Column Bioleaching Research Articles

WITHDRAWN: The effect of CO2 on heat generation during column bioleaching of a copper porphyry ore under simulated autothermal conditions

This article has been withdrawn at the request of the author (Jochen Petersen) since the sponsor of the research work has withdrawn permission to publish therefore have to withdraw the paper with immediate effect. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy .

Column bioleaching of low-grade copper ore by Acidithiobacillus ferrooxidans in pure and mixed cultures with a heterotrophic acidophile Acidiphilium sp.

The aim of this investigation was to compare a pure culture of Acidithiobacillus ferrooxidans GF with a mixed culture with Acidiphilium sp. DX1-1 in the bioleaching of low-grade copper ore. The leaching experiments were carried out at ambient temperature. The influence of temperature, pH, redox potential and concentration of total iron and ferric ion in solution on the performance of column bioleaching was also investigated. Total DNA was extracted from the mineral samples taken at different depths from the column top surface, and the corresponding microbial community structures were examined using amplified ribosomal DNA restriction analysis (ARDRA). Copper extractions by the pure and mixed cultures achieved 14.87% and 20.11% respectively over a period of 117days, including 15days of acid pre-leaching and 102days of bioleaching. The ratios between autotrophic and heterotrophic bacteria at the top and bottom portions of the columns were 1.20:1 and 2.14:1, respectively.

Column Bioleaching of Arsenic and Heavy Metals from Gold Mine Tailings by Aspergillus fumigatus

AbstractA column bioleaching experiment was carried out to compare the effectiveness of the fungus Aspergillus fumigatus to bioleach arsenic (As) and heavy metals from the tailings using two different methods. In the first method, which is named as distribution method (DM), the fungus was distributed in the column by means of vertical and horizontal layers of coarse sand. In the other method, named as surface applied method (SAM), the fungus was cultivated on the surface of the tailings, which was covered with a few centimeters of coarse sand. Results showed that in the DM, oxalic acid production was stimulated and maximum removal of As, Fe, Mn, and Zn was 53, 51, 81, and 62%, respectively. However, Pb removal was low (8%), which might be due to the precipitation of Pb as its oxalates. On the other hand, the maximum removal of As, Fe, Mn, Pb, and Zn were 22, 28, 37, 64, and 34%, respectively, for the SAM. Results of the sequential extraction study showed that the DM was effective in removing the water soluble, exchangeable, carbonate, and Fe/Mn oxide fractions of As, Fe, Mn, and Zn. Our study suggested that A. fumigatus has a potential to be used in remediation of heavy metal contaminated sites. Distributing the fungus throughout the entire tailings columns improved the bioleaching of heavy metals by the fungus.

Column bioleaching of low-grade mining ore containing high level of smithsonite, talc, sphaerocobaltite and azurite

Present work describes the bioleaching potential of metals from low-grade mining ore containing smithsonite, sphaerocobaltite, azurite and talc as main gangue minerals with adapted consortium of Sulfobacillus thermosulfidooxidans strain-RDB and Thermoplasma acidophilum. Bioleaching potential improved markedly by added energy source, acid preleaching and adaptation of microbial consortium with mixed metal ions. During whole leaching period including acid preleaching stage of 960h and bioleaching stage of 212days about 76% Co, 70% Zn, 84% Cu, 72% Ni and 63% Fe leached out.

Column bioleaching of uranium embedded in granite porphyry by a mesophilic acidophilic consortium

A mesophilic acidophilic consortium was enriched from acid mine drainage samples collected from several uranium mines in China. The performance of the consortium in column bioleaching of low-grade uranium embedded in granite porphyry was investigated. The influences of several chemical parameters on uranium extraction in column reactor were also investigated. A uranium recovery of 96.82% was achieved in 97days column leaching process including 33days acid pre-leaching stage and 64days bioleaching stage. It was reflected that indirect leaching mechanism took precedence over direct. Furthermore, the bacterial community structure was analyzed by using Amplified Ribosomal DNA Restriction Analysis. The results showed that microorganisms on the residual surface were more diverse than that in the solution. Acidithiobacillus ferrooxidans was the dominant species in the solution and Leptospirillum ferriphilum on the residual surface.

Column Bioleaching of a Low-Grade Silicate Ore of Uranium

The bioleaching of a low-grade Indian uraninite ore (triuranium octoxide, U3O8: 0.024%), containing ferro-silicate and magnetite as the major phases, and hematite and pyrite in minor amounts, has been reported. Experiments were carried out in laboratory scale column reactors inoculated with enriched culture of Acidithiobacillus ferrooxidans isolated from the source mine water. The pH effect on uranium recovery was examined with the same amounts of ores in different columns. With the presence of 10.64% Fe in the ore as ferro-silicate, the higher uranium biorecovery of 58.9% was observed with increase in cell count from 6.4 × 107 to 9.7 × 108 cells/mL at pH 1.7 in 40 days as compared to the uranium recovery of 56.8% at pH 1.9 with a corresponding value of 9.4 × 108 cells/mL for 2.5-kg ore in the column. The dissolution of uranium under chemical leaching conditions, however, recorded a lower value of 47.9% in 40 days at room temperature. Recoveries were similar with 6-kg ore when column leaching was carried out at pH 1.7. The bioleaching of uranium from the low-grade ore of Turamdih may be correlated with the iron(II) and iron(III) concentrations, and redox potential values.

Column bioleaching of metals from electronic scrap

The present work was aimed at studying the column bioleaching feasibility of metals from electronic scrap by the selected moderately thermophilic strains of mixed adapted consortium of acidophilic chemolothotrophic and acidophilic heterotrophic bacteria. These included Sulfobacilllus thermosulfidooxidans and Thermoplasma acidophilum. The tolerance of bacterial cultures to mixed metal ions (Ag +, Al 3+, Cu 2+, Fe 3+, Ni 2+, Pb 2+, Sn 2+and Zn 2+) could be improved markedly after nearly two year adaptation from 12 g/L to 20 g/L. During whole leaching process included acid pre-leaching operation of 27 days and bioleaching operation of 280 days about 80% Zn, 64% Al, 86% Cu and 74% Ni was leached out.

An Experimental Approach for Studying Chalcopyrite Leaching and Passivation in Column Bioleaching

The effect of different microbial consortia on the leaching of chalcopyrite was studied at different temperatures and solution compositions with Boliden’s Aitik ore in column reactors simulating heap bioleaching. The columns were equipped with sampling chambers and chalcopyrite mineral electrodes in order to investigate the passivation of chalcopyrite. The sampling chambers were filled with agglomerated ore and pieces of chalcopyrite-rich ore. In addition to chemical analysis of the leaching solution and solids the progress of leaching of chalcopyrite was studied by continuous potential measurements with chalcopyrite electrodes. The occurrence and composition of potentially passivating layers on the surfaces of the electrodes and the samples taken from sample chambers were examined by optical and scanning electron microscopy.

Bioleaching of Low-Grade Copper Sulfide Ore Using a Colum Reactor

The effects of several variables on the column bioleaching of copper sulphide ore have been investigated. The copper ore contained chalcopyrite as the main sulfide minerals and bornite and chalcocite as the minor minerals. The experiment was carried out using bench-scale column leach reactors designed in Key Lab of Biometallurgy of Ministry of Education, which were inoculated with the pure mesophile bacteria (Acidithiobacillus ferrooxidans) and thermophile bacteria (Sulfobacillus), respectively, and the mixed bacteria which contain both iron- and sulfur-oxidizing bacteria. The results show that the mixed cultures were more efficient than the pure cultures alone and the maximum copper recovery 53.64% was achieved using the mixed cultures after 85 days. The leaching rate of chalcopyrite tended to increase with the increased dissolved ferric iron concentration. The effect of particle size on the rate of the copper leaching was also investigated, and it was shown that the copper bioleaching rate decreases as the amount of fines increase, which limits the permeability, thus decreases leaching rate. Jarosite and elemental sulphur formed in the column were characterized by the X-ray and EDS.

Leaching of a low-grade, copper–nickel sulfide ore. 1. Key parameters impacting on Cu recovery during column bioleaching

This study was prompted by the disparate recoveries of nickel (> 70%) and copper (< 20%) from a test heap of copper–nickel sulfide ore after about 200 days of leaching. Variables tested in bioleaching columns charged with a pyrrhotite-rich, chalcopyrite and pentlandite ore were acid pre-conditioning, inoculation and aeration. The results indicated that the rapid reaction of pyrrhotite with acid created conditions that impacted directly and/or indirectly on copper recovery. Important reactions were hydrogen sulfide formation, high soluble iron concentrations and the formation of large amounts of elemental sulfur. It was hypothesized that copper loss, evidenced by copper re-distribution during passage through the ore, was mainly the result of reaction with hydrogen sulfide to form covellite, although this could not be confirmed by XRD analysis of leached residues. A layer of iron-oxy-hydroxy-sulfate “scale” on particle surfaces encapsulated sulfide grains as well as elemental sulfur formed by the oxidation of pyrrhotite and was of sufficient depth and integrity to have hindered but not prevented leaching and bioleaching. Lack of aeration (oxygen, carbon dioxide) impacted on ferrous ion biooxidation and probably sulfur biooxidation. More extensive sulfur biooxidation to form acid might have lowered the solution pH and reduced the amount of scale formation, resulting in higher ferric ion concentrations and better chalcopyrite oxidation.

Column bioleaching of a low grade nickel-bearing sulfide ore containing high magnesium as olivine, chlorite and antigorite

This work investigates the bioleaching of Jinchuan low grade nickel-bearing sulfide ore containing rather high levels of olivine, chlorite and antigorite (MgO 30–35%) present in the main gangue minerals using a mixed mesophiles which are composed of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. It aims to test the technical feasibility to recover valuable metals from Jinchuan low-grade nickel-bearing sulfide ore by bioleaching process. The tolerance of the mixed bacteria to Mg 2+ could be improved markedly from 10 g/L to 25 g/L after nearly 2 years adaptation. A nickel recovery of 91% and a cobalt recovery of 81% were achieved in 312 days column leaching process including 60 days acid pre-leaching stage and 252 days bioleaching stage.

Silicate mineral dissolution during heap bioleaching

Silicate minerals are present in association with metal sulfides in ores and their dissolution occurs when the sulfide minerals are bioleached in heaps for metal recovery. It has previously been suggested that silicate mineral dissolution can affect mineral bioleaching by acid consumption, release of trace elements, and increasing the viscosity of the leach solution. In this study, the effect of silicates present in three separate samples in conjunction with chalcopyrite and a complex multi-metal sulfide ore on heap bioleaching was evaluated in column bioreactors. Fe(2+) oxidation was inhibited in columns containing chalcopyrite samples A and C that leached 1.79 and 1.11 mM fluoride, respectively but not in sample B that contained 0.14 mM fluoride. Microbial Fe(2+) oxidation inhibition experiments containing elevated fluoride concentrations and measurements of fluoride release from the chalcopyrite ores supported that inhibition of Fe(2+) oxidation during column leaching of two of the chalcopyrite ores was due to fluoride toxicity. Column bioleaching of the complex sulfide ore was carried out at various temperatures (7-50 degrees C) and pH values (1.5-3.0). Column leaching at pH 1.5 and 2.0 resulted in increased acid consumption rates and silicate dissolution such that it became difficult to filter the leach solutions and for the leach liquor to percolate through the column. However, column temperature (at pH 2.5) only had a minor effect on the acid consumption and silicate dissolution rates. This study demonstrates the potential negative impact of silicate mineral dissolution on heap bioleaching by microbial inhibition and liquid flow.

Bioleaching of low-grade sphalerite using a column reactor

The effects of several variables on zinc recovery in column bioleaching have been investigated. The ore contained sphalerite and pyrite as the main sulfide minerals and chalcopyrite and galena as minor minerals. Tests were carried out using a bench-scale column leach reactor which was inoculated with mesophilic ( Acidithiobacillus ferrooxidans) and thermophilic ( Sulfobacillus) iron oxidizing bacteria; initially isolated from the Sarcheshmeh chalcopyrite concentrate (Kerman, Iran) and Kooshk sphalerite concentrate (Yazd, Iran), respectively. In the inoculated column, jarosite and elemental sulfur were formed. The leaching rate of sphalerite tended to increase with dissolved ferric ion concentration. Microscopic counts of bacteria in the solution tended to be higher at lower pH ranges. Furthermore, the effect of a decreasing particle size on the rate of zinc leaching was enhanced at low pH values. Results show that the maximum zinc recovery was achieved using a thermophilic culture. Zinc dissolution reached 72% and 85% for the mesophilic and thermophilic strains, respectively, after 120 days at column temperatures ranging from 28 to 42 °C.

Bacterial leaching of complex sulfide ore samples in bench-scale column reactors

Several variables were examined in column bioleaching of a complex sulfide ore material which contained chalcopyrite, pentlandite, pyrite, pyrrhotite and sphalerite as the main sulfide minerals. Samples were used with varying proportions of pyrrhotite, pyrite, quartzite (low acid consumption) and skarn (high acid consumption). The experiments were carried out using bench-scale column leaching reactors which were inoculated with acidophilic, Fe- and S-oxidizing bacteria, initially derived from the source mine water. Leaching rates in sterile controls were negligible. In inoculated columns new solid phases (covellite, jarosite, Fe (III) oxide and elemental sulfur) were formed. Acid consumption was highest under low pH and low redox potential conditions. The solubility of ferric iron was controlled by jarosite and an Fe (III) hydroxide (initially amorphous). The leaching rates of Co (from pyrite and pentlandite), Cu (chalcopyrite), and Zn (sphalerite) showed a tendency to increase with dissolved ferric iron concentration. The leaching of Ni (from pyrrhotite and pentlandite) did not correlate with the concentration of ferric iron in solution. Microscopic counts of bacteria in solution, deemed insufficient to represent total bacterial counts, showed a tendency to be higher at the lower pH and intermediate redox potential ranges. Trickle-leaching conditions yielded higher acid production and redox-potential values compared with flood leaching. The leaching rates of Co, Cu, Ni and Zn each responded differently to redox potential and pH regimes. The accelerating effect of a decreasing particle size on the metal leaching rates was amplified by low pH values.

Biooxidation of an arsenic-bearing refractory gold ore

Biological oxidation of a refractory arsenic-bearing gold ore was investigated to determine the fate of arsenic during processing and to assess the effect of biological pretreatment on gold extraction. Experiments were conducted using a consortium of iron and sulfide oxidizing bacteria in semi-batch and continuous-flow stirred bioreactors, and also in a tall column bioleaching system. Sulfide oxidation and arsenic solubilization were monitored during biooxidation and the data were correlated with precious metals extraction during subsequent cyanidation tests. In addition, the concentrations of arsenite [As(III)] and arsenate [As(V)] species present in the liquors were monitored as a function of time using an anion exchange high performance liquid chromatograpy/atomic absorption spectroscopy technique. The stabilities of the final tailings and the arsenic-bearing sludges obtained by neutralization of the biooxidation liquors were also assessed. Leaching results showed that over 95% sulfide oxidation and 47% arsenic extraction could be obtained from this ore using the biooxidation process. Gold extraction during subsequent cyanidation was increased from 49% to about 80% after biological pretreatment. Total arsenic concentrations as high as 17 g/L in solution were obtained with no apparent detrimental effect on the bacterial populations. In all cases, arsenic was initially solubilized as As(III). Typical leaching solutions contained up to 18 times as much As(III) as As(V). Since As(III) compounds are less stable and much more toxic than As(V) compounds, long-term stability of sludge materials in the environment is of concern. Results from Toxicity Characteristic Leaching Procedure stability tests performed on the sludges will be discussed.

Solubilization of manganese from ores by heterotrophic micro-organisms

The potential for using heterotrophic micro-organisms to solubilize manganese from low-grade domestic ores is being assessed at the Reno Research Center, U.S. Bureau of Mines. More than 90% of the manganese has been extracted from a variety of oxide ores in shake-flask tests using molasses as a source of nutrients for the micro-organisms. It has also been demonstrated that high recoveries of manganese can be obtained from a domestic wad ore using column bioleaching. The isolation and identification of organisms responsible for manganese extraction are discussed, as are the mechanisms responsible for manganese solubilization.