No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Current scenario of chalcopyrite bioleaching: A review on the recent advances to its heap-leach technology
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.
... Since elevating temperature and pressure require high energy consumption and expensive equipment, biological oxidation, also called biooxidation, came into prominence as a cost-effective, energy-efficient and environmentally friendly alternative to pressure oxidation [2]. Moreover, biooxidation is preferred for processing large volumes of low-grade ore and dirty concentrates as it is profitable and eco-friendly [3]. ...
... Thus, the amount of sulfur oxidation increased. Over time, the ORP of the solution increased to 540 mV indicating high ferric iron concentration which can limit A. ferrooxidans growth [3]. It should be mentioned that the solution colour of the mixed culture was less brown than those of A. ferrooxidans and L. ferrooxidans individually; this indicates a lower amount of jarosite precipitation. ...
... It should be mentioned that elemental sulfur on the ore surface acts as a mass transfer barrier and decreases metal solubilization [23]. Equations (2-4) describe the overall reactions of the thiosulfate pathway [3]. ...
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.
... 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. ...
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. ...
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.
... 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. ...
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.
... 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). ...
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.
... Additionally, the iron content in chalcopyrite can lead to the formation of passivating layers on the mineral surface, further impeding the leaching process. To address this issue, a range of ways is used, including high-temperature pressure leaching [9][10][11], bioleaching [12][13][14][15], chemical pretreatment [16,17], and a combination of leaching methods [18][19][20]. The use of sulfate, nitrate, chloride, and other leaching agents has been investigated. ...
In this study, SDS is used to enhance the sulfuric acid leaching of chalcopyrite in aqueous and isopropanol media. The presence of SDS increased copper extraction into the solution in both solvents. However, it was the “isopropanol–sulfuric acid–SDS” system that proved to be particularly effective for copper recovery from chalcopyrite. The positive effect of SDS can be attributed to the reduction in the solution’s surface tension and the enhancement of mineral wetting. Additionally, the presence of SDS as a surfactant induces changes in the adsorption patterns of formed sulfur species on the mineral surface. SDS competes with sulfur for occupancy on the surface binding sites. This competitive interaction has the potential to diminish the formation of a substantial sulfur layer on the mineral surface. Under optimal conditions (isopropanol media, 2 M H2SO4, 65 °C, 120 min, 0.6 g/L SDS), copper recovery into the solution was 83%, and this is a considerable achievement for chalcopyrite leaching at ambient pressure in the absence of strong oxidizers.
... These methods are well known for generating large amounts of hazardous waste at the end [8,9]. Use of advanced alternative technologies that will be less energy-intensive, low cost and environmentally friendly copper extraction technologies are needed especially in resource-limited countries like Zambia [10,11]. It is important because high-grade and oxide ores are depleting rapidly [12] while the demand for copper in the world market is high. ...
... Its industrial application is known as bioleaching, which is mostly suited to treat low-grade sulfide ores. This cost-effective process exhibits a high copper recovery from secondary sulfides (Deveci and Ball 2010;Fu et al. 2016;Olubambi, Potgieter, and Borode 2008;Panda et al. 2015;Watling 2006). In this context, Akcil, Ciftci, and Deveci (2007) carried out a study to compare the bioleaching of a chalcopyrite ore assaying 15.75% Cu, by the mesophile microorganisms Acidithibacillus ferrooxidans, Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans at 30ºC. ...
Chalcopyrite ores are processed mostly by pyrometallurgical techniques due to the refractory nature of the mineral to the current hydrometallurgical techniques. In order to overcome such refractoriness, pretreatment steps such as sulfurization may be applied to produce different copper phases and therefore improve the metal dissolution in the leaching step. The current study investigated the reaction products of the reaction between chalcopyrite and elemental sulfur at different chalcopyrite/sulfur ratios (1/1 and 1/2), reaction time (60 min and 90 min), and temperature (350ºC, 400°C and 450ºC). The sulfurization experiments revealed that covellite, nukundamite, bornite, and pyrite-like compounds were produced according to the experimental conditions applied. Then, the sulfurization products were submitted to chemical leaching tests at temperatures ranging from 32ºC to 70ºC, whereas bioleaching tests were also carried out with Acidithiobacillus ferrooxidans, at 32ºC. In the chemical leaching experiments at 70ºC, only 14% copper was recovered from the original chalcopyrite sample while the maximum copper extraction was 78% from bornite produced at 450ºC (90 min and mass ratio of chalcopyrite/sulfur of 1/2). On the other hand, copper extraction achieved 96% from the same sulfurization product containing synthetic bornite within 20 days of bioleaching. Bioleaching of the original chalcopyrite sample implied in a copper recovery of only 25% in the same period. Summarizing, the current work showed that chalcopyrite sulfurization at 450ºC was able to transform chalcopyrite into a bornite-like phase, which was chemically leached and bioleached by At. ferrooxidans.
... Therefore, chalcopyrite is considered as the alternate Fenton catalyst that rapidly releases Fe 2+ , Cu 2+ , and protons in the system (Eq. 4-8) [103,104]. The iron leaching was found to be much lesser in case of chalcopyrite,while the Cu leaching by chalcopyrite imposes higher toxicity than that of pyrite [105]. ...
Removal of recalcitrant organic pollutants via advance oxidation process (AOP) is an effective and green approach in the field of wastewater treatment. Fenton process is one such kind of AOP technique that employs iron (Fe) materials and oxidizing agent to attain degradation of organic pollutants though the generation of reactive organic species (ROS). In this review, the utility of natural and synthetic iron materialstowards water remediation process has been discussed in detail in relation to Fenton chemistry. The geochemistry of natural iron materials (oxides and sulfides) and chemistry of synthetic iron materials (nanomaterials and their impregnated forms) has been discussed to understand their role in Fenton processes. Additionally, the emergence of ferrates as a new and promising candidate for the removal of organic pollutants has been highlighted. A detailed investigation on the effect of various operational parameters such as pH, catalyst dose, foreign ion, oxidant concentration, and chelating agents in affecting the performance of iron materials has been highlighted. A summary on the potency of various iron materialstowards removing diverse kind of organic compounds from aqueous medium has been provided. At last, the review has been concluded with emphasizing the drawbacks and benefits of using Fe material for realizing Fenton and Fenton-like processes.
... Biofilmforming bacteria differ from planktonic bacteria in that they are highly resistant to antibiotics, harsh environments, and host immune defenses Narenkumar et al. 2021). Biofilm-forming bacteria possess distinctive characteristics in terms of physiology, metabolism, degradation, and utilization (Miller et al. 1992, Panda et al. 2015 of substrates. Sabrina et al. discovered that biofilmforming bacteria, such as Halobacterium salinarum, were more resistant to metal ions such as Cu 2+ and Ni 2+ than planktonic bacteria (Volkel et al. 2018). ...
As the demand for metal resources increases and the quality and availability of rich ore resources decline, the focus is shifting to low-cost, eco-friendly bioleaching technologies that can effectively utilize low-grade minerals. The stress on bioleaching microorganisms due to high concentrations of metal ions in the bioleaching system is one of the most important factors limiting the effectiveness of bioleaching. Using the common copper-bearing ore bioleaching process as an example, the copper ion concentration reached 6 g/L. An in-depth examination of the copper defensive mechanism of bioleaching microorganisms will help elucidate the physiological mechanism of such extremophiles and pave the way for future genetically engineered highly efficient strains. We elaborate on the copper tolerance mechanism of extremophiles through the lens of biofilms, cell membranes, metal transport mechanisms, intracellular buffer mechanisms, and energy metabolism.
... These species oxidize ferrous iron to ferric iron and/or reduced sulfur compounds to sulfuric acid, which leach metals from minerals and wastes via redoxolysis and acidolysis, respectively [5]. Bioleaching also is the metal-extracting practice from sulfides and/or iron-containing ores by microorganisms [6]. Shewanella oneidensis is a bacterium notable for its ability to reduce metal ions and lives in environments with or without oxygen. ...
Conventional method for gold extraction using cyanide is not environmentally friendly and harmful to the environment. Thus, we investigate the potential of Shewanella oneidensis as bioleaching agent for gold extraction to replace the cyanide leaching process. The concentration of Fe (II) was determined via Ferrozine Assay method using Spectrophotometer, while the concentration of gold (Au) was determined using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Some minerals such as pyrite, arsenopyrite, hematite, magnetite, and quartz were detected in the ore samples using XRD. The results show, S. oneidensis MR-1 was able to reduce Fe (III) to Fe (II) that can increase gold concentration. Gold concentrations were increased from 19 ppb to 28.5 ppb with 50% of percentage yield increased. In addition, the result shows hematite and magnetite in the samples was also reduced after bioleaching which might lead to the increasing amount of gold concentration. As a conclusion, S. oneidensis MR-1 was shown to be effective for bioleaching to improve gold extraction process.
... Meanwhile, a previous study has also found a high relative abundance of Sulfurifustis near the smelting area (Liu et al. 2022b). Thiobacillus is iron-oxidizing, sulfur-oxidizing, and acidophilic bacterial strain, which is frequently found in acidic soil of mining areas, bioleaching process, and acid mine wastewater (Panda et al. 2015). Thiobacillus can extract HMs from sewage sludge and bioleach HMs (Leduc et al. 1997) from contaminated soil by direct biooxidation or indirect chemical oxidation of HMs via Fe 3+ produced in the bioleaching process (Zhang et al. 2009). ...
Mining causes extreme heavy metal (HM) contamination to surrounding environments and poses threats to soil microbial community. The effects of HMs on soil microbial communities are not only related to their total amounts but also associated with the distribution of chemical fractions. However, the effects of chemical fractions on soil microbes and their interactions remain largely unclear. Here we investigated soil physicochemical properties and bacterial and fungal communities of soil samples from the control area and lightly (L), moderately (M), and heavily (H) contaminated areas, respectively, which were collected from long-term Pb–Zn slag contamination area in the southern China. The results showed that bacterial and fungal community composition and structure were significantly affected by HMs, while community diversity was not significantly affected by HMs. The critical environmental factor affecting bacterial and fungal communities was pH, and the impacts of chemical fractions on their changes were more significant than the total amounts of HMs. Variance partitioning analysis (VPA) revealed fungal community changes were mostly driven by HM total amounts, but bacterial community changes were mostly driven by soil chemical properties. Co-occurrence network indicated that interactions among species of fungal network were sparser than that of bacterial network, but fungal network was more stable, due to a more significant number of keystone taxa and a lower percentage of positive associations. These illustrated that the fungal community might serve as indicator taxa for HM-contaminated status, and specific HM-responsive fungal species such as Triangularia mangenotii, Saitozyma podzolica, and Cladosporium endophytica, and genus Rhizophagus can be considered relevant bioindicators due to their less relative abundance in contaminated areas. Additionally, HM-responsive bacterial OTUs representing five genera within Sulfurifustis, Thiobacillus, Sphingomonas, Qipengyuania, and Sulfurirhabdus were found to be tolerant to HM stress due to their high relative abundance in contaminated levels.
... intensive, low cost and environmentally friendly copper extraction technologies (Panda et al., 2015). It is important because high-grade and oxide ores are depleting rapidly while the demand for copper in the world market is higher. ...
... middle residues in columns B and C (Figs. 6f and 6i). These short rod-like cells had the same morphology as the leaching bacteria found by Panda et al. [45], and the porous surface was similar to the model proposed by Ghahremaninezhad et al. [18] for chalcopyrite dissolution catalyzed by Ag + . Compared to the column A, the surface of residues in columns B and C were covered by less deposits and attached by more cells. ...
Chalcopyrite is the most abundant copper ores in nature and the main source of copper resources. Low energy consumption but slow kinetics occurred in the microbial fuel cell (MFC)-assisted chalcopyrite bioleaching process. High price and low recovery limited the use of silver-bearing chemicals as catalysts for the chalcopyrite bioleaching. Besides, the process of extracting silver-bearing chemicals from silver-bearing ores was complex and energy-intensive. Silver-bearing ores were low-cost and could release Ag⁺, which could be used as the alternative to silver-bearing chemicals in the chalcopyrite bioleaching. This study proposed the catalytic effect and catalytic pathway of silver-bearing ores on copper extraction in the MFC-assisted chalcopyrite bioleaching. After 216 days bioleaching, the maximum Cu²⁺ leaching efficiency of 10.03% was achieved in column reactor mixed with silver-bearing ores. Replacing silver-bearing chemicals (Ag2SO4) with silver-bearing ores in MFC-assisted bioleaching processes promoted the copper extraction efficiency by 1.5 times (10.03% vs. 6.63%). In contrast, the Cu²⁺ leaching efficiency was observed to be 5.37% in the absence of silver. Compared with the regeneration of Ag⁺ only from Ag2S in the system mixed with Ag2SO4, the continuous release of Ag⁺ from silver-bearing ores maintained an appropriate concentration, which facilitated the bacterial growth and chalcopyrite dissolution. Ag⁺ promoted the formation of porous surfaces and increased surface roughness, which enhanced the adsorption of bacteria on chalcopyrite surface. Additionally, both Ag⁺ and MFC better reduced passivation and maintained the optimum ORP, which facilitated the continuous dissolution of chalcopyrite.
... Bio-hydrometallurgical technologies have been widely utilized in the copper industry [81,82], especially for the processing of chalcopyrite, which is well-known for being refractory to conventional leaching methods [83]. Gold has been mainly produced using hydrometallurgical methods based on cyanide leaching [29]. ...
This white paper covers the fundamentals of hydrometallurgical process synthesis, design, and economic evaluation. Metallurgical and Materials Engineering students and engineers with limited process design experience find it particularly useful. It features theory on process synthesis and analysis, material on hydrometallurgical process simulation, and presents a thorough methodology for estimation of capital and operating costs. It also includes the following five detailed process examples modeled and analyzed with SuperPro Designer: 1) Extraction of Lithium from Spodumene Ore, 2) Bio-Hydrometallurgical Recovery of Copper and Gold, 3) Recycling of Solar Photovoltaic Panels, 4) Hydrometallurgical Recycling of Lithium-Ion Batteries and 5) Manufacturing of NMC 811 Cathode Material for Lithium-Ion Batteries. For additional hydrometallurgical examples of SuperPro Designer, please visit https://www.intelligen.com/industries/metallurgy/
... Solar radiation, wind, and extreme temperatures will all have a great impact on the leaching effect. Some researchers have found that climatic conditions have an important influence on the dissolution process of chalcopyrite [83], especially for insoluble low-grade chalcopyrite, usually the leaching time can be as long as several months or even half a year. During this period, rainfall and nighttime temperature will affect the activity and growth rate of bacteria in the pile, and slow the dissolution of chalcopyrite, which intensifies the formation of a passivation layer on the mineral surface and reduces the leaching efficiency. ...
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.
... 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. ...
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.
... Copper is a precious and widely used element in various industries because of its high ductility, thermal and electrical conductivity (Wang, Zhang, et al. 2018). Nowadays, hydrometallurgical processes are used in copper extraction due to their high efficiency and advantages (Panda, Akcil et al. 2015). A raffinate is produced in a hydrometallurgical process which contains ions of the target element, heavy metals, and high concentrations of acid. ...
The mining industry has traditionally relied on conventional fossil-based fuel sources to meet its growing energy demand. The industry is now tasked with responding to the challenges of increasing fuel prices while commodity prices tighten, resulting in ever-narrowing operating margins and increased opposition from communities to new conventional energy sources. So far, research about such decision-making on the use of renewable energy in production scheduling (PS) problem for open pit mining operations is underdeveloped. Due to the conflicting nature of economic and environmental objectives, the PS becomes a multi-objective problem. In this paper, a multi-objective gravitational search algorithm is used to provide Pareto optimal solutions which present the possible tradeoff between the cost and environmental objectives of the PS problem. To solve the problem, the weighted sum method is applied to convert multi-objective optimization to scalar optimization. The numerical results demonstrate the
effectiveness of the proposed approach in solving multi-objective PS problems.
... 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). ...
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.
... 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). ...
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.
... 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). ...
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.
... Microbial leaching is a viable commercial process. Approximately 20% of the world's copper supply is the direct result of microbial leaching of copper sulfide ores (Panda et al., 2015) and 5% of the world's gold is recovered through biooxidation (Brierley and Brierley, 2013). Bioleaching and biooxidation are operating in commercial scale with gold and base metal (e.g., copper, nickel, cobalt, and zinc) sulfide mining occurring in several countries such as (but not limited to) Australia, South America, South Africa, India, China, and Finland (Hubau et al., 2020). ...
The aim of this chapter is to review the link between resources, technology, and changing environmental impacts over time as a basis for informing future research priorities in technology and resource governance models. Given that the iron ore sector has shown boom-bust cycles in the past, it is important to assess in detail the current state of Australia’s iron ore industry, especially in comparison to global trends and issues, with a view to ensuring the maximum long-term benefit for and from Australia’s mining sector. This chapter presents an assessment of Australia’s iron ore mineral resources, production trends, economic aspects, existing and future production challenges, and links these to sustainability aspects, especially environmental issues such as greenhouse gas emissions. The chapter therefore provides a sound basis for ongoing policy development to ensure that Australia can maintain and enhance the benefits that our iron ore resource endowment brings.
... 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). ...
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.
... 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]. ...
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.
... They differ in the nutrient substrates they use and in the bioleaching functions they can perform, so their share in the variants is clearly influenced by the additives, and the variation in their share in the different variants leads to changes in community function. According to their respective functional characteristics (Panda et al., 2015;Chen et al., 2016;Li et al., 2017) and proportions (Fig. 5), the distribution of microbial functions poten-tially performed in each variant was obtained, as shown on Fig. 8. ...
The effect of mineral salts on an acidophilic mixed culture was investigated. The tested mixed culture included representatives of the genera Leptospirillum, Sulfobacillus, and Acidiplasma. Elimination of each mineral salt studied led to a decrease in the diversity of the mixed culture. The influence of mineral salts and elements in the 9K medium on microbial reproduction follow the sequence: FeSO4·7H2O > MgSO4·7H2O > (NH4)2SO4 > CaNO3 > K2HPO4 > KCl and Fe > N > Mg > K > Ca > P > Cl. In terms of microbial function, the sequence is as follows: FeSO4·7H2O > K2HPO4 > CaNO3 > MgSO4·7H2O > (NH4)2SO4 > KCl and Fe > K > P > Ca > Mg > N > Cl. The significantly influenced genera were Cuniculiplasma, A-plasma, Ferroplasma, Sulfobacillus, and Leptospirillum. Sulfur oxidation and nitrogen fixation were the most severely affected microbial functions. This research provides a basis for the improvement of microbial cultures applied for the bioleaching and optimization of the biometallurgical process.
... 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. ...
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.
... 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. ...
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.
... 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). ...
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 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). ...
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.
The extraction and processing of silver minerals produce significant amounts of waste, which poses environmental challenges due to their low metal content and the potential release of toxic elements. The study investigates the application of Acidithiobacillus ferrooxidans ( AF ) bacteria to the bioleaching of these waste materials, with the aim of maximizing the recovery of iron, copper and arsenic. The objectives of the study include characterizing waste materials, optimizing the bioleaching process parameters and evaluating metal extraction efficiency. The samples were leached with additives (CuSO 4 5H 2 O and AgNO 3 ) to accelerate the kinetics of metal dissolution in solution and reduce the bacterial leaching time. The results showed that samples 1-2 and 2-2 containing additives had higher values of dissolved iron and copper in the leachate compared to samples 1-1 and 2-1 without additive application.
The extraction of various minerals is commonly conducted through froth flotation, which is a versatile separation method in mineral processing. In froth flotation, depressants are employed to improve the flotation selectivity by modifying the wettability of the minerals and reducing their natural or induced floatability. However, the environmental impact of many current flotation chemicals poses a challenge to the sustainability and selectivity of the ore beneficiation processes. To mitigate this issue, cellulose, particularly nanocelluloses, has been explored as a potential alternative to promote sustainable mineral processing. This study focused on silylated cellulose nanocrystals (CNCs) as biodepressants for sulfide minerals in froth flotation. CNCs containing thiol silane groups or bifunctional CNCs containing both thiol and propyl silanes were synthesized using an aqueous silylation reaction, and their performance in the flotation of chalcopyrite and pyrite was investigated in the presence of a sodium isobutyl xanthate collector. The results showed that the modified CNCs exhibited preferential interaction between chalcopyrite, and the flotation recovery of chalcopyrite decreased from ∼76% to ∼24% in the presence of thiol-grafted CNCs at pH 6, while the pyrite recovery decreased only from ∼82% to ∼75%, indicating the efficient selectivity of thiol-silylated CNCs toward chalcopyrite depression.
The purpose of this article is to explore potential solutions for hydrometallurgical processes using semiconductor electrochemistry as an approach, that has received limited attention from the scientific community. Hydrometallurgy involves more sustainable methods for obtaining metallic resources through dissolution, offering the possibility to leach low-grade ores and recycle waste with low metal concentrations. Several minerals of interest are semiconductors, such as stibnite (Sb2S3), chalcopyrite (CuFeS2), chalcocite (Cu2S), bornite (Cu5FeS4), and sphalerite (ZnS). Thus, understanding the nature of these minerals in contact with an electrolyte solution is crucial for promoting efficiency and scalability of hydrometallurgy, as the efficiency of the reactions involved in the process is dictated by the charge transfer at the interface between the semiconductor and the electrolyte solution containing the redox pairs. Furthermore, this article proposes new models and cost-effective strategies for solubilizing ores from the perspective of semiconductor electrochemistry.
Due to the increasing complexity and dilution of copper resources, a large number of refractory polymetallic complex chalcopyrite are produced. In this study for resolving puzzle in oxygen pressure acid leaching of polymetallic complex chalcopyrite, such as prone to produce dangerous solid wastes like lead jarosite and high iron content in leaching solution, the technology of hydrothermal leaching under oxygen pressure without acid is proposed to extract copper efficiently and selectively and to precipitate iron by hematite process simultaneously. The results show that under the experimental conditions of initial sulfuric acid concentration of 0 g/L, reaction temperature of 200 °C, oxygen partial pressure of 1.2 MPa, liquid–solid ratio of 10 mL/g, sodium lignosulfonate addition of 0.5 pct mass of raw material, leaching time of 120 minutes, and stirring speed of 400 r/min, copper leaching rate can reach 99.86 pct. At this time, the iron content of leaching solution is only 4.3 g/L; Chalcopyrite (CuFeS2), porphyrite (Cu5FeS4), pyrite (FeS2), galena (PbS), and other mineral phases can completely react in the system to form corresponding metal sulfate, and Fe3+ is converted to hematite by directed hydrolysis, thus inhibiting the generation of dangerous solid waste such as lead jarosite.
Microbial attachment and biofilm formation is a ubiquitous behaviour of microorganisms and is the most crucial prerequisite of contact bioleaching. Monazite and xenotime are two commercially exploitable minerals containing rare earth elements (REEs). Bioleaching using phosphate solubilizing microorganisms is a green biotechnological approach for the extraction of REEs. In this study, microbial attachment and biofilm formation of Klebsiella aerogenes ATCC 13048 on the surface of these minerals were investigated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). In a batch culture system, K. aerogenes was able to attach and form biofilms on the surface of three phosphate minerals. The microscopy records showed three distinctive stages of biofilm development for K. aerogenes commencing with initial attachment to the surface occurring in the first minutes of microbial inoculation. This was followed by colonization of the surface and formation of a mature biofilm as the second distinguishable stage, with progression to dispersion as the final stage. The biofilm had a thin-layer structure. The colonization and biofilm formation were localized toward physical surface imperfections such as cracks, pits, grooves and dents. In comparison to monazite and xenotime crystals, a higher proportion of the surface of the high-grade monazite ore was covered by biofilm which could be due to its higher surface roughness. No selective attachment or colonization toward specific mineralogy or chemical composition of the minerals was detected. Finally, in contrast to abiotic leaching of control samples, microbial activity resulted in extensive microbial erosion on the high-grade monazite ore.
Magnetite is one of the common associated minerals of chalcopyrite. However, so far, no studies have elucidated the effect of magnetite on the dissolution behaviors of chalcopyrite. In this paper, the impact of magnetite on the dissolution of chalcopyrite in sulfuric acid was investigated by leaching experiments, electrochemical measurements, XRD, Raman, and FTIR techniques. Results show that the presence of magnetite significantly enhances the dissolution of chalcopyrite. Different additions of magnetite in the leaching system of chalcopyrite contribute to remarkable differences in the redox potentials. When 0.5 g of magnetite was added, the redox potential was maintained in the range of 650–700 mV (vs. SHE) where chalcopyrite was reduced to chalcocite and then oxidized to Cu2+. But for magnetite additions of 1 g and 2 g, the redox potential exceeded the appropriate range for chalcocite formation, so the dissolution of chalcopyrite was dominated by the direct oxidation by Fe3+. Electrochemical measurements verified the existence of the galvanic interaction between magnetite and chalcopyrite, but its effect is much less than that of iron ions on chalcopyrite dissolution. The study suggests that copper extraction of chalcopyrite can be improved by the addition of proper amount of magnetite.
In this paper, a novel process leaching complex chalcopyrite without acid under oxygen pressure is proposed, and the leaching behavior and kinetic characteristics of copper in the complex chalcopyrite is studied. The results show that in the process of oxygen pressure leaching of complex chalcopyrite the oxidation dissolution of FeS2 occurs first, and then the sulfuric acid required by the reaction is generated, which destroys the embedded structure of various mineral phases in chalcopyrite and makes it dissolve into the leaching solution. The copper in the mineral reacts with sulfuric acid to form copper sulfate which enter into the leaching solution, and the iron in the mineral is mainly transformed to hematite and then remained in the leaching slag. Under the optimal leaching conditions (initial sulfuric acid concentration 0 g/L, reaction temperature 200 ℃, partial pressure of oxygen 1.2 MPa, mineral particle size − 48 + 38 µm), the leaching efficiency of copper reached 99.86% after 120 min reaction. The analysis of the kinetic process of oxygen pressure leaching of complex chalcolite based on the "shrinkage core model" showed that the leaching process of chalcopyrite is mainly controlled by chemical reaction. The apparent activation energy of the reaction is 50.646 kJ/mol. In the process of chemical reaction control, the parameters of partial pressure of oxygen and initial radius of mineral particles are 4.040 and − 0.773, respectively. The kinetic equation can be expressed as 1-1-X13=1.123×104×PO24.040r0-0.773e-6092Tt.
The anthropogenic activities in agriculture, industrialization, mining, and metallurgy combined with the natural weathering of rocks, have led to severe contamination of soils by toxic metal(loid)s. In an attempt to remediate these polluted sites, a plethora of conventional approaches such as Solidification/Stabilization (S/S), soil washing, electrokinetic remediation, and chemical oxidation/reduction have been used for the immobilization and removal of toxic metal(loid)s in the soil. However, these conventional methods are associated with certain limitations. These limitations include high operational costs, high energy demands, post-waste disposal difficulties, and secondary pollution. Bioleaching has proven to be a promising alternative to these conventional approaches in removing toxic metal(loid)s from contaminated soil as it is cost-effective, environmentally friendly, and esthetically pleasing. The bioleaching process is influenced by factors including pH, temperature, oxygen, and carbon dioxide supply, as well as nutrients in the medium. It is crucial to monitor these parameters before and throughout the reaction since a change in any, for instance, pH during the reaction, can alter the microbial activity and, therefore, the rate of metal leaching. However, research on these influencing factors and recent innovations has brought significant progress in bioleaching over the years. This critical review, therefore, presents the current approaches to bioleaching and the mechanisms involved in removing toxic metal(loid)s from contaminated soil. We further examined and discussed the fundamental principles of various influencing factors that necessitate optimization in the bioleaching process. Additionally, the future perspectives on adding omics for bioleaching as an emerging technology are discussed.
The growing worldwide demand for copper implies the need to process increased amounts of its ores. Chalcopyrite is the most abundant copper mineral, but due to its refractory nature it presents slow kinetics and low metal recovery when submitted to hydrometallurgical processes. Researchers have proposed the application of high temperatures and the use of reagents such as sodium chloride in order to overcome such refractoriness. Within hydrometallurgy, bioleaching has been suggested as an economic and environmental alternative to traditional chemical processes. However, most acidophilic microorganisms used in bioleaching cannot tolerate high chloride concentrations - similar to those found in seawater. Therefore, this review aims to present the main aspects of these systems, as the application of chloride in bioleaching is still a challenge. Nevertheless, if this problem is overcome, chloride bioleaching can become an alternative to process low grade chalcopyrite- bearing ores and tailings, particularly when saline waters are used in bioleaching processes to reduce the demand for fresh water.
The selective depression effect and mechanism of the organic depressant sodium dimethyl dithiocarbamate (SDD) on pyrite in the flotation system of chalcopyrite and pyrite at low alkalinity (pH 8.5) were investigated. The results of single mineral microflotation tests indicated that the recovery efficiency of pyrite decreased from 80.23% to 39.18% after SDD was added, while the recovery efficiency of chalcopyrite decreased from 97.74% to 93.07%. This indicates that SDD has a clear selective depression effect on pyrite, but it has little depression effect on chalcopyrite. X-ray photoelectron spectroscopy (XPS) showed that at low alkalinity (pH 8.5), SDD chemical adsorbed on the surface of pyrite to form water-insoluble complexes, the flotability of pyrite surface was decreased. However, adsorption of SDD on the surface of chalcopyrite was weaker than that on pyrite, which increases the flotability difference between the two surfaces and leads to selective depression of pyrite.
The disposal of the Wastes of Electronic and Electric Equipment (WEEE) is an emerging stream of waste that has been increasing drastically recently. The intensifying of the quantity of WEEE is due to rapid technological advancement, thus reducing the End-of-Life (EOL) and hastening the obsolescence of Electronic and Electric Equipment (EEE). The approach of handling WEEE determines the fate of contaminant substance either recycling, disposed to landfill or being incinerated, releasing toxic and hazardous chemical to environment. Nevertheless, WEEE is also known as the urban mine where it can be the source of rare earth metal (REM) and precious metal such as gold and platinum. The most important element in managing the WEEE is the enforcement of the legislation/law with initiatives from stakeholders. The option of recycling for a particular material is summarized in this book chapter. Lastly, the hazard associated with recycling is being briefly discussed at the end of a chapter.KeywordsWastes of electronic and electric equipment (WEEE)Electronic and electric equipment (EEE)End-of-life (EOL) wasteDisposalRecycleLegislation
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Thermophiles have been shown to be the only micro-organisms to leach chalcopyrite successfully. Heap leaching may be a feasible alternative to conventional bio-reactors, providing a high temperature environment can be maintained within the heap without external heating.In the present study thermophilic heap leaching of a chalcopyrite concentrate coated onto inert support rocks (the GEOCOAT™ process) was studied in sets of small heated columns. The temperature was gradually increased to 70 °C, while successively introducing various mesophile and thermophile cultures. Individual columns were dismantled after progressively longer leach periods and the residual concentrates analysed. Copper extractions in excess of 90% were achieved within 100 days.On the basis of head and residue analyses the rate of reaction heat generated was calculated. A comprehensive heap heat conservation model was used to determine whether the experimental temperatures can be achieved and maintained in a full scale heap. Results indicate that operating hot heaps successfully is possible within a certain range of process parameters.
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.
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.
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.
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
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.
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.
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.
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.
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.
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%.
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.
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.
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.
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.
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.