Bioleached Residue Research Articles

Bioleaching of V, Ni, and Cu from residual produced in oil fired furnaces using Acidithiobacillus ferrooxidans

This study presents bioleaching of metals from a vanadium-rich oil-fired ash (OFA) sample using adapted Acidithiobacillus ferrooxidans. OFA is a major by-product of thermal power plants that contains metals such as V, Ni and Cu. The adaptation of bacteria to the ash sample was carried up to 4% (w/v), then three factors affecting metals recovery including initial pH, initial Fe2+ concentration and inoculum percentage were selected to be optimized. Initial pH of 1, inoculum of 1% and initial Fe2+ concentration of 1g/l were determined as optimal condition. Under optimum condition after 10days the maximum recovery for V, Ni and Cu was obtained 82%, 86%, and 87%, respectively. Results showed that in comparison with chemical leaching, bioleaching recovery of V, Ni and Cu were improved 20%, 16% and 8%, respectively. To determine the rate limiting step of the process, modified shrinking core model was used and result showed that diffusion step controlled the overall dissolution. The morphology and crystallinity of the samples before and after bioleaching were investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. Risk assessments of OFA before and after bioleaching by the toxicity characteristic leaching procedure (TCLP) were done and results indicated the bioleaching process detoxified OFA and the bioleached residue was well within the regulatory limits.

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

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 the 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%Cudissolution/day) was obtained in 6days of bioleaching in the presence of 2gL−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 the 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.

Extraction of copper from copper slag: Mineralogical insights, physical beneficiation and bioleaching studies

Copper slag was subjected to in-depth mineralogical characterization by integrated instrumental techniques and evaluated for the efficacy of physical beneficiation and mixed meso-acidophilic bioleaching tests towards recovery of copper. Point-to-point mineral chemistry of the copper slag is discussed in detail to give better insight into the association of copper in slag. Characterization studies of the representative sample revealed the presence of fayalite and magnetite along with metallic copper disseminated within the iron and silicate phases. Physical beneficiation of the feed slag (~0.6% Cu) in a 2 L working volume flotation cell using sodium isopropyl xanthate resulted in Cu beneficiation up to 2–4% and final recovery within 42–46%. On the other hand, a mixed meso-acidophilic bacterial consortium comprised of a group of iron and/or sulfur oxidizing bacteria resulted in enhanced recovery of Cu (~92–96%) from the slag sample. SEM characterization of the bioleached slag residue also showed massive coagulated texture with severe weathered structures. FE-SEM elemental mapping with EDS analysis indicated that the bioleached residues were devoid of copper.

Effect of mixed moderately thermophilic adaptation on leachability and mechanism of high arsenic gold concentrate in an airlift bioreactor

A refractory gold concentrate with 19% arsenic was treated by a mixed moderately thermophiles in an airlift bioreactor through an adaptation protocol. The moderately thermophiles could respond well to 20% (w/v) pulp density with less than 10% loss of productivity, and resist arsenic up to 15 g/L. There were a lot of jarosite, arsenolite and sulfur, but not scorodite and ferric arsenate in the bioleached residue. Jarosite passivation and lower sulfur-oxidizing activity of the cells due to the toxicity of the high concentrations of soluble arsenic and iron ions at low pH value should mainly response for the incomplete extraction at high pulp density. The initial bacterial community did not change in nature except for new found P aeruginosa ANSC, but sulfur-oxidizing microorganisms have been dominant microorganisms after a long time of adaptation. Pseudomonas aeruginosa originating from the gold concentrate should be closely relative to the metabolism of the organic matters contained in the refractory gold concentrate.

Bioleaching of Pyrrhotite by Moderately and Extremely Thermophilic Bacteria

Pyrrhotite ores are always mingled with very finely disseminated gold and other precious metal particles, which raise the disposal of such refractory ores to bacterial leaching level. In this paper, the bioleaching tests of pyrrhotite were carried out in Erlenmeyer flasks with moderately thermophilic Leptospirillum ferriphilum (at 40°C) and extremely thermophilic Acidianus manzaensis(at 65°C). The effects of bacterial strains, temperature, and acid tolerance on the extraction of iron were investigated, and the bioleaching residues were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that high temperature and low pH have important positive effects on the dissolution of iron under abiotic control, and extreme thermophilies are unsuitable for leaching pyrrhotite. As the pH value rapidly increased to above 4.4 and amounts of sulfur and goethite were generated at the initial stage during the process of bioleaching by A. manzaensis, the cell concentration dramatically declined. In comparison, more than 44% extraction of iron was achieved in the presence of L. ferriphilumafter four days of leaching. At the end of bioleaching, jarosite, sulfur and goethite, which could effectively block bioleaching process, were detected on the surface of residues by using XRD and SEM.

Bioprocessing of Mining and Metallurgical Wastes Containing Non-Ferrous and Precious Metals

Mining and metallurgical treatments of sulphide ores are characterised by present significant losses of non-ferrous and precious metals as different types of waste. These elements are accumulated in heaps due to the lack of efficient technology for the recovery of the metals from metallurgical waste. The treatment of two types of industrial metallurgical waste (copper converter slag and old flotation pyrite tailings) containing non-ferrous and precious metals were examined in the laboratory. Leaching of the slag containing 2.74% Cu (as digenite, bornite, and free metal) and 2.49% Zn (as a ferrite ZnFe2O4 and silicate) by an Fe3+-containing solution was studied. The effect of various experimental parameters on the leaching dynamics of copper, zinc, and iron under batch conditions was investigated. The following experimental parameters were recommended: a pH of 1.5, a pulp density of 10% (w/v), a temperature of 70 °C, and an initial Fe3+ concentration of 15 g/L. Leaching under these conditions resulted in the solubilisation of 89.4% copper and 35.3% zinc within 2.5 hours. Percolation leaching of the pyrite tailings containing 0.29% Cu (as chalcopyrite), 0.26% Zn (as sphalerite), 0.00007% gold, and 0.00108% silver was also studied. Acidic percolation leaching and the resulting biooxidation lasting 134 days resulted in the solubilisation of 73.4% zinc and 50.8% copper. The recovery rates of gold and silver from the bioleaching residues by cyanidation were 57.2% and 50.7%, respectively. The data obtained in the present work may be used to estimate the operating parameters for the industrial-scale processing of non-ferrous and precious metals from mining and metallurgical waste.

Microbial depyritisation of three different coals by Acidithiobacillus ferrooxidans in a batch stirred tank reactor

The present study aimed to investigate the depyritisation potential of Acidithiobacillus ferrooxidans on two different types of coals, namely lignite and anthracite collected from three different countries (Korea, China and Indonesia). The experimental work was conducted on a batch mode in a stirred tank reactor. All the batch biooxidation of pyrite in the different coal samples were conducted in a pH controlled condition (pH = 1·5). The growth medium employed for the batch biooxidation of pyritic coal was free from iron supplement. At. ferrooxidans oxidised mineral pyrite of Korean anthracite at a greater rate (98%) compared to 96 and 92% of pyrite oxidation for Indonesian and Chinese lignite respectively. The ratio of bioleach residue to the feed was reasonably good with range of 8·56–9·06 stating the net mass loss of 9–14. Coal depyritisation was carried out by the available Fe3+ ion in the inoculum producing Fe2+ ion as a product and this Fe2+ ion was further oxidised to Fe3+ ion by At. ferrooxidans. This Fe3+ ion produced by At. ferrooxidans continued the oxidation of the residual pyrite in the coal until all pyrite content was oxidised completely. The three different coals were found to be feasible for biological depyritisation of the coal could be scaled up for further studies in a continuous stirred tank bioreactor.L’étude présente avait pour but d’examiner le potentiel d’enlèvement de la pyrite par Acidithiobacillus ferrooxidans dans deux types de charbons, soit le lignite et l’anthracite, récoltés dans trois pays, soit la Corée, la Chine et l’Indonésie. On a effectué le travail expérimental dans un mode en vrac, dans un réacteur agité. On a effectué toute la bio-oxydation en vrac de la pyrite des échantillons de charbon à un pH contrôlé de 1·5. Le médium de croissance utilisé pour la bio-oxydation en vrac du charbon pyritique ne contenait pas de supplément de fer. At. ferrooxydans oxydait le minerai de pyrite de l’anthracite coréen en plus grande proportion (98%) que l’oxydation de la pyrite du lignite indonésien (96%) ou chinois (92%), respectivement. Le rapport de résidu de biolixiviation à l’alimentation était raisonnablement bon, avec une gamme de 8·56 à 9·06, établissant la perte de masse nette de 9 à 14. L’enlèvement de la pyrite du charbon était effectué par l’ion Fe3+ disponible dans l’inoculum, donnant lieu à l’ion Fe2+ comme produit et cet ion Fe2+ était davantage oxydé en ion Fe3+ par At. ferrooxidans. Cet ion Fe3+ produit par At. ferrooxidans continuait l’oxydation de la pyrite résiduelle dans le charbon jusqu’à ce que toute la pyrite soit complètement oxydée. On a trouvé qu’il était possible d’effectuer l’enlèvement biologique de la pyrite des trois charbons et d’augmenter l’échelle pour des études futures dans un bioréacteur en continu agité.

Bench-scale batch bioleaching of spent petroleum catalyst using mesophilic iron and sulfur oxidizing acidophiles

Microbial leaching of a petroleum spent catalyst was carried out using mixed mesophilic iron and sulfur oxidizing acidophiles. Bench-scale batch stirred tank reactors with a working volume of 1 L were used in this study at 35 °C. The pulp density considered for the study was 10% (w/v), while the particle size of the spent catalyst was varied by 45–106, 106–212 and >212 μm. The leaching percentage of Ni from the spent catalyst was found to be highest (97–98%) with varying particle size. However, the leaching yield for rest of the metals like Al, Fe, V and Mo was 70–74%, 66–85%, 33–43% and 22–45%, respectively. Influence of particle size was predominant on the recovery of all metals except Ni. Assessment of the generation of the bioleach residue after bioleaching showed a weight loss of 54–62% due to the dissolution of the metal values from the spent catalyst. The mineralogical study conducted by X-ray diffraction and scanning electron microscopy supports the dissolution of metals from the spent catalyst. Jarosite mineral phase was the dominant mineral phase in the bioleach residue due to the dissolution of the oxidic and sulfidic mineral phases present in the feed spent catalyst.

Effect of moderately thermophilic bacteria on metal extraction and electrochemical characteristics for zinc smelting slag in bioleaching system

The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied. The results show that the extraction rates of Fe, Cu and Zn from the slag reach 86.7%, 90.3% and 66.7% after adsorbed bacteria sterilize, while those with adsorbed bacteria are 91.9%, 96.0% and 84.5% in conditions of pulp density 2%, pH 1.0, temperature 65 °C and stirring rate 120 r/min, respectively. Some stretching peaks of functional groups from bacterial secretes on the bioleached residue surface, such as 1007 cm−1 and 1193 cm−1, turn up through FI-IR analysis and indirectly reveal the presence of the adsorbed bacteria on the slag particles surface. Besides, the corrosion of zinc smelting slag is enhanced by bacteria according to the characteristics of cyclic voltametry and Tafel curves in bioleaching system.

Material size distribution in concurrent bio-leaching and precipitation: Experimental procedure and modelling

This study presents the approach used to develop a model for a continuous bioleaching system in stirred tank reactors. In bioleaching of metallic sulfides, precipitation concurrently occurs with dissolution of sulfides. Therefore, the model incorporates both the leaching and the precipitation kinetics. It is based on a shrinking particle model for the leaching part and a Mixed Suspension Mixed Product Removal (MSMPR) crystallizer model with germination and growing kinetics for the precipitation part.To establish the model, it was necessary to have access to the size distribution of both sulfide and precipitated particles. A procedure for the bioleached residue characterization was developed in the BRGM laboratory to be able to dissociate sulfide and precipitated particles in the solid phase.The current paper presents the analytical procedure, the mathematical model in detail and its application to a continuous pilot plant test.

A novel sequential process of bioleaching and chemical leaching for dissolving Ni, V, and Mo from spent petroleum refinery catalyst

Two step leaching experiments were carried out to extract nickel, vanadium, and molybdenum present in spent refinery catalyst. A bioleaching process was applied in the first step. Pulp density, initial Fe(II) concentration, initial pH, particle size, and temperature were varied to optimize the bioleaching process. Ni, V, and Mo were leached out with maximum recoveries of 97%, 92% and 53%, respectively, at an optimized bioleaching condition of initial ferrous ion of 2g/L, initial pH of 2, pulp density of 10% (w/v), particle size of (−106+45) μm, and a temperature of 35°C. As the Mo leaching rate was very low, a second leaching step for the bioleached residue was applied with different concentrations of (NH4)2CO3, Na2CO3, or H2SO4. The second step leaching was optimum at a concentration of 30g/L (NH4)2CO3 with respect to Mo extraction. The rate of Mo dissolution with respect to concentration of lixiviant in the second leaching step was evaluated. The percentages of Ni, V, and Mo leached were 97%, 97% and 99%, respectively, by combining the first step under optimized conditions and the second step with 30g/L (NH4)2CO3.

Effect of sodium chloride on sulfur speciation of chalcopyrite bioleached by the extreme thermophile Acidianus manzaensis

The influence of sodium chloride on dissolution of chalcopyrite and surface sulfur speciation during bioleaching of chalcopyrite with the extreme thermophile Acidianus manzaensis YN-25 was studied. The addition of sodium chloride accelerated the dissolution of chalcopyrite by reducing the accumulation of elemental sulfur layers on the mineral surface, resulting in an increase in the concentration of copper ions from 2.37g/L to 2.67g/L. Jarosite and elemental sulfur were found in the bioleached residues, while the amount of elemental sulfur accumulating on the mineral surface decreased drastically from 25.4% to 3.0% when 0.66g/L of sodium chloride was present during bioleaching. Therefore, the accumulation of elemental sulfur on the mineral surface is likely mainly responsible for the slowdown in the dissolution rate. The results indicated that bioleaching chalcopyrite with extreme thermophiles possessing high sulfur oxidation activity likely enhances dissolution of chalcopyrite by effectively removing elemental sulfur accumulating on the mineral surface.

Effects of pH, pulp density and particle size on solubilization of metals from a Pb/Zn smelting slag using indigenous moderate thermophilic bacteria

A series of bioleaching experiments were designed to elucidate the effect of pH, pulp density and particle size on solubilization of heavy metals, such as As, Fe, Cu, Zn, Pb and Mn, from a Pb/Zn smelting slag using indigenous moderate thermophilic bacteria, and the surface morphological characteristics of the residues were observed by SEM. The results showed that the solubilization of heavy metals from the slag was significantly influenced by pH and pulp density in bioleaching, however, it was slightly influenced by particle size of the slag when the particle size is less than 0.83 mm. Under the optimum condition (pH 1.5, pulp density 10%, and particle size of the slag less than 0.83 mm, respectively), about 86%–91% of As, 90%–93% of Cu, 90%–94% of Mn and 81%–87% of Zn from the slag have been bioleached after 6 days. The surface morphological characteristics of the residues after 6 days bioleaching analyzed by SEM showed that metal solubilization can be improved by acid leaching but significantly contributed to the activities of the ingenious bacteria. Consequently, metals in the slag can be extracted by bacteria according to the corrosive holes on the surface of the bioleached residues.

Bioleaching of an organic-rich polymetallic concentrate using stirred-tank technology

The bioleaching of a concentrate produced from a black shale ore in an industrial operation in Poland was assessed. Following preliminary batch culture tests, processing in continuous conditions was tested to determine the main specifications for the application of the stirred-tank technology to this organic-rich polymetallic concentrate. The experimental work was carried out in a laboratory-scale unit consisting of three stirred tanks (50 L or 20 L) using an acidophilic and moderate thermophilic (42 °C) bacterial population. Different configurations of the unit and key operating parameters were tested (nutrient medium composition, solids concentration, agitation and aeration rates). The analysis of both bacterial community structure and mineralogical characteristics of the concentrate and the bioleach residues were implemented in order to better understand the chemical and biochemical reactions occurring in the system. Using the data produced during the continuous operation, downstream processing assessment for both copper and silver recovery was also carried out. The best copper recovery obtained in the continuous operation was 92% and hot brine leaching of the bioleaching residue (PLINT Process) permitted the recovery of 92% of the silver. Copper and silver recoveries seemed to be limited by incomplete chalcopyrite dissolution. A preliminary techno-economical evaluation of the concentrate bioleach processing, including bioleaching and copper and silver recoveries, demonstrated the potential economical feasibility. Silver recovery plays an important role in the process's finances. This study presents promising results that encourage further investigation of bioleach processing.

Control of the Redox Potential by Oxygen Limitation Inhibits Bioleaching of Pyrite

Based on the bioleaching mechanism and electrochemical studies of metal sulfides, the dissolution rate of secondary copper sulfides and pyrite are controlled by redox potentials. Experiment on the bioleaching of the secondary copper sulfides under constant potential by sparging with nitrogen gas demonstrated, by analyzing Cu and Fe content of the bioleaching solution and residues, the pyrite and secondary cooper sulfides dissolution rates have large difference in various redox potential. The pyrite and secondary cooper sulfides have good selection when the redox potential controlled between 700mV and 760mV, we can realize the secondary copper sulfides bioleaching process be controlled, then supply theoretical guide for the iron-acid balance during copper bioleaching process.

Improved epoxidation process

In this work, a new technique process for processing Cu-Zn mixed ores containing chalcopyrite and marmatite was proposed to avoid the complex Cu-Zn flotation and extraction separation processes, as well as for the comprehensive utilization of abandoned silver-containing zinc leaching residue (ZLR). In the first step, stepwise bioleaching of Cu-Zn mixed ores in the presence of mixed moderately thermophilic microorganisms and Fe3 + was conducted for recovering Zn from marmatite. Copper was then efficiently extracted from the copper-containing bioleaching residues through catalytic bioleaching by using ZLR as catalyst. The final bioleaching residues were subsequently leached by thiourea for recovering Ag efficiently. The provided technique process accomplished the stepwise dissolution of Cu-Zn mixed ores and the comprehensive utilization of silver-bearing ZLR. The intermediate species, the electrochemical dissolution process and the electrochemical interactions between chalcopyrite and marmatite were also discussed to interpret the detailed mechanisms of stepwise bioleaching.

Bioleaching of spent hydro-processing catalyst using acidophilic bacteria and its kinetics aspect

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 MoO 3. Bioleach residues were characterized by EDX and XRD.

Exploring process options to enhance metal dissolution in bioleaching of Indian Ocean nodules

AbstractPolymetallic Indian Ocean nodules offer a lucrative resource for valuable strategic metals such as Cu, Co and Ni. A novel bioleaching process using cell‐free spent growth medium from a fully‐grown culture of a marine organism isolated from the nodules (Bacillus M1) dissolved about 45% Co, and 25% Cu and Ni at a the pH of 8.2 in 4 h. To enhance metal dissolution, different modifications in the bioleaching process, such as increasing the pH of the spent growth medium, carrying out leaching in multiple steps, and introducing organic reductant in the leach pulp, were investigated in this study. Increasing the initial pH of the spent growth medium to above 12 resulted in a 25–30% increase in dissolution of Cu, Co and Ni. The pKa value for the spent growth medium was observed to be in the range of 11.5–12.5. UV‐visible spectroscopy of the growth medium at pH values above 10.0 suggested a change in the structure of complexing phenolic substances present therein. A four‐step leaching process using the spent growth medium, each step lasting for about 4 h, was able to bring around 60% Cu and Ni and 85% Co in solution. About 85% Co, 90% Cu and 60% Ni were dissolved in two‐stage leaching, in which the bioleached residue was treated with the spent growth medium from Acidithiobacillus thiooxidans in the second cycle. The effects of concentration of starch (0.1–10%) as an organic reductant to the spent growth medium were also studied. The dissolution of Cu, Co and Ni stabilized at about 80–85% at a starch concentration of 3% and did not increase much thereafter. Copyright © 2004 Society of Chemical Industry

Zinc and lead extraction from complex raw sulfides by sequential bioleaching and acidic brine leach

This research was designed to investigate zinc and lead extraction by combined sequential biooxidation and acidic brine leaching from a raw complex sulfide ores containing sphalerite, pyrite, and galena. For the biooxidation, the zinc dissolution from the sulfide ores by the adapted bacteria was examined. The effects on ore particle size, pH, pulp density, and temperature on bacterial leaching was studied systematically. From the experiments it was shown that about 95% of zinc was extracted after 20 days of bioleaching at 30 °C. Subsequently, 98% of the lead was extracted from the bioleached residues using an acidic sodium chloride solution as the lead lixiviant at a temperature of 60 °C for 90 min leach. Leaching kinetics indicated that diffusion through the product layer was the rate controlling process during zinc bioleaching, and that the overall rate of chemical reaction at the surface was the rate controlling process during lead brine leaching. The relative activation energies of the overall rate during the two different leaching stages were calculated to be 32.09 and 44.35 kJ/mol, respectively.

Silver, gold and lead recovery from bioleaching residues using the PLINT process

Single, or complex copper, nickel and zinc ores and concentrates, frequently contain important amounts of silver and gold, together with other minor metals. Cu, Ni and Zn are easily and efficiently dissolved in mesophilic or thermophilic bioleaching processes, while Au, Ag and Pb remain in the residue. Having a mainly jarositic matrix, these residues are usually refractory to conventional cyanidation or concentration processes. The PLINT technology developed by Técnicas Reunidas is a simple, clean and efficient procedure for gold and silver recovery from bioleaching residues (especially of a jarositic nature) unable to be treated by conventional processes. This process is very flexible and adaptable to suit every specific application requirement. Results of a preliminary feasibility study on the application of the PLINT technology on a copper bioleaching residue are presented in this paper. Very appealing economic figures are shown together with main technical performance parameters and a summarised process description.