Article

Reductive dissolution by waste newspaper for enhanced meso-acidophilic bioleaching of copper from low grade chalcopyrite: A new concept of biohydrometallurgy

Authors:
  • Gujarat Biotechnology University
  • College of Engineering & Technology, Bhubaneswar
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Abstract

Dumping of low-grade chalcopyrite encompasses several environmental problems. Despite slow dissolution rate, meso-acidophilic bioleaching is preferred for the extraction of copper from such ores. In the present study, meso-acidophilic bioleaching of a low-grade chalcopyrite in presence of an acid-processed waste newspaper (PWp) is discussed for the first time. The study illustrated a strong catalytic response of PWp with enhanced bio-recovery of copper from acid-conditioned chalcopyrite. A maximum of 99.13% copper recovery (0.36% Cu dissolution/day) was obtained in 6 days of bioleaching in presence of 2 gL- 1 PWp in contrast to only 5.7% copper in its absence. FTIR analysis of bioleached residues revealed similar spectral patterns to the original acid-conditioned ore in presence of PWp, thus indicating less development of passivation layer which was also confirmed through a complementary raman characterization of the bioleached residues. Further, a reaction mechanism (chemistry) was proposed suggesting the possible role of PWp as the electron donor under oxygen limiting conditions which facilitated microbial reduction of Fe (III). The resulting biochemical changes provided an energy source for the bacteria, thus allowing free flow of electrons through the ore surface, thus contributing towards enhanced bioleaching of copper.

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... The peaks in the bioleached residues at the range 1001-1080 cm À1 ; and 772.84 cm À1 show variations and became narrower as compared to control peaks and are ascribed to the dissolution of some quartz portion existed in higher quantity in the ore body. Comparable bands variation patterns were observed by Prasad et al. (2006); Panda, Biswal et al. (2015). Similarly, variations at the ranges 515-700, 800-818.43, ...
... These results show the bacterial dissolution of the iron and sulfur contents existing in the ore. These findings are supported by the results of Ruan et al. (2001); Ding et al. (2007) and Panda, Biswal et al. (2015). The bands present at 3434.5-3455.2 ...
... The bands present at 3434.5-3455.2 cm À1 could be ascribed to adsorbed water stretching on the ore surface or OH functional group attached to numerous iron oxides mainly goethite (FeOOH) (Panda, Biswal et al. 2015;Prasad et al. 2006;Ruan et al. 2001). Moreover, the mineral of goethite is strongly bonded by hydrogen with n(OH) stretching mode at 3100-3150 cm À1 (Libowitzky and Rossman 1997;Russell and Fraser 1994). ...
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This study aimed to investigate the ability of pure and consortia of indigenous iron-oxidizing bacteria to enhance the dissolution of trace metals from Cu and Zn-bearing ore. Three bacterial strains Acidithiobacillus ferrooxidans strain WG101, Leptospirillum ferriphilum strain WG102, Leptospirillum ferrooxidans strain WG103 isolated from Baiyin copper mine, China were used in this study. The biotechnological potential of these indigenous isolates was evaluated both in pure and in consortia to extract cobalt, chromium, and lead from the copper and zinc bearing ore. The sulfur and iron-oxidizing bacterial isolate Acidithiobacillus ferrooxidans strain WG101 exhibited efficient dissolution compared to sole iron-oxidizing Leptospirillum ferriphilum strain WG102, and Leptospirillum ferrooxidans strain WG103. Initial medium pH, pulp density, and temperature were studied as influential parameters in bioleaching carried out by bacterial consortia. The achieved optimum conditions were; initial pH of 1.5, 10% of pulp density, and temperature 30 C with 68.7 ± 3.9% cobalt, 56.6 ± 3.9% chromium, and 36 ± 3.7% lead recovery. Analytical study of oxidation reduction potential and pH fluctuation were observed during this whole process that shows the metal dissolution efficiency of bacterial consortia. Alterations in spectral bands of processed residues were reported through FTIR analysis compared with control ore sample. M€ ossbauer spec-troscopy analysis showed the influence of bacterial consortia on iron speciation in bioleached samples. The findings confirm that the indigenous acidophilic iron-oxidizing bacterial strains are highly effective in the dissolution of trace elements present in ore samples. This study not only supports the notion that indigenous bacterial strains are highly effectual in metal dissolution but provides the basic vital conditions to upscale the bioleaching technique for metals dissolution. ARTICLE HISTORY
... Though, these catalytic additives significantly enhanced the metals recovery from the chalcopyrite ores, however, these catalysts are often uneconomical and associated with harmful effects on microbial structural communities. The use of Ag + enhances the overall processing cost and the chloride ions create osmotic stress and inhibit bacterial growth while, sonication is generally associated with the degradation of living cells of microbes (Panda et al., 2015). Therefore, an appropriate catalyst, which can control the overall oxidation-reduction reaction during the process, improve the metal recovery rate, and can be scaled up, would significantly improve the metals recovery from the low-grade ores. ...
... The use of indigenous iron-oxidizing bacterial consortia of known nature is more effectual in metals recovery (Sajjad et al., 2018a(Sajjad et al., , 2019b. The use of an appropriate catalytic agent is advantageous for bioleaching like an acid treated newspaper (Panda et al., 2015) and acid-treated rice straw (Yin et al., 2019) that is cost-effective, eco-friendly with enhanced metals extraction. However, it is not only essential to probe the influence of catalytic agents on metals recovery but also on bacterial structural community dynamics in a more controllable way. ...
... However, it is not only essential to probe the influence of catalytic agents on metals recovery but also on bacterial structural community dynamics in a more controllable way. Panda et al. (2015) did not check the influence of catalytic agent on bacterial community structural shifts. While, Yin et al. (2019) probed the influence of catalytic agent on bacterial structural shifts in the middle and at the end of the bioleaching process. ...
Article
Disposing of low-grade ores involves numerous environmental issues. Bioleaching with acidophilic bacteria is the preferred solution to process these ores for metals recovery. In this study, indigenous iron-oxidizing bacteria Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum, and Leptospirillum ferrooxidans were used in consortia supplemented with acid-treated bamboo sawdust (BSD) for copper and zinc recovery. Findings showed the extreme catalytic response of BSD with the best recovery of metals. Maximum of 92.2 ± 4.0% copper (0.35%) and 90.0 ± 5.4% zinc (0.33%) were recovered after 8 days of processing in the presence of 2 g/L BSD. Significant variations were reported in physicochemical parameters during bioleaching in the presence of a different concentration of BSD. Fourier Transform Infrared spectroscopy results of bioleached residues showed significant variations in spectral pattern and maximum variations were reported in 2.0 g/L BSD, which indicates maximum metals dissolutions. The impact of bacterial consortia and BSD on iron speciation of bioleached ores was analyzed by using Mössbauer spectroscopy and clear variations in iron speciation were reported. Furthermore, the bacterial community structure dynamics revealed significant variations in the individual bacterial proportion in each experiment. This finding shows that the dosage concentration of BSD influenced the microenvironment, which effect the bacterial abundance and these variations in the bacterial structural communities were not associated with the initial proportion of bacterial cells inoculated in the bioleaching process. Moreover, the mechanism of chemical reactions was proposed by explaining the possible role of BSD as a reductant under micro-aerophilic conditions that facilitates the bacterial reduction of ferric iron. This type of bioleaching process with indigenous iron-oxidizing bacteria and BSD has significant potential to further upscale the bioleaching process for recalcitrant ore bodies in an environment friendly and cost-effective way.
... Depletion of highgrade ore resources due to global rise in human population and industrial development has increased the demands of metals. Over the previous several years, extraction of metals from low-and lean-grade ores using microorganisms has been developed into an effective and growing area in biotechnology (Panda et al. 2015). These microorganisms catalyze the metals recovery by dissolution of metals present in low-grade sulfide minerals through bioleaching technique or dissolve sulfide minerals to unlock the associated metals within refractory ores (biooxidation) such as gold that would be finally extracted through conventional methods (Johnson 2013). ...
... Reduction of high-grade ore resources is not only concern for mining industry but the concurrent increase in low-grade ores leads to numerous environmental issues and Communicated by A. Driessen. occupies additional land area because of higher dump activities (Panda et al. 2015). ...
... Recently, consortia of acidophilic bacteria such as At. ferrooxidans, At. thiooxidans, and Leptospirillum ferrooxidans have shown auspicious results for copper extraction from low-grade ores and a favored consortium for large-scale heap bioleaching process (Panda et al. 2012(Panda et al. , 2015. It is strongly believed that the indigenous microorganisms obtained from the same site would be more efficient to recover metals from the ores as indigenous bacteria are more compatible with the mineralogy of the rocks. ...
Article
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Indigenous iron-oxidizing bacteria were isolated on modified selective 9KFe2+ medium from Baiyin copper mine stope, China. Three distinct acidophilic bacteria were isolated and identified by analyzing the sequences of 16S rRNA gene. Based on published sequences of 16S rRNA gene in the GenBank, a phylogenetic tree was constructed. The sequence of isolate WG101 showed 99% homology with Acidithiobacillus ferrooxidans strain AS2. Isolate WG102 exhibited 98% similarity with Leptospirillum ferriphilum strain YSK. Similarly, isolate WG103 showed 98% similarity with Leptospirillum ferrooxidans strain L15. Furthermore, the biotechnological potential of these isolates in consortia form was evaluated to recover copper and zinc from their ore. Under optimized conditions, 77.68 ± 3.55% of copper and 70.58 ± 3.77% of zinc were dissolved. During the bioleaching process, analytical study of pH and oxidation-reduction potential fluctuations were monitored that reflected efficient activity of the bacterial consortia. The FTIR analysis confirmed the variation in bands after treatment with consortia. The impact of consortia on iron speciation within bioleached ore was analyzed using Mössbauer spectroscopy and clear changes in iron speciation was reported. The use of indigenous bacterial consortia is more efficient compared to pure inoculum. This study provided the basic essential conditions for further upscaling bioleaching application for metal extraction.
... The Raman spectrum for the original ore had broad bands with sharp peaks at ~340 cm -1 and ~380 cm -1 that could be assigned to pyrite [5]. The peak at ~480 was ascribed to anorthite which was confirmed by XRD results. ...
... XRD results indicated that this iron precipitated in form of iron sulfate hydrate. Previous studies suggested a log linear relation between the ferric in solution and pH [5]. In the chemical leaching test pH increased above critical acidity and this cause iron precipitation. ...
... In the chemical leaching test pH increased above critical acidity and this cause iron precipitation. According to the FTIR spectrum, high peaks in the range of 1000 to 1200 (cm -1 ) were detected which show the elemental sulfur band [5,7]. According to the FTIR graphs, the unprocessed sample contained no elemental sulfur. ...
Article
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The mineral surface chemistry characterization is essential to describe the dissolution kinetics in leaching and bioleaching. Five different methods, including X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy, have been applied to study the surface chemistry changes during pyrite, sphalerite and molybdenite bioleaching. The surface characterizations have been done for samples before and after biological and chemical leaching. The SEM images illustrated that the minerals surfaces were smooth before processing, while they covered with an ash layer after biological treatment. Although EDS analysis and Raman spectrum demonstrated the potassium jarosite formation on the pyrite surface during bioleaching, the formation of jarosite layer did not occur on the sphalerite surfaces during bioleaching. On the other hand, a sulfur layer formation on the sphalerite surface was confirmed by mentioned characterization methods. Finally, according to the XRD and EDS spectrum the molybdenite surface had been covered both with sulfur and jarosite
... In recent years, lignocellulosic is attracting considerable critical attention in the bioleaching process. Panda et al. (2015) tried to speed up the chalcopyrite bioleaching process by adding waste newspaper. The Cu leaching extent with 2 g⋅L − 1 waste newspaper was increased by 38% after 6 days. ...
... (1) and (2), and improving the biooxidation kinetics of pyrite. In the presence of RH, the pyrite biooxidation process can be expressed by Eq. (5) (Panda et al., 2015). The generated CO 2 can be used by carbon-fixing microorganisms to promote the respiration of related microorganisms. ...
... Jarosite (Henao and Godoy, 2010) 827 Carbonate (Godočı́ková et al., 2002) 631, 633 Jarosite (Yang et al., 2020) 515 Jarosite (Panda et al., 2015) ...
Article
This work seeks to understand the role of hydrolyzed rice husk in pyrite bio-oxidation. Solution parameters during the bio-oxidation process were monitored, and the bio-oxidation residues were characterized by Scanning Electron Microscopy, Raman Spectroscopy, and Fourier Transform Infrared Spectroscopy. Results showed that rice husk mainly affected pyrite bio-oxidation by promoting microbial reproduction and changing microbial community. It mainly inhibited the reproduction of Sulfobacillus and promoted the reproduction of Leptospirillum. There was a significant positive correlation between pyrite oxidation and the proportion of Leptospirillum. Rice husk had no obvious impact on the adhesion of different microorganisms on the pyrite surface. Quantity and hydrolysis of rice husk are the two factors that affect microbial communities. 1 g·L⁻¹ of fully hydrolyzed rice husk can maximize the pyrite bio-oxidation by about 20% after 14 days. The promoting mechanism of rice husk on pyrite bio-oxidation is summarized based on the results, which provides theoretical support for future industrial applications.
... A consortium of meso-acidophiles is always preferred over the pure cultures for bioleaching [21]. In the present study, a laboratory stock culture of mixed meso-acidophiles consisting of Acidithiobacillus ferrooxidans (A. ...
... The cumulative rate of metal dissolution (CRD) is an important industrial factor for scale up and feasibility studies that determines the productivity of the system [21,26]. The CRD and the productivity of the bioleaching system for Cu, Co, Zn and As for each studied parameter is summarized in Table.3. ...
Article
Pyrite ash, a waste by-product formed during roasting of pyrite ores, is a good source of valuable metals. The waste is associated with several environmental issues due to its dumping in sea and/or land filling. Although several other management practices are available for its utilization, the waste still awaits and calls for an eco-friendly biotechnological application for metal recovery. In the present study, chemolithotrophic meso-acidophilic iron and sulphur oxidisers were evaluated for the first time towards simultaneous mutli-metal recovery from pyrite ash. XRD and XRF analysis indicated higher amount of Hematite (Fe2O3) in the sample. ICP–OES analysis indicated concentrations of Cu > Zn > Co> As that were considered for bioleaching. Optimization studies indicated Cu −95%, Co −97%, Zn − 78% and As −60% recovery within 8 days at 10% pulp density, pH −1.75, 10% (v/v) inoculum and 9 g/L Fe²⁺. The productivity of the bioleaching system was found to be Cu −1696 ppm/d (12% dissolution/d), Co −338 ppm/d (12.2% dissolution/d), Zn −576 ppm/d (9.8% dissolution/d) and As −75 ppm/d (7.5% dissolution/d). Synergistic actions for Fe²⁺ −S° oxidation by iron and sulphur oxidisers were identified as the key drivers for enhanced metal dissolution from pyrite ash sample.
... Chalcopyrite (CuFeS 2 ) is the richest copper-bearing mineral, accounting for nearly two-third of the world's copper reserves [1], while it is also extremely recalcitrant to (bio)hydrometallurgical processing [2]. In practice, industrial-scale bioleaching is generally carried out by the use of mesophilic microorganisms like Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans because they are dominant species at normal atmospheric temperatures [3]. ...
... ferrooxidans. When S 0 is biooxidized into sulfate, the solution pH value decreases, as illustrated by Reaction (1). Therefore, the sulfur oxidation rate could be evaluated indirectly by the change of the pH value of the medium. ...
Article
Full-text available
Chalcopyrite is the richest copper sulfide mineral in the world, but it is also the most resistant to biohydrometallurgical processing. To promote the bioleaching of chalcopyrite, a nonionic surfactant, t-octyl phenoxy polyethoxy ethanol (Triton X-100), was employed in this paper. Action of Triton X-100 in chalcopyrite leaching using Acidithiobacillus ferrooxidans was explored in shake flasks. Results showed that 30 mg·L−1 of Triton X-100 increased the bioleaching yield of copper by 42.21% compared to the process without additive after 24 days. Under the stress of Triton X-100, the bioleaching efficiency of chalcopyrite slightly dropped at an early stage, but remarkably increased afterwards. XRD and XPS analysis of the leach residues demonstrated that potassium jarosite and elemental sulfur resulted in surface leaching passivation. Surfactant Triton X-100 appeared to induce the oxidation of elemental sulfur by bacteria owing to the increase in the sulfur surface hydrophobicity. These results suggest that Triton X-100 itself has no ability to leach chalcopyrite, but under its induction, the bioleaching of chalcopyrite can be enhanced due to the removal of the passivation layer.
... During direct bioleaching bacteria are involved in maintaining high redox potential by constantly oxidizing Fe 2+ to Fe 3+ Since bacteria use Fe 2+ as an energy source to support their growth, their number concurrently increases with the regeneration of Fe 2+ from Fe 3+ maintaining a continuous bioleaching cycle with metal solubilization. ORP increased to > 600 mV in direct systems as a result of biological oxidation of Fe 2+ to Fe 3+ , but in the chemical-control ORP remained below 350 mV [28,[33][34][35][36]. As shown in Fig. 4(b), the profiles of redox potential under the single-step and two-step direct conditions were similar. ...
... A strong band near 1000 cm −1 was assigned to O-H bending. However, the IR absorbance frequencies observed at 3400 cm −1 can be assigned to the loosely bonded or free water molecules adsorbed on the surface or the stretching of OH groups of iron oxides especially goethite (FeOOH) [34,48,49]. ...
... It is important to note that Acidithiobacillus ferrooxidans, an iron and sulfuroxidizing microbe belonging to the c-proteobacteria group, is the well studied microorganism ( [35] and references therein). Acidithiobacillus ferrooxidans along with Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans constitute a remarkably important consortium for metal sulfide oxidation and in particular finds a number of applications for bioleaching of metals, biodesulfurization of coal, etc., [3,[31][32][33][36][37][38][39][40][41]. The chemical activity of biogenic Fe ?3 also contribute towards acid generation. ...
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Acid mine drainage (AMD) is recognised as a serious and global environmental problem. The major producer of these toxic effluents is the mining industry. Owing to the severe effects of these effluents, their prevention and treatment have been a primary focus of research over several decades. The problems have invited the attention of a large group of researchers, governmental bodies, educational and research establishments, mining industries, general public and environmental specialists. A preferable option is to prevent the formation and movement of AMD from its source of origin; however, it is not possible in many locations. It, therefore, becomes essential to collect and treat AMD to which a number of treatment techniques are available. Despite the extreme environmental conditions, several communities of autotrophic and heterotrophic bacteria and archaea are seen to flourish that mainly drive the rate of release of sulfur and toxic metals into the environment. The present review briefly discusses the cause and occurrence of AMD and the microbial diversity observed in such ecosystems. In addition, the bioremediation options are briefly presented with a discussion on the role of sulfidogenic biosystems in the bioremediation of the AMD.
... Apart from the use of several heterotrophs (discussed in section 2.2), many acidophilic microorganisms have been reported to possess an ability to desulphurize coal, especially the inorganic (pyritic) portion [91]. Among the reported acidophilies, the γ-proteobacterium A. ferrooxidans is the most widely studied and industrially important microorganism [143][144][145][146]. A list of some acidophilies and their application for biodesulphurization is given in Table 4. ...
Article
In the current era, the alarming rate at which coal is being burned as a fuel is causing concern with regard to the release of sulphur oxides. According to reports, global coal consumption has increased by 0.4% in 2014. While countries like UK, Ukraine etc. have witnessed a decline in coal consumption, some others like India, China, Africa and North America have increased their use of coal to meet the energy requirements of the growing human population. The increasing use of coal has led to extensive investigations for finding an ecofriendly clean coal technology. Dibenzothiophene (DBT) and some of its alkylated derivatives present in the form of organic sulphur in coal have received a great deal of attention in the past few years because of their recalcitrant nature. Considering the economic and environmental prospects, biodesulphurization is being regarded as an effective tool for the degradation of DBT, with concomitant application towards sulphur removal from coal. Owing to the importance of microbial applications towards production of clean coal, the present review discusses some of the recent findings in the area of DBT biodegradation. In addition, current advances in coal biodesulphurization are reviewed, concluding with a consideration of future prospects for the rapidly growing energy sector.
... The pH of the bioleaching solution showed an initial increase followed by a slight fluctuation (pH2.8-3.3). The dissolution of alkaline gangue and chalcopyrite in the initial stage was an acid-consuming process (Panda et al., 2015b), which led to this initial increase of pH. The pulp density (w/v) in current study (68% in columns 1#−2# and 120% in columns 3#−4#) was much higher than that in other reports Ma et al., 2018). ...
Article
A proof-of-concept of copper sulfide mineral bioleaching assisted by microbial fuel cells (MFCs) was demonstrated in current study. Simultaneous copper extraction and electricity generation were obtained in this bioleaching process, providing a novel approach for copper sulfide mineral bioleaching. Compared with bioleaching of a mixture of chalcopyrite concentrate and porphyry molybdenite, bioleaching of chalcopyrite concentrate achieved higher coulomb production but lower copper extraction concentration. After 320 days bioleaching of chalcopyrite concentrate, the copper ion concentration in bioleaching solution was 244.2 mg/L and the average coulomb production was 4.4 ± 2.2C/d. The introduction of MFCs into bioleaching processes promoted copper extraction, mainly via the decrease of pH deriving from the anodic sulfide/sulfur oxidation.
... Apart from the use of several heterotrophs (discussed in section 2.2), many acidophilic microorganisms have been reported to possess an ability to desulphurize coal, especially the inorganic (pyritic) portion [91]. Among the reported acidophilies, the γ-proteobacterium A. ferrooxidans is the most widely studied and industrially important microorganism [143][144][145][146]. A list of some acidophilies and their application for biodesulphurization is given in Table 4. ...
... To shed more light on the metal dissolution aspects from the material, cumulative rate of metal dissolution (CRD) was calculated. It is important to note that CRD is considered as an important scaleup feature that determines the productivity of the leaching system and helps in designing of the downstream processing steps for an industrial application [22,23]. In the present case, the CRD (% dissolution/day) values for Cu were seen to be 11.75% at an initial sulphur concentration of 1 g/L while it was 9.76%, 10.83% and 11.92% at 0.1, 0.5 and 1.5 g/L sulphur concentrations respectively (Fig. 1b). ...
Article
Simultaneous multi-metal leaching from industrial pyrite ash is reported for the first time using a novel bioreactor system that allows natural diffusion of atmospheric O2 and CO2 along with the required temperature maintenance. The waste containing economically important metals (Cu, Co, Zn & As) was leached using an adapted consortium of meso-acidophilic Fe(2+) and S oxidising bacteria. The unique property of the sample supported adequate growth and activity of the acidophiles, thereby, driving the (bio) chemical reactions. Oxido-reductive potentials were seen to improve with time and the system's pH lowered as a result of active S oxidation. Increase in sulphur dosage (>1g/L) and agitation speed (>150rpm) did not bear any significant effect on metal dissolution. The consortium was able to leach 94.01% Cu (11.75% dissolution/d), 98.54% Co (12.3% dissolution/d), 75.95% Zn (9.49% dissolution/d) and 60.80% As (7.6% dissolution/d) at 150rpm, 1g/L sulphur, 30°C in 8days.
... The final pH of the growth medium was maintained at1.8. Adaptation is considered as a unique biotechnological feature of acidophiles that improves their ability to leach metal values from ores or industrial wastes (desulphurization in this case) (Panda et al., 2015a). Following complete iron oxidation, the active culture was adapted to 2% (w/v) of lignite sample in the same growth medium and the coal adapted culture was further used for biodesulphurization experiments. ...
Article
Coal has been serving as a profuse source of energy since centuries and several attempts are being made to reduce sulphur emission levels from coal. Recently, pretreatment techniques such as ultrasonication and utilization of surfactants as additives have surfaced aiming at improving the biodesulphurization of coal. In the present study, biodesulphurization of Turkish lignite was studied for the first time using Leptospirillum ferriphilum. Attempts have been made to study the biodesulphurization aspects of the lignite sample where the effect of Fe²⁺ iron, surfactant Span 80 and ultrasonication were studied under shake flask conditions. The study indicated Fe²⁺ to be an essential component in the growth media for improving biodesulphurization performance (with 56.2% total sulphur removal). Span 80 (0.05% v/v) marginally enhanced the biodesulphurization of the lignite sample (nearly 61% of total sulphur removal). The carbon content in the lignite sample increased following biodesulphurization. Ultrasonication of the lignite sample, on the other hand, did not yield significant sulphur removal when compared to the effect of Span 80. About 57.6% of total sulphur could be removed from the sample when ultrasonicated for 60 min. Mineralogical characterization along with thermal analysis of the samples pre and post biodesulphurization provided more information on different phases present in coal and the effect of microbial treatment on them.
... One of the best examples of indirect bioleaching process by A. ferrooxidans is the extraction of copper from chalcopyrite. According to Eq. 10, the indirect bioleaching process causes the monovalent copper (Cu 1+ ) which is not water soluble convert to divalent copper (Cu 2+ ) which is soluble in water (Panda et al. 2015a(Panda et al. , 2015b. ...
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Bio-hydrometallurgical applications have been receiving more attention globally for processing of several metal bearing wastes. Compared to the conventional methods, bioleaching has proved to be a more effective way in treating low-grade ores, due to its economic and ecofriendly advantages. Developments in bioleaching enables this technique to be utilized as an alternative process for extraction of base metals from complex ores (copper, gold etc.) or even concentrates, consequently solving several environmental issues. A variety of parameters can influence the bioleaching efficiency such as physicochemical and microbiological factors, properties of the minerals and processing conditions. Certain organic and inorganic reagents or additives used during the process such as flotation and SX reagents, Ag+, Fe2+, Fe3+, Cu2+, Mg2+, Ni2+, silica, pyrite, activated carbon etc., affect the microorganisms activity and their efficiency for metal leaching. More precise investigation on the effect such materials can provide insights and hence studies have been directed to understand such aspects. Owing to their importance, the present review discusses the influence of certain organic-inorganic reagents and other materials or additives on the growth, oxidation activity and bioleaching efficiency of acidophiles on metal dissolution.
... Bioleaching is the dissolution of metals from their mineral source by the activity of specific microorganisms. Bioleaching with Mn solubilising microorganisms is the most promising green technique applied in a large scale (Srichandan et al., 2013;Panda et al., 2015). Mn solubilizing microorganisms play a vital role in evaluating the significance of microbes in Mn biomining. ...
Chapter
Full-text available
Biomining is defined as the technologies that utilize microbial community for the extraction of metals from its ore or wastes and facilitate a greener recovery. Extraction of manganese by biomining is now a thing of the present and not just a hypothesis, as it was few decades back. The severe industrial importance of manganese has led to augmented global production of manganese in the last few years which has led to a decrease in the amount of high grade ores. It has also resulted in pollution of both terrestrial and aquatic ecosystems due to the generation of massive amounts of manganese containing wastes. Therefore, biomining is now being employed to recover manganese low grade ores and solid mining wastes which serve a dual purpose of both resource recycling and bioremediation. Manganese bio recovery can be accomplished by a wide range of bacterial and fungal strains capable of growing under diverse environmental conditions. They solubilise manganese by direct and indirect mechanisms thereby aiding its recovery. Bacterial solubilisation is mainly carried out by direct mechanism which involves the direct contact of the cell with the metal. However fungal solubilisation is mostly correlated with indirect mechanism which does not require direct contact of the cells with metal particles and involves solubilisation by the help of bio generated metabolites that mainly includes organic acids. Many enzymes like Muilticopper oxidase, Manganese reductase and Peptidyl-prolyl-cis-trans isomerise have been linked to manganese solubilisation. The present scenario of commercial manganese recovery through booming is very encouraging and this technology holds immense potential for future metal recovery and bioremediation endeavours. KEYWORDS: Biomining, Manganese, Bioremediation, Waste, Bacteria, Fungus
... Bioleaching of metals is carried out by a largely diverse group of microorganisms, mainly including three groups of microorganisms, namely (i) chemolithotrophic prokaryotes, (ii) heterotrophic bacteria and (iii) fungi [47]. In nature, a large variety of chemolithotrophic and organotrophic microorganisms are involved in bioleaching of ores [48] (Panda et al. [189]). Current state-of-the-art research on metal recovery from WEEE via biotechnology involves both autotrophic (i.e. ...
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Critical raw materials (CRMs) are essential in the development of novel high-tech applications. They are essential in sustainable materials and green technologies, including renewable energy, emissionfree electric vehicles and energy-efficient lighting. However, the sustainable supply of CRMs is a major concern. Recycling end-of-life devices is an integral element of the CRMs supply policy of many countries. Waste electrical and electronic equipment (WEEE) is an important secondary source of CRMs. Currently, pyrometallurgical processes are used to recycle metals from WEEE. These processes are deemed imperfect, energy-intensive and non-selective towards CRMs. Biotechnologies are a promising alternative to the current industrial best available technologies (BAT). In this review, we present the current frontiers in CRMs recovery from WEEE using biotechnology, the biochemical fundamentals of these bio-based technologies and discuss recent research and development (R&D) activities. These technologies encompass biologically induced leaching (bioleaching) from various matrices,biomass-induced sorption (biosorption), and bioelectrochemical systems (BES).
... Bioleaching is the dissolution of metals from their mineral source by the activity of specific microorganisms. Bioleaching with Mn solubilising microorganisms is the most promising green technique applied in a large scale (Srichandan et al., 2013;Panda et al., 2015). Mn solubilizing microorganisms play a vital role in evaluating the significance of microbes in Mn biomining. ...
... Bioleaching is another green alternative to extract metals from electronic and industrial waste and several authors have reported significant extraction efficiency using bioleaching methods (Bas et al., 2013;Willner and Fornalczyk, 2013;Madrigal-Arias et al., 2015;Panda et al., 2015a). Sequential bioreduction-bioleaching and bioreduction-chemical leaching hybrid experiments were performed to recover copper from an industrial waste (Panda et al., 2015b). ...
Article
Technology innovations resulted into a major move from agricultural to industrial economy in last few decades. Consequently, generation of waste electronic and electrical equipments (WEEE) has been increased at a significant rate. WEEE contain large amount of precious and heavy metals and therefore, can be considered a potential secondary resource to overcome the scarcity of metals. Also, presence of these metals may affect the ecosystem due to lack of adequate management of WEEE. Building upon our previous experimental investigations for metal extraction from spent catalyst, present study explores the concept of Green Technology for WEEE management. Efforts have been made to recover base metal from a printed circuit board using eco-friendly chelation technology and results were compared with the conventional acid leaching method. 83.8% recovery of copper metal was achieved using chelation technology whereas only 27% could be recovered using acid leaching method in absence of any oxidant at optimum reaction conditions. Various characterization studies (energy dispersive X-ray analysis, scanning electron microscopy, X-ray Diffraction, inductive coupled plasma spectrophotometry) of printed circuit board (PCB) and residues were performed for qualitative and quantitative analysis of samples. Significant metal extraction, more than 96% recovery of chelating agent, recycling of reactant in next chelation cycle and nearly zero discharge to the environment are the major advantages of the proposed green process which articulate the transcendency of chelation technology over other conventional approaches. Kinetic investigation suggests diffusion controlled process as the rate determining step for the chelate assisted recovery of copper from WEEE with activation energy of 22kJ/mol.
... Fig. 11 depicted the FTIR spectrum for two mentioned samples. Peaks in range of 1000 to 1200 (cm − 1 ) show the elemental sulfur bands (Shi and Fang, 2004;Varotsis et al., 2014;Panda et al., 2015). According to the FTIR graphs, the feed sample contained no elemental sulfur. ...
Article
The leaching kinetics of a sphalerite concentrate containing 38.25% zinc was studied in the presence of biological and chemical ferric reagents. To produce the biological ferric reagent (BFR), a pyrite concentrate sample was oxidized to ferric ions by iron and sulfur oxidizing bacteria, and this pregnant leach solution was then applied as oxidizing reagent in ZnS leaching. This process is commonly referred to as two-step bioleaching. This biological reagent contained 12.75 g/l ferric and its pH was 0.86. The chemical ferric reagents (CFR) were made by dissolution of Fe2(SO4)3 and FeCl3 salts in deionized water. Leaching experiments were carried out at different temperatures to study the mechanism of ZnS dissolution and its kinetics. The kinetic modeling of ZnS dissolution with BFR followed the interfacial transfer and diffusion across the product layer mechanism within the first minutes (about 60 min) while it changed to the diffusion-control mechanism after passing this initial period. On the other hand, the ZnS dissolution in presence of ferric sulfate was described by a diffusion mechanism. The surface analysis by SEM and FTIR confirmed that sulfur layer formation on the mineral surfaces could prevent the solvent diffusion to the minerals surface, and consequently it controls the dissolution reaction. The highest zinc recoveries were 70%, 99% and 83% in presence of biological ferric reagent, ferric sulfate and ferric chloride at 90 °C after 200 min, respectively. The zinc recovery for one-step bioleaching was 90% and was achieved after 20 days at 35 °C, by iron and sulfur oxidizing bacteria.
... Recently, the researches on microbial community structure in chalcopyrite bioleaching have been extensively reported owing to the tight correlation with bioleaching efficiency (Yu et al., 2014;Panda et al., 2015). It is believed that the microbial ecology is closely associated with the key biochemical parameters in bioleaching (Johnson, 2014;Vardanyan et al., 2015). ...
... Chalcopyrite is also an important cause of AMD because of its wide distribution and large demand for mining. Chalcopyrite is the most abundant copper sulphide mineral on the earth, and is the primary mineral source for copper extraction (Panda et al., 2015). However, chalcopyrite mining generates large amounts of mineral wastes, most of which are stored on the surface of mine sites (Chopard et al., 2017). ...
... The addition of 0.66 g/L sodium chloride can reduce the elemental sulfur content on the mineral surface from 26% to 3% (Chang- . Recently, some authors found that lignocellulose can reduce the amount of jarosite (Panda et al. 2015b;Yin et al. 2019), which gives us some ideas. It may be beneficial to lay a thin layer of plant stalks at every certain height (e.g. 1 m). ...
Article
Heap bioleaching is a microbial technology that catalyzes the decomposition of ore without grinding. The crushed ore is stacked on the liner, and the microbial solution flows through the heap from top to bottom. Under the oxidation action of Fe³⁺, valuable metals in sulfide enter the liquid phase as ions, which are then recovered from the subsequent process. The main function of microorganisms are the regeneration of Fe³⁺. This technology has the advantages of low cost, environment friendliness, simple requirements, and suitability for the treatment of low-grade ore. It has been applied to industrial production. However, the technology is still evolving because there are still many problems that are not well explained, such as synergistic effect between microorganisms, the role of extracellular polymeric substances, passivation phenomenon, galvanic interaction between minerals, mode of ore treatment and heap running, the impact of the natural environment, reasonable disposal of tailings, etc. This paper adequately discusses these aspects based on plentiful excellent researches, including the latest ideas, which can provide a comprehensive and in-depth knowledge of heap bioleaching for the readers. Besides, commercial process data, effective improvement measures, environmental protection ways, laboratory research, and optimization methods were reviewed. Based on the comparative analysis of these knowledges, the recommended technical parameters and the remaining challenges are displayed, which can guide a new commercial or pilot-scale heap. Researchers can make new explorations from the potential research directions and methods proposed in this paper, so that heap bioleaching technology can better serve social development.
... From day 1 to day 70, the pH of the leachate of two columns changed drastically, and the concentrations of copper ion, ferrous iron, and TFe were low; the pH increment after each pH adjustment and the pH in both columns maintained below 2.5 from day 71 to day 136, it can be found the concentrations of copper ion, ferrous iron, and TFe increased. Low-grade chalcopyrite is often accompanied by a large amount of alkaline gangue, which affected the iron ions and H + in the leachate during the dissolution process of chalcopyrite (Panda et al. 2015b;Mwase et al. 2012). Low pH of leachate was beneficial a gradual increase of copper ion accumulation (Fig. 2) (Muddanna and Baral 2021;Wang et al. 2018c). ...
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Low-grade ores, tailings, and solid wastes contain small amounts of valuable heavy metals. Improper disposal of these substances results in the waste of resources and contamination of soil or groundwater. Accordingly, the treatment and recycling of low-grade ores, tailings, and solid wastes attracted much attention recently. Bioelectrochemical system, an innovative technology for the removal and recovery of heavy metals, has been further developed and applied in recent years. In the current study, the low-grade chalcopyrite was bioleached with the assistance of microbial fuel cells. Copper extraction along with electricity generation from the low-grade chalcopyrite was achieved in the column bioleaching process assisted by MFCs. Results showed that after 197 days bioleaching of low-grade chalcopyrite, 423.9 mg copper was extracted from 200 g low-grade chalcopyrite and the average coulomb production reached 1.75 C/d. The introduction of MFCs into bioleaching processes promoted the copper extraction efficiency by 2.7 times (3.62% vs. 1.33%), mainly via promoting ferrous oxidation, reducing ORP, and stimulating bacterial growth. This work provides a feasible method for the treatment and recycling of low-grade ores, tailings, and solid wastes. But balancing energy consumption of aeration and circulation frequency and chemical consumption of acid to improve the copper extraction efficiency need further investigation.
... Copper is released into environment by industrial and agricultural activities such as mining, metallurgy, sewage irrigation, and fertilization (Araújo et al., 2019). Chalcopyrite is the most abundant copper sulfide mineral in the word (Panda et al., 2015), which is an important source of copper release into the environment. A large amount of mineral waste produced during the chalcopyrite mining is stored on the surface of the mining area (Chopard et al., 2017). ...
... Therefore, research on the generation of AMD due to mining activities has primarily focused on the oxidation/dissolution of pyrite, while research on AMD generation caused by chalcopyrite oxidation/dissolution has not been performed. Chalcopyrite is the most abundant copper-containing sulfide mineral in the lithosphere and the main mineral source for copper extraction (Panda et al., 2015). However, chalcopyrite mining generates a large amount of mineral waste that is stored on the surface of the mine site (Chopard et al., 2017). ...
... For the surface properties study, Raman spectroscopy (BRUKER-SENTERRA, Liège, Germany) was done. The Raman spectrum for the original ore had broad bands with sharp peaks at approximately 340 and approximately 380 cm −1 that can be assigned to pyrite (Panda et al. 2015). The peak at approximately 480 is ascribed to anorthite, which is confirmed by XRD. ...
Article
Leaching of zinc from sulfide minerals is a subject of considerable interest over the last few years. Ferric solutions were commonly reported to leach base metals sulfide concentrates. The current study investigates the potential of biological ferric solutions for Zn and Pb extractions from a sphalerite concentrate at 65°C. Comparative leaching experiments with ferric sulfate and ferric chloride are also performed. Actually, biological ferric ions have resulted from pyrite bio-oxidation. The aim of this work is to introduce a potential application of this metabolite as a mineral oxidizing agent to recover zinc from the sphalerite concentrate. To produce a biogenic reagent with the highest ferric, the bio-oxidation process is optimized by investigating the effects of different factors including pH, pulp density, and inoculum percent. At the optimum conditions, a metabolite with 7.87 g/L of ferric ions and a pH = 0.98 is produced. The results indicate that pyrite bio-oxidation includes three phases: chemical dissolution, lag phase, and biological dissolution. The scanning electron microscope (SEM) images showed that a layer of crystals was present on the surface of pyrite. Based on energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, this layer is related to the presence of potassium jarosite. The metabolite was then used for ZnS direct leaching and results were compared with sulfide and chloride leaching. The final zinc recoveries with biological ferric ions, ferric sulfate, and ferric chloride were 78.0%, 88.9%, and 85.4%, respectively.
... As shown in Fig. 4a, the pH in both columns appeared an increase after each pH adjustment, which was attributed to the acid consumption for the dissolution of alkaline gangue and chalcopyrite (Panda et al., 2015b). It should be noted that the pH increment after each pH adjustment gradually narrowed with time, and the pH in both columns maintained below 2.5 from day 71 to day 136. ...
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Low-grade ores, tailings and solid wastes contain small amounts of valuable heavy metals. Improper disposal of these results in the waste of resources and contamination of soil or groundwater. Accordingly, the treatment and recycling of low-grade ores, tailings and solid wastes attracted much attention recently. Bioelectrochemical system, an innovative technology for the removal and recovery of heavy metals, has been further developed and applied in recent years. In current study, the low-grade chalcopyrite was bioleached with the assistance of microbial fuel cells. Copper extraction along with electricity generation from the low-grade chalcopyrite were achieved in the column bioleaching process assisted by MFCs. Results showed that after 197 days bioleaching of low-grade chalcopyrite, 423.9 mg copper was extracted from 200 g low-grade chalcopyrite and the average coulomb production reached 1.75 C/d. The introduction of MFCs into bioleaching processes promoted the copper extraction efficiency by 2.7 times (3.62% vs. 1.33%), mainly via promoting ferrous oxidation, reducing ORP and stimulating bacterial growth. This work provides a feasible method for the treatment and recycling of low-grade ores, tailings and solid wastes. But balancing energy consumption of aeration and circulation frequency and chemicals consumption of acid to improve the copper extraction efficiency need further investigation.
... The N -O bond in the -C=N -OH group often appears at the range of 1125-1100 cm −1, and also, the elemental sulfur bands emerge within 1000-1200 cm −1 . The bands at 1194 and 1187 cm −1 asymmetric stretching vibrations of -SO 4 2- (Panda et al. 2015;Varotsis et al. 2014). The vibration of aromatic groups associated with LIX 984N and Acorga M5640 appears within 1630 and 1450 cm −1 (Li et al. 2019). ...
Article
Due to entrainment or dissolution, organic extractants can contaminate aqueous raffinate during the solvent extraction (SX) process. This study aims to evaluate the effect of conventional SX reagents on the bio-oxidation and metabolism of industrial bacteria. Evaluating the effect of LIX 984N, Chemorex CP 150, D2EHPA, and Acorga M5640 at three concentrations on mesophiles and moderate thermophiles revealed that all extractants reduced the bacterial efficiency at different extents. It was observed that organic phases at 0.02% v/v resulted in a decrement of ferrous iron bio-oxidation rate and a negligible decrease in the bacterial population. At high dosages like 2% v/v, bio-oxidation and bacterial reproduction were utterly disrupted. The oxime-based extractants had a more significant effect on bacteria due to their lower stability and production of toxic substances by hydrolysis. Organic phases more impacted moderate thermophiles at a higher temperature compared to mesophiles. The analysis of Kendall tau-b revealed a strong inter-correlation between the concentration of organic phase and bio-oxidation parameters such as pH, ORP, bacterial population, bio-oxidation rate, and iron precipitation.
... An experimental study was conducted for bioleaching of low-grade chalcopyrite using a mixed culture of meso-acidophilic microorganisms in the presence of acidprocessed waste newspaper. This study, for the first time, reported that the presence of acidprocessed waste newspaper enhanced the bio-recovery of copper up to a maximum of 99.13% [26]. Some experimental studies also described that the effect of ultrasound pretreatment on nickel leaching using A.niger 95% nickel could be leached along with 12.5% of iron from lateritic ore [27]. ...
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Bioleaching is an environmentally safe as well as economically feasible alternative to the conventional process of metal extraction from low-grade ores. It involves the recovery of metals through microbial oxidation of metallic and/or sulfuric compounds. Wide varieties of acidophilic microbes present in the mining sites, which are necessary to decrease the pH, eventually contribute to the biomining efficiency. Ongoing development and recent advanced techniques will ensure that the implementation of genetic engineering might improve the extraction rate within less time period. The use of OMIC (genomics, proteomics, metabolomics, etc.) techniques in bioleaching is gaining interest worldwide. In the last decade, a number of studies have been carried out for the determination of bioleaching diversity, development of conceptual and functional metabolic models, analysis of microbe-mineral interaction, etc. by using various OMIC technologies. These technologies are used to improve the understanding of various microbial activities during the bioleaching process, which helps in the development of industrial-scale bioleaching process.
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In view of unremitting diminution of mineral resources, rising energy economics along with increasing global consumption of Manganese (Mn), development of environment friendly technologies for tapping alternate sources of Mn has gained importance lately. Mn recovery from mining residues using conventional approaches is extremely expensive due to high capital and energy costs involved. However lean grade ores present in millions of tons awaits the development of competent and cost effective extractive process. Mn recovery by biomining with diverse microbes is thereby recommended as a superior and green alternative to the current pyro metallurgical techniques. The synergistic effects of different factors are known to influence microbial leaching of mineral ores which includes microbiological, mineralogical, physicochemical and process parameters. Bacterial bioleaching is mostly due to enzymatic influence, however fungal bioleaching is non enzymatic. Genomic studies on microbial diversity and an insight of its metabolic pathways provides unique dimension to the mechanism of biomining microorganisms. The extraction of Mn has a massive future prospective and will play a remarkable role in altering the situation of ever-decreasing grades of ore. This review aims to encompass the different aspects of Mn bioleaching, the plethora of organisms involved, the mechanisms driving the process and the recent trends and future prospects of this green technology.
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Even though biodissolution of chalcopyrite is considered to be one of the key contributors in the formation of acid mine drainage (AMD), there are few studies to control AMD by inhibiting chalcopyrite biodissolution. Therefore, a novel method of using hematite to inhibit chalcopyrite biodissolution was proposed and verified. The results indicated that chalcopyrite biodissolution could be significantly inhibited by hematite, which consequently decreased the formation of AMD. In the presence of hematite, the final biodissolution rate of chalcopyrite decreased from 57.9% to 44.4% at 20 day. This in turn suggested that the formation of AMD was effectively suppressed under such condition. According to the biodissolution results, mineral composition and morphology analyses, and electrochemical analysis, it was shown that hematite promoted the formation and accumulation of passivation substances (jarosite and Cu2−xS) on chalcopyrite surface, thus inhibiting the biodissolution of chalcopyrite and limiting the formation of AMD.
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As the world’s second largest economy experiencing rapid economic growth, China has a huge demand for metals and energy. In recent years, China ranks first, among all the countries in the world, in the production and consumption of several metals such as copper, gold, and rare earth elements. Bioleaching, which is an approach for mining low grade and refractory ores, has been applied in industrial production, and bioleaching has made great contributions to the development of the Chinese mining industry. The exploration and application of bioleaching in China are reviewed in this study. Production and consumption trends of several metals in China over the past decade are reviewed. Technological processes at key bioleaching operations in China, such as at the Zijinshan Copper Mine and Mianhuakeng Uranium Mine, are presented. Also, the current challenges faced by bioleaching operations in China are introduced. Moreover, prospects such as efficiency improvement and environmental protection are proposed based on the current situation in the Chinese bioleaching industry.
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Owing to industrial evolution, a huge mass of toxic metals, including Co, Cu, Cr, Mn, Ni, Pb, and Zn, and metalloids, such as As and Sb, has inevitably been released into the natural environment and accumulated in soils or sediments. Along with modern industrialization, many mineral mines have been explored and exploited to provide materials for industries. Mining industries also generate a vast amount of waste, such as mine tailings, which contain a high concentration of toxic metals and metalloids. Due to the low economic status, a majority of mine tailings are simply disposed into the surrounding environments, without any treatment. The mobilization and migration of toxic metals and metalloids from soils, sediments, and mining wastes to water systems via natural weathering processes put both the ecological system and human health at high risk. Considering both economic and environmental aspects, bioleaching is a preferable option for removing the toxic metals and metalloids because of its low cost and environmental safety. This chapter reviews the recent approaches of bioleaching for removing toxic metals and metalloids from soils, sediments, and mining wastes. The comparison between bioleaching and chemical leaching of various waste sources is also discussed in terms of efficiency and environmental safety. Additionally, the advanced perspectives of bioleaching for environmental remediation with consideration of other influencing factors are reviewed for future studies and applications.
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Bioleaching is considered to be a low-cost, eco-friendly technique for leaching valuable metals from a variety of matrixes. However, the inherent slow dissolution kinetics and low metal leaching yields have restricted its wider commercial applicability. Recent advancements in bio-hydrometallurgy have suggested that these critical issues can be successfully alleviated through the addition of a catalyst. The catalyzing properties of a variety of metals ions (Ag+, Hg++, Bi+++, Cu++, Co++ etc.) during bioleaching have been successfully demonstrated. In this article, the role and mechanisms of these metal species in catalyzing bioleaching from different minerals (chalcopyrite, complex sulfides, etc.) and waste materials (spent batteries) are reviewed, techno-economic and environmental challenges associated with the use of metals ions as catalysts are identified, and future prospectives are discussed. Based on the analysis, it is suggested that metal ion-catalyzed bioleaching will play a key role in the development of future industrial bio-hydrometallurgical processes.
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The uneven distribution of ore granular media affects the solution seepage law in heap dumping process. To investigate the solution seepage law with fine interlayers existed, the seepage simulation of column with fines interlayers existed was carried out by using the computed tomography (CT) technology and COMSOL Multiphysics modeling software. The fluid flow trajectory, distribution law of seepage velocity and pressure field with fine interlayers existed were ascertained. The results show that fine interlayers influence flow trajectory and formation of preferential flow. In detail, the preferential flow is emerged after the most solution bypassed the fine interlayers, and the plenty of small tributaries flow across fine interlayers. Stagnant regions of fluid flow are emerged where the solution is hard to reach in the internal of fine interlayers. The drops of speed and pressure are small in the fine interlayers, and the speed and pressure increase significantly when the fluid passes through the pore throats connecting the adjacent fine interlayers.
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Zinc bioleaching from sphalerite associated with pyrite ore using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidant was studied. The ore containing 3.4 wt% zinc and in some experiments its combination with sphalerite concentrate was prepared. The effect of culture media, pH, Fe2+ iron concentration, and the addition of different materials including shredded newspaper, starch, and sugar as a catalyst on the zinc bioleaching were evaluated. It was found that 9 K media, pH of 1.8, and 10 g L−1 Fe2+ iron concentration were optimum conditions. The catalysts acted as an electron acceptor for Fe3+ iron reduction. The amount of zinc bioleaching was obtained 88% for the ore and 95% for the second sample at the optimum pH of 1.8 in 18 days. The addition of starch and shredded newspaper increased the bioleaching rate of zinc. Also, the bioleaching time was decreased from 18 days to 10 and 13 days in the presence of shredded newspaper and starch, respectively.
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Tailings used as backfilling material in the presence of mixed bacteria are discussed, and the relationship between mixed bacteria and compressive strength, size variation, water-holding capacity is analyzed in this study. The results illustrate a strong improving response of mixed bacteria with enhanced compressive strength, small size variation and low water-holding capacity of cemented tailings backfill (CTB) specimens. The binder dosage and mixed bacteria proportion have great influence on CTB specimens, which indicate that with the increase of mixed bacteria proportion and binder dosage, compressive strength increased obviously. The maximum compressive strength (4.01 MPa) is obtained in the presence of 100.00% mixed bacteria in contrast to only 2.79 MPa in its absence. Samples added high mixed bacteria proportion yield low water-holding capacity and small size variation. 16 S rDNA analysis illustrates that bacteria community is influenced significantly during experiment. Further, possible reaction mechanism is proposed suggesting the possible role of mixed bacteria as promoter to form precipitation (KFe3(SO4)2(OH)6, (NH4)Fe3(SO4)2(OH)6 and (KH3O)4Fe3(SO4)2(OH)6), which reduces tiny cracks in CTB specimens. The technique of using mixed bacteria to reduce binder consumption in this study shows economic benefits to some extent.
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Bacteria community and copper recovery in presence of acid-processed rice straw (ARW) were explored during low-grade copper sulphide bioleaching. The results indicated a strongly promoting response of appropriate-quality ARW with improved bacteria concentration and enhanced copper recovery. The highest bacteria concentration reached 9.54 × 107 cells·mL-1 with an increase by 69.15%. And a maximum of 95.32% copper leaching rate with a relatively low Fe3+ concentration (329.00 mg·L-1) was obtained in presence of 1.0 g powdered ARW compared to only 83.40% in its absence. That is due to less development of passivation layer formed by Fe3+ hydrolysis, which is contributed by reducing ARW. 16S rDNA analysis illustrated the dominant leaching bacteria (Acidithiobacillus ferrooxidans) was influenced significantly, whose proportion reached 40.38% to the total bacteria when the ARW was added compared to 15.92% in its absence. And Stenotrophomonas accounted for the highest proportion of the bacteria community throughout bioleaching process.
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Conventional leaching methods for Manganese (Mn) recovery require strong acids and are threatening to the environment. Alternatively, the use of microbes for Mn recovery is environment friendly in nature. The present investigation compares the capacity of pure and mixed cultures of native bacterial strains for bioleaching of low grade Mn ores. The ability of the isolated microorganisms to recover Mn was evaluated in shake flasks for 20 days under optimized conditions of pulp density (2%), sucrose concentration (2/g/100 ml), initial pH 6.5 and 30 °C incubation temperature. In pure culture form, Acinetobacter sp. MSB 5 (70%) was found to have a higher bioleaching potential than Lysinibacillus sp. MSB 11 (67%). Mixed culture of Acinetobacter sp. MSB 5 and Lysinibacillus sp. MSB 11 was found to perform better than the pure cultures with 74% extraction of Mn. The presence of mixed culture increased the dissolution rate and the recovery percentage of Mn. The respective growth pattern of the cultures was in synchronisation to their Mn bioleaching performances. This study underlines the importance of mixed cultures and, Mn solubilising activity of native bacterial strains for efficient Mn biorecovery.
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A process of the high temperature ferric leaching of the copper-zinc concentrate and pyrite product during a two-step biohydrometallurgical technology was studied. It was shown that the use of the galvanic effect during the leaching of the copper-zinc concentrate enabled to obtain a copper concentrate with low zinc content in the relatively short time (approximately 5.7 h), while zinc concentration in the liquid phase was sufficient for zinc and copper recovery by extraction and cementation, respectively. Zinc content in the concentrate decreased from 7.36 to 0.5% in the process of leaching. The recovery of zinc and copper into the liquid phase was 96.1 and 40.3%, respectively. The leaching of copper-zinc pyrite product and galvanic interactions of minerals made it possible to recover nonferrous metals from it almost completely and to leave the main amount of sulfur and iron in leach residues. Operation of the laboratory unit with the use of bioregeneration of the liquid phase showed the principal possibility of functioning of a two-step biohydrometallurgical technology under semi-continuous conditions with the closed cycle of technological flows. Zinc content decreased from 15.25 to 1.3% during the first step of the leaching process, whereas during the second (biological) step it declined to 1.03% (within 24 h). The recovery of zinc and copper into the liquid phase was 92.6 and 54.6%, respectively. Flow sheet of the copper-zinc concentrate treatment, which can serve as a basis for modernization of the treatment of sulfidic raw materials, is proposed.
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Acidithiobacillus ferrooxidans cells can oxidize iron and sulfur and are key members of the microbial biomining communities that are exploited in the large‐scale bioleaching of metal sulfide ores. Some minerals are recalcitrant to bioleaching due to the presence of other inhibitory materials in the ore bodies. Additives are intentionally included in processed metals to reduce environmental and microbially influenced corrosion (MIC). We have previously reported a new aerobic corrosion mechanism where A. ferrooxidans cells combined with pyrite and chloride can oxidize low grade stainless steel (SS304) with a thiosulfate‐mediated mechanism. Here we explore process conditions and genetic engineering of the cells that enable corrosion of a higher grade steel (SS316). The addition of elemental sulfur and an increase in the cell loading resulted in a 74% increase in the corrosion of SS316 as compared to the initial sulfur‐ and cell‐free control experiments containing only pyrite. The overexpression of the endogenous rus gene, which is involved in the cellular iron oxidation pathway, led to further 85% increase in the corrosion of the steel in addition to the improvements made by changes to the process conditions. Thus, the modification of the culturing conditions and the use of rus‐overexpressing cells led to a more than 3‐fold increase in the corrosion of SS316 stainless steel, such that 15% of the metal coupons was dissolved in just 2 weeks. This work demonstrates how the engineering of cells and the optimization of their cultivation conditions can be used to discover conditions that lead to the corrosion of a complex metal target. This article is protected by copyright. All rights reserved.
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Bioleaching is regarded as an essential technology to treat low grade minerals, with the distinctive superiorities of lower-cost and environment-friendly compared with traditional pyrometallurgy method. However, the bioleaching efficiency is unsatisfactory owing to the passivation film formed on the minerals surface. It is of particular interest to know the dissolution and passivation mechanism of sulfide minerals in the presence of microorganism. Although bioleaching can be useful in extracting metals, it is a double-edged sword. Metallurgical activities have caused serious environmental problems such as acid mine drainage (AMD). The understanding of some common sulfide minerals bioleaching processes and protection of Amd environment is reviewed in this article.
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Compared with the traditional pyrometallurgical process, copper bioleaching has distinctive advantages of high efficiency and lower cost, enabling efficiently extracts of valuable metal resources from copper sulfides. Moreover, during long-term industrial applications of bioleaching, many regulatory enhancements and technological methods are used to accelerate the interfacial reactions. With advances in microbial genetic and sequencing technologies, bacterial communities and their mechanisms in bioleaching systems have been revealed gradually. The bacterial proliferation and dissolution of sulfide ores by a bacterial community depends on the pH, temperature, oxygen, reaction product regulation, additives, and passivation substances, among other factors. The internal relationship among the influencing factors and the succession of microorganism diversity are discussed and reviewed in this paper. This paper is intended to provide a good reference for studies related to enhanced bioleaching.
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The main measure to reduce energy losses is the usage of insulating materials. When the temperature exceeds 500 °C, silicate and ceramic products are most commonly used. In this work, high-crystallinity 1.13 nm tobermorite and xonotlite were hydrothermally synthesized from lime and Ca–Si sedimentary rock, opoka. By XRD, DSC, TG and dilatometry methods, it has been shown that 1.13 nm tobermorite becomes the predominant compound in stirred suspensions at 200 °C after 4 h of synthesis in the mixture with a molar ratio CaO/SiO2 = 0.83. It is suitable for the production of insulating products with good physical–mechanical properties (average density < 200 kg·m−1, compressive strength ~0.9 MPa) but has a limited operating temperature (up to 700 °C). Sufficiently pure xonotlite should be used to obtain materials with a higher operating temperature. Even small amounts of semi-amorphous C–S–H(I) significantly increase its linear shrinkage during firing. It has also been observed that an increase in the strength values of the samples correlated well with the increase in the size of xonotlite crystallites. The optimal technological parameters are as follows: molar ratio of mixture CaO/SiO2 = 1.2; water/solid ratio W/S = 20.0; duration of hydrothermal synthesis at 220 °C—8 h, duration of autoclaving at 220 °C—4 h. The average density of the samples was ~180 kg·m−1, the operating temperature was at least 1000 °C, and the compressive strengths exceeded 1.5 MPa.
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Pyrite oxidation rates were examined at various concentrations of dissolved oxygen (DO) in the presence of the sulfur and iron oxidizer Acidithiobacillus ferrooxidans. Five different batch experiments were performed at room temperature for 75 days under various DO levels (273, 129, 64.8, 13.2, and ≤0.006 μM), containing pyrite grains (particle size 63–250 μm) and a modified 9K nutrient medium at pH 3. The reactors were inoculated with A. ferrooxidans. In all experiments, pH decreased with time and sulfur and iron were released to the solution, indicating pyrite oxidation at all DO levels. Pyrite oxidation rates (ca. 5×10−10 mol m−2 s−1 at 273 μM DO) from all experiments showed positive correlation with DO, Fe(III), and bacterial concentration. These rates were significantly slower than rates presented in other published studies, but this is probably due to the significantly greater Fe(III) concentration at lower pH in these previous studies. The results obtained in this study suggest that ferric iron reduction at the pyrite surface is the primarily mechanism for microbial pyrite oxidation in the presence of DO. The results from our study support the indirect mechanism of sulfide oxidation, where A. ferrooxidans oxidizes ferrous iron in the presence of DO, which then oxidizes pyrite.
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Chalcopyrite passivation greatly reduces the yields from leaching and bioleaching but the problem has not been successfully resolved. Passivation involves the formation of a layer of secondary minerals on chalcopyrite surface, which becomes a diffusion barrier to fluxes of reactants and products. This study aims to identify secondary minerals formed during chalcopyrite passivation in the presence of iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) in mineral salts solution. The minerals were characterized with X-ray diffraction, Fourier transform-infrared spectroscopy, and Raman spectroscopy. Potassium jarosite was the initial product covering chalcopyrite grains, followed by the formation of ammonio-jarosite. Covellite and elemental sulfur were also detected in the passivation layer. The results suggest that passivation may be reduced by controlling jarosite precipitation and prior acclimatization of bacteria to oxidize CuS and elemental S in the presence of ferrous and ferric iron.
Abstract Bioleaching of a low grade chalcopyrite (ball mill spillage material) was tested for copper recovery in shake flasks. The original samples (as received) were thermally activated (600°C, 30 min) to notice the change in physico-chemical and mineralogical characteristics of the host rock and subsequently its effect on copper recovery. A mixed culture of acidophilic chemolithotrophic bacterial consortium predominantly entailing Acidithiobacillus fer- rooxidans strain was used for bioleaching studies and optimization of process parameters of both original and thermally activated samples. Mineralogical characteriza- tion studies indicated the presence of chalcopyrite, pyrite in the silicate matrix of the granitic rock. Field emission scanning electron microscopy coupled with Energy dispersive spectroscopy (FESEM-EDS) and X-ray Fluor- escence (XRF) analysis indicated mostly SiO2. With pH 2, pulp density 10% w/v, inoculum 10% v/v, temperature 30°C, 150 r$min–1 ,49% copper could be recovered in 30 days from the finest particle size ( – 1 + 0.75 mm) of the original spillage sample. Under similar conditions 95% copper could be recovered from the thermally activated sample with the same size fraction in 10 days. The study revealed that thermal activation leads to volume expansion in the rock with the development of cracks, micro and macro pores on its surface, thereby enabling bacterial solution to penetrate more easily into the body, facilitating enhanced copper dissolution. Keywords ball mill spillage, thermal activation, bioleach- ing, copper
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Meso-acidophilic bacterial leaching of ball mill spillage (containing chalcopyrite >80%) was carried out in an innovative two-step bioleaching method. The major drawback of meso-acidophilic bioleaching limiting industrial application is the passivation phenomenon over the ore surfaces in iron-sulfur rich environments. In the present study, we present a novel wash solution that efficiently removed the passivation layer. FTIR characterization of the bioleached sample indicated that the residues could be further leached to recover extra copper after wash solution application. XRD study indicated accumulation of sulfates (SO(4)(-)) of Na, K, Fe and oxy hydroxides of iron [FeO(OH)] in the form of jarosite outlining the passivation layer. SEM, FESEM-EDS studies indicated severe corrosion effects of the wash solution on the passivation layer. Two step bioleaching of the ore sample yielded 32.6% copper in 68days in the first interlude and post wash solution application yielded 10.8% additional copper.
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Silico-antimonate as inorganic ion exchange material has been synthesized and characterized using different available tools (X-ray diffraction (XRD) pattern, X-ray fluorescence, infrared spectroscopy and differential thermal analysis). From the analysis data, the empirical formula of silico-antimonate was obtained to be H2SiSb4O13·10H2O. Sorption kinetics for Cu2+, Zn2+, Cd2+ and Ni2+ ions on silico-antimonate were studied and found to be follow the first order kinetics obeying the Freundlich isotherm over the entire range for the bulk concentration of the metal ions. Thermodynamic parameters (i.e. ΔG°, ΔS° and ΔH°) have also been calculated for the adsorption of Cu2+, Zn2+, Cd2+ and Ni2+ ions on silico-antimonate showing that the overall adsorption process is spontaneous and exothermic.
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Nickel laterites represent the major ore reserves of this base metal present in the lithosphere. However, processing these ores by conventional technologies involves considerable energy or reagent expenditure and consequently is less cost-effective than extracting nickel from sulfide ores. Biological options, using metal-complexing organic acids and mineral acids generated by fungi and bacteria, have been investigated but generally found to be ineffective in terms of extraction dynamics or yields. We have examined the possibility of using bacteria that can bring about the reductive dissolution of ferric iron minerals and thereby facilitate the extraction of nickel from a lateritic ore at relatively low (<30-45 degrees C) temperatures. Four species of iron-reducing acidophilic bacteria were screened for their abilities to solubilise nickel from a limonitic laterite ore in which the major iron mineral present was goethite. One of these (Acidithiobacillus ferrooxidans) was selected for further study only the basis of it being able to use a cost-effective energy source (elemental sulfur) to mediate the dissolution of goethite at mildly acidic conditions (pH < 2). Cultures were set up in 2 L bioreactors, maintained at pH 1.8 (+/-0.1) and 30 degrees C. and initially aerated (to promote growth of the bacteria on sulfur) and then switched to anaerobic conditions when nickel laterite ore (crushed to <6 mm, with a nickel grade of 0.5%) was added. Over 70% of the nickel present in the ore was solubilised within 14 days, and solubilised metals remained in solution due to the low pH of the leachate. In contrast, only 10% of the nickel was solubilised (by non-reductive acid dissolution) when the cultures were continuously aerated. The results suggest that biological processing of limonitic nickel laterites is technically feasible and, more generically, that reductive dissolution can be used to bioprocess ferric oxide mineral ores.
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The formation and consumption of elemental S were investigated in the bioleaching of chalcopyrite within and without a CE dialysis membrane in Acidithiobacillus caldus cultures. The bacteria were supplemented with tetrathionate outside the membrane. XPS analysis showed that monosulfide species and elemental S were formed on CuFeS 2 surface regardless of the enclosure in the dialysis membrane. They diminished over time in the inoculated systems. In the membrane enclosure, colloidal S partially dissolves and can pass the dialysis membrane for bacterial oxidation to sulfuric acid. Anaerobic pre-oxidation of CuFeS 2 by Fe 3+ produced S-rich deposition on mineral surface. The solubilization of Cu from membrane-enclosed pre-oxidized chalcopyrite in the A. caldus culture was much slower as compared to direct contact with bac-teria. The difference is attributed to slow diffusion through the dialysis membrane as well as clogging caused by polymerized S on the inside of the membrane.