidithiobacillus caldus are dominant at pH 2.0 and 2.5; and Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans are often detected at pH 2.0 [30]. ...
... The pH level is also a key factor for microbial colonization and metabolism. According to [27], the growth of Leptospirillum ferriphilum is inhibited below pH 1.0 and above 3.0, with an optimum pH between 1.3 and 1.8 [30]; Sulfobacillus thermosulfidooxidans and Acidithiobacillus caldus are dominant at pH 2.0 and 2.5; and Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans are often detected at pH 2.0 [30]. ...
... According to [30], archaea growing heterotrophically have played a significant role in bioleaching along with the autotrophs. Mesophiles that utilize organic substrates (but often not Fe(II)) belonging to the genera Acidiphillum, Acidocella, Acidisphaera, and Acidobacterium have been isolated from acidic environments along with chemolithotrophs such as Acidithiobacillus ferrooxidans. ...
Article
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This paper reports on a study of column bioleaching of a low-grade chalcopyrite ore that is currently dump-leached under natural biological conditions without any control over microbial populations. The experimental methodology was focused on the effect of managing the bacterial populations in a raffinate solution sourced from a dump-leach operation. This study presents results from columns of two heights (0.45 and 1.0 m). We demonstrated that intermittent irrigation enhanced the chalcopyrite dissolution during column leaching, but excessively long rest periods negatively affected the chemical and bacterial activity due to the shortage of oxidizing agents and/or nutrients for microorganisms. The recovery of low-grade chalcopyrite ore was enhanced by increasing the microbial cell density. The addition of 1.5 × 108 cells/mL to the 0.45 m column and 5.0 × 107 cells/mL to the 1 m column resulted in increased extraction, with the copper dissolution increasing from 32% to 44% in the 0.45 m column and from 30% to 40% in the 1.0 m column over 70 days of leaching. Under these conditions, the pH level remained constant at ~1.8, and the redox potential was around 840 mV vs. the SHE throughout the experiment. These results provided useful insights for evaluating a sustainable controlled dump-based technology for mineral bioprocessing
... By contrast, the overall process involved in bioleaching of acid-insoluble metals sulfides is called the "thiosulfate mechanism", since it includes formation of thiosulfate as an intermediate product of metal sulfide dissolution. The mechanism of this transformation has been extensively studied and reviewed (e.g., Rohwerder et al., 2003;Schippers, 2004;Panda, Akcil, Pradhan, & Deveci, 2015). Thiosulfate is further quantitatively oxidized into tetrathionate, which is further degraded into various sulfur compounds such as trithionate, pentathionate, elemental sulfur, and sulfite. ...
... The formation of jarosite reduces the concentration of ferric iron in the solution, which can negatively affect the dissolution kinetics of metal sulfides. Many authors have also pointed out that the formation of iron sulfate precipitates is implicated in hindering the complete dissolution of some minerals such as chalcopyrite in bioleaching processes (e.g., Stott, Watling, Franzmann, & Sutton, 2000;Córdoba, Muñoz, Blázquez, González, & Ballester, 2008b;Panda et al., 2015). The jarosite forms a coating on the surface of the minerals preventing the transport of reagents and reaction products, which slows down or even stops the leaching reactions. ...
... Chalcopyrite dissolution was limited to 45% and completely stopped after four days. The refractory nature of chalcopyrite to leaching in atmospheric conditions has been extensively studied and reviewed (e.g., Pradhan et al., 2008;Watling, 2006;Panda et al., 2015) and is due to the passivation of the mineral in acidic ferric sulfate media at ambient temperature, which slows or stops chalcopyrite dissolution. The nature of the passivating layer is complex and poorly understood. ...
Chapter
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This chapter compiles basic knowledge and most recent developments regarding bioleaching of copper ores and concentrates. It is divided in two parts, the fundamentals and the practical aspects of this technology, and includes (i) the principles of bioleaching chemistry, (ii) data regarding bioleaching microbiology, (iii) descriptions of the major mechanisms involved in bioleaching operations, and (iv) the engineering aspects of copper bioproduction. It will outline the current research, particularly with respect to chalcopyrite bioleaching, and assess the most promising developments. The content of the chapter is restricted to the investigation of bioleaching practices that are used at the industrial scale and thus will include only data related to chemolithoautrophic microorganisms. Bioleaching based on heterotrophic bacteria or fungi is not within the scope of the chapter since it remains at the laboratory stage.
... Compared with physical and chemical methods, bioleaching has been widely used to treat a variety of sulfide ores, because of its environmental friendliness, simple operation, strong oxidation ability, and low cost (Gu et al., 2018;Srichandan et al., 2019). Bioleaching has been investigated as a method for recovering valuable metals from pyrite (Yin et al., 2020), chalcopyrite (Panda et al., 2015), lead-zinc ore (Liao et al., 2021), uranium ore (Kaksonen et al., 2020) and other minerals. More than 40 microbial species with leaching capabilities have been found in bioleaching systems (Panda et al., 2015). ...
... Bioleaching has been investigated as a method for recovering valuable metals from pyrite (Yin et al., 2020), chalcopyrite (Panda et al., 2015), lead-zinc ore (Liao et al., 2021), uranium ore (Kaksonen et al., 2020) and other minerals. More than 40 microbial species with leaching capabilities have been found in bioleaching systems (Panda et al., 2015). Based on their functional categories, acidophilic microorganisms can be divided into ferrous/sulfur oxidizers, ferrous oxidizers, and sulfur oxidizers (Mendez-Garcia et al., 2015). ...
Article
Unwieldy fine sulfide ores are produced during mining; without being appropriately disposed of, they can cause environmental pollution and waste resources. This study investigated the leaching performance of a moderately thermophilic consortia (Leptospirillum ferriphilum + Acidithiobacillus caldus + Sulfobacillus benefaciens) for fine lead-zinc sulfide raw ore. The results showed this microbial community created a low pH, high ORP, and high cell concentration environment for mineral leaching, improving bioleaching efficiency. Under the action of this consortia, the zinc leaching rate reached 96.44 in 8 days, and reached 100% after 12 days. EPS analysis indicated that the consortia could mediate the secretion of more polysaccharides to ensure leaching efficiency. EPS levels and amino acids were the main factors affecting bioleaching. An analysis of mineral surface characteristics showed the consortia effectively leached pyrite and sphalerite from the fine sulfide ore, and prevented the mineral surface forming the jarosite that could hinder bioleaching. This study found that bioleaching reduced the potential environmental toxicity of the minerals, providing an important reference for guiding the bioleaching of unwieldy fine sulfide raw ore.
... Based on stoichiometry, the growth of microorganisms on pyrite and the oxidation rate of pyrite were not congruent with the direct bioleaching mechanism (Boon and Heijnen 2001). Some authors observed that bioleaching is a chemical process and that microorganisms provide the required oxidant (Fe 3+ , Eq.3) and the environment in the EPS (extracellular polymeric substances) (Crundwell 2003;Gu 2018;Panda et al. 2015a). Consequently, microorganisms obtain energy and nutrients for growth (Pradhan et al. 2008). ...
... Common microorganisms used in heap bioleaching are acidophilic bacteria. They occur mostly in acidic pit water, acidic hot springs, and acidic soils, and have been summarized focus on growth environment and function (Jia et al. 2019;Johnson 2014;Natarajan 2018b;Panda et al. 2015a;Yang and Yang 2006). In bioleaching, there were not only synergistic effects of different bioleaching pathway but also synergistic effects among different microorganisms and microorganisms in different surroundings. ...
Article
Heap bioleaching is a microbial technology that catalyzes the decomposition of ore without grinding. The crushed ore is stacked on the liner, and the microbial solution flows through the heap from top to bottom. Under the oxidation action of Fe³⁺, valuable metals in sulfide enter the liquid phase as ions, which are then recovered from the subsequent process. The main function of microorganisms are the regeneration of Fe³⁺. This technology has the advantages of low cost, environment friendliness, simple requirements, and suitability for the treatment of low-grade ore. It has been applied to industrial production. However, the technology is still evolving because there are still many problems that are not well explained, such as synergistic effect between microorganisms, the role of extracellular polymeric substances, passivation phenomenon, galvanic interaction between minerals, mode of ore treatment and heap running, the impact of the natural environment, reasonable disposal of tailings, etc. This paper adequately discusses these aspects based on plentiful excellent researches, including the latest ideas, which can provide a comprehensive and in-depth knowledge of heap bioleaching for the readers. Besides, commercial process data, effective improvement measures, environmental protection ways, laboratory research, and optimization methods were reviewed. Based on the comparative analysis of these knowledges, the recommended technical parameters and the remaining challenges are displayed, which can guide a new commercial or pilot-scale heap. Researchers can make new explorations from the potential research directions and methods proposed in this paper, so that heap bioleaching technology can better serve social development.
... Bioleaching is an economical and green technology for the recovery of precious metals from minerals. Notably, approximate 7% of the world's copper production was statistically produced from low-grade copper ore and mine tailing by using bioleaching technologies [4]. In fact, bioleaching technology has been shown to strictly rely on indigenous bacterial consortia colonizing sulfide ores, consisting of members of the genera Acidithiobacillus, Pseudomonas, Leptospirillum, Sulfobacillus, and Bacillus [1,5,6]. ...
... Enrichment and Isolation of Acidophilic Bacteria Ten grams or milliliters of samples were enriched in 250 ml flask containing 90 ml of sterile modified 0K mineral salts medium containing (NH 4 )SO 4 3 g/L, KCl 0.1 g/L, K 2 HPO 4 0.5 g/L, MgSO 4 · 7H 2 O 0.5 g/L, Ca(NO 3 ) 2 0.01 g/L, pH 3.0 adjusted by H 2 SO 4 and autoclaved at 121°C for 15 min [6,18]. The modified 9K medium was composed of the 0K medium supplemented with 4 g of FeSO 4 as the sole energy source, used for isolation of indigenous iron-oxidizing bacteria. ...
Article
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To date, bioleaching using bacterial consortia is widely regarded as an eco-friendly alternative to the traditional mining approaches due to its cost-effectiveness, feasibility, and sustainability. In the present study, for the first time, gold-bearing sulfide ore collected at Ta Nang mine, Vietnam was mineralogically characterized and subjected to bioleaching trial using indigenous bacterial consortia. The ore contains arsenopyrite, pyrite, galena, sphalerite, and chalcopyrite, of which the major metals were iron (4.78%), arsenic (1.73%), lead (0.43), and zinc (0.33%). After enrichment, a total of 19 iron- and sulfur-oxidizing bacteria were isolated and classified into six distinct genera including three previously described Bacillus, Pseudomonas, Acidithiobacillus, and three firstly reported heterotrophic Glutamicibacter, Providencia, and Stenotrophomonas from gold ore origin. Moreover, an autotrophic Acidithiobacillus sp. TNG6.3, sharing a 16S rRNA sequence of 95.1% identity with the closest sequence of the type strain A. caldus KU, represented a novel candidate species. The establishment of bioleaching utilizing enriched bacteria from gold ore consequently led to the removal of Ag (99.1%), Zn (37.9%), As (37.0%), and Fe (32.2%) from ore after 21 days of treatment, respectively. The present findings highlighted the potential of acidophilic bacteria originated from gold ores for extending applications in bioleaching of metals in Vietnam.
... The PSD in agglomerations is an essential parameter that strongly affects the bonding behavior and extraction efficiency [33]. In this study, we used the variance of the particle size to indicate the effect of the PSD. ...
Article
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The chemical binder is one of the critical factors affecting ore agglomeration behavior and leaching efficiency. In this study, we investigated the effect of the type of binder and mass fraction of the H2SO4 solution used on the curing, soaking, and leaching behavior of agglomerations. The results revealed that Portland cement (3CaO·SiO2, 2CaO·SiO2, and 3CaO·Al2O3) was the optimal binder for obtaining a well-shaped, stable agglomeration structure. A higher extraction rate was achieved when using Portland cement than that obtained using sodium silicate, gypsum, or acid-proof cement. An excessive geometric mean size is not conducive to obtaining well-shaped agglomerations and desirable porosity. Using computed tomography (CT) and MATLAB, the porosity of two-dimensional CT images in sample concentrations L1–L3 was observed to increase at least 4.5vol% after acid leaching. Ore agglomerations began to be heavily destroyed and even to disintegrate when the sulfuric acid solution concentration was higher than 30 g/L, which was caused by the excessive accumulation of reaction products and residuals.
... It has been widely employed in soil remediation (Calderon et al., 2017), sewage sludge treatment (Rodriguez-Rodriguez et al., 2014), fermentation process (Haeggman and Salovaara, 2008), and other bio-treatment systems (Wen et al., 2013;Callac et al., 2015). Compared to other systems, in the extremely acidic bioleaching system, it is more common to carry out the introduction or inoculation of exogenous species due to its lower diversity and simpler composition (Panda et al., 2015). Previous studies have demonstrated that introducing exogenous acidophiles, whether a single strain or more complex consortia, into the bioleaching systems improved the bio-oxidization of copper sulfide minerals, removed restricting factors, and changed the original community composition (Liu et al., 2011;Zhang et al., 2015a;Ma et al., 2018). ...
Article
Introducing exogenous species into an environment is an effective method to strengthen ecological functions. The traits of the exogenous species and the indigenous communities, as well as the resistance and subsequent succession of the community to exogenous species, are not well-understood. Here, three different functional consortia were introduced into two extremely acidic systems, leaching heap (LH) and leaching solution (LS), derived from the Zijin copper mine in China. The results showed that the structures of both LS and LH communities were affected by the three consortia, but not all the structural changes were in line with variations of community function. Among the three consortia, only the complementary sulfur oxidizers greatly enhanced copper extraction efficiency of LS (by 50.42%). This demonstrated that functional niche novelty gave exogenous species an advantage to occupy an ecological niche in a complementary manner, thus leading to successful colonization. The resistance to, and subsequent succession by, exogenous organisms varied between the two indigenous communities. More specifically, the LS community with low community diversity and simple composition was susceptible to exogenous species, and the community structural changes of LS were both divergent and irreversible. In comparison, the LH community with greater community diversity and more complex composition was more resistant to exogenous species, with the community structures showing a convergent trend over time despite different species being introduced. Therefore, we propose that diverse communities compete for resources more intensely with exogenous species and resist their introduction, and that communities with complex composition are able to cope with exogenous disturbances.
... One of the topics of interest is using mixed cultures in the bioleaching of sulfide minerals. It has been shown that using mixed cultures resulted in a higher metal extraction rate than using pure cultures (Akcil et al., 2007;Liu et al., 2011;Panda et al., 2015). On mesophilic and/or moderate thermophilic conditions, Acidithiobacillus spp., Leptospirillum spp., Sulfobacillus spp., and Ferroplasma spp. ...
Article
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Low-temperature biohydrometallurgy is implicated in metal recovery in alpine mining areas, but bioleaching using microbial consortia at temperatures <10°C was scarcely discussed. To this end, a mixed culture was used for chalcopyrite bioleaching at 6°C. The mixed culture resulted in a higher copper leaching rate than the pure culture of Acidithiobacillus ferrivorans strain YL15. High-throughput sequencing technology showed that Acidithiobacillus spp. and Sulfobacillus spp. were the mixed culture’s major lineages. Cyclic voltammograms, potentiodynamic polarization and electrochemical impedance spectroscopy unveiled that the mixed culture enhanced the dissolution reactions, decreased the corrosion potential and increased the corrosion current, and lowered the charge transfer resistance and passivation layer impedance of the chalcopyrite electrode compared with the pure culture. This study revealed the mechanisms via which the mixed culture promoted the chalcopyrite bioleaching.
... For example, mesophiles under acidic conditions need relatively long contact times to leach recalcitrant Cu-sulfides. In contrast, increased rates of bioleaching of Cu-sulfides are achieved with thermophiles (Hedrich et al. 2018;Kaksonen et al. 2020;Panda et al. 2015;Tao and Dongwei 2014;Zeng et al. 2010). In this study, the total contact time of the leaching was limited to 6 days, with 2 days and the appropriate inoculum at each temperature. ...
Article
Copper smelters produce solid waste streams that pose potential pollution problems because of the dust and metal content. Dust from flash and electric furnace smelters is normally recycled to the smelting process, but this decreases the capacity for concentrate feed, and increases impurities and carryovers in the dust with time. The purpose of this study was to test an acid bioleaching process for recovering copper from a sample of smelter dust. The dust sample contained delafossite, chalcocyanite, and chalcopyrite as the main Cu-minerals. Smelter dust (10% pulp) in acid leach solution was subjected to three microbial cultures in a sequence of 35°C, 50°C, and 70°C incremental temperatures for 2 days each. Up to 83% copper dissolution from the dust was achieved by the combined action of the three-phase bioleaching and chemical leaching over the contact time of 6 days. Chemical acid demand at 70°C solubilized 68% Cu from smelter dust within 2 h, attributed to chalcocyanite dissolution in the dust. The monovalent copper minerals chalcopyrite and delafossite were more recalcitrant than the sulfate phase chalcocyanite. A 16-day bioleaching experiment at 35°C and 50°C yielded copper recoveries, which were comparable to those obtained in the three-phase bioleaching. It was concluded that further increases in copper yields from smelter dust require extended contact time ideally at the extreme thermophilic temperature range and stirred bioreactor conditions to control key parameters.
... Copper has been widely used in various electronic fields due to its stable performance, cold/heat resistance, pressure resistance, electrical conductivity and ductility (Panda et al., 2015). There is no doubt that, there will be a greater demand for copper in the future due to the rapid developing of the electronic technology industry and the expansion of the consumer electronics market. ...
Article
Full-text available
The recovery of precious metals from solid waste through bioleaching has become a research hotspot in recent years. Thus, in this study, different strategies, such as chemical sulfuric acid leaching and mixed consortium bioleaching, were adopted to extract copper from Copper-Containing Electroplating Sludge. The results showed that, compared to chemical leaching, bioleaching showed a much better performance. Indeed, copper bioleaching efficiency reached 94.3% on day 7 (21.1% higher than that of chemical leaching). The results also indicated that the process of bioleaching involved more mechanisms and reactions than that of chemical leaching. The SEM and EDX tests showed that the surface morphology of the sludge changed significantly after bioleaching, and that an insignificant amount of copper remained in the leached residues. Furthermore, the leached residues passed the characteristic leaching toxic test and thus can be considered as non-hazardous raw materials for the construction industry. Hence, adopting a mixed consortium leaching process to extract copper from Copper-Containing Electroplating Sludge will not only significantly reduce environmental pollution, but will also use metal resources more efficiently.
... One of the most important challenges that face the copper industry is the development of sustainable technologies to leach complex ores composed of mixed copper mineral species in low grades, with a prevalence of primary copper sulfides. The major component of these materials is usually chalcopyrite (CuFeS 2 ), followed by bornite (Cu 5 FeS 4 ) (Panda et al., 2015). To this end, bioleaching has emerged as an efficient technology to leach secondary sulfides under mesophilic conditions (ambient temperature) (Bustos et al., 1993) and primary sulfides mostly under thermophilic conditions above 60 • C (Duarte et al., 1993) or at moderate thermophilic (45-50 • C) in stirred tank bioreactors (Cancho et al., 2007;Hedrich et al., 2018). ...
Article
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Biofilm formation within the process of bioleaching of copper sulfides is a relevant aspect of iron- and sulfur-oxidizing acidophilic microorganisms as it represents their lifestyle in the actual heap/dump mining industry. Here, we used biofilm flow cell chambers to establish laminar regimes and compare them with turbulent conditions to evaluate biofilm formation and mineralogic dynamics through QEMSCAN and SEM-EDS during bioleaching of primary copper sulfide minerals at 30°C. We found that laminar regimes triggered the buildup of biofilm using Leptospirillum spp. and Acidithiobacillus thiooxidans (inoculation ratio 3:1) at a cell concentration of 106 cells/g mineral on bornite (Cu5FeS4) but not for chalcopyrite (CuFeS2). Conversely, biofilm did not occur on any of the tested minerals under turbulent conditions. Inoculating the bacterial community with ferric iron (Fe3+) under shaking conditions resulted in rapid copper recovery from bornite, leaching 40% of the Cu content after 10 days of cultivation. The addition of ferrous iron (Fe2+) instead promoted Cu recovery of 30% at day 48, clearly delaying the leaching process. More efficiently, the biofilm-forming laminar regime almost doubled the leached copper amount (54%) after 32 days. In-depth inspection of the microbiologic dynamics showed that bacteria developing biofilm on the surface of bornite corresponded mainly to At. Thiooxidans, while Leptospirillum spp. were detected in planktonic form, highlighting the role of biofilm buildup as a means for the bioleaching of primary sulfides. We finally propose a mechanism for bornite bioleaching during biofilm formation where sulfur regeneration to sulfuric acid by the sulfur-oxidizing microorganisms is crucial to prevent iron precipitation for efficient copper recovery.
... The leachate streams and true mining/petrochemicals possess high sulfate minerals and sulfates as well as acid chemotherapy (ACB) bacteria that can complicate the restoration of mineral/deletion (Fig. 4). In particular, it was not clear to what extent the sharing of sulfates and ACB microbes affected the extraction of energy from these mineral-laden channels (Panda et al., 2015). ...
Article
Metals represent a large proportion of industrial effluents, which due to their high hazardous nature and toxicity are responsible to create environmental pollution that can pose significant threat to the global flora and fauna. Strict ecological rules compromise sustainable recovery of metals from industrial effluents by replacing unsustainable and energy-consuming physical and chemical techniques. Innovative technologies based on the bioelectrochemical systems (BES) are a rapidly developing research field with proven encouraging outcomes for many industrial commodities, considering the worthy options for recovering metals from industrial effluents. BES technology platform has redox capabilities with small energy-intensive processes. The positive stigma of BES in metals recovery is addressed in this review by demonstrating the significance of BES over the current physical and chemical techniques. The mechanisms of action of BES towards metal recovery have been postulated with the schematic representation. Operational limitations in BES-based metal recovery such as biocathode and metal toxicity are deeply discussed based on the available literature results. Eventually, a progressive inspection towards a BES-based metal recovery platform with possibilities of integration with other modern technologies is foreseen to meet the real-time challenges of viable industrial commercialization.
... At present, chemical methods occupy a dominant position in the process of leaching tailings, but chemical leaching is often costly, harsh reaction conditions, and easy to cause secondary pollution, thus researchers have turned their attention to metal extraction technology using microbial leaching (Yan et al. 2018). Bioleaching technology has the advantages of energy saving and environmental protection, low investment, and can handle low-grade mineral resources that cannot be processed or difficult to process by traditional beneficiation methods, which has promising prospects in realizing tailings resource utilization (Panda et al. 2015). ...
Article
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Among the many extraction technologies for recovering metal resources from tailings, bioleaching technology is gradually showing its momentum. In our research, the enhanced effect of biochar on the bioleaching of stone coal tailings by Thiobacillus ferrooxidans (T. ferrooxidans) has been explored. In the static bioleaching experiment for 10 days, the leaching rate of vanadium (V) and copper (Cu) increased by 26.8% and 21.0% respectively after adding 5 g/L biochar. The dynamic bioleaching experiment further verified that under the promotion of biochar, the 44 day cumulative leaching rate of V and Cu increased by 15.3% and 14.5%, respectively. The promoting effect of biochar on T. ferrooxidans was mainly reflected in two aspects. The unique porous structure of biochar created a microenvironment for free microorganisms for inhabitation, while storing abundant nutrients. Biochar can also act as an excellent electronic medium to promote electron transfer, improving the oxidation ability of T. ferrooxidans on Fe²⁺. Furthermore, the presence of biochar may effectively inhibit the formation of jarosite precipitation on tailings in bioleaching, thereby improving the dissolution of tailings and the release of metal elements. This study demonstrates that biochar-enhanced bioleaching may be an efficient and environmentally friendly method for recovering metal resources from tailings.
... The biological method is similar to the chemical leaching route, except for it utilizes the reagents generated by microbes for metal extraction [84]. In addition, it is also Leaching considered to be an economically feasible and eco-friendly approach with higher efficacy, safety and easier management [85,86]. Several diverse microbial groups are involved in the leaching process including bacteria, fungi and yeast. ...
Article
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There is a growing interest in electronic wastes (e-wastes) recycling for metal recovery because the fast depletion of worldwide reserves for primary resources is gradually becoming a matter of concern. E-wastes contain metals with a concentration higher than that present in the primary ores, which renders them as an apt resource for metal recovery. Owing to such aspects, research is progressing well to address several issues related to e-waste recycling for metal recovery through both chemical and biological routes. Base metals, for example, Cu, Ni, Zn, Al, etc., can be easily leached out through the typical chemical (with higher kinetics) and microbial (with eco-friendly benefits) routes under ambient temperature conditions in contrast to other metals. This feature makes them the most suitable candidates to be targeted primarily for metal leaching from these waste streams. Hence, the current piece of review aims at providing updated information pertinent to e-waste recycling through chemical and microbial treatment methods. Individual process routes are compared and reviewed with focus on non-ferrous metal leaching (with particular emphasis on base metals dissolution) from some selected e-waste streams. Future outlooks are discussed on the suitability of these two important extractive metallurgical routes for e-waste recycling at a scale-up level along with concluding remarks.
... The ferric, ferrous ions continuously regenerated in bio/chemical leaching of copper sulfides (Hansford and Vargas, 1999;Nielsen et al., 2005). The participate of ferric and ferrous ions in sulfide leaching could be described that: the ferric ions were converted to ferrous ions due to the minerals dissolutions, then the ferrous ions regenerated from ferric ions under the intervention of leaching bacteria or reaction oxidant (Panda et al., 2015;Watling, 2014). The mineralogy of copper sulfide is complicated. ...
Article
The seawater is purified or pre-treated to obtain the acidic seawater-based media (ASM), which has been gradually utilized in copper hydrometallurgical industries, resulting in desirable copper recovery efficiency. In the chemical/bio leaching of chalcocite, chalcopyrite, and other low-grade copper sulfide minerals, the ASM is proved to have a good catalytic effect and it could potentially intervene the leaching reaction and interface condition. In this regard, to further understand the effects of ASM, this paper critically discussed the pivotal ions (ferric/ferrous ions, cupric/cuprous ions, elemental sulfur, passivation ions, silver catalytic ions, etc.) and its compounds, regeneration behavior in the leaching reaction. The current studies tightly related to the effects of these pivotal ions on the redox potential, reaction activation energy, and leaching kinetics were also comparatively analyzed. The tolerances of microorganisms and reactions to ASM were carefully explored. Relied on the previous studies and reviewing in this paper, it inferred that as an efficient, potential alternative of freshwater, the ASM could provide a good expected possibility to accelerate copper sulfide leaching, especially in areas with scarce water resources.
... Unfortunately, metal extraction from these low-grade ores using traditional smelting techniques is uneconomical. Therefore, most low-grade ores have been discarded [6][7][8]. ...
Article
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Exploring efficient methods to enhance leaching efficiency is critical for bioleaching technology to deal with sulfide concentrate. In our study, a novel artificial microbial community was established to augment the bioleaching efficiency and recovery of copper (Cu) and zinc (Zn). The optimum parameters in bioleaching experiments were explored according to compare a series of conditions from gradient experiments: the pH value was 1.2, temperature was 45 °C, and rotation speed was 160 r/min, which were different with pure microorganism growth conditions. Under optimal conditions, the result of recovery for Cu and Zn indicated that the average leaching rate reached to 80% and 100% respectively, which almost increased 1.8 times and 1.2 times more than control (aseptic condition) group. Therefore, this method of Cu and Zn recovery using a new-type artificial microbial community is expected to be an environmentally-friendly and efficient bioleaching technology solution, which has the potential of large-field engineering application in the future.
... The depletion of mineral resources and the continuous decrease of ore grades stimulate the development of hydrometallurgical technology which has the advantages of low cost, simple operation, and environmental friendliness (Natarajan 2009;Panda et al. 2015;Yang, Liu and Chen 2013). Bioleaching has been proved to be an effective pretreatment method for low-grade refractory ores (Abhilash and Pandey 2013;Andrews 1998;De Carvalho et al. 2019;Misra 1993;Natarajan 1998Natarajan , 1992Srichandan et al. 2020) . ...
Article
To expound the relationship between bioleaching behaviors and mineralogical properties of pristine pyrite samples, chemical compositions, semiconductive properties, surface morphologies, and chemical species of synsedimentary pyrite (SSP) and mesothermal pyrite (MTP) were compared, accompanying with bioleaching behaviors analysis by three thermophiles. Mineralogical characterizations showed that both pyrites belonged to p-type semiconductors with an S/Fe ratio higher than 2, and the arsenic content in MTP was as high as 0.6%. The fractured surface of SSP had more kinks and steps, and higher concentrations of S²⁻ and oxides, as compared with that of MTP. Bioleaching results indicated that SSP was leached faster than MTP. The more kinked and stepped structures and the larger contents of S²⁻ and oxides on pyrite surfaces were the dominant reasons for the faster bioleaching kinetics of SSP. The high arsenic content in MTP limiting the cell growth was another cause for its slower leaching.
... Much recent research and technological development has been directed at leaching of residual metals from waste rocks in mines, to enhance the efficiency and economics of mineral extraction (Dold, 2008;Watling et al., 2009;Mudd, 2010;Northey et al., 2014;Dockrey et al., 2014;Henne et al., 2018). Since mine wastes are by definition subeconomic materials, the efficiency of additional metal extraction is typically small and dependent on commodity prices, and reprocessing is focused on the most readily extractable minerals in these materials (Strömberg and Banwart, 1999a,b;Dold, 2008;Watling et al., 2009;Cropp et al., 2013;Liu et al., 2013;Shaw et al., 2013;Panda et al., 2015). Additional comminution and/or leaching time can enhance mineral reaction surfaces for hydrometallurgical processing (Strömberg and Banwart, 1999b;Bhatti et al., 2010;Liu et al., 2013), although this may be marginally economic at best. ...
Article
Copper-bearing silicate minerals are relatively resistant to hydrometallurgical leaching. More efficient extraction of this residual Cu requires detailed knowledge of the mineralogical and textural settings of the minerals, which we outline in this study. Supergene oxidation and alteration of Fe-rich rocks at the Salobo iron-oxide copper–gold (IOCG) mine, Brazil, has caused transformation of primary phyllosilicates, especially biotite, to Cu-bearing clay minerals. The Cu replaced Fe and Mg most likely in the octahedral sites of vermiculite (up to 10 wt% Cu) and the Cu became part of the silicate structure, rather than being merely adsorbed to surfaces. This alteration from biotite has involved negligible textural changes, so that much of the Cu-vermiculite is encapsulated in less-altered biotite at µm to mm scales. More advanced alteration yielded Cu-bearing kaolinite (typically ~ 1 wt% Cu). Mobilisation of Cu under circumneutral pH conditions also led to local formation of veins of Cu-bearing minerals including chrysocolla. The most intense supergene alteration produced mm- to sub-μm-scale veins and cement made up of Cu-bearing quartz, kaolinite and goethite. Titanium derived from alteration of Fe-silicates pervades the altered rocks, coating Cu-silicate material at the μm-scale and this coating may further hinder leachability. Experimental acid (pH 2.2) (bio)leaching columns demonstrated that the presence of the bacterium Acidithiobacillus ferrooxidans did not significantly enhance Cu leach efficiency. However, the experiments, combined with thermodynamic modelling suggest that residual Cu from Cu-silicates can be extracted with acid solutions, although long-term leaching (months-years) may be required. Interactions between acid solutions and clay-altered silicates caused partial neutralisation (to ~ pH 5), further hindering leaching of residual Cu. Our study on the differences between alteration and precipitation textures provides useful context for designing suitable extraction processes for residual Cu from Cu-bearing silicate minerals in weathered rocks.
... Various clean-up techniques, based on microbial cells or their enzymes, have been suggested and practiced for the clean-up of heavy metals from polluted areas (Okoduwa et al. 2017;Siddiquee et al. 2015). Bioremediation using microorganisms is receiving much attention due to their good performance and employed to transform toxic heavy metals into a less adverse form (Akcil et al. 2015;Watanabe 2001). This technique is cost-effective and environmentally friendly for revitalization of the polluted environment (Turpeinen et al. 2004;Ma et al. 2016;Yang et al. 2020). ...
Chapter
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Metal-rich natural and artificial habitats are extreme environments for the evolution of unique microbial communities, which have adapted to deal with the toxic levels of the metals. Diverse microbial groups belonging to Archaea and Bacteria domain possessing different metal-resistance strategies have been found in different metal-contaminated environments using cultivation and molecular approaches. Various metal-resistant bacteria belonging to Bacillus, Arthrobacter, Pseudomonas, Ralstonia, Stenotrophomonas, Desulfovibrio, and other genera were demonstrated a high capacity to the bisorbtion of the different heavy metals. Bacteria and archaea belonging to the genera Acidithiobacillus, Leptospirillum, Sulfobacillus, and Ferroplasma are mostly associated with metal minerals and are involved in the bioleaching processes. Thus, the microbial resistance to toxic heavy metals has fundamental importance in the bioremediation of metal-contaminated natural habitats and bioleaching of valuable metals from complex minerals.
... In column 2#, the TFe concentration increased continually, but the ferrous iron concentration maintained at a low level (below 288 mg/L) except in the initial phase of stage III. During the stop of circulation (from day 136 to day 155), the ferrous iron concentration in column 1# decreased due to the leakage of leachate, while that in column 2# increased due to insufficient oxygen supply hindering the oxidation of ferrous iron to ferric iron (Panda et al. 2015a). By comparison, the TFe concentration in column 1# was always higher than that in column 2# before the leachate of column 1# leaked (before day 155). ...
Article
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Low-grade ores, tailings, and solid wastes contain small amounts of valuable heavy metals. Improper disposal of these substances results in the waste of resources and contamination of soil or groundwater. Accordingly, the treatment and recycling of low-grade ores, tailings, and solid wastes attracted much attention recently. Bioelectrochemical system, an innovative technology for the removal and recovery of heavy metals, has been further developed and applied in recent years. In the current study, the low-grade chalcopyrite was bioleached with the assistance of microbial fuel cells. Copper extraction along with electricity generation from the low-grade chalcopyrite was achieved in the column bioleaching process assisted by MFCs. Results showed that after 197 days bioleaching of low-grade chalcopyrite, 423.9 mg copper was extracted from 200 g low-grade chalcopyrite and the average coulomb production reached 1.75 C/d. The introduction of MFCs into bioleaching processes promoted the copper extraction efficiency by 2.7 times (3.62% vs. 1.33%), mainly via promoting ferrous oxidation, reducing ORP, and stimulating bacterial growth. This work provides a feasible method for the treatment and recycling of low-grade ores, tailings, and solid wastes. But balancing energy consumption of aeration and circulation frequency and chemical consumption of acid to improve the copper extraction efficiency need further investigation.
... Bio-hydrometallurgical technologies have been widely utilized in the copper extractive metallurgy industry [6,7], especially the one processing chalcopyrite, which is well-known for being refractory to common leaching methods [8]. On the other hand, gold has been mainly produced using hydrometallurgical methods based on cyanide leaching [9]. ...
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This example analyzes a bio-hydrometallurgical process for the extraction, purification and recovery of copper and gold from a refractory concentrate. The process features preparation and bioleaching of the concentrate, solvent extraction, and electrowinning of copper as well as gold extraction by thiosulfate-ammonia leaching, ion-exchange and electrowinning of gold. The results include detailed material and energy balances, equipment sizing, capital, and operating cost estimation.
... The determining factors and parameters for the use of underground leaching of uranium include the availability of reserves for the organization of work on UWL; parameters of water cut and permeability of ore-bearing rocks; mineralization depth; type of ore mineralization; the material composition of orebearing rocks; parameters of carbonate and sulfuric acid solubility of minerals; parameters of occurrence and groundwater pressure; presence of water storage; expected uranium mining costs. The degree of suitability of the field for efficient exploitation by underground leaching depends on specific combinations of parameters of natural and production conditions [12][13][14][15][16][17][18][19][20][21][22]. ...
Article
Existing traditional uranium mining technologies have major drawbacks, do not meet the requirements of a market economy, are ineffective, require the use of a large number of expensive injection and pumping wells, low leaching rates, require a large consumption of chemical reagent, sulfuric acid (to produce 1 ton of uranium concentrate requires a flow of 100 tons sulfuric acid). Here, a productive solution refers to a chemical solution containing the concentration of the leached therein of various useful components (metals), including uranium, dissolved therein. In the practice of exploitation of hydrogenous uranium deposits, the arrangement of technological wells has been adopted: linear (or in-line), areal (or cellular) and combined. Our proposed innovative technology for the exploitation of hydrogenous uranium deposits will be developed on the principle of piston wells using the effect of activation of a chemical solution supplied to the array of a hydrogenated uranium layer for leaching and other useful components. In the process of activation, the chemical solution is heated to t = 70 ° C, the water in the solution becomes a good solvent. Pumping wells are used as piston wells without changing the design, i.e. pumping wells are also used as injection wells. This article presents the mining and geological characteristics of technogenic uranium deposits in Kazakhstan. The basis of the raw material base of Kazakhstan's uranium is exogenous type deposits, combined into a subgroup called “infiltration”. Uranium infiltration deposits are formed by groundwater associated with regional formation zones and zones of soil-layer oxidation. The development and implementation of the method of underground well leaching of uranium (UWL) is one of the most important scientific and technical achievements of the mining industry. The main advantages of the underground leaching method compared to traditional mining methods of developing deposits are as follows: the possibility of involving poor and off-balance ores in deposits with complex geological and hydrogeological conditions, but with large reserves of uranium; Significant reduction in capital investments and terms of commissioning deposits; improving working conditions, reducing the number of miners and increasing labor productivity by 2.5-3.5 times; reducing the negative impact of uranium mining on the environ-ment.
... Hydrometallurgy is the primary technology for the treatment of lowgrade ores which accounted for 20% of China's copper production due to its simple operation, high product quality, low cost and low pollutant emission (Brierley, 2008;Panda et al., 2015;Petersen, 2016). Notably, some stages of hydrometallurgy, such as leaching and electrowinning, are power-intensive, whereas thermal power generation will cause great emissions of greenhouse gas and environmental pollution (Yi et al., 2020). ...
Article
Understanding the environmental and economic impacts of copper hydrometallurgy throughout the whole life cycle is necessary for sustainable development of the copper industry. In this study, the environmental impacts and economic costs throughout the two major copper hydrometallurgical routes in China, including heap leaching and heap-agitation leaching, are analyzed and compared using the life cycle assessment (LCA) and life cycle cost (LCC) technique. The life cycle inventory compiled from the annual statistics of the Muliashi Copper Mine, and the data regarding energy and materials process are based on the GaBi databases. The environmental impacts are quantified into 12 indicators. The results show that compared with heap leaching route, heap-agitation leaching route reduces 36.8% of abiotic depletion potential (ADP elements), but increases over half of cumulative energy demand (CED), marine aquatic ecotoxicity potential (MAETP) and human toxicity potential (HTP). Furthermore, the stage of electrowinning and agitation leaching contributes the largest environmental impact to heap leaching and heap-agitation leaching route, respectively. This is mainly due to huge consumption of electricity and sulfuric acid. The analysis of economic cost reveals that heap leaching route needs internal cost of $3225/t Cu and external cost of $426/t Cu. Compared with heap leaching route, heap-agitation leaching route increased the internal and external cost by 18.9% and 54.2%, respectively. But the economic return from heap-agitation leaching is double that from heap leaching. Together, these results indicate heap-agitation leaching has a larger environmental impact and higher economic benefit than heap leaching, which is helpful for the government to design ecological compensation policies in the balance between ecological environment and economic development.
... Thus, mining industries have to recover copper from low-grade ores that used to be considered as waste. By considering high costs of traditional processes and growing concern for the environment, mining industries finally increasingly use bioleaching combined with solvent extraction (SX) and electrowinning (BL-SX-EW) to recover and produce copper from low-grade ores (Songrong et al., 2002;Panda et al., 2015;Gentina and Acevedo, 2016). ...
Article
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Heap bioleaching, the solubilization of metal ions from metal sulfides by microbial oxidation, is often combined with solvent extraction (SX) and electrowinning to recover, e.g., copper from low-grade ores. After extraction, the leaching solution is recycled, but the entrained organic solvents may be toxic to the microorganisms. Here Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Sulfobacillus thermosulfidooxidans were selected to perform bioleaching of chalcopyrite waste rock in the presence of the SX reagent (2.5% v/v LIX984N in kerosene). Possibly inhibitory effects have been evaluated by copper extraction, bacterial activity, number of actively Fe(II)-oxidizing cells, and biofilm formation. Microcalorimetry, most probable number determination, and atomic force microscopy combined with epifluorescence microscopy were applied. The results show that 100 and 300 mg/L SX reagent could hardly inhibit At. ferrooxidans from oxidizing Fe2+, but they seriously interfered with the biofilm formation and the oxidization of sulfur, thereby hindering bioleaching. L. ferrooxidans was sensitive to 50 mg/L SX reagent, which inhibited its bioleaching completely. Sb. thermosulfidooxidans showed different metabolic preferences, if the concentration of the SX reagent differed. With 10 mg/L LIX984N Sb. thermosulfidooxidans preferred to oxidize Fe2+ and extracted the same amount of copper as the assay without LIX984N. With 50 mg/L extractant the bioleaching stopped, since Sb. thermosulfidooxidans preferred to oxidize reduced inorganic sulfur compounds.
... Arsenopyrite (FeAsS) is the most abundant arsenic-bearing sulfide mineral in the lithosphere, whereby it has become important for the mineral processing industries that have been focusing their interest on finding new technologies to recover commercially valuable metals such as copper, nickel, and gold from these ores with lower economic and energy costs [1,2]. Low grade refractory sulfide gold ores are usually associated with high amounts of pyrite and arsenopyrite. ...
Article
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Arsenopyrite is the most abundant arsenic-bearing sulfide mineral in the lithosphere, usually associated with sulfide gold ores. The recovery of this highly valuable metal is associated with the release of large quantities of soluble arsenic. One way to mitigate the effects of high concentrations of arsenic in solution is to immobilize it as scorodite precipitate, a more stable form. Hence, we addressed the scorodite formation capacity (under mesophilic conditions) of psychrotolerant Acidithiobacillus ferrivorans ACH isolated from the Chilean Altiplano. Bio-oxidation assays were performed with 1% arsenopyrite concentrate as unique energy source and produced solids were evaluated by X-ray diffraction (XRD) and QEMSCAN analysis. Interestingly, the results evidenced scorodite generation as the main sub-product after incubation for 15 days, due to the presence of the microorganism. Moreover, the QEMSCAN analysis support the XRD, detecting a 3.5% increase in scorodite generation by ACH strain and a 18.7% decrease in arsenopyrite matrix, implying an active oxidation. Finally, we presented the first record of arsenopyrite oxidation capacity and the stable scorodite production ability by a member of A. ferrivorans species under mesophilic conditions.
Article
Mercury contamination has attracted global attentions in the past decades, which posed great threats to the whole ecosystem and human health because of its cumulative hypertoxicity, persistence and migration in the atmosphere. Due to the inferior mercury capture performances and tedious modification procedures of carbon-based sorbents, mineral chalcogenides were regarded as the preferable candidates for gaseous elemental mercury (Hg⁰) immobilization from industrial flue gas. Mineral chalcogenides exhibit several advantages, such as simple preparation, excellent capture performance, and less secondary pollution in Hg⁰ adsorption. This review focuses on the latest research advances in Hg⁰ abatement by mineral chalcogenides. At the beginning, the research status of different typical sorbents for Hg⁰ removal was overviewed. Then, the performances and application conditions of most mineral chalcogenides for Hg⁰ removal were introduced in detail. The Hg⁰ adsorption performance comparison of various mineral chalcogenides was also conducted. Moreover, the influential factors, i.e. reaction temperature, flue gas components, and involved mechanisms for Hg⁰ removal over different mineral chalcogenides were discussed comprehensively. The objective of this review was to strengthen the comprehension of the developing field and generalize the research directions in the future.
Article
Challenges in the course of sustainable development, predominantly dearth of natural resources and waste management have suggested scientific community across the globe to seek novel processes to reduce ecological disturbances. For this purpose, microbial leaching process; a commercial application of bio-hydrometallurgy, could be a better option as it serves as a potential candidate for the retrieval of precious metals from low grade ores containing very low metal concentration, and sulfide minerals. It can also effectively remove excess of metals from soil and sediments and even recover metals from discarded solid waste. The present article intends to highlight the valuable metals which are being recovered by the process of microbial leaching from various kind of solid waste, the mechanism by which metals are mobilized, commercially used bioleaching processes along with their benefits and shortcomings, conditions and factors necessary for the optimization of the microbial leaching process. Emphasis is also being given to the extraction of metals from metal polluted soil and sediments using leaching organisms. It is to be concluded that microbial leaching is a revolutionizing technique bringing out both recovery of metals from solid materials including metal contaminated soil as well as remediation of soil using micro-organisms.
Article
The mobility of gold and silver metals from refractory ores is very low due to free metal ions in their bodies that bind the transportable and free metal molecules or they are encapsulated in minerals such as sulfides, arsenosulfides, carbonaceous, and clayey materials which make it difficult to extract them. As known from the literature, the enrichment of oxide refractory gold, silver ores, Ag, and Au-rich flotation concentrated from sulfur refractory ores can be leached in the chloride-hypochlorite solutions. In this work, the leaching approach was studied to extract silver ions from refractory ores in the presence of hypochlorite media under high pressure. The mineralogical and scanning electron microscopy analysis of the sample indicated that the silver was encapsulated in barite and quartz minerals in fine sizes. In order to obtain the optimum leaching conditions for the silver ore, the effects of several parameters, namely, temperature, leaching time, NaCl and NaOCl concentration, solid ratio, and particle size on the leaching recovery were investigated in detail. The leaching experiments showed that the highest silver recovery of 62.35% was obtained under the following conditions: temperature of 150 °C, oxygen pressure of 1800 kPa, leaching time of 2 h, concentrations of 2 mol/dm3 and 0.4 mol/dm3 for NaCl and NaOCl, respectively, the solid ratio of 30%, and particle size (d80) 15 μm. The results obtained from this study indicated that the enrichment of refractory silver ores to extract the silver encapsulated in barite and quartz minerals could be possible in the chlorite-hypochlorite under high pressure, a relatively shorter leaching time compared to conventional cyanide leaching.
Article
Bioleaching of copper from electronic waste (e-waste) in the form of high grade waste printed circuit boards (WPCBs) collected from obsoletemobile phones is assessed using a consortium of iron (Fe2+) & sulphur (Sº) oxidizing bacteria in a semi-pilot reactor system. Results from the study indicated that the microorganisms were able to grow in the presence of WPCB and efficiently solubilize Cu from it. At a solid/liquid ratio of 10% (w/v)with a particle size of <250 μm, maximum bioleaching efficiency of around 95% Cu was observed in 8 days of leaching under oxidation-reduction potentials (ORP) of >600 mV and pH 1.8. In order to recover the metallic values, electrowinning (EW) of copper from the bioleach solutions was investigated in detail. Direct EW of the bioleach solution yielded low current efficiencies (66.1% over 4h.), ascribed due to the high concentrations of iron (i.e., 9.1 g/L). As a novel approach, a downstream purification and concentration process was further tested, that involved ferric hydroxide (Fe(OH)3) precipitation and solvent displacement crystallisation (SDC) to eliminate iron and increase the concentration of copper in solution prior to its application for EW. This significantly improved the current efficiency (by ~22%) during the EW of copper. A process flow-sheet for Cu recovery from WPCBs was developed and the downstream process was found to be profitable even though its margin was small with techno-economic analysis. It is believed that the two-step hybrid process i.e. bioleaching technique followed by the novel approach proposed (i.e., iron precipitation + SDC) can be suitably employed for the extraction of copper from WPCBs.
Conference Paper
Ionic liquids are green agents, which have very good properties such as low volatility, high conductivity, thermal stability and a wide range of working temperatures. These characteristics allow them to be installed in different industries and therefore be considered in hydrometallurgical processes. In the p resent work, the solution of pure chalcopyrite in the presence of 1-butyl-3-methylimidazolium hydrogen sulfate [bmim]HSO4 is investigated, injecting oxygen into a chlorinated medium. The system is compared to another test under the same conditions, but wit hout oxygen injection. The results showed that an excess of dissolved oxygen in the system caused by a high injection of O2, can cause chalcopyrite passivation. The best Cu extraction with a value of 65.53% working at 80 ° C, with a reagent concentration of [bmim]HSO4 20% (v/v), without oxygen injection and using the complexing agent as chloride.
Article
As a gangue mineral, talc is usually associated with chalcopyrite. Therefore, the depression of talc is required in the field of sulphide mineral flotation. Herein, the depression mechanism of pullulan in the flotation separation of chalcopyrite from talc was investigated via flotation tests and characterisation techniques, such as Fourier transform infrared analysis (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The flotation test results showed that chalcopyrite can be selectively separated from talc with 20 mg/L pullulan as a depressant, and that the separation effect remains unaffected when the depressant dosage is increased to 80 mg/L. Additionally, the zeta potential, FTIR and adsorption measurements indicated that pullulan is selectively adsorbed on talc surfaces, and that talc surfaces adsorb more depressants than chalcopyrite. The XPS results indicated that the pullulan adsorption on talc surfaces is physical. The AFM results indicated that pullulan adsorption on talc surfaces forms polymer layers. Therefore, pullulan is considered a potential depressant of talc in the flotation industry.
Article
This study developed a sustainable method for gold extraction from low-grade refractory ore by combining acidic biooxidation and thiocyanate (SCN) leaching (BIOX-TC) in one system to avoid neutralization and minimize the complexity of the process. Among leachant candidates, thiocyanate was proposed as a less toxic reagent for gold leaching. Furthermore, thiocyanate requires ferric iron as an oxidant for gold extraction and ferric iron can be provided by the microorganisms during biooxidation. In the first step, acidic biooxidation was done using a mixture of acidophiles including Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans resulting in 59.6% sulfur oxidation. A preliminary static incubation of Acidithiobacillus thiooxidans also improved biooxidation efficiency achieving higher sulfur oxidation of 87.8%. Following biooxidation, thiocyanate leaching using 0.2M SCN was performed under three different conditions: (1) in a separate flask with 0.01M ferric iron addition; (2) in-situ leaching, in the biooxidation flask with the mixed bacterial culture); (3) in-situ leaching in the biooxidation flask with the bacterial culture and with 0.01M additional ferric iron. It was found that in-situ thiocyanate leaching of the biooxidized ore in presence of bacterial culture and without ferric iron addition resulted in the highest gold recovery (86.9%). The biooxidation mechanism and its kinetics have been extensively discussed in this paper.
Article
This review discusses the latest trend in recovering valuable metals such as lithium, cobalt, nickel, and manganese from spent lithium-ion batteries (LIBs) to avoid the technological world's critical metal demands. LIBs are a secondary source of valuable metals such as Li (5%-7%), Ni (5%-10%), Co (5%-25%), Mn (5-11%), and non-metal graphite. Recycling is essential for the battery industry to extract valuable critical metals from secondary sources to develop new and novel high-tech LIBs for various applications such as eco-friendly technologies, renewable energy, emission-free electric vehicles, and energy-saving lightings. LIB waste is currently undergoing high-temperature pyro-metallurgical or hydrometallurgical processes to recover valuable metals, and these processes have proven to be successful and financially feasible. These methods, however, are not advisable due to the difficulties in controlling the process, secondary waste produced, high operational cost, and high risk of scaling up. Biotechnological approaches can be promising alternatives to pyro-metallurgical and hydrometallurgical technologies in metal recovery from LIB waste. Microbiological metal dissolution or bioleaching has gained popularity for metal extraction from ores, concentrates, and recycled or residual materials in recent years. This technology is eco-friendly, safe to handle, and reduces operating costs and energy demands. The pre-treatment process (material preparation), microorganisms used in the bioleaching of LIBs, factors influencing the bioleaching process, methods of enhancing the leaching efficiency, regeneration of electrode materials, and future aspects have been discussed in detail.
Article
Temperature is considered to be one of the main factors affecting bioleaching, but few studies have assessed the effects of diurnal temperature range (DTR) on the bioleaching process. This study investigates the effects of different bioleaching temperatures (30 and 40 °C) and DTR on the bioleaching of metal sulfide ores by microbial communities. The results showed that DTR had an obvious inhibitory effect on the bioleaching efficiency of the artificial microbial community, although this effect was mainly concentrated in the early and middle stages (0–18 days) of exposure, gradually decreasing until almost disappearing in the late stage (18–24 days). Extracellular polymeric substance (EPS) analysis showed that DTR did not change the composition of the EPS matrix (humic acid-like substances, polysaccharides and protein-like substances), but had a significant effect on the generative behavior of EPS, inhibiting the secretion of EPS during the early and middle stages of the bioleaching process. However, the continual increase in EPS secretion in the bioleaching system gradually reduced the adverse effects of DTR on mineral dissolution. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy- energy dispersive spectrometry (SEM-EDS) analysis of the bioleached residue showed that DTR had no obvious effect on the mineralogical characteristics of sulfide ore. Therefore, in industrial sulfide ore bioleaching applications, in order to accelerate the artificial microbial community start-up process, temperature control measures should be increased in the bioleaching process to reduce the adverse effects of DTR on mineral dissolution.
Article
As the world’s second largest economy experiencing rapid economic growth, China has a huge demand for metals and energy. In recent years, China ranks first, among all the countries in the world, in the production and consumption of several metals such as copper, gold, and rare earth elements. Bioleaching, which is an approach for mining low grade and refractory ores, has been applied in industrial production, and bioleaching has made great contributions to the development of the Chinese mining industry. The exploration and application of bioleaching in China are reviewed in this study. Production and consumption trends of several metals in China over the past decade are reviewed. Technological processes at key bioleaching operations in China, such as at the Zijinshan Copper Mine and Mianhuakeng Uranium Mine, are presented. Also, the current challenges faced by bioleaching operations in China are introduced. Moreover, prospects such as efficiency improvement and environmental protection are proposed based on the current situation in the Chinese bioleaching industry.
Article
The bioleaching technology has been considered as a promising green technology for remediation of contaminated sediments in recent years. Bioleaching technology was generally conducted in the batch bioreactor; however, the continuous bioreactor should be developed for the application of bioleaching technology in the future. The purposes of this study were to establish a continuous bioleaching process, and to evaluate the effects of sulfur dosage on the efficiency of metal removal during this continuous bioleaching process. The obtained results show that the pH decrease, sulfate production and metal removal efficiency all increased with increasing sulfur dosage in the continuous bioleaching process due to high substrate concentration for sulfur-oxidizing bacteria. After 30 days of operation time, the maximum solubilization efficiencies for Zn, Ni, Cu and Cr were found to be 78%, 90%, 88% and 68%, respectively, at 5% of sulfur dosage. After the bioleaching process, heavy metals bound in the carbonates, Fe-Mn oxides and organics/sulfides in the sediment were effectively removed and the potential ecological and toxic risks of treated sediment were greatly reduced. The results of bacterial community analyses demonstrated that this continuous bioleaching process were dominated by several acidophilic sulfur-oxidizing bacteria; S. thermosulfidooxidans, At. thiooxidans/At. ferrooxidans, S. thermotolerans and At. albertensis, whereas the percentage of less-acidophilic sulfur-oxidizing bacteria (T. thioparus and T. cuprina) was lower than 15% of total bacteria. In addition, the cell numbers of sulfur-oxidizing bacteria increased as the sulfur dosage was increased in the continuous bioleaching process.
Article
Chalcopyrite is the most abundant copper-bearing mineral in nature. Due to technological limitations, a large amount of low-grade chalcopyrite is discarded, which causes a large waste of resources and a series of environmental problems. Bioleaching is a low-consumption technology that plays an important role in treating low-grade minerals. However, the leaching efficiency of chalcopyrite is too low for industrial production. This study proposes the use of polyoxyethylene nonyl phenyl ether (NP-15) to improve the bioleaching efficiency of chalcopyrite. The effects of concentration and adding time of NP-15 on copper extraction were investigated. After 30 days bioleaching, the copper concentration in the leaching solution was 930.91 mg/L with the addition of 20 mg/L of NP-15. In contrast, the copper concentration was observed to be 385.62 mg/L in the absence of NP-15. The optimum adding time was the 6th day after the start of the bioleaching process. The analysis of the results of X-ray diffraction (XRD), Raman spectroscopy, and the electrochemical tests revealed that the presence of NP-15 was beneficial to reduce the deposition of elemental sulfur on the chalcopyrite surface. Moreover, NP-15 promoted the oxidation of elemental sulfur by Acidithiobacillus ferrooxidans. The contents of elemental sulfur and polysulfide in the passivation layer were reduced. Additionally, NP-15 reduced the surface tension of the leaching solution, which was beneficial for improving the contact between the leaching solution and chalcopyrite surface. Thus, the bioleaching efficiency was improved. This study provides a reference for the application of surfactants to enhance the bioleaching of chalcopyrite ores.
Article
Chalcopyrite is the main mineral source of copper ore for extracting and producing copper. However, with the continuous mining of copper ore, the grade of chalcopyrite decreases year by year and its composition becomes more and more complex. The traditional pyrometallurgical extraction process has been unable to make efficient use of such resources, and it is extremely urgent to explore an efficient and environmentally friendly hydrometallurgical leaching method of chalcopyrite. In this paper, the research progress of hydrometallurgical leaching of low-grade complex chalcopyrite is reviewed, and the advantages and disadvantages of mainstream leaching processes such as oxidation leaching, coordination leaching, and biological leaching are analyzed. The analysis shows that bioleaching is suitable for the leaching copper from low-grade chalcopyrite and even original ore, but the leaching rate is not high, and the time for bacterial culture and domestication, as well as the leaching cycle is long. The time of the oxidation leaching is short, the reaction conditions are mild, but the oxidant is difficult to recycle resulting large consumption. Coordination leaching is highly selective, but the system is highly corrosive and requires high investigation in equipment. No matter what kind of process is adopted, the passivation layer composed of elemental sulfur, polysulfide, and jarosite will be produced in the process, hindering the leaching. Increasing the research on the adaptability and selectivity of microorganisms is the direction of bioleaching, and the selective leaching in coordination leaching under ammonia medium with the synergy of oxidant and coordination agent can be realized. In addition, the formation of passivated layer can be inhibited by controlling acidity and redox potential, and the passivated layer can be stripped or eroded by microwave or ultrasonic reinforcement, so as to improve the efficiency of leaching reaction.
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Low-grade ores, tailings and solid wastes contain small amounts of valuable heavy metals. Improper disposal of these results in the waste of resources and contamination of soil or groundwater. Accordingly, the treatment and recycling of low-grade ores, tailings and solid wastes attracted much attention recently. Bioelectrochemical system, an innovative technology for the removal and recovery of heavy metals, has been further developed and applied in recent years. In current study, the low-grade chalcopyrite was bioleached with the assistance of microbial fuel cells. Copper extraction along with electricity generation from the low-grade chalcopyrite were achieved in the column bioleaching process assisted by MFCs. Results showed that after 197 days bioleaching of low-grade chalcopyrite, 423.9 mg copper was extracted from 200 g low-grade chalcopyrite and the average coulomb production reached 1.75 C/d. The introduction of MFCs into bioleaching processes promoted the copper extraction efficiency by 2.7 times (3.62% vs. 1.33%), mainly via promoting ferrous oxidation, reducing ORP and stimulating bacterial growth. This work provides a feasible method for the treatment and recycling of low-grade ores, tailings and solid wastes. But balancing energy consumption of aeration and circulation frequency and chemicals consumption of acid to improve the copper extraction efficiency need further investigation.
Article
There has been a strong interest in technologies suited for mining and processing of low-grade ores because of the rapid depletion of mineral resources in the world. In most cases, the extraction of copper from such raw materials is achieved by applying the leaching procedures. However, its low extraction efficiency and the long extraction period limit its large-scale commercial applications in copper recovery, even though bioleaching has been widely employed commercially for heap and dump bioleaching of secondary copper sulfide ores. Overcoming the technical challenges requires a better understanding of leaching kinetics and on-site microbial activities. Herein, this paper reviews the current status of main commercial biomining operations around the world, identifies factors that affect chalcocite dissolution both in chemical leaching and bioleaching, summarizes the related kinetic research, and concludes with a discussion of two on-site chalcocite heap leaching practices. Further, the challenges and innovations for the future development of chalcocite hydrometallurgy are presented in the end.
Chapter
Biobeneficiation to upgrade low-grade sulfide and iron ores has the potential to turn closed mines or uneconomic mineral deposits and secondary wastes and materials into economic resources. Microorganisms and their metabolites have been commercially applied in the bioleaching of metals from medium- and low-grade sulfide minerals for many years. Efforts are now being directed to the application of biomining to oxide ore systems as high-grade ore becomes scarce and for the removal of phosphorus from phosphorus-containing iron ores. This chapter discusses the potential exploitation of microorganisms and their metabolites as bioreagents for the selective flotation and flocculation of iron ore minerals, and for the bioleaching of phosphorus from iron ore.
Article
Chalcopyrite bioleaching has developed rapidly because of the advantages such as environmental protection, low capital investment and simple operation, but its application has been limited by the slow reaction rate and other problems. Bioelectrochemical system (BES) as a promising wastewater treatment technology could solve the problem of reaction abort due to insufficient electron acceptors inside the mineral heap. In this study, the effect of pulp density, anode material and silver ion on the copper bioleaching were carried out. Experimental results showed that the maximum bioleaching efficiency (1.70 ± 0.18%) in 11 d was achieved at a pulp density of 1% with the application of titanium-silver anode and the assistance of BES. BES promoted the bioleaching of Cu mainly by promoting the bacterial reproduction and the Fe²⁺ production from the chalcopyrite. Moreover, the introduction of BES promoted the release of Ag²⁺, further enhancing the bioleaching of Cu by 1.5 times (187.7 ± 18.1 mg/L vs. 120.9 ± 22.2 mg/L). In addition, the inhibition of conductive silver glue on the copper bioleaching and bacteria was alleviated by the BES. As an anode material, carbon cloth couldn't improve the leaching of Cu as compared to titanium foam, but it could increase the electron transfer efficiency.
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Microorganisms play a key role in the natural circulation of various constituent elements of metal sulfides. Some microorganisms (such as Thiobacillus ferrooxidans) can promote the oxidation of metal sulfides to increase the release of heavy metals. However, other microorganisms (such as Desulfovibrio vulgaris) can transform heavy metals into metal sulfides crystals. Therefore, insight into the metal sulfides transformation mediated by microorganisms is of great significance to environmental protection. In this review, first, we discuss the mechanism and influencing factors of microorganisms transforming heavy metals into metal sulfides crystals in different environments. Then, we explore three microbe-mediated transformation forms of heavy metals to metal sulfides and their environmental applications: (1) transformation to metal sulfides precipitation for metal resource recovery; (2) transformation to metal sulfides nanoparticles (NPs) for pollutant treatment; (3) transformation to “metal sulfides-microbe” biohybrid system for clean energy production and pollutant remediation. Finally, we further provide critical views on the application of microbe-mediated metal sulfides transformation in the environmental field and discuss the need for future research.
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Bioelectrochemical systems (BES) are considered efficient and sustainable technologies for bioenergy generation and simultaneously removal/recovery metal (loid)s from soil and wastewater. However, several current challenges of BES-based metal removal and recovery, especially concentrating target metals from complex contaminated wastewater or soil and their economic feasibility of engineering applications. This review summarized the applications of BES-based metal removal and recovery systems from wastewater and contaminated soil and evaluated their performances on electricity generation and metal removal/recovery efficiency. In addition, an in depth review of several key parameters (BES configurations, electrodes, catalysts, metal concentration, pH value, substrate categories, etc.) of BES-based metal removal and recovery was carried out to facilitate a deep understanding of their development and to suggest strategies for scaling up their specific application fields. Finally, the future intervention on multifunctional BES to improve their performances of mental removal and recovery were revealed.
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Risk assessment is increasingly used in the context of mining activities, at various stages of mining projects. This applies also to mineral heap leach pads that are used for the recovery of gold, copper, silver and several other metals and non-metals. A heap leach pad consists of a lined facility (typically a composite liner) onto which ore is placed and then leached using, for example a strong acid or alkaline solution. This paper proposes an assessment of the risk of leakage through the composite liner of a heap leach pad, with the objective of illustrating how different types of uncertainty can be jointly propagated through the risk model. The proposed approach aims at avoiding the biases introduced by the common confusion between aleatory uncertainties (reflecting random variability) and epistemic uncertainties (reflecting the incomplete nature of available information). The joint propagation method provides estimates of the (imprecise) probability that leakage through the base of a heap leach pad should be lower than a certain value. It is shown how the proposed method aims to promote a more consistent approach to uncertainty representation and propagation in risk assessment, in order to contribute to the decision-making process in a more robust and transparent fashion.
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Recovery of metal value, especially from low-grade ores and overburden minerals using acidophilic bacteria through the process of bioleaching is an environmentally benign and commercially scalable biotechnology. In recent years, while the 'OMICS' landscape has been witnessing extensive application of computational tools to understand and interpret global biological sequence data, a dedicated bioinformatic server for analysis of bacterial information in the context of its bioleaching ability is not available. We have developed an on-line Bacterial Bioleaching Protein Finder (BBProF) System, which rapidly identifies novel proteins involved in a bacterial bioleaching process and also performs phylogenetic analysis of 16S rRNA genes. BBProF uses the features of Asynchronous Java Script and XML (AJAX) to provide an efficient and fast user experience with minimal requirement of network bandwidth. In the input module the server accepts any bacterial or archaeal complete genome sequence in RAW format and provides a list of proteins involved in the microbial leaching process. BBProF web server is integrated with the European Bioinformatics Institute (EBI) web services such as BLAST for homology search and InterProScan for functional characterization of output protein sequences. Studying evolutionary relationship of bacterial strains of interest using Muscle and ClustalW2 phylogeny web services from EBI is another key feature of our server, where 16S rRNA gene sequences are considered as input through a JQUERY interface along with the sequences present in the BBProF database library. Complete genome sequences of 24 bioleaching microorganism characterized by genomic and physiological study in the laboratory and their respective 16S rRNA gene sequences were stored in the database of the BBProF library. To our knowledge BBProF is the first integrated bioinformatic web server that demonstrates its utility in identifying potential bioleaching bacteria. We hope that the server will facilitate on-going comparative genomic studies of bioleaching microorganisms and also assist in identification and design of novel microbial consortia that are optimally efficient bioleaching agents.
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The effect of activated carbon on chalcopyrite bioleaching by extreme thermophile Acidianus manzaensis YN25 at 65°C was evaluated, together with the investigation of the sulfur speciation transformation on the mineral by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy. Bioleaching experiments show activated carbon significantly accelerated the dissolution of copper from chalcopyrite concentrate. The optimum concentration of activated carbon enhancing copper dissolution is 2g/L, under which the copper yields increased from 64% to 95%. The catalysis could mainly be attributed to the galvanic interaction between activated carbon and chalcopyrite. Jarosite, elemental sulfur and chalcocite were detected in the solid phase, and the formation of potassium jarosite was prior to ammonio-jarosite. Activated carbon did not change the species of sulfur-containing compounds, but accelerated the formation of them.
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The HeapSim model developed to design heap leach processes was employed herein to evaluate unknown parameters and to identify the rate-controlling steps governing a simple leach system consisting of only pyrite under isothermal conditions. The temperature at which the column tests were performed encompassed the range of the mesophilic cells (15–40 °C), moderate thermophilic cells (30–55 °C), and extreme thermophilic cells (50–80 °C).The ore-, geometry-, and hydrology-related parameters characteristic of the column tests were known from previous experiments. This left only the biological parameters of iron- and sulfur-oxidizing cells and the oxygen gas–liquid mass transfer rate to be found by trial and error from simultaneous best fits of five important leach data sets: extent of sulfide oxidation, effluent solution potential, iron concentration, cell numbers, and sulfur grade. The challenge was to find a unique value of the oxygen mass transfer rate common to all temperatures.Good to excellent fits of the leach indicators were obtained, while the values of the parameters were largely within the ranges expected. The model revealed the rate-limiting step to shift from particle kinetics to oxygen gas–liquid mass transfer with increasing temperature, increasing proportion of fine pyrite grains, and higher pyrite head grades. Competition for oxygen between sulfur- and iron-oxidizing microorganisms lowered potentials and retarded pyrite oxidation.
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Most investigators regard CuFeS2 as having the formal oxidation states of Cu⁺Fe3 +(S2 −)2. However, the spectroscopic characterisation of chalcopyrite is clearly influenced by the considerable degree of covalency between S and both Fe and Cu. The poor cleavage of CuFeS2 results in conchoidal surfaces. Reconstruction of the fractured surfaces to form, from what was previously bulk S2 −, a mixture of surface S2 −, S2² and Sn2 − (or metal deficient sulfide) takes place. Oxidation of chalcopyrite in air (i.e. 0.2 atm of O2 equilibrated with atmospheric water vapour) results in a Fe(III)–O–OH surface layer on top of a Cu rich sulfide layer overlying the bulk chalcopyrite with the formation of Cu(II) and Fe(III) sulfate, and Cu(I)–O on prolonged oxidation. Cu2O and Cu2S-like species have also been proposed to form on exposure of chalcopyrite to air.
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Biomining is currently used successfully for the commercial-scale recovery of met- als such as copper, cobalt, and gold from their ores. The mechanism of metal extraction is mainly chemistry-driven and is due to the action of a combination of ferric and hydrogen ions, depending on the type of mineral. These ions are produced by the activity of chemolithotrophic microorganisms that use either iron or sulfur as their energy source and grow in highly acidic conditions. Therefore, metal extraction is a combination of chemistry and microbiology. The mixture of organisms present may vary between processes and is highly dependent on the temperature at which mineral oxidation takes place. In general, rel- atively low-efficiency dump and heap irrigation processes are used for base metal recovery, while the biooxidation of difficult-to-treat gold-bearing arsenopyrite concentrates is carried out in highly aerated stirred-tank reactors. Bioleaching reactions, the debate as to whether the reactions are direct or indirect, the role of microorganisms, and the types of processes by which metals are extracted from their ores are described. In addition, some new processes under development and the challenges that they present are discussed.
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Gene transcription (microarrays) and protein levels (proteomics) were compared in cultures of the acidophilic chemolithotroph Acidithiobacillus ferrooxidans grown on elemental sulfur as the electron donor under aerobic and anaerobic conditions, using either molecular oxygen or ferric iron as the electron acceptor, respectively. No evidence supporting the role of either tetrathionate hydrolase or arsenic reductase in mediating the transfer of electrons to ferric iron (as suggested by previous studies) was obtained. In addition, no novel ferric iron reductase was identified. However, data suggested that sulfur was disproportionated under anaerobic conditions, forming hydrogen sulfide via sulfur reductase and sulfate via heterodisulfide reductase and ATP sulfurylase. Supporting physiological evidence for H2S production came from the observation that soluble Cu2+ included in anaerobically incubated cultures was precipitated (seemingly as CuS). Since H2S reduces ferric iron to ferrous in acidic medium, its production under anaerobic conditions indicates that anaerobic iron reduction is mediated, at least in part, by an indirect mechanism. Evidence was obtained for an alternative model implicating the transfer of electrons from S0 to Fe3+ via a respiratory chain that includes a bc1 complex and a cytochrome c. Central carbon pathways were upregulated under aerobic conditions, correlating with higher growth rates, while many Calvin-Benson-Bassham cycle components were upregulated during anaerobic growth, probably as a result of more limited access to carbon dioxide. These results are important for understanding the role of A. ferrooxidans in environmental biogeochemical metal cycling and in industrial bioleaching operations.
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The microbial leaching of metal sulfides is now an established biotechnological technology. Over the past 25 years, refinements in the engineering design of bioleaching processes have paralleled advances in our understanding of the diversity and role of the micro-organisms driving the process and the mechanisms by which micro-organisms enhance metal sulfide oxidation. Commercial success started with the treatment of refractory gold concentrates using mesophilic micro-organisms, followed by the development of tank bioleaching processes for the treatment of base metal concentrates. This was, initially, a mesophilic process with limited potential for recovery of copper from chalcopyrite concentrates due to slow rates and low copper extractions. The exploitation of thermophiles represents a major breakthrough in the development of bioleaching technology for the treatment of chalcopyrite-containing ores and concentrates. This development also opened the route to heap bioleaching of chalcopyrite ores, which is now a major focus of research programmes and piloting campaigns. This paper reviews the historical development of minerals bioleaching processes and gives an update on the current status of commercial tank and heap bioleach operations around the world.
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Modern commercial application of biohydrometallurgy for processing ores became reality in the 1950s with the advent of copper bioleaching at the Kennecott Copper Bingham Mine. Early application entailed dump leaching of low-grade, low-value, run-of-mine material. Dump bioleaching has evolved into a commercially accepted option for bioheap copper leaching of higher-grade, higher value ores. This commercial practice is exemplified by at least 11 mining operations. Paradoxically, application of biohydrometallurgy in the pretreatment of refractory gold ores began with processing high value concentrates, using biooxidation-tank processes and was followed by extension to processing low-grade, lower value ores in heaps. Now, bioleaching has been extended to the commercial extraction and recovery of cobalt. Even with the current success of biohydrometallurgical applications in the mining industry, the real potential of biotechnology in mining remains to be realized. As confidence in commercial bioprocessing grows and experience extends the application's knowledge base, innovations and new commercial practices will emerge. Near-term future commercial applications will likely remain focused on recoveries of copper, gold and possibly nickel. Recent technical advances show that very refractory chalcopyrite can be successfully bioleached. Processes for copper recovery from this mineral will include both heap and stirred-tank reactors. Next generation technologies for pretreatment of refractory gold ores will be based on use of thermophilic bacteria for sulfide oxidation. For biohydrometallurgy to commercially advance, the microbiologist must work cooperatively with the practitioners of the technology for mutual understanding of operational limitations and practical constraints affecting the microbiological component. q 2001 Elsevier Science B.V. All rights reserved.
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Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters
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Dumping of low-grade chalcopyrite encompasses several environmental problems. Despite slow dissolution rate, meso-acidophilic bioleaching is preferred for the extraction of copper from such ores. In the present study, meso-acidophilic bioleaching of a low-grade chalcopyrite in presence of an acid-processed waste newspaper (PWp) is discussed for the first time. The study illustrated a strong catalytic response of PWp with enhanced bio-recovery of copper from acid-conditioned chalcopyrite. A maximum of 99.13% copper recovery (0.36% Cu dissolution/day) was obtained in 6 days of bioleaching in presence of 2 gL- 1 PWp in contrast to only 5.7% copper in its absence. FTIR analysis of bioleached residues revealed similar spectral patterns to the original acid-conditioned ore in presence of PWp, thus indicating less development of passivation layer which was also confirmed through a complementary raman characterization of the bioleached residues. Further, a reaction mechanism (chemistry) was proposed suggesting the possible role of PWp as the electron donor under oxygen limiting conditions which facilitated microbial reduction of Fe (III). The resulting biochemical changes provided an energy source for the bacteria, thus allowing free flow of electrons through the ore surface, thus contributing towards enhanced bioleaching of copper.
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Heap leaching technology is moving forward rapidly as it satisfies most techno-economic considerations and provides several benefits such as low cost, cleaner environment and product, flexibility, and diversified process conditions. Factors such as proper feed preparation, adequate mineralogical analysis, implementation of eco-comminution, and the precise use of characterization tools should be undertaken in order to provide for a successful heap leach process. In view of the important role of comminution and agglomeration in heap leaching systems, both of which have to do with particle size distribution (PSD), improved characterization methods have become of significance in the design and operation of heap leaching systems. An increase in fundamental understanding using advanced characterization tools such as X-ray computed tomography (CT) will make heap leach technology even more adaptable to ever-increasing complex ores in the foreseeable future. High pressure grinding rolls (HPGRs) may become more popular in heap leach operations since they offer several advantages over conventional crushing technologies such as lower energy consumption and increased particle damage. The potential applications of X-ray CT to heap leaching technology and future directions are reported.
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A model was developed to describe microbial growth and transport in the flowing bulk solution and ore-associated phases within a mineral bioleaching heap. The retention of micro-organisms was assumed to be a function of microbial transport between the ore surface and the bulk solution, as well as growth in each of these phases. Transient variations in the corresponding microbial concentrations are presented together with predicted microbial growth, transport and oxidation kinetics within the agglomerate-scale, whole ore environment. The transport model presented in this paper, was developed under the assumption that the microbial concentration gradient between the identified phases was the driving force for microbial transport. Further the population balance model was super-imposed to account for available reaction surface. The model was able to predict the change in microbial concentrations in both the bulk solution and ore-associated phase. The resulting microbial transport rates to and from the ore-associated phase were found to be significantly lower than the maximum specific microbial growth rates presented, suggesting that microbial transport is not governed by the microbial concentration difference. These findings confirm the value of the modelling approach in which the population balance model is included, while demonstrating that concentration gradient as the driving force is not the main contributor to microbial transport.
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Copper slag was subjected to in-depth mineralogical characterization by integrated instrumental techniques and evaluated for the efficacy of physical beneficiation and mixed meso-acidophilic bioleaching tests towards recovery of copper. Point-to-point mineral chemistry of the copper slag is discussed in detail to give better insight into the association of copper in slag. Characterization studies of the representative sample revealed the presence of fayalite and magnetite along with metallic copper disseminated within the iron and silicate phases. Physical beneficiation of the feed slag (~0.6% Cu) in a 2 L working volume flotation cell using sodium isopropyl xanthate resulted in Cu beneficiation up to 2-4% and final recovery within 42-46%. On the other hand, a mixed meso-acidophilic bacterial consortium comprised of a group of iron and/or sulfur oxidizing bacteria resulted in enhanced recovery of Cu (~92-96%) from the slag sample. SEM characterization of the bioleached slag residue also showed massive coagulated texture with severe weathered structures. FE-SEM elemental mapping with EDS analysis indicated that the bioleached residues were devoid of copper.
Article
The shift of microbial community under the adjustment of different pH was analyzed by denaturing gradient gel electrophoresis (DGGE). The results indicated, at initial pH 1.0, 2.0 and 3.0, the copper extraction in 22days amounted to 84.6%, 88.2% and 77.5%, respectively; however, when the initial pH was 2.0, processing pH was adjusted to 1.0 and 3.0 on day 16, the copper extraction in 32days was 85% and 62.6%, respectively. DGGE analysis showed Acidithiobacillus caldus, Leptospirillum ferriphilum, Sulfobacillus thermosulfidooxidans and Ferroplasma thermophilum existed in bioleaching systems. At initial pH 1.0 and 3.0, S. thermosulfidooxidans and A. caldus were main microorganisms. While at initial pH 2.0, L. ferriphilum, A. caldus and S. thermosulfidooxidans were always detected. At processing pH 1.0 and 3.0, the adjustment of pH greatly inhibited the growth of L. ferriphilum; it was also found microbial community would recover gradually only if pH stimulation did not fatally affect microorganisms.
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Bioleaching studies for chalcopyrite contained ball mill spillages are very scarce in the literature. We developed a process flow sheet for the recovery of copper metal from surface activated (600 A degrees C, 15 min) ball mill spillage through bio-hydrometallurgical processing route. Bioleaching of the activated sample using a mixed meso-acidophilic bacterial consortium predominantly A. ferrooxidans strains was found to be effective at a lixiviant flow rate of 1.5 L/h, enabling a maximum 72.36% copper recovery in 20 days. Mineralogical as well as morphological changes over the sample surface were seen to trigger the bioleaching efficiency of meso-acidophiles, thereby contributing towards an enhanced copper recovery from the ball mill spillage. The bio-leach liquor containing 1.84 g/L Cu was purified through solvent extraction using LIX 84I in kerosene prior to the recovery of copper metal by electrowinning. Purity of the copper produced through this process was 99.99%.
Article
This paper studies the effects of quartz on bioleaching of chalcopyrite by Acidithiobacillus ferrooxidans, LD-1 through shaking flask experiments. The results showed that quartz concentration can affect the copper extraction. After 32 days, copper extraction of the leaching system at 50 g L−1 quartz concentration increased by about 20%, compared with that of the leaching system without quartz. XRD analysis showed that the amounts of jarosite on the chalcopyrite surface may reduce by the mechanical friction action between fine particles of quartz and chalcopyrite. The analysis of SEM indicated that the surfaces of chalcopyrite particles were eroded by different degrees and the degrees of change were the same as the effects of quartz concentration on copper extraction.
Article
A study of the effect of different variables (inoculation, pulp density, [Ag], nutrient medium, pH and [Fe3+]) on the silver-catalyzed bioleaching of a low-grade copper sulfide ore has been carried out in shake flasks. Chalcopyrite was the dominant copper mineral in the ore. Preliminary tests showed that addition of other ions (Sb, Bi, Co, Mn, Ni and Sn) did not enhance the copper dissolution rate. Conversely, an inoculation with mesophilic microorganisms and the addition of silver had a markedly catalytic effect on the extraction of copper. The kinetics of the silver-catalyzed chalcopyritic ore bioleaching was greatly affected by pulp density and silver concentration. Small amounts of silver (14.7 g Ag/kg Cu) dramatically accelerated the copper dissolution process while large amounts (294.12 g Ag/kg Cu) had an inhibitory effect. The copper dissolution rate was slightly affected in the range of pH between 1.2 and 2.5 but was significantly slower at pH 3.0. The effect of [Fe3+] in the presence of silver was studied both in abiotic and biotic conditions. High ferric iron concentrations in abiotic tests recovered similar copper amounts (∼ 95%) to those obtained without or with low [Fe3+] in the presence of bacteria. The leaching of copper from the low-grade copper ore can be very effectively enhanced with silver and mesophilic microorganisms. For that system, the onset of oxidizing conditions starts at an Eh value slightly higher than 650 mV. Above that critical value of potential the copper dissolution rate slows down. This also corresponds with the completion of the leaching process. As the potential rises past 650 mV, the copper extraction reaches a plateau.
Article
Draft genome sequences of Acidthiobacillus thiooxidans and A. caldus have been annotated and compared to the previously annotated genome of A. ferrooxidans. This has allowed the prediction of metabolic and regulatory models for each species and has provided a unique opportunity to undertake comparative genomic studies of this group of related bioleaching bacteria. In this paper, the presence or absence of predicted genes for eleven metabolic processes, electron transfer pathways and other phenotypic characteristics are reported for the three acidithiobacilli: CO2 fixation, the TCA cycle, sulfur oxidation, sulfur reduction, iron oxidation, iron assimilation, quorum sensing via the acyl homoserine lactone mechanism, hydrogen oxidation, flagella formation, Che signaling (chemotaxis) and nitrogen fixation. Predicted transcriptional and metabolic interplay between pathways pinpoints possible coordinated responses to environmental signals such as energy source, oxygen and nutrient limitations. The predicted pathway for nitrogen fixation in A. ferrooxidans will be described as an example of such an integrated response. Several responses appear to be especially characteristic of autotrophic microorganisms and may have direct implications for metabolic processes of critical relevance to the understanding of how these microorganisms survive and proliferate in extreme environments, including industrial bioleaching operations.
Article
The changes of pH, redox potential, concentrations of soluble iron ions and Cu2+ with the time of bioleaching chalcopyrite concentrates by acidithiobacillus ferrooxidans were investigated under the different conditions of initial total-iron amount as well as mole ratio of Fe(III) to Fe(II) in the solutions containing synthetic extracellular polymeric substances (EPS). When the solution potential is lower than 650 mV (vs SHE), the inhibition of jarosites to bioleaching chalcopyrite is not vital as EPS produced by bacteria can retard the contamination through flocculating jarosites even if concentration of Fe(III) ions is up to 20 g/L but increases with increasing the concentration of Fe(III) ions; jarosites formed by bio-oxidized Fe3+ ions are more easy to adhere to outside surface of EPS space on chalcopyrite; the EPS layer with jarosites acts as a weak diffusion barrier to further rapidly create a high redox potential of more than 650 mV by bio-oxidizing Fe2+ ions inside and outside EPS space into Fe3+ ions, resulting in a rapid deterioration of ion diffusion performance of the EPS layer to inhibit bioleaching chalcopyrite severely and irreversibly.
Article
The chemical and physical conditions in sulphide heaps provide a complex environment for micro-organisms, with differences in redox potential, acidity, temperature, oxygen and solution chemistry conditions being experienced both temporally and spatially. One of the most important parameters for successful microbial colonisation and active microbial metabolism is suitable pH conditions in the heap. Typically heaps reach tens of metres high and the pH of irrigation solution travelling through heap changes significantly.In this study, we investigated the effect of pH and acid stress for moderately thermophilic and thermophilic mixed cultures, operating at 50–60°C in a heap bioleaching environment. Results collected from laboratory scale column reactors packed with the low grade whole ore and irrigated with different pH solutions during a temperature shift from moderately thermophilic conditions to thermophilic conditions are discussed.
Article
Recovery of metal value, especially from low-grade ores and overburden minerals using acidophilic bacteria through the process of bioleaching is an environmentally benign and commercially scalable biotechnology. In recent years, while the 'OMICS' landscape has been witnessing extensive application of computational tools to understand and interpret global biological sequence data, a dedicated bioinformatic server for analysis of bacterial information in the context of its bioleaching ability is not available. We have developed an on-line Bacterial Bioleaching Protein Finder (BBProF) System, which rapidly identifies novel proteins involved in a bacterial bioleaching process and also performs phylogenetic analysis of 16S rRNA genes. BBProF uses the features of Asynchronous Java Script and XML (AJAX) to provide an efficient and fast user experience with minimal requirement of network bandwidth. In the input module the server accepts any bacterial or archaeal complete genome sequence in RAW format and provides a list of proteins involved in the microbial leaching process. BBProF web server is integrated with the European Bioinformatics Institute (EBI) web services such as BLAST for homology search and InterProScan for functional characterization of output protein sequences. Studying evolutionary relationship of bacterial strains of interest using Muscle and ClustalW2 phylogeny web services from EBI is another key feature of our server, where 16S rRNA gene sequences are considered as input through a JQUERY interface along with the sequences present in the BBProF database library. Complete genome sequences of 24 bioleaching microorganism characterized by genomic and physiological study in the laboratory and their respective 16S rRNA gene sequences were stored in the database of the BBProF library. To our knowledge BBProF is the first integrated bioinformatic web server that demonstrates its utility in identifying potential bioleaching bacteria. We hope that the server will facilitate on-going comparative genomic studies of bioleaching microorganisms and also assist in identification and design of novel microbial consortia that are optimally efficient bioleaching agents.
Article
The application of bacterial oxidation as a pretreatment step for the extraction of gold from arsenical gold sulphide concentrates offers potentially significant economic advantages over oxidative pretreatment alternatives. In this study the bacterial oxidation of an extremely refractory gold sulphide concentrate, from Olympias, Greece, is examined.Leaching tests were conducted in air-stirred pachuca reactors in order to determine the effect of pulp density on the degree of pyrite and arsenopyrite oxidation.Cyanidation tests were conducted in order to determine the degree of gold and silver liberation in relation to the degree of each sulphide phase oxidised and to the cyanide consumed.Mathematical analysis of the leaching data allowed the gold distribution in each sulphide mineral phase to be estimated and the gold recoveries according to the degree of each mineral oxidised predicted.