Direct and Indirect Bioleaching of Cobalt from Low Grade Laterite and Pyritic Ores by Aspergillus niger

Abstract

The bioleaching efficiency and mechanism of recovery of cobalt (Co) and nickel from laterites and pyritic ores by Aspergillus niger were investigated. Recoveries of Co from laterites and pyritic ores by direct bioleaching were 65.9?±?1.8% and 4.9?±?2.7%, respectively, while 30.9?±?0.6% and 10.9?±?6.2% recovery of Ni were obtained from laterites and pyritic ores, respectively. Recovery of Co via indirect bioleaching in the absence of the fungal biomass from laterite was significantly lower when compared with Co released by direct bioleaching. In the latter, hyphal penetration and colonization of the laterites were clearly observed by scanning electron microscopy (SEM). X-ray powder diffraction (XRPD) analysis of mineral phases before and after bioleaching indicated that cobalt-bearing goethite was the main phase bioleached in the laterites. No significant difference was found between Co recoveries from synthesized cobalt-bearing goethite by both direct and indirect bioleaching. Therefore, we propose that two processes are involved in bioleaching from laterites: (1) cobalt-bearing goethite was exposed via direct interactions between the fungus and the minerals and (2) cobalt-bearing goethite was dissolved by released metabolites of A. niger, such as organic acids. An incongruent pattern of Co and Fe bioleaching from the laterites was also a feature of the metal recovery process.     

Bioleaching and bioprecipitation of nickel and iron from laterites

Abstract: Leaching of silicate ores, particularly nickel laterites, with the aid of heterotrophic organisms has been briefly reviewed. Samples of laterite ores from Greece were characterised mineralogically and a number of microorganisms isolated from them. One of these organisms (code FI) was successfully acclimatized to 6400 ppm nickel. Samples of the high-grade Greek Kastoria nickel laterite were leached with sulphuric acid and a number of organic acids. Sulphuric and citric acids extracted over 60 and 40% of the contained nickel, respectively, but the other acids employed were less efficient leachants. Oxalic acid precipitated nickel oxalate. Roughly the same extraction of iron was observed. The main leaching parameter was confirmed to be hydrogen ion concentration, although complexation with organic anions was a contributor. Organism FI (a strain of Penicillium ) was used in comparison with organisms from various culture collections to bioleach nickel from samples of the low-grade Greek Litharakia nickel laterite. The organisms were cultivated in a mixture of a sugar-based nutrient mineral medium and finely ground ore. Several penicillia and aspergilli leached 55–60% of the contained nickel and cobalt, and 25–35% of the iron when sucrose was the carbon source, but FI was not efficient. However, in molasses medium, Fl extracted nearly 40% of the nickel. Biosorption and bioprecipitation reactions were observed. The mechanism of bioleaching or in situ leaching is discussed in terms of close physical and chemical association between the fungal hyphae and mineral phases in the ore. This accounted for the low overall hydrogen ion concentration observed during bioleaching.     

Mineral leaching of non-sulphide nickel ores using heterotrophic micro-organisms

Laboratory studies were conducted on microbial leaching of non-sulphide nickel ores not amenable to conventional mineral processing operations. The results showed that extensive low-grade laterite domestic sources are generally amenable to bioleaching when micro-organisms were cultivated in the presence of the ore. Nickel recoveries were as high as 60% using hydroxycarboxylic acid producing strains of Aspergillus and Penicillium codes A3, P2. Cobalt recovery achieved was around 50%. Losses of soluble nickel in the fungal biomass were found to be 3.5–10.8%. Chemical analysis of the leach liquors showed the presence of significant amounts of citric, oxalic and other organic acids, indicating that leaching may be ascribed to the production of these metabolic products of fungal activity.     

Bioleaching of copper from chalcopyrite ore by fungi

Microorganisms have been geologically active in mineral formation, mineral diagenesis and sedimentation via direct action of their enzymes or indirectly through chemical action of their metabolic products. This property of microorganisms is being harnessed during the recent years for extraction of metals from their ores, especially from low-grade ores. In the present study bioleaching of copper from its low-grade chalcopyrite ore using 26 isolates of acidophilic fungi is reported. Most of these fungal strains belonged to the genera Aspergillus, Penicillium and Rhizopus. The leaching experiments were conducted in Czepek Dox minimal medium containing 1% (100 mesh) ore with shaking at room temperature for 20 days. Out of these, 4 isolates exhibited significant bioleaching activities. Maximum leaching of copper (78 mg/L) was observed with Aspergillus flavus (DSF-8) and Aspergillus niger (DOF-1). Nutritional and environmental conditions for optimum bioleaching were standardized. Present study indicates the usefulness of acidophilic fungi in bioleaching of copper from its low-grade ores.     

Characterization and bioleaching of nickel laterite ore using Bacillus subtilis strain

There are two principal types of nickel (Ni) deposits: sulfide and laterite ores. Interest in low-grade Ni-laterite ores has increased in recent years as high-grade Ni-sulfide deposits are being quickly depleted. However, processing of Ni laterites has proven technically difficult and costly, and the development of alternative low-cost biotechnologies for Ni solubilization has been encouraged. In this context, by the first time, a sample of Brazilian Ni-laterite ore was analyzed mineralogically and subjected to bioleaching tests using a heterotrophic Bacillus subtilis strain. SEM-analysis indicated that the primary Ni carrier mineral is goethite. Chemical analysis of different grain size fractions indicated a homogeneous distribution of Ni. XRF-analysis showed that the ore consists mainly in lizardite (32.6% MgO) and contains1.0% NiO (0.85% Ni). Bioleaching batch experiments demonstrated that about 8.1% Ni (0.7 mg Ni/g ore) were solubilized by the B. subtilis after 7 days. Application of microwave heating as a Ni-laterite pretreatment was also tested. This pretreatment increased the bioextraction of Ni from 8% to 26% (2.3 mg Ni g⁻¹ ore).     

Bioleaching of cobalt from smelter wastes byThiobacillus ferrooxidans

Summary The bioleaching of cobalt from domestic, industrial smelter wastes was studied.Thiobacillus ferrooxidans solubilized Co from sulfidic dross furnace mattes. At pulp densities of 4% (w/v) up to 600 mg of Co per liter of leaching solution was released from nickel matte, corresponding to removal of about two-thirds of the original amount of Co in the matte. Bioleaching methods may be useful as a component of a process for solubilization and recovery of Co from sulfidic smelter mattes.     

Enhancing Manganese Recovery from Low-Grade Ores by Using Mixed Culture of Indigenously Isolated Bacterial Strains

Conventional leaching methods for manganese (Mn) recovery require strong acids and are threatening to the environment. Alternatively, the use of microbes for Mn recovery is environment friendly in nature. The present investigation compares the capacity of pure and mixed cultures of native bacterial strains for bioleaching of low-grade Mn ores. The ability of the isolated microorganisms to recover Mn was evaluated in shake flasks for 20 days under optimized conditions of pulp density (2%), sucrose concentration (2 g/100 mL), initial pH 6.5, and 30°C incubation temperature. In pure culture form, Acinetobacter sp. MSB 5 (70%) was found to have a higher bioleaching potential than Lysinibacillus sp. MSB 11 (67%). Mixed culture of Acinetobacter sp. MSB 5 and Lysinibacillus sp. MSB 11 was found to perform better than the pure cultures with 74% extraction of Mn. The presence of mixed culture increased the dissolution rate and the recovery percentage of Mn. The respective growth pattern of the cultures was in synchronization to their Mn bioleaching performances. This study underlines the importance of mixed cultures and Mn solubilizing activity of native bacterial strains for efficient Mn biorecovery.     

Leaching of copper converter slag withAspergillus niger culture filtrate

Leaching of copper converter slag of M/s Hindustan Copper Ltd, Ghatshila (Bihar, India) was carried out usingAspergillus niger culture filtrate. The effects of the duration of leaching, temperature, pulp density and the addition of hydrochloric acid were studied.A. niger culture filtrate solubilized metals from the converter slag at levels of 18.70% copper, 7.40% nickel and 4.00% cobalt. Addition of hydrochloric acid was found to improve copper, nickel and cobalt solubilization to 46.52, 27.90 and 37.96%, respectively. HPLC analysis of the fungal culture filtrate revealed the presence of succinic and citric acids. Therefore, leaching of the slag was also carried out with matching concentrations of these organic acids individually as well as with both mixed together. Results are discussed.     

Bioleaching of nickel from equilibrium fluid catalytic cracking catalysts

Summary This study investigates the possibility of reusing metal-contaminated equilibrium fluid catalytic cracking (FCC) catalyst after bioleaching. Leaching with Aspergillus niger culture was found to be more effective in the mobilization of nickel from the catalyst particles compared to chemical leaching with citric acid. Bioleaching achieved 32% nickel removal whereas chemical leaching achieved only 21% nickel removal from catalyst particles. The enhanced nickel removal from the catalysts in the presence of A. niger culture was attributed to the biosorption ability of the fungal mycelium and to the higher local concentration of citric acid on the catalyst surface. It was found that 9% of solubilized nickel in the liquid medium was biosorbed to fungal biomass. After nickel leaching with A. niger culture, the hydrogen-to-methane molar ratio and coke yield, which are the measures of dehydrogenation reactions catalysed by nickel during cracking reactions, decreased significantly.     

Combined degradation of covellite by Thiobacillus thiooxidans and Thiobacillus ferrooxidans

Summary In the presence of iron, which is always associated with natural sulphide ores, the percentages of copper dissolution in the bioleaching of covellite were 34 and 45 % when Thiobacillus thiooxidans and Thiobacillus ferrooxidans were used together and when an indirect bioleaching with attached bacteria was performed respectively. In the latter, the percentage of copper dissolution was still higher than the percentages obtained with pure cultures (36 % with a T. thiooxidans culture and 40 % with a T. ferrooxidans culture).     

Metals tolerance in moderately thermophilic isolates from a spent copper sulfide heap, closely related to Acidithiobacillus caldus, Acidimicrobium ferrooxidans and Sulfobacillus thermosulfidooxidans

Selective enrichments enabled the recovery of moderately thermophilic isolates with copper bioleaching ability from a spent copper sulfide heap. Phylogenetic and physiological characterization revealed that the isolates were closely related to Sulfobacillus thermosulfidooxidans, Acidithiobacillus caldus and Acidimicrobium ferrooxidans. While isolates exhibited similar physiological characteristics to their corresponding type strains, in general they displayed similar or greater tolerance of high copper, zinc, nickel and cobalt concentrations. Considerable variation was found between species and between several strains related to S. thermosulfidooxidans. It is concluded that adaptation to metals present in the bioleaching heap from which they were isolated contributed to but did not entirely explain high metals tolerances. Higher metals tolerance did not confer stronger bioleaching performance, suggesting that a physical, mineralogical or chemical process is rate limiting for a specific ore or concentrate.     

Progress in bioleaching: part B: applications of microbial processes by the minerals industries

This review presents developments and applications in bioleaching and mineral biooxidation since publication of a previous mini review in 2003 (Olson et al. Appl Microbiol Biotechnol 63:249–257, 2003). There have been discoveries of newly identified acidophilic microorganisms that have unique characteristics for effective bioleaching of sulfidic ores and concentrates. Progress has been made in understanding and developing bioleaching of copper from primary copper sulfide minerals, chalcopyrite, covellite, and enargite. These developments point to low oxidation–reduction potential in concert with thermophilic bacteria and archaea as a potential key to the leaching of these minerals. On the commercial front, heap bioleaching of nickel has been commissioned, and the mineral biooxidation pretreatment of sulfidic-refractory gold concentrates is increasingly used on a global scale to enhance precious metal recovery. New and larger stirred-tank reactors have been constructed since the 2003 review article. One biooxidation–heap process for pretreatment of sulfidic-refractory gold ores was also commercialized. A novel reductive approach to bioleaching nickel laterite minerals has been proposed.     

Metal Leaching and Reductive Dissolution of Iron from Contaminated Soil and Sediment Samples by Indigenous Bacteria and Bacillus Isolates

The purpose of this study was to leach Cu, Zn, As, and Fe from contaminated soil and sediment samples with indigenous heterotrophic bacteria isolated from the study sites. The sediment contained Fe in the form of goethite and low concentrations of other metals. The soil contained hematite and high concentrations of other metals. The environmental conditions affected the bacterial activity in the metals dissolution. As and Fe were the major metals leached from the sediment sample while a minor fraction of Cu was solubilized. Cu and Zn were the major metals leached from the soil sample while only a minor fraction of Fe was dissolved. As a control, a disinfectant was used for partial inactivation of indigenous bacteria. This treatment had a negative effect on the leaching of Fe, Zn and As from soil and sediment samples, but it increased Cu dissolution from the sediment. Bacterial different dissolution of Fe during soil and sediment bioleaching was also investigated with ferrihydrite. The iron concentration was much higher during ferrihydrite dissolution when indigenous bacteria from sediment were used compared to indigenous bacteria isolated from soil. The indigenous bacterial inoculum provided more biological and metabolic diversity which may account for the difference in reductive iron reduction from ferrihydrite. The Bacillus cultures isolated from soil and sediment samples showed similar efficiencies in reductive dissolution of ferrihydrite. The synergetic bacterial inhibition effect created by the environmental conditions can influence bioremediation effect.     

Extraction, isolation and NMR data of the tetraether lipid calditoglycerocaldarchaeol (GDNT) from Sulfolobus metallicus harvested from a bioleaching reactor

The successful extraction and isolation of the hydrolysed tetraether lipid calditoglycerocaldarchaeol (GDNT) from Sulfolobus metallicus, a key thermophilic bioleaching archaeon, is described. The archaeal biomass was recovered directly from a thermophilic (68 degrees C) bioleaching tank reactor used to extract nickel from a pentlandite mineral concentrate. The initial Soxhlet extraction method employed was scaled to a bench-scale extraction procedure suitable for the preparation of gram-scale quantities of GDNT. The GDNT so obtained was analysed by 1D- and 2D-NMR techniques, providing the first complete 13C and 2D-NMR data-set for GDNT, including that for the intact underivatised calditol moiety. The study demonstrates the feasibility of recovering high-quality GNDT from thermophilic archaeal-mediated bioleaching reactors. The recovery of these lipids at relatively low cost, as a by-product from bioleaching reactors used in the metals processing industry, has important implications for future tetraether lipid availability and costs.     

Bacterial Oxidation of Refractory Sulfide Ores for Gold Recovery

Abstract

The microbiological leaching of refractory sulfide ores (pyrite, arsenopyrite) for recovery of gold is reviewed in this article. The underlying physiological, biochemical, and genetic fundamentals of the bacteria involved (Thiobacillus and Sulfolobus spp.) are complex and have yet to be elucidated in depth. The chemistry of acid and biological leaching of pyrite and arsenopyrite minerals is also complex, and many of the individual reactions are not known in detail. Bacterial leaching is discussed in relation to chemical speciation at acid pH values. Attempts to develop models for a better understanding of bioleaching processes are summarized. The importance of pH, redox potential, temperature, sulfur balance, and toxic metals is evaluated for optimizing conditions for bacterial activity. Gold is finely disseminated in refractory sulfide ores, thereby decreasing Au recoveries upon conventional cyanidation for gold dissolution. In the bioleaching process, bacteria remove the sulfide minerals by oxidative dissolution and thus expose Au to extraction with cyanide solution. Stirred tank reactors appear most suited for this biological leaching process. The overall oxidation of the sulfides is an important variable for gold recovery. Pilot- and commercial-scale bioleaching processes for gold-containing pyrite and arsenopyrite ores are reviewed. This application of mineral biotechnology competes favorably with pressure leaching and roasting processes, both of which are problematic and energy-intensive alternatives for pretreatment of auriferous pyrite/arsenopyrite ores.     

Bioleaching of a Spanish uranium ore

Abstract: The bioleaching of a low-grade uranium ore in shaker and columns using natural, pure and mixed cultures has been studied. Initially, a chemical and microscopical characterization of the mineral was carried out. Orbital shaker experiments were performed to quickly obtain the best bacterial leaching conditions. Afterwards, small columns were used to determine other variables related to percolation leaching. Finally, an uranium ore from the F6 mine (Ciudad Rodrigo, Spain) was leached in the presence of bacteria using large columns (24 cm diameter and 275 cm height). The most important results were: (i) the ore contains sufficient pyrite in order for uranium bioleaching to take place under optimum conditions; (ii) shaker experiments showed that temperature, pH and type of inoculum are the most important variables in bioleaching; (iii) two different ores were attacked in the columns: altered and non-altered. In the first case, the extraction rate of uranium was higher. However, in both cases the final efficiency was very similar (95%).     

Arsenic precipitation in the bioleaching of enargite by Sulfolobus BC at 70 °C

Enargite (Cu₃AsS₄) was leached at 70°C by Sulfolobus BC in shake-flasks. The highest copper dissolution (52% after 550 h of leaching) was obtained with bacteria and 1 g l^–1 ferric ion. In the absence of ferric ion, Sulfolobus BC catalyzes the bioleaching of enargite through a direct mechanism after adhesion onto the mineral surface. In ferric bioleaching, arsenic precipitated as ferric arsenate and arsenic remained associated to the solid residues, preventing the presence of a high dissolved arsenic concentration in the leaching solution. About 90% inhibition of bacterial growth rate and activity was observed for dissolved arsenic concentrations above 600 mg l^–1 for As(III) and above 1000 mg l^–1 for As(V). Arsenic-bearing copper ores and concentrates could be leached by Sulfolobus BC in the presence of ferric iron due to the favourable precipitation of arsenic ion as ferric arsenate, avoiding significant bacterial inhibition.     

Laugung lateritischer Nickelerze mit heterotrophen Mikroorganismen

Organic acids that are excreted by microorganisms dissolve nickel from lateritic ores. In chemical leaching experiments, fifteen organic acids were tested in the concentration range of 0.05–0.5 M. The most effective were hydroxycarboxylic acids. The leaching of nickel is dependent on the type of mineralization. With completely limonitized ore, no mobilization occurred, while up to 90% of the nickel was extracted from silicate-bearing laterites by 0.5 M citric acid. In biological leaching tests, Penicillium was found to be the most effective microorganism. After improvement of the leaching conditions, up to 70% of the nickel was extracted at considerably lower citric acid concentrations than with the chemical leaching process. Generally, leaching of nickel from lateritic ores with heterotrophic microorganisms is possible and seems to be promising. Possibilities for future investigations are discussed.     

Evaluation of the Biotechnological Potential of Pure and Mixture of Indigenous Iron-Oxidizing Bacteria to Dissolve Trace Metals from Cu Bearing Ore

Abstract

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. Mössbauer spectroscopy 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.     

Surface alteration of realgar (As4S4) by Acidithiobacillus ferrooxidans

The chemical and physical characteristics of realgar (an arsenic sulfide mineral that occurs in several crystalline forms) in the presence of Acidithiobacillus ferrooxidans BY-3 were investigated in this work. Grains of the mineral were incubated for 10, 20, and 30 days with A. ferrooxidans cultured in 9K medium at 30 °C and at 150 rpm agitation. Abiotic control experiments were conducted in identical solutions. The effect of bioleaching on the surface properties of realgar was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), inductively coupled plasma atomic emission spectroscope (ICP-AES), X-ray diffraction (XRD), and Raman spectroscopy. SEM and EDS analyses confirmed the ability of A. ferrooxidans to modify surfaces of realgar and to efficiently enhance its dissolution. ICP-AES showed the dissolution and precipitation of realgar during bioleaching. Based on the XRD pattern and the Raman spectra, the decrease in arsenic in the liquid phase was due to co-precipitation of the mineral with Fe(III) or Fe(III) compounds (e.g., jarosite or goethite). Thus, not only did Fe(III) alter the surface of realgar, but it also promoted its dissolution during bioleaching.