Article

Synergistic effect of biogenic Fe3+ coupled to S° oxidation on simultaneous bioleaching of Cu, Co, Zn and As from hazardous Pyrite Ash Waste

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Abstract

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.

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... It is important to note that industrial pyrite ash still await for the introduction of an efficient biotechnological application for recov-ery of valuable metals and very few or no studies are available in this regard. A preliminary attempt has been made towards optimization of several physico-chemical and biological parameters in shake flask for bioleaching of Cu, Co, Zn and As from pyrite ash obtained from Bandirma Etibank sulphuric acid production factory in Turkey [17]. Based on the optimized conditions and owing to the fine nature of the pyrite ash sample, bench scale stirred tank batch bioreactor studies are reported in this study with optimization of sulphur dose and agitation speeds. ...
... The sample is herein referred to as PAE throughout the text where PAE refer to Pyrite Ashes from Electro-filter Unit. The mineralogical characterization of the sample has been discussed in our previous study [17]. The laboratory stock culture of adapted mixed meso-acidophilic microorganisms (used in our previous lab scale optimization experiments) was chosen for the bioleaching studies. ...
... thiooxidans) and both iron and sulphur oxidising strain Acidithiobacillus ferrooxidans (A. ferrooxidans) [17]. The strains were grown over a modified 9 K medium with the following chemical composition: (NH 4 ) 2 SO 4 -3 gL −1 , K 2 HPO 4 -0.5 gL −1 , MgSO 4 ·7H 2 O − 0.5 gL −1 , FeSO 4 ·7H 2 O − 44.2 gL −1 , Ca(NO 3 ) 2 -0.1 gL −1 , Sulphur − 1 gL −1 [18]. ...
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.
... 42 Further investigation, however, would be required to assess the role of iron oxidation in this study, for example, by parallel monitoring of FeIJII) : FeIJIII) ratios in the leach solution by chromatographic or titration methods. 32,42,43 Greater increases in acid generation were seen in inoculated flasks which were stirred and heated, and were continuing to increase at the time the experiments were terminated. In addition to oxidation of added sulphur, there may have also been oxidation of reduced sulphur present in the substrate, such as metal sulphides. ...
... 50 However, as pH values were on a downward trajectory, it may be that significant increases in solubilisation of these metals would have occurred if experiments had continued. This has been observed by other researchers during lower pH conditions, 27,43,51 notably Panda et al. determine that an optimum pH of 1.75 provides simultaneous dissolution of copper, zinc, cobalt and arsenic. 43 In their manuscript, they note that pre-culturing of microbes was undertaken within the substrate, so that colonies were well adapted to the leaching environment to improve leaching efficiency. ...
... This has been observed by other researchers during lower pH conditions, 27,43,51 notably Panda et al. determine that an optimum pH of 1.75 provides simultaneous dissolution of copper, zinc, cobalt and arsenic. 43 In their manuscript, they note that pre-culturing of microbes was undertaken within the substrate, so that colonies were well adapted to the leaching environment to improve leaching efficiency. 43 Pre-culturing the microbial populations may therefore offer a mechanism of accelerating acid generation and thus metal recovery rates. ...
Article
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A proof of concept study is presented, using acid mine drainage (AMD) to leach metals (Zn, Cd, Ni, Mn, Fe, Pb, Cu) from a passive treatment system substrate. The substrate, taken from a sulphate-reducing bioreactor treating mine drainage at another site, was heavily contaminated with metals and could not be disposed of in landfill under UK regulations. Laboratory scale batch leaching experiments were conducted under aerobic conditions, in order to harness microbial sulphur oxidation to generate sulphuric acid and re-mobilise metals. Acid mine drainage, normally considered to be waste or an environmental liability, was used as a microbial inoculum and leach solution for the experiments, with added zero-valent sulphur as a supplementary nutrient source for sulphur oxidising bacteria. The initial reactor pH of 4.0 decreased to ≤2.8 in inoculated reactors, whereas the final pH of the sterile controls was 4.1. Metals data showed removal efficiencies of 71–100% for Zn, Cd, Ni and Mn in inoculated reactors upon completion of the 1600 hour leach period. These findings suggest that AMD can be used as a convenient leach solution and inoculum for the leaching of these metals from spent bioreactor treatment system substrates.
... During pH fluctuation, minor increased in pH of bioleaching system occurred during first 2 days and further decreased for about 6 days happened that clearly indicate the maximum bacterial activity, which mostly produced sulfuric acid and further became constant. Our findings are comparable with the results of Panda et al. (2017). Panda et al. faced this situation of pH fluctuation in similar pattern. ...
... However, acid addition results higher cost in commercial bioleaching process; therefore, the use of indigenous bacterial consortia could be more effective as reported in the present study. Initial pH fluctuation in control system was observed that might be due to the H + consumption by gangue materials in our sample (Panda et al. 2017). Figure 3d shows the ORP fluctuation during bioleaching experiment. ...
... The control system had smooth ORP fluctuation due to the absence of bacterial ferrous oxidation. Our findings are supported by the study of Panda et al. (2017). ...
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.
... Initially, a slight increase in the pH was reported and further decreased and became constant that exhibit maximum bacterial activity. Panda et al. (2017) also reported the pH variation in comparable pattern. The initial pH rise happens either due to the presence of minor carbonate minerals present in the ore or due to the H þ consumption during oxidation as shown in Equation 1. ...
... Moreover, low pH inhibits the passivation layer formed on the ore surface (Fu et al. 2008). The initial fluctuation of pH in the control system could be due to the H þ ion consumption by gangue ingredients (Panda et al. 2017). ...
... This clearly showed the efficiency of iron-oxidizing bacteria in consortia, which rapidly consumed ferrous iron as an energy source. The main role of these bacteria is to regenerate the required ferric iron (Equation 1) and sustain higher ORP and enhance the metals dissolution (Panda et al. 2017;Sand et al. 2001;Schippers and Sand 1999). The ORP changes pattern depends upon the consumption and regeneration of ferric iron. ...
Article
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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
... The sample "as received" contains no identifiable sulfur source; hence, sulfur was externally added to the medium to generate the acidity required for maintaining the system's pH (since the sample is alkaline in nature). Based on previous experience, both Fe and S oxidizing bacteria were used to provide the necessary Fe 3+ (biogenic) and H 2 SO 4 (biogenic) that can act on the sample and facilitate enhanced dissolution of the targeted metals under study (Panda et al. 2017 ...
... Step -1: Pre-Treatment Fig. 1 Schematic representation of the process flow adopted for the present experiment (Baba et al. 2011). Prior to bioleaching studies, the fully active microbial consortium was adapted to the respective IBAM and IBAN samples (5 g), following Panda et al. (2017). After attaining an iron oxidation rate (IOR) > 600 kg/m 3 /h, the adapted consortium (for the respective sample) was used for bioleaching studies. ...
Article
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Ferrous fractions in incinerated bottom ash (IBA) are linked to lower metal dissolution. In the present study, a novel eco-friendly biotechnological approach has been tested for multi-metal leaching using meso-acidophilic Fe²⁺/S° oxidizing bacterial consortium from magnetically separated IBA, owing to the inherent property of IBA to release Fe²⁺. Comprehensive lab-scale studies, first-of-its-kind, considered all the potential elements to understand targeted metal dissolutions from the sample under differential conditions. Concentrations of metals, Al > Ti > Ni > Zn > Cu, as analyzed by ICP-OES, were targeted to be bioleached. XRD analysis indicated the sample to be amorphous with magnetite (Fe3O4) and iron (Fe) forming major phases in the magnetic part (IBAM) and titano-magnetite (Fe3–x. TixO4) and iron (Fe) for the nonmagnetic part (IBAN). The study indicated that 73.98% Cu, 98.68% Ni, 59.09% Zn, 58.84% Al, and 92.85% Ti could be leached from IBAM when the bioleaching system operates at pH 1.5, 5% pulp density for 8 days. Under similar conditions, within 6 days, 37.55% Cu, 87.99% Ni, 45.03% Zn, 40.72% Al, and 63.97% Ti could be leached from IBAN. Two routes were identified and the mechanism of action has been proposed for the leaching of metals.
... Each sample was firstly filtered through a 0.22 μm membrane to remove cell debris and precipitates prior to measurements. The pH was measured using a pH meter (UB-7, Denver, USA) and the concentration of Fe 2+ was determined using a previously described ferrozine assay (Panda et al., 2017). Next, a certain amount of filtrate was diluted to an appropriate concentration range with 2% HNO 3 , after which the concentration of soluble V and W were determined by inductively coupled plasma-optical emission spectrometry (Optima 7000DV, PerkinElmer, USA). ...
... It has been reported that the oxidation of S 0 is catalyzed by sulfur-oxidizing bacteria, producing several intermediate sulfur species among which the sulfite ion is the uppermost, and H 2 SO 4 is the final product (Eqs. (1) and (2)) (Panda et al., 2017). Fig. 1. ...
Article
Solid wastes are currently produced in large amounts. Although bioleaching of metals from solid wastes is an economical and sustainable technology, it has seldom been used to recycle metals from abandoned catalyst. In this study, the bioleaching of vanadium from V2O5-WO3/TiO2 catalyst were comprehensively investigated through five methods: Oligotrophic way, Eutrophic way, S-mediated way, Fe-mediated way and Mixed way of S-mediated and Fe-mediated. The observed vanadium bioleaching effectiveness of the assayed methods was follows: S-mediated > Mixed > Oligotrophic > Eutrophic > Fe-mediated, which yielded the maximum bioleaching efficiencies of approximately 90%, 35%, 33%, 20% and 7%, respectively. The microbial community analysis suggested that the predominant genera Acidithiobacillus and Sulfobacillus from the S-mediated bioleaching way effectively catalyzed the vanadium leaching, which could have occurred through the indirect mechanism from the microbial oxidation of S0. In addition, the direct mechanism, involving direct electron transfer between the catalyst and the microorganisms that attached to the catalyst surface, should also help the vanadium to be leached more effectively. Therefore, this work provides guidance for future research and practical application on the treatment of waste V2O5-WO3/TiO2 catalyst.
... The bacteria will then use Fe 2+ to regenerate Fe 3+ from Fe 2+ oxidation. Therefore, the rise in Fe 3+ concentration reflects the elevation of metal recovery [39]. This suggests that on the first few days, copper, nickel, and gallium were dissolved due to chemical reactions. ...
... The morphology of the WLED sample after indirect bioleaching was cube shaped with an approximate size of 0.5-12 μm. Jarosite is a yellowish-brown mineral with a crystalline structure [39]. The jarosite layer covered the surface of WLED powder after bioleaching. ...
... Contaminated water is toxic in nature and is associated with diverse environmental issues affecting drinking, bathing and other uses of water [5].The effects of different pollutant wastes are illustrated in Table 2. Science now helps us to develop new technologies and materials that can reduce and decompose different pollutant. At present phytoextraction of heavy metals is being done by many species as given in Table 3. [6,7,8,9] Electrochemical treatment helps in minimizing and removing the metals, but it is effective only for some metallic ions. ...
... In advanced oxidation processes a number of intermediates are formed. Table (5) explains that most of the experimental researches did not analyze intermediates and were only focused on the degradation rate of inorganic and organic pollutants. Few of the intermediates produced during degradation of organic pollutants have been mentioned in the present study. ...
Article
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Water, a gift of nature is facing increased pollution by many industrial and house hold activities which comprise pollutants of organic and inorganic origin. In the past few years advanced oxidation process (AOP) involving ozone have been used more frequently but there is a need of more AOP for combating the ever increasing issue of water pollution. Ozonation is the most suitable technique for waste water treatment but this is not sufficient for the present time, due to continuously increasing pollution load in water bodies. High cost associated with this technique also limits its applicability. Under such circumstances alternative technologies have been developed so as to meet the requirement of clean and potable water .An efficient photocatalytic oxidation process using nanomaterials (TiO 2 , WO 3 , TiO 2-RGO, CNT) has been tried which efficiently produces highly reactive free radicals thereby taking part in higher oxidation. The use of photocatalytic nanomaterials is beneficial due to its use based on sunlight. For the last few years most of the people, have developed hybrid nanomaterial (TiO 2-RGO), which is active in visible light due to Ti-O-C bond and RGO enhances the absorption of solar light due to its high surface area. In this review two alternative techniques have been discussed. The chemical effect of various variables on the rate of degradation of different pollutants is discussed. The mechanism has also been reported. Therefore, it can be concluded as, absorption and degradation of pollutant is increased by nanomaterials qualitatively and quantitatively in comparison to oxidation with ozone and oxygen.
... This clearly showed the efficiency of iron-oxidizing acidophilic bacteria in consortia, which rapidly consumed ferrous iron as an energy source. The significant role of these bacterial strains is to reproduce the required ferric iron and sustain higher ORP and enhance the dissolution of metals (Schippers and Sand, 1999;Sand et al., 2011;Panda et al., 2017). The ORP variations pattern depends upon the consumption and regeneration of the ferric iron. ...
... Higher ORP reported here in this study shows the maximum efficiency of the indigenous bacterial consortia in iron oxidation compared to the ORP in pure bacterial inoculum reported by Ghassa et al. (2014). The plane ORP pattern in the control system was due to the lack of bacterial inoculum for iron oxidation, which supports the findings of Panda et al. (2017). The variation in ORP during the rapid dissolution phase was according to the controlled range of 380-680 mV (vs. ...
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.
... This method proposed development of a microbial ecosystem with the synergistic effects of acidophilic heterotrophs and autotrophs. Panda et al. (2017) observed that the microbial community leans toward better performance when mixed cultures of microorganisms are used in bioleaching rather than pure cultures. Peng et al. (2012) studied the influence of surfactants on bioleaching. ...
... High pH values are related to acidic behavior in various locations of Kerala due to the discharge of industrial waste into the river (Muruga Lal Jeyan and Akhila 2017). Uncontrollable use of insecticides, pesticides in cement factories, lime kilns process results in water pollution in Madhya Pradesh (Mishra 2017). The states having many polluted rivers in the range [11][12][13][14][15][16][17][18][19][20] are Goa, Gujarat, Karnataka, Odisha, Uttar Pradesh, and West Bengal. ...
Chapter
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Ethanol production from sustainable and inexpensive farming residues decreases greenhouse gas emissions, for instance, carbon dioxide, nitrogen dioxide, sulfur oxide, and eliminate smog from the atmosphere. A certain number of agricultural residues and plentifully misused materials are oat straw, rice straw, and wheat straw; waste potato, switchgrass, corn steep liquor, sweet sorghum, bagasse, sugar beet tubers, etc. are used as potential material for bioethanol making in different countries. Wheat straw deposits are one among the residues produced in substantial amounts globally, including Ethiopia. However, the elimination of lignin out of lignocelluloses untreated residues is the most critical step. Various pretreatment methods are explained before by numerous researchers with chemical, physical, biological, and ionic liquid pretreatment. This review carefully evaluates the performance of highly capable and recent techniques of hydrolysis and discusses the potential of wheat straw residue for bioethanol production, using less energy-demanding and more eco-friendlier techniques than the recent commercial pretreatment techniques. The most popular of these is the ionic liquids (ILs). Important pretreatment steps by ionic liquids, such as 1-allyl-3-methylimidazolium chloride,1-ethyl-3-methylimidazolium acetate, 1-butyl-3methylimiazolium,1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-methyl-3-(4-sulfobutyl) imidazolium bisulfate, and cholinium taurate, will be evaluated. Additionally, critical parameters affecting the treatment process, such as temperature, the ratio of ionic liquids to residue dose, concentration of ionic liquids, and time taken, would also be discussed.
... This method proposed development of a microbial ecosystem with the synergistic effects of acidophilic heterotrophs and autotrophs. Panda et al. (2017) observed that the microbial community leans toward better performance when mixed cultures of microorganisms are used in bioleaching rather than pure cultures. Peng et al. (2012) studied the influence of surfactants on bioleaching. ...
... High pH values are related to acidic behavior in various locations of Kerala due to the discharge of industrial waste into the river (Muruga Lal Jeyan and Akhila 2017). Uncontrollable use of insecticides, pesticides in cement factories, lime kilns process results in water pollution in Madhya Pradesh (Mishra 2017). The states having many polluted rivers in the range [11][12][13][14][15][16][17][18][19][20] are Goa, Gujarat, Karnataka, Odisha, Uttar Pradesh, and West Bengal. ...
Chapter
The exorbitant usage of heavy metal in industries leads to accumulation in the ecosystem and causes various disorders. Many physico-chemical methods have developed for the removal of heavy metals from industrial wastewaters as well as the polluted environments. However, these conventional technologies are providing expensive, generate toxic secondary sludge, and not complete abatement. An alternative, the biological methods especially using algae for the treatment of metal-contaminated environments provides a cost-effective, rapid, and eco-friendly approach. Using algae (macro or micro) for removing pollutants (phycoremediation) is a versatile approach since algae can adapt easily with any environmental conditions and recognized as a sustainable technology for removing noxious heavy metals. Algal biomass contains a polyanionic cell wall that can bind heavy metals through the principle of adsorption (passive) onto the cell surface and absorption (active) into the cell with metal-binding peptides or contained in the vacuole. Moreover, various factors (pH, temperature, metal concentration, contact time, agitation speed) affect the biosorption of heavy metal. Thus, this review article deals with the abatement of heavy metals using macro and microalgae, factors involved and mechanisms, and functional groups involved in the cell surface. Besides, suggested that the industrial-scale data’s are required for the real application.
... This method proposed development of a microbial ecosystem with the synergistic effects of acidophilic heterotrophs and autotrophs. Panda et al. (2017) observed that the microbial community leans toward better performance when mixed cultures of microorganisms are used in bioleaching rather than pure cultures. Peng et al. (2012) studied the influence of surfactants on bioleaching. ...
... High pH values are related to acidic behavior in various locations of Kerala due to the discharge of industrial waste into the river (Muruga Lal Jeyan and Akhila 2017). Uncontrollable use of insecticides, pesticides in cement factories, lime kilns process results in water pollution in Madhya Pradesh (Mishra 2017). The states having many polluted rivers in the range [11][12][13][14][15][16][17][18][19][20] are Goa, Gujarat, Karnataka, Odisha, Uttar Pradesh, and West Bengal. ...
Chapter
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E-waste refers to waste from electronic devices and electrical appliances that are widely discarded. It includes televisions, washing machines, refrigerators, air conditioners, printers, cell phones, computers, and monitors. Currently, increasing technological developments reduce the lifespan of electronic and electrical equipment. Hence, much more e-waste is being produced. Based on recent statistics, the worldwide production of e-waste is increasing at a rate of 4.6% annually, and it is expected to reach about 52.2 metric tons in 2021. Its processing produces a sludge that is a great threat to the environment since it contains numerous toxic heavy metals. For environmental protection, physical methods have been extensively implemented by some enterprises that dismantle e-waste. The alkali and acid reagents used to extract metals from e-waste are quite costly. However, research communities globally are focusing on bio-hydrometallurgical techniques to treat e-waste for ecofriendly treatment and safe disposal. Although several treatment techniques are applied to leach heavy metals from e-wastes, this chapter focuses on bacterial leaching, colloquially called bioleaching. This method is proven and can be effectively applied for leaching heavy metals from e-waste. Three sections are developed in this chapter. First, the sources of various e-wastes and their heavy metal contents are examined. Second, the specific microorganisms that can be applied for bioleaching processes are discussed. Last, the optimal conditions, bioleaching mechanisms, and influences are presented.
... Due to the fact that it has the potential to reduce operating costs and energy requirements, as well as being environmentally sound, bio-hydrometallurgical approaches to waste recycling have been increasing day by day. As seen in Table 1, iron and sulfur-oxidizing bacteria (e.g., Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans) are widely used in the bio-hydrometallurgical process to dissolve copper by a series of biological and chemical reactions (Brandl et al., 2001;Erust et al., 2013;Panda et al., 2013Panda et al., , 2017. ...
Article
Bioleaching of copper from electronic waste (e-waste) in the form of high grade waste printed circuit boards (WPCBs) collected from obsoletemobile phones is assessed using a consortium of iron (Fe2+) & sulphur (Sº) oxidizing bacteria in a semi-pilot reactor system. Results from the study indicated that the microorganisms were able to grow in the presence of WPCB and efficiently solubilize Cu from it. At a solid/liquid ratio of 10% (w/v)with a particle size of <250 μm, maximum bioleaching efficiency of around 95% Cu was observed in 8 days of leaching under oxidation-reduction potentials (ORP) of >600 mV and pH 1.8. In order to recover the metallic values, electrowinning (EW) of copper from the bioleach solutions was investigated in detail. Direct EW of the bioleach solution yielded low current efficiencies (66.1% over 4h.), ascribed due to the high concentrations of iron (i.e., 9.1 g/L). As a novel approach, a downstream purification and concentration process was further tested, that involved ferric hydroxide (Fe(OH)3) precipitation and solvent displacement crystallisation (SDC) to eliminate iron and increase the concentration of copper in solution prior to its application for EW. This significantly improved the current efficiency (by ~22%) during the EW of copper. A process flow-sheet for Cu recovery from WPCBs was developed and the downstream process was found to be profitable even though its margin was small with techno-economic analysis. It is believed that the two-step hybrid process i.e. bioleaching technique followed by the novel approach proposed (i.e., iron precipitation + SDC) can be suitably employed for the extraction of copper from WPCBs.
... KL3 increased by 40% and peaked at 80% on day 30. The shift in the relative abundance of the two type strains was induced by their synergistic bioleaching mechanism in the column (Panda et al. 2017). At the early stages of bioleaching, Acidithiobacillus sp. ...
Article
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Biochar can improve manganese ore extraction during bioleaching by inducing redox reactions and providing a porous matrix for bacterial attachment. In this research, the effect of variations in biochar concentration on the performance of a bioleaching column with a mixed culture of Acidithiobacillus sp. KL3 and Bacillus niacini KB3B1 were studied comprehensively for 30 days. Addition of 0.4% biochar resulted in 89% manganese extraction. Bioleaching with biochar promoted the oxidation of sulfur and yielded high sulfate concentrations, much better pH, and excellent oxidation–reduction potential conditions. The bacteria in the mixed culture survived and adapted to the extreme column environment by releasing extracellular polymeric substance, as evidenced by the sharp increase in the content of the material in the column to 135.7 mg/g over 30 days of incubation. The synergistic effect of the bacteria in the mixed culture greatly contributed to the mechanism of manganese extraction in the column, as indicated by changes in relative bacterial abundance, which is related to bacterial community succession during bioleaching. The relative abundance of B. niacini KB3B1 gradually increased and peaked at 30% over 9 days of measurements. By comparison, the abundance of Acidithiobacillus sp. KL3 first decreased over 9 days of bioleaching and then increased to a maximum of 80% in the final stages of the process. This finding reveals that biochar addition could enhance the mechanisms of bioleaching and improve the yield of manganese extraction. © 2021, Society for Indonesian Biodiversity. All rights reserved.
... 36 Recovery of metals (Al, Co, Cu, Zn, Mo, U, V) and radionuclides from their respective ores by chemolithoautotrophs is gaining more attention. [37][38] Thiobacillus and other autotrophs are also capable in bioleaching of shales, schist, and ores originating from fossil fuels. 37,39 Heterotrophic microbes thrive on organic carbon produced by autotrophs for survival and excrete organic acids as metabolites. ...
Article
Abstract Biomining of copper from ores was started during ancient era without even knowing the role of microorganisms in the process. The ever-increasing demand of metals, declination of natural resources, huge reserves of low-grade metallic ores and generation of massive amount of metallic wastes from mining and beneficiation process has led to the evolution and commercial scale adoption of biomining. The ability of microorganisms to bioamine metals depends on redox reactions, organic or inorganic acid formation an d the release of complexing agents. Redox reaction is the key step of biomining process which is based either on direct or indirect bioleaching. The main difference between the two mechanisms is the direct contact between the microorganisms and the reduced minerals. Apart from the economic benefits, biomining also reduces the problem of acid mine drainage (AMD). Biomining is successfully utilized in metal recovery from low grade ores, mine tailings, mine wastes, municipal solid waste dump sites, legacy wastes, incinerator ash, E-wastes and, shales and tars etc. In this way, biomining inhibits the release of heavy metals from various types of wastes to the environment and release of toxic gases from the municipal solid waste dump sites and legacy wastes. Keywords Archaebacteria; bioleaching; chemolithoautotrophic bacteria
... Similarly, the activity of the bacterium Acidithiobacillus thiooxidans is seen to cause the production of sulfuric acid thereby decreasing the pH level of the bioleaching system. Therefore, ORP and pH level have been often used as an indirect index for bacterial growth and activity [28]. Sample solutions were withdrawn regularly for pH level and ORP measurements. ...
Article
The present study investigates the influence of ferrous iron (as FeSO4) and ferric iron (as Fe2 (SO4)3), and pyrite (FeS2) on the ability of bacterial leaching of a high-grade sulfide Zn–Pb ore. In this regard, shake flask experiments were carried out at 5% (w/v) pulp density of the ore sample (having 40.7% Zn and 12.4% Pb initial metal content) using a consortium of mesophilic iron and sulfur-oxidizing acidophiles. A concentration of 0.04 mol/L of ferric iron in the leaching media was found to be optimum for zinc extraction without affecting growth of the microorganisms. Under this concentration, the dissolution of Zn, Pb, Cd, and As was found to be 57%, 0.2%, 0.03%, and 9.9% in 25 days. Using ferrous iron in the media, 0.16 mol/L of Fe²⁺ was found to be the optimum concentration for efficient bacterial growth and metal dissolution (54.6% Zn, 0.08% Pb, 0.03% Cd, and 10.2% As) from the sample in 25 days. On the other hand, using pyrite as the source of energy for bacterial growth, an initial 12-day lag period was observed when compared to the effect of ferrous iron in the media. Under the optimum concentration (test with 0.24 mol/L iron in the form of pyrite), the dissolution of Zn, Pb, Cd, and As was found to be 39.8%, 0.1%, 0.03%, and 10% in 25 days. The surface chemistry analysis indicated formation of a sulfur layer over the particle surface that hindered reagent diffusion and affected metal recovery through bioleaching.
... Furthermore, the fine size of pyrite cinder often leads to the dust problem in the disposal site. In China, a large amount of pyrite cider is collected in chemical manufacturing yearly [4], and its stacking has caught acute ecological problems [5][6][7]. Owing to the low grade of pyrite ore, the iron grade of pyrite cinder is too low to be efficiently utilized. Only a small portion of pyrite cinder has been used in paving, brickmaking, cement, and auxiliary additives [8][9][10][11][12]. ...
Article
Full-text available
Nova tehnika karburizacije posle koje sledi magnetna separacija predstavljena je za pripremu visokokvalitenog karbida gvožda od šljake pirita da bi se unapredila upotreba šljake pirita sa visokom dodatom vrednošću. Istraživani su efekti temperature karburizacije, vreme karburizacije i doziranje Na2SO4 na karburizovani pelet, kao i efekti doziranja Na2SO4 i finoća mlevenja magnetnog koncentrata. Predloženi su sledeći optimizirani parametri procesa: karburizacija na 650 °C u trajanju od 180 minuta u CO-CO2-H2 mešavini gasova, doziranje Na2SO4 od 9%, intenzitet magnetnog polja 130 mT, i finoca mlevenja gde je 92.25% praha 0.025mm. Sadržaj gvožda, ukupan sadržaj karbida, ukupan sadržaj gvožda i karbida magnetnog koncentrata bili su 82.62%, 5.60%, i 88.22%. Stopa dobijanja gvožda dostigla je 88.67%. Ponašanje i mehanizmi karburizacije, separacije, i Na2SO4, potvrdeni su uz pomoć optičke mikroskopije, XRD, i SEM.
... For the bioleaching tests, the effect of variation in four parameters such as initial pH, solid concentration, inoculum percent and time on Cu, Mo and Re extraction from the concentrate were assessed. In general, these parameters are one of the important aspects when optimization studies for bioleaching are considered (Panda et al., 2017). For every bioleaching test, 5 g FeSO 4 ·7H 2 O along with 1 g sulfur were added as an energy source to 100 mL media solution in each flask. ...
Article
This paper presents the application of an artificial neural network (ANN) in order to predict the effects of operational parameters on the dissolution of Cu, Mo and Re from molybdenite concentrate through meso-acidophilic bioleaching. The initial pH, solid concentration, inoculum percent and time (days) were used as inputs to the network. The outputs of the models included the percent of Cu, Mo and Re recovered. The development and training of a feed-forward back-propagation artificial neural network (BPNN) was used to model and predict their recoveries. 105 sets of data were used to develop the neural network architecture and train it. To reach the network with highest generalizability, the space of neural networks with different hidden layers (one up to three hidden layers) and with the varying number of neurons each layer were searched. As a result, it was found that (4-5-5-2-1); (4-7-5-2-1) and (4-7-1-1-1) arrangements could give the most accurate prediction for Cu, Mo and Re extraction respectively. The regression analysis of the models tested gave a good correlation coefficient of 0.99968, 0.99617 and 0.99768 respectively for Cu, Mo and Re recoveries. The results demonstrated that ANN has a good potential to predict Cu, Mo and Re recoveries. Also, genetic algorithm (GA) was used to find out the optimum levels of parameters in the best models defined by ANN. The maximum recovery of Cu, Mo and Re on the 30th day were nearly 73%, 2.8% and 27.17% respectively.
... Application of Thiobacillus and other autotrophs in commercial-scale bioleaching of fossil fuels originating from shales, schist, and ores, is well establishes [7,81]. Current exploration establishes the metals recovery, such as Al, Co, Cu, Zn, Mo, U, V, and radionuclides via chemolithotrophs from acidic environments [7,93]. Such microbes are utilized for metals extraction from their respective ores [4,165]. ...
Article
Nowadays, due to fast global industrial progress and near diminution of high-grade ore reserves, there has been massive call to cost-effectively process the resources of low-grade ores and industrial effluents for metal extraction. However, conventional approaches cannot be used to process such resources due to high capital cost and energy, also causing environmental pollution. Alternatively, bioleaching is highly environmental friendly and economic method to process such resources. Metal recovery from metal sulfide ore is carried out by chemolithotrophic bacteria like Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. The same is done by heterotrophic microorganisms in non-sulfide ores. Additionally, for gold and copper extractions, bioleaching is used to extract cobalt, zinc, nickel, and uranium from low-grade ores and industrial effluents. In this review, the fundamental process of bioleaching from low-grade metal sulfide ores are discussed with emphasis on mechanism, types, pathways, techniques, and bioleaching development.
... The CFA particles concentrated on the fine size grade of < 45 μm exhibited a characteristic gray appearance. The mineral samples were then prepared by the conventional Coning and Quartering method to obtain representative samples for the analyses [42]. X-ray diffraction (XRD, TTR III, Rigaku, Japan) analysis indicated that CFA was mainly composed of mullite (Al 6 Si 2 O 13 ), sillimanite (Al 2 SiO 5 ), and quartz (SiO 2 ), and the original pyrite sample was mainly composed of pyrite. ...
... The greater the proportion of Fe 3þ in the solution results in the higher the redox potential and is more conducive to the dissolution of pyrite. However, an excessive high proportion of Fe 3þ will inhibit the growth of bacteria and lead to the formation of jarosite and other products (Shrihari et al., 1990;Panda et al., 2017). Excessive proportion of Fe 2þ will also reduce the ability of bacteria to attach to the ore and prolong the time for corrosion. ...
Article
Although pyrite bio-dissolution plays an important role in the processing of sulfide ores, the formation of passivation film inhibited the further dissolution of sulfide ores. In order to enhance the dissolution of sulfide ores, a novel method for destroying the passivation film using ozone was proposed and verified. The generated passivation film inhibiting pyrite dissolution in the presence of Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans was studied. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicate that a passivation film mainly consisting of jarosite and polysulfide (Snⁿ⁻/S⁰) might be formed during biotic stage, which can be eliminated with the introduction of ozone (2 g/minutes) in 30 minutes. Electrochemical results show that ozone significantly increased the electrochemical reactivity of passivated pyrite, further proving that ozone enhanced the dissolution of passivated pyrite through destroying the passivation layer. Hence, a bi-stage method for dissolution of sulfide ores can be proposed.
... The metal contents in solutions were analyzed using an inductively coupled plasma-optical emission spectrometer (ICP-OES) (Optima 5300 DV, PerkinElmer Instrument). Ferrous iron concentration in the media was estimated by titration (o-phenalthronine) method (Panda et al., 2017). The surface morphology of the original and bioleached residue particles was analyzed by scanning electron microscopy (JSM-6701F, JEOL, Japan). ...
Article
Metals removal from industrial process residues is essential to alleviate the potential threat to environment and avoid the resource waste. Because of very low concentration of metals and complexity of residues, conventional pyrometallurgical and hydrometallurgical routes suffer high cost and uncompleted removal. Here acid catalysis coupling bioleaching strategy was proposed for cost-efficient cleaning of metals from waste resin powder by applying double stress adapted consortium. The results showed that low pH bioleaching significantly improved the metals release, near 100% metals was leached out and no impurities of Fe(III)-precipitates was present in bioleached residue at pulp density of 10% and pH 0.7, which indicated the positive effects of acid in bioleaching of waste resin powder. Economic analysis exhibited that more profits of 33.7 $/t and 56.2 $/t residue were obtained respectively from metals recovery in case of pH 0.7 bioleaching compared with bioleaching at pH 1.5 and acid leaching at pH 0.7. Further stirring bioleaching and static leaching showed similar metals extraction rate under high pulp density conditions and TCLP tests indicated all bioleached residues could be reused as nonhazardous materials safely. However, static bioleaching showed higher ferric iron regeneration capacity and more stable community composition. These findings demonstrated that static low pH bioleaching might be more feasible for treatment of solid waste in full-scale applications from a technological and economical perspective.
... 1(c and d)]. After Day 70, the acidity increased with a steeper slope, reflecting an increase in the activity of sulfur-oxidizing bacteria (Panda et al. 2017). Along with redox potential, the pH declined with a sharper slope for Tests 4 and 15 showing that these tests had better conditions for bacterial activity (Plumb et al. 2008). ...
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.
... This microbial behavior has been investigated in the literature (Baba et al., 2011;Li et al., 2020). Panda et al. revealed the synergistic effects of two species of sulfur oxidizing bacteria A. ferrooxidans and A. thiooxidans and found that ore oxidation was promoted leading to better metal dissolution (Panda et al., 2017). The maximum recoveries for using the mixed culture were 100% Zn, 41.9% Ba, 98.5% Ni and 97.8% Li at pulp density 0.5% (w/v). ...
Article
Carbide slag generated from industrial sites can contain many organic and inorganic impurities such as toxic metals and organic compounds, which should be treated before disposal. Bioleaching using Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and their combination was investigated. The effects of important factors including pH and pulp density were assessed. It was found that under optimal conditions 100% Zn, 41.9% Ba, 98.5% Ni and 97.8% Li were extracted with the mixed culture of Acidithiobacillus at pH 1 with pulp density 0.5% (w/v) after 14 days. To ensure risk reduction of the carbide waste for the soil environment, ecological risk criteria and plant seed germination potentials were evaluated. The results showed that bioleaching significantly reduced slag toxicity, and plant seed germination from leached waste was observed.
... Optimal amounts of ferrous iron to sustain an active microbial population of iron oxidizers (like At. ferrooxidans) should be determined, also to enhance synergistic bioleaching effects. In these circumstances, a stepwise inoculation strategy or nutrients addition can regulate the microbial community structure to promote secondary microbial growth to maintain a moderate trade-off between microbial community performance and iron and sulfur metabolism (Feng et al., 2015;Panda et al., 2017) in effective bioleaching systems. Finally, IBA treated in this way will have acidic pH and the formation of calcium sulfate is promoted (Funari et al., 2017). ...
Article
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Municipal solid waste incineration (MSWI) is one of the leading technologies for municipal solid waste (MSW) treatment in Europe. Incineration bottom ash (IBA) is the main solid residue from MSWI, and its annual European production is about 20 million tons. The composition of IBA depends on the composition of the incinerated waste; therefore, it may contain significant amounts of ferrous and non-ferrous (NFe) metals as well as glass that can be recovered. Technologies for NFe metals recovery have emerged in IBA treatment since the 1990s and became common practice in many developed countries. Although the principles and used apparatus are nearly the same in all treatment trains, the differences in technological approaches to recovery of valuable components from IBA – with a special focus on NFe metals recovery – are summarized in this paper.
... 46 Activation of the microbes (IOR >600 kg m -3 h -1 ) was completed when Fe (II) was fully oxidized to Fe (III) in the presence of 2 g WPCB sample (with repeated subculturing) in order to adapt the microbial culture to the sample before the bioleaching studies. 47 In order to achieve high solution potentials, 10% (v/v) of this active and adapted culture was repeatedly subcultured over fresh 9 K medium until concentration of 1.0 × 10 9 cells mL -1 and ORP >750 mV were obtained. Thus, the intensified culture with high solution potentials was used directly for bioleaching studies. ...
Article
BACKGROUND: The waste printed circuit boards (WPCBs), today, offer a wide array of metals and are of great importance because their metal concentration is much more than that in the ores. Largely, studies have been devoted to Cu bioleaching from WPCBs because it has the highest ratio among all metallic elements ( ̴ 10-30%). In the present study, an intensified mixed meso-acidophilic bacterial leaching of multi-metals has been studied from WPCBs of spent mobile phones, with the system operating under high oxido-reductive potentials (HORPs). ICP-OES, XRD and SEM-EDX characterization indicated the sample to have recoverable contents of Cu, Al, Ni & Zn which were targeted for bioleaching. RESULTS: Shake flask optimization studies, under HORP of >750 mV indicated dissolutions of Cu – 98.1%, Al – 55.9%, Ni – 79.5% and Zn – 66.9% under optimized conditions of 9 g/L Fe (II), 10% pulp density, 1.8 initial pH and 10% (v/v) as initial inoculum. Under these conditions, at ORP >650 mV, Cu – 97.3%, Al – 55.8%, Ni – 79.3% and Zn – 66.8% were achieved in bench scale (1L) bioreactor systems without any significant reduction in efficiency (compared to shake flasks) in 8 days of operation. CONCLUSION: Variations in the co-relatable parameters, to metal leaching, such as pH, ORP and Fe (II) concentrations indicated that these parameters significantly contributed to metal leaching. Operating the system under high and controlled ORPs is a faster and efficient way to leach multi-metals from WPCBs.
... initial Fe 2þ [7.3e9.0 g/L], and particle size [10e95 mm] (Potysz et al., 2016;Panda et al., 2017;Ahmadi et al., 2017;Georgiev et al., 2017). The mineralogical composition of the waste affects the bioleaching process as the high carbonate content increases the pH of the leaching liquid and inhibits or completely suppresses the bacterial activity. ...
Article
The recovery of copper from secondary waste resources (e.g. electronic wastes, slag, fly-ash, sludge and spent catalysts) via oxidative and reductive bioleaching becomes a running trend and a potential alternative to limited metal supply. The motive of this review is to ponder over recycling of secondary waste towards the circular economy to reduce environmental risks as well as to increase the economic profitability of the mining industry. The biochemistry of iron/sulfur minerals, bacteria–mineral interactions and adaptive behavior allowing the acidophiles to survive are among the key parameters to be optimized during the bio recovery of copper. The use of OMICS approaches such as genomics, proteomics, transcriptomics and metabolomics is also crucial to elucidate a comprehensive view of the bioleaching communities, their mechanisms and interactions with minerals. This handy information can act as a boon to develop potential strains by adopting synthetic biology and antiviral CRISPR-Cas9 technologies to efficiently control the bioleaching process. Furthermore, some of these recent discoveries to design bioelectrochemical system (BES) and to achieve higher rate of metal recovery are discussed. Finally, the objective of this study is to narrow the gap between fundamental and applied research to fully address scientific, technological and economic challenges and bottlenecks of bioleaching process in general and BES in particular.
Article
Removal of metals from high pressure acid leaching (HPAL) residue was essential to alleviate potential environmental threat and avoid valuable metals loss. However, cost-effective metals extraction from HPAL residue remains a difficulty. In this study, a hybrid bioleaching process was developed for Co and Cu extraction from HPAL residue of Cu-Co sulfide ores. Results for microbial community structure optimization showed that moderate thermophilum consortium with coexistence of iron oxidizer and sulfur oxidizer was more efficient on metal extraction compared with mesophiles. Further addition of citric acid, Fe (II) and S0 significantly enhanced the release of metals through improving the total biomass, attached cells and community diversity. As a result, 87.91% of cobalt and 58.52% of copper were extracted at initial pH 1.4 and pulp density of 50 g/L by hybrid bioleaching. The hazardous potential assessments revealed that the bioleached residue could be disposed safely. These findings demonstrated that organic acids assisting bioleaching with community adjusting was a promising strategy for metals removal from HPAL residue.
Article
Chalcopyrite bioleaching by 2, 4 and 6 acidophilic strains with the same inoculation density were studied, respectively. The results indicated that the 6-strain community firstly adapted to bioleaching environment, dissolved the chalcopyrite rapidly and maintained an efficient work until late stage. Transcriptome profiles of the 6-strain community at 6th and 30th day during bioleaching process were investigated by RNA-seq. Comparative transcriptomics identified 226 and 737 significantly up-regulated genes at early and late stage, respectively. Gene annotation results revealed that microorganisms adapted to the oligotrophic environment by enhancing cell proliferation, catalytic activation and binding action to maintain their life activities at early stage, and genes related to signal transduction, localization and transporter were highly expressed as an effective response to the stressful late stage. A graphical representation was presented to show how microorganisms adapted and resisted to the extreme environment by their inner functional properties and promoted the bioleaching efficiency.
Article
This mini-review article summarizes the available technologies for the recycling of heavy metals (HMs) in municipal solid waste incineration (MSWI) fly ash (FA). Recovery technologies included thermal separation (TS), chemical extraction (CE), bioleaching, and electrochemical processes. The reaction conditions of various methods, the efficiency of recovering HMs from MSWI FA and the difficulties and solutions in the process of technical development were studied. Evaluation of each process has also been done to determine the best HM recycling method and future challenges. Results showed that while bioleaching had minimal environmental impact, the process was time-consuming. TS and CE were the most mature technologies, but the former process was not cost-effective. Overall, it has the greatest economic potential to recover metals by CE with scrubber liquid produced by a wet air pollution control system. An electrochemical process or solvent extraction could then be applied to recover HMs from the enriched leachate. Ongoing development of TS and bioleaching technologies could reduce the treatment cost or time.
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ABSTRACT The by-products of zinc refineries are used as the primary mineral resources for the commercial production of indium. The discarded LCDs containing adequate amount of indium is rather worth as its secondary resources compared to the by-products of zinc refineries. Mining and recycling rates of indium, respectively from minerals and waste LCDs are in progress to meet its huge demand. Recycling of the LCDs has been dominating over mining, as presently 480t of indium are produced annually from mining, however, that of 650t annually from recycling. Different aspects of the extractive metallurgy of indium are summarized in this review paper. KEYWORDS: Indium, pyrometallurgy, hydrometallurgy, biometallurgy, recycling, recovery https://www.tandfonline.com/eprint/hF4dWP3eMjyeq7trE9zV/full
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AbstractSpent Zn-Mn button cells are one of the fastest-growing battery waste streams containing considerable amounts of Zn (12-28% (w/w)) and Mn (26-45% (w/w)) that could be considered as a potential industrially demanded source of Mn and Zn. However, due to the very toxic, stable, and refractory nature of the button cell batteries, applying microbial leaching for metal extraction from spent batteries is limited. In this regard, this study focused on detoxicate, enriching, and mobilizing major elements through thermal treatment assisted by acidic bioleaching. It was witnessed after thermal pretreatment of BCBs powder at 600 oC, the A. ferrooxidans could tolerate up to 20 g/L BCBs containing a high concentration of Mn and Zn by serial step-wise adaptation process. The use of thermal pretreatment increased by 76% and 75% extraction yields of Mn and Zn compared with the results obtained using un-thermally pretreated BCBs powder. The result indicated that 95% of zinc and 91% manganese were efficiently extracted from thermally pretreated BCBs. A. ferrooxidans and Fe3+ play an important role to improve Mn and Zn extraction efficiency. The structural and morphological analyses showed that the proposed approach could successfully overcome spent button cell batteries complexities and extract most of the major metals.
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Metal leachability from ash and combustion slag is related to the physico-chemical properties, including their speciation in the waste. Metals speciation is an important factor that influences the efficiency of metal bioleaching from combustion wastes in a mixed culture of acidophilic and biosurfactant-producing bacteria. It was observed that individual metals tended to occur in different fractions, which reflects their susceptibility to bioleaching. Cr and Ni were readily removed from wastes when present with a high fraction bound to carbonates. Cd and Pb where not effectively bioleached when present in high amounts in a fraction bound to organic matter. The best bioleaching results were obtained for power plant slag, which had a high metal content in the exchangeable, bound to carbonates and bound to Fe and Mg oxides fractions- the metal recovery percentage for Zn, Cu and Ni from this waste exceeded 90%. Copyright © 2015 Elsevier B.V. All rights reserved.
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Gene transcription (microarrays) and protein levels (proteomics) were compared in cultures of the acidophilic chemolithotroph Acidithiobacillus ferrooxidans grown on elemental sulfur as the electron donor under aerobic and anaerobic conditions, using either molecular oxygen or ferric iron as the electron acceptor, respectively. No evidence supporting the role of either tetrathionate hydrolase or arsenic reductase in mediating the transfer of electrons to ferric iron (as suggested by previous studies) was obtained. In addition, no novel ferric iron reductase was identified. However, data suggested that sulfur was disproportionated under anaerobic conditions, forming hydrogen sulfide via sulfur reductase and sulfate via heterodisulfide reductase and ATP sulfurylase. Supporting physiological evidence for H2S production came from the observation that soluble Cu2+ included in anaerobically incubated cultures was precipitated (seemingly as CuS). Since H2S reduces ferric iron to ferrous in acidic medium, its production under anaerobic conditions indicates that anaerobic iron reduction is mediated, at least in part, by an indirect mechanism. Evidence was obtained for an alternative model implicating the transfer of electrons from S0 to Fe3+ via a respiratory chain that includes a bc1 complex and a cytochrome c. Central carbon pathways were upregulated under aerobic conditions, correlating with higher growth rates, while many Calvin-Benson-Bassham cycle components were upregulated during anaerobic growth, probably as a result of more limited access to carbon dioxide. These results are important for understanding the role of A. ferrooxidans in environmental biogeochemical metal cycling and in industrial bioleaching operations.
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The acid-insoluble metal sulfides FeS2, MoS2, and WS2 are chemically attacked by iron(III) hexahydrate ions, generating thiosulfate, which is oxidized to sulfuric acid. Other metal sulfides are attacked by iron(III) ions and by protons, resulting in the formation of elemental sulfur via intermediary polysulfides. Sulfur is biooxidized to sulfuric acid. This explains leaching of metal sulfides by Thiobacillus thiooxidans.
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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.
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The pyrite ashes formed as waste material during the calcination of concentrated pyrite ore used for producing sulphuric acid not only has a high iron content but also contains economically valuable metals. These wastes, which are currently landfilled or dumped into the sea, cause serious land and environmental pollution problems owing to the release of acids and toxic substances. In this study, physical (sulphation roasting) and hydrometallurgical methods were evaluated for their efficacy to recover non-iron metals with a high content in the pyrite ashes and to prevent pollution thereby. The preliminary enrichment tests performed via sulphation roasting were conducted at different roasting temperatures and with different acid amounts. The leaching tests investigated the impact of the variables, including different solvents, acid concentrations and leach temperatures on the copper and cobalt leaching efficiency. The experimental studies indicated that the pre-enrichment via sulphation roasting method has an effect on the leaching efficiencies of copper and cobalt, and that approximate recoveries of 80% copper and 70% cobalt were achieved in the H2O2-added H2SO4 leaching tests.
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Dumping of poor but metal containing industrial waste is associated with several environmental issues. Exposure of these wastes to the natural environment offers serious concerns for the mineral processing industries to utilize them for metal recovery and check environmental pollution. In the present study, a novel sequential bioreduction-bioleaching and bioreduction-chemical leaching route as a hybrid process is compared and discussed for the enhanced recovery of copper from an industrial concentrator plant ball milling unit rejected sample. A mixed consortium of metal reducing bacteria (DMRB) initially adapted to high Fe(III) concentrations was found to cause mineralogical/matrix alteration (possibly silicate weathering) including Fe(III) bioreduction in the sample and dissolute 29.73% copper during the first 35 days under facultative anaerobic conditions. Sequential leaching of the bioreduced waste sample (generated from the first step) using a mixed meso-acidophilic bacterial consortium predominantly Acidithiobacillus ferrooxidans showed additional 28.72% copper dissolution within 2 days using 1 gL- 1 Fe(II). On the other hand, a comparative chemical leaching of the same bioreduced sample using 0.5 M H2SO4 yielded additional 32.17% copper within 4 days of leaching and indicated better performance than the bioleaching tests.
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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.
Article
Bioleaching of spent batteries was often conducted at pulp density of 1.0% or lower. In this work, metallic ions catalytic bioleaching was used for release Zn and Mn from spent ZMBs at 10% of pulp density. The results showed only Cu(2+) improved mobilization of Zn and Mn from the spent batteries among tested four metallic ions. When Cu(2+) content increased from 0 to 0.8g/L, the maximum release efficiency elevated from 47.7% to 62.5% for Zn and from 30.9% to 62.4% for Mn, respectively. The Cu(2+) catalysis boosted bioleaching of resistant hetaerolite through forming a possible intermediate CuMn2O4 which was subject to be attacked by Fe(3+) based on a cycle of Fe(3+)/Fe(2+). However, poor growth of cells, formation of KFe3(SO4)2(OH)6 and its possible blockage between cells and energy matters destroyed the cycle of Fe(3+)/Fe(2+), stopping bioleaching of hetaerolite. The chemical reaction controlled model fitted best for describing Cu(2+) catalytic bioleaching of spent ZMBs. Copyright © 2015. Published by Elsevier B.V.
Article
Coal collected from Meghalaya state situated in northeastern (NE) region of India contains about 6.17% total sulphur (4.7% organic) with a gross calorific value of 26,208 J/g. In the present study, the coal sample was subjected to biodesulphurization along with optimization of various process parameters using a bacteria isolated from the native coal mine site. The native bacterium was identified to be Sinomonas flava 1C and reported first time for the capability to remove about 40% of sulphur from the coal. An innovative two-step sequential leaching using S. flava 1C followed by Acidithiobacillus ferrooxidans was used in the present study to enhance desulphurization. Sequential leaching resulted in 50-53% of sulphur removal from the coal sample. Sequential leaching reduced the sulphur content to 3.08% (organic 2.15% + pyritic 0.1% and 0.85% of sulphate sulphur) in -500+300 mu m size fraction of coal. Analytical characterization indicated that the energy value of coal was not affected adversely due to the biodesulphurization process rather its calorific value increased from 26,208 J/g to 29,481 J/g.
Article
The nickeliferous Chromite overburden (COB) awaits a suitable technology to extract the obstinate nickel ingrained in its goethite matrix. In the present study, a novel Bio-Reduction Acid Leaching (BRAL) approach has been proposed using dissimilatory iron reducing bacteria (DIRB) which is inherently capable of transforming iron mineral phases via bio-reduction (BR). Mineralogical characterization of the bio-reduced COB using XRD and FTIR confirmed the phase transformation of goethite to hematite and magnetite with exposure of the nickel oxide peaks. Further, morphological characterization using FESEM vividly highlighted the changes of acicular goethite to granular magnetite deposits on the extra polymeric substance (a scaffold for electron transfer) secreted by the DIRB consortium over the surface of COB. Further, enhanced nickel extraction was achieved with a reductive acid leaching (AL) approach with 6 N sulphuric acid and 2% glucose (reducing agent) at 65 °C for 6 h. A cumulative of 83.6% nickel was achieved through this BRAL approach. The pregnant leach solution (PLS) generated as a result of the AL approach was subjected to the hydrometallurgical route to recover metallic nickel. Solvent extraction (SX) of the PLS was performed using 0.5 M NaD2EHPA as extractant. The pregnant nickel-loaded electrolyte was subjected to electrowinning (EW) to recover metallic nickel of 99.6% purity. The process flow-sheet is believed to provide a suitable eco-friendly, potential method to efficiently extract nickel from low grade nickel laterites to meet the ever growing demands caused by depletion of high grade nickel sulphidic ores. Keywords Dissimilatory iron reducing bacteria; Acid leaching; Solvent extraction; Electrowinning; Nickel; Flowsheet
Article
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.
Article
Bioleaching studies for chalcopyrite contained ball mill spillages are very scarce in the literature. We developed a process flow sheet for the recovery of copper metal from surface activated (600 A degrees C, 15 min) ball mill spillage through bio-hydrometallurgical processing route. Bioleaching of the activated sample using a mixed meso-acidophilic bacterial consortium predominantly A. ferrooxidans strains was found to be effective at a lixiviant flow rate of 1.5 L/h, enabling a maximum 72.36% copper recovery in 20 days. Mineralogical as well as morphological changes over the sample surface were seen to trigger the bioleaching efficiency of meso-acidophiles, thereby contributing towards an enhanced copper recovery from the ball mill spillage. The bio-leach liquor containing 1.84 g/L Cu was purified through solvent extraction using LIX 84I in kerosene prior to the recovery of copper metal by electrowinning. Purity of the copper produced through this process was 99.99%.
Article
Heap bioleaching of low grade chalcopyrite (CuFeS2) was carried out in 1000 tons scale over a time period of 383 days. Bacterial solution was prepared and re‐circulated in specially designed BACFOX (BACterial Film OXidation) tank. The micro‐organisms used in the pilot scale were a mixed culture of acidophilic bacteria predominantly of the Acidithiobacillus ferrooxidans strain. Effect of rest period, solution recirculation, acid concentration, frequency of solution transfers and seasonal effects on copper recoveryweremonitored. The leaching studies showed a cumulative copper dissolution rate of 0.14% per day (2.37 kg d−1). The overall recovery of the heapwas 30%. Variation in leaching efficiency and some of the precautionary measures to improve performance of heap bioleaching are also discussed.
Article
In Turkey, pyrite, copper melting gases and sulfur are used as a raw material in sulfuric acid production. Pyrite ashes are obtained as a result of the sulfuric acid production process during the roasting of pyrite ores. These wastes are generally landfilled or dumped into the sea.Pyrite ash wastes can be utilized as a raw material in the production of iron ore, and thus environmental pollution can be avoided; however, these wastes need to achieve certain physical and chemical properties before they are used. Pyrite ashes are agglomerated into pellets to allow them acquire the required properties for use as iron ore in a blast furnace.The essential parameters affecting the pelletization of pyrite ashes are studied using bentonite as a binder. The metallurgical properties of pyrite ash, bentonite, a mixture of pyrite ash and bentonite, and sintered pellets are studied using X-ray analyses. Wet-drop, wet-crush, dry-crush and sintered-crush tests are carried out to investigate the strength of the pyrite ash wastes pellets prepared from feeds with different sieve size and bentonite content. The results of this analysis demonstrate that pyrite ashes can be agglomerated into pellets and used as feed for the blast furnace in the iron production industry.
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
Article
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.
Article
Zn(II) and Pb(II) from Nigerian sphalerite and galena ores were bioleached by a mixed culture of acidophilic bacteria. The influences of pH and ferric ion on the bioleaching rates of sphalerite and galena were examined. The result shows that pH 2.1 and 2.7 are favourable for the leaching of Zn(II) and Pb(II) from sphalerite and galena, respectively. It was observed that the use of agarose-simulated media caused cells to excrete exopolymers containing ferric ions which enhanced oxidation. The oxidation equilibrium for sphalerite and galena took 3 and 4 d, respectively. About 38.3% sphalerite and 34.2% galena were leached within 1 d and approximately 92.0% Zn(II) and 89.0% Pb(II) were recovered in 5 d, respectively. The unleached residual products were examined by X-ray diffraction for sphalerite, revealing the presence of elemental sulphur(S), zinc sulphate (ZnSO4) and few traces of calcium aluminate (Ca3Al2O6). The XRD pattern also indicates the presence of elemental sulphur (S), lead sulphate (PbSO4) and few traces of itoite [Pb(S,Ge)(O,OH)4] and cobalt lead silicate [Pb8Co(Si2O7)3] in the unleached galena ore.
Article
Low grade copper ore (ball mill spillage) obtained from Malanjkhand Copper Mine was processed through heap bioleaching at pilot scale. Bioleach liquor (Pregnant Leach Solution) from the heap contains (g/L of) Cu (II) 0.45, Fe (III) 0.838, Zn (II) 0.006, Ni (II) 0.0014, Mn (II) 0.011 and Pb (IV) 0.004. Solvent extraction of copper from Pregnant Leach Solution was carried out using LIX 984N-C. Effect of different operational factors such as equilibrium pH (pHe), extractant concentration, strip solution concentration, phase ratio was examined to optimize the condition for selective and quantitative extraction of copper. Based on the results of extraction as well as stripping isotherm, a 6-cycle counter current simulation study (CCS) was conducted for the conformational study. The extraction of copper was quantitative in 2-stages using 1.5% (v/v) LIX 984N-C at A: O ratio of 1:2 and pHe 1.85. The CCS condition (two stages, phase ratio A:O = 1:4) obtained from the stripping isotherm study, further attributes to the enrichment (4 folds) of copper concentration in the strip solution.
Article
The kinetics of oxidation of aqueous acidic ferrous sulphate by Thiobacillus ferrooxidans has been studied in a batch reactor. The contribution of cell wall envelopes to the oxidation rate has been shown to be negligible. A model which accounts for the oxidation of Fe2 +, death of bacteria due to Fe3 + poisoning, existence of an optimal pH and precipitation of Fe3 + has been proposed. The model is able to predict the concentration of Fe2 + and pH quite satisfactorily. The predictions of Fe3 + are not so accurate because of simplifying assumptions made about its precipitation.
Article
The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials.
Article
Bioleaching of metal sulfides is effected by bacteria, like Thiobacillus ferrooxidans, Leptospirillum ferrooxidans, Sulfolobus/Acidianus, etc., via the (re)generation of iron(III) ions and sulfuric acid.According to the new integral model for bioleaching presented here, metal sulfides are degraded by a chemical attack of iron(III) ions and/or protons on the crystal lattice. The primary iron(III) ions are supplied by the bacterial extracellular polymeric substances, where they are complexed to glucuronic acid residues. The mechanism and chemistry of the degradation is determined by the mineral structure.The disulfides pyrite (FeS2), molybdenite (MoS2), and tungstenite (WS2) are degraded via the main intermediate thiosulfate. Exclusively iron(III) ions are the oxidizing agents for the dissolution. Thiosulfate is, consequently, degraded in a cyclic process to sulfate, with elemental sulfur being a side product. This explains, why only iron(II) ion-oxidizing bacteria are able to oxidize these metal sulfides.The metal sulfides galena (PbS), sphalerite (ZnS), chalcopyrite (CuFeS2), hauerite (MnS2), orpiment (As2S3), and realgar (As4S4) are degradable by iron(III) ion and proton attack. Consequently, the main intermediates are polysulfides and elemental sulfur (thiosulfate is only a by-product of further degradation steps). The dissolution proceeds via a H2S*+-radical and polysulfides to elemental sulfur. Thus, these metal sulfides are degradable by all bacteria able to oxidize sulfur compounds (like T. thiooxidans, etc.). The kinetics of these processes are dependent on the concentration of the iron(III) ions and, in the latter case, on the solubility product of the metal sulfide.
Article
A copper-catalyzed bioleaching process was developed to recycle cobalt from spent lithium-ion batteries (mainly LiCoO(2)) in this paper. The influence of copper ions on bioleaching of LiCoO(2) by Acidithiobacillus ferrooxidans (A.f) was investigated. It was shown that almost all cobalt (99.9%) went into solution after being bioleached for 6 days in the presence of 0.75 g/L copper ions, while only 43.1% of cobalt dissolution was obtained after 10 days without copper ions. EDX, XRD and SEM analyses additionally confirmed that the cobalt dissolution from spent lithium-ion batteries could be improved in the presence of copper ions. The catalytic mechanism was investigated to explain the enhancement of cobalt dissolution by copper ions, in which LiCoO(2) underwent a cationic interchange reaction with copper ions to form CuCo(2)O(4) on the surface of the sample, which could be easily dissolved by Fe(3+).
Article
This minireview presents recent advances in our understanding of iron oxidation and homeostasis in acidophilic Bacteria and Archaea. These processes influence the flux of metals and nutrients in pristine and man-made acidic environments such as acid mine drainage and industrial bioleaching operations. Acidophiles are also being studied to understand life in extreme conditions and their role in the generation of biomarkers used in the search for evidence of existing or past extra-terrestrial life. Iron oxidation in acidophiles is best understood in the model organism Acidithiobacillus ferrooxidans. However, recent functional genomic analysis of acidophiles is leading to a deeper appreciation of the diversity of acidophilic iron-oxidizing pathways. Although it is too early to paint a detailed picture of the role played by lateral gene transfer in the evolution of iron oxidation, emerging evidence tends to support the view that iron oxidation arose independently more than once in evolution. Acidic environments are generally rich in soluble iron and extreme acidophiles (e.g. the Leptospirillum genus) have considerably fewer iron uptake systems compared with neutrophiles. However, some acidophiles have been shown to grow as high as pH 6 and, in the case of the Acidithiobacillus genus, to have multiple iron uptake systems. This could be an adaption allowing them to respond to different iron concentrations via the use of a multiplicity of different siderophores. Both Leptospirillum spp. and Acidithiobacillus spp. are predicted to synthesize the acid stable citrate siderophore for Fe(III) uptake. In addition, both groups have predicted receptors for siderophores produced by other microorganisms, suggesting that competition for iron occurs influencing the ecophysiology of acidic environments. Little is known about the genetic regulation of iron oxidation and iron uptake in acidophiles, especially how the use of iron as an energy source is balanced with its need to take up iron for metabolism. It is anticipated that integrated and complex regulatory networks sensing different environmental signals, such as the energy source and/or the redox state of the cell as well as the oxygen availability, are involved.
Article
The sulfur oxidation activities of four pure thermophilic archaea Acidianus brierleyi (JCM 8954), Metallosphaera sedula (YN 23), Acidianus manzaensis (YN 25) and Sulfolobus metallicus (YN 24) and their mixture in bioleaching chalcopyrite were compared. Meanwhile, the relevant surface sulfur speciation of chalcopyrite leached with the mixed thermophilic archaea was investigated. The results showed that the mixed culture, with contributing significantly to the raising of leaching rate and accelerating the formation of leaching products, may have a higher sulfur oxidation activity than the pure cultures, and jarosite was the main passivation component hindering the dissolution of chalcopyrite, while elemental sulfur seemed to have no influence on the dissolution of chalcopyrite. In addition, the present results supported the former speculation, i.e., covellite might be converted from chalcocite during the leaching experiments, and the elemental sulfur may partially be the derivation of covellite and chalcocite.
Article
The objectives of this study were to evaluate the solubility of copper in waste printed circuit boards (PCBs) by bacterial consortium enriched from natural acid mine drainage, and to determine optimum conditions of bioleaching copper from PCBs. The results indicated that the extraction of copper was mainly accomplished indirectly through oxidation by ferric ions generated from ferrous ion oxidation bacteria. The initial pH and Fe(2+) concentration played an important role in copper extraction and precipitate formation. The leaching rate of copper was generally higher at lower PCB powder dosage. Moreover, a two-step process was extremely necessary for bacterial growth and obtaining an appropriate Fe(2+) oxidation rate; a suitable time when 6.25 g/L of Fe(2+) remained in the solution was suggested for adding PCB powder. The maximum leaching rate of copper was achieved 95% after 5 days under the conditions of initial pH 1.5, 9 g/L of initial Fe(2+), and 20 g/L of PCB powder. All findings demonstrated that copper could be efficiently solubilized from waste PCBs by using bacterial consortium, and the leaching period was shortened remarkably from about 12 days to 5 days.
Article
The Sotiel-Coronada abandoned mining district (Iberian Pyrite Belt) produced complex massive sulphide ores which were processed by flotation to obtain Cu, Zn and Pb concentrates. The crude pyrite refuses were roasted for sulphuric acid production in a plant located close to the flotation site, and waste stored in a tailing dam. The present study was focused on the measurements of flow properties, chemical characterization and mineralogical determination of the roasted pyrite refuses with the aim of assessing the potential environmental impact in case of dam collapse. Chemical studies include the determination of the total contaminant content and information about their bio-availability or mobility using sequential extraction techniques. In the hypothetical case of the tailing dam breaking up and waste spilling (ca. 4.54Mt), a high density mud flow would flood the Odiel river valley and reach both Estuary of Huelva (Biosphere Reserve by UNESCO, 1983) and Atlantic Ocean in matter of a couple of days, as it was predicted by numerical simulations of dam-break waves propagation through the river valley based on quasi-2D Saint-Venant equations. The total amount of mobile pollutants that would be released into the surrounding environment is approximately of 7.1.10(4)t of S, 1.6.10(4)t of Fe, 1.4.10(4)t of As, 1.2.10(4)t of Zn, 1.0.10(4)t of Pb, 7.4.10(3)t of Mn, 2.2.10(3)t of Cu, 1.5.10(2)t of Co, 36t of Cd and 17t of Ni. Around 90-100% of S, Zn, Co and Ni, 60-70% of Mn and Cd, 30-40% of Fe and Cu, and 5% of As and Pb of the mobile fraction would be easily in the most labile fraction (water-soluble pollutants), and therefore, the most dangerous and bio-available for the environment. This gives an idea of the extreme potential risk of roasted pyrite ashes to the environment, until now little-described in the scientific literature.
Article
In Turkey, pyrite ash is created as waste from the roasting of pyrite ores in the production of sulfuric acid. These processes generate great amounts of pyrite ash waste that creates serious environmental pollution due to the release of acids and toxic substances. Pyrite ash waste can be used in the iron production industry as a raw material because of its high Fe(2)O(3) concentration. The aim of this study was to investigate the reduction behaviour of pyrite ash pellets. The pyrite ashes were reduced to obtain the iron contained in pellets. Pyrite ashes samples were pelletized dried at 105 degrees C for 24 h and sintered at 1200 degrees C for 30 min. then reduced in a pressure of 4 atm. under argon gas. The mineralogical transformations that occurred during reduction were analysed by X-ray diffraction and X-ray fluorescence. The X-ray diffraction and X-ray fluorescence measurements of these samples showed that Fe(3)O(4) was successfully reduced to a metallic iron phase in a laboratory-scale electric arc furnace.
Article
Microorganisms that have a pH optimum for growth of less than pH 3 are termed "acidophiles". To grow at low pH, acidophiles must maintain a pH gradient of several pH units across the cellular membrane while producing ATP by the influx of protons through the F(0)F(1) ATPase. Recent advances in the biochemical analysis of acidophiles coupled to sequencing of several genomes have shed new insights into acidophile pH homeostatic mechanisms. Acidophiles seem to share distinctive structural and functional characteristics including a reversed membrane potential, highly impermeable cell membranes and a predominance of secondary transporters. Also, once protons enter the cytoplasm, methods are required to alleviate effects of a lowered internal pH. This review highlights recent insights regarding how acidophiles are able to survive and grow in these extreme conditions.
Article
Bioleaching of metals from hazardous spent hydro-processing catalysts was attempted in the second stage after growing the bacteria with sulfur in the first stage. The first stage involved transformation of elemental sulfur particles to sulfuric acid through an oxidation process by acidophilic bacteria. In the second stage, the acidic medium was utilized for the leaching process. Nickel, vanadium and molybdenum contained within spent catalyst were leached from the solid materials to liquid medium by the action of sulfuric acid that was produced by acidophilic leaching bacteria. Experiments were conducted varying the reaction time, amount of spent catalysts, amount of elemental sulfur and temperature. At 50 g/L spent catalyst concentration and 20 g/L elemental sulfur, 88.3% Ni, 46.3% Mo, and 94.8% V were recovered after 7 days. Chemical leaching with commercial sulfuric acid of the similar amount that produced by bacteria was compared. Thermodynamic parameters were calculated and the nature of reaction was found to be exothermic. Leaching kinetics of the metals was represented by different reaction kinetic equations, however, only diffusion controlled model showed the best correlation here. During the whole process Mo showed low dissolution because of substantiate precipitation with leach residues as MoO3. Bioleach residues were characterized by EDX and XRD.
Article
Spent Ni-Cd batteries bring a severe environmental problem that needs to be solved urgently. A novel continuous flow two-step leaching system based on bioleaching was introduced to dissolve heavy metals in batteries. It consists of an acidifying reactor which was used to culture indigenous thiobacilli and a leaching reactor which was used to leach metals from spent batteries. The indigenous acidophilic thiobacilli in sewage sludge was used as the microorganisms and the sludge itself as culture medium. Bioleaching tests at different hydraulic retention time (HRT) and process load in the leaching reactor were performed. The results showed that the longer the HRT (1, 3, 6, 9 and 15 days) was, the more time required to achieve the complete leaching of Ni, Cd and Co. The maximum dissolution of cadmium and cobalt was achieved at higher pH values (3.0-4.5) while the leaching of nickel hydroxide and nickel in metallic form (Ni0) were obtained separately in different acidity (pH 2.5-3.5). It cost about 25, 30 and more than 40 days to remove all of the three heavy metals with the process load of two, four and eight Ni-Cd batteries under the conditions that the ingoing bio-sulphuric acid was 1Ld(-1) and HRT was 3 days.
II) from Nigerian Sphalerite and Galena ores by a mixed culture of acidophilic bacteria
  • Pb
Pb(II) from Nigerian Sphalerite and Galena ores by a mixed culture of acidophilic bacteria, Trans. Non-ferrous Met. Soc. China 21 (2011) 2535-2541.
Insights into heap bioleaching of low grade chalcopyrite ores: A pilot scale study
  • S Panda
  • K Sanjay
  • L B Sukla
  • N Pradhan
  • T Subbaiah
  • B K Mishra
  • M S R Prasad
  • S K Ray
S. Panda, K. Sanjay, L.B. Sukla, N. Pradhan, T. Subbaiah, B.K. Mishra, M.S.R. Prasad, S.K. Ray, Insights into heap bioleaching of low grade chalcopyrite ores: A pilot scale study, Hydrometallurgy 125-126 (2012) 157-165.
  • W Sand
  • T Gehrke
  • P G Jozsa
  • A Schippers
W. Sand, T. Gehrke, P.G. Jozsa, A. Schippers, Biochemistry of bacterial leachingdirect vs. indirect bioleaching, Hydrometallurgy 59 (2001) 159-175.