Papers by Keyword: Biohydrometallurgy

Abstract: Tank bioleaching of substandard arsenic-bearing sulfide copper–zinc concentrate, containing 1.70, 6.22, and 7.30% of arsenic, copper, and zinc, was performed. The concentrate contained pyrite, chalcopyrite, tennantite, and sphalerite. Bioleaching was performed at 40°C using a mixed culture of acidophilic microorganisms in two modes. In the first mode, pulp density was 10%, while in the second it comprised 15%. Bioleaching made it possible to extract 17 and 70% of copper and zinc in the first mode, and 15 and 72% of copper and zinc in the second mode. The results obtained that bioleaching can be an effective approach to remove zinc from substandard copper-zinc concentrates. At the same time, copper minerals, including arsenic-bearing mineral tennantite, may be comparatively resistant to bioleaching, so requires the development of novel hydrometallurgical approaches for effective processing.

Abstract: The goal of the present work was to compare the rates of pyrite oxidation by different microorganisms, representatives of the groups predominating in biohydrometallurgical processes. The experiments were conducted in flasks with 100 mL of the medium containing mineral salts, 0.02% of yeast extract, and 2 g of pyrite at 45°C on rotation shaker (200 rpm) for 30 days. Strains Acidithiobacillus caldus MBC-1, Sulfobacillus thermosulfidooxidans VKMV 1269^T, and Acidiplasma sp. MBA-1 were used in the study. Different combinations of the strains were used in the experiments (pure cultures of S. thermosulfidooxidans VKMV 1269^T, Aсidiplasma sp. MBA-1, A. caldus MBC-1, as well as mixed cultures S. thermosulfidooxidans VKMV 1269^T + A. caldus MBC-1, Aсidiplasma sp. MBA-1 + A. caldus MBC-1, S. thermosulfidooxidans VKMV 1269^T + Aсidiplasma sp. MBA-1). Iron concentrations in the medium were the highest in the variants “S. thermosulfidooxidans VKMV 1269^T + A. caldus MBC-1”, “Aсidiplasma sp. MBA-1 + A. caldus MBC-1”, and “Sb. thermosulfidooxidans VKMV 1269^T + Aсidiplasma sp. MBA-1” and achieved 3.8, 3.5, and 3.3 g/L, respectively. Iron concentration in sterile control as well as in the experiments with pure cultures of Aсidiplasma sp. MBA-1 and A. caldus MBC-1 were very low. It demonstrated that in these variants pyrite was almost not oxidized. In the experiment with the pure culture of S. thermosulfidooxidans VKMV 1269^T, the rate of oxidation was high during 10 d of the experiment but then the oxidation activity drastically decreased. The ferric iron concentration achieved a maximum of 1.8 g/L and then decreased, whereas the ferrous iron concentration began to increase. Revealed differences in pyrite oxidation rates can be explained by differences in the physiological properties between the microorganisms. Results of the present work suggest that different groups of microorganisms have different impact in pyrite biooxidation.

Abstract: Biohydrometallurgy has broad application prospect in the treatment of low-grade nickel sulfide ore. However, quite a number of nickel sulfide deposits are associated with basic gangue minerals such as contain olivine, serpentine. The high basic gangue minerals will lead to a higher acid consumption and make it difficult to bioleach at pH below 2.5. It is crucial to improve processes and adapt bacteria with this kind of ore. This paper reviews the experimental researches and industrial applications for bioleaching of the high acid consumption nickel sulfide ores. It is suggested that bioleaching at elevated pH will have similar leaching rate compared with pH below 2.5, meanwhile the cost will be decreased remarkably due to a lower acid consumption and less dissolved impurity ions.

Abstract: Resistance of microorganisms predominating in biohydrometallurgical processes including bacteria of the genus Sulfobaсillus and archaea of the genus Acidiplasma to ferric iron ions was studied. Capabilities of the strains for growth and ferrous iron oxidation in the media containing high concentrations of ferric iron ions (of 250 to 1000 mM) were evaluated. Ferric iron ions significantly inhibited oxidative activity and growth of the studied microorganisms. It was revealed that bacteria of the genus Sulfobacillus were not able to oxidize ferrous iron actively when ferric iron concentration exceeded 500 mM, whereas archaea of the genus Acidiplasma completely oxidized ferrous iron in the medium containing 1000 mM of Fe³⁺. Growth of the microorganisms was inhibited by relatively low concentrations of ferric iron. Microorganisms did not grow in the medium containing more than 750 mM of Fe³⁺ and cells of all studied strains lysed in presence of high concentrations of ferric iron. It was shown, that archaea of the genus Acidiplasma of the family Ferroplasmaceae were more resistant to high concentrations of ferric iron than bacteria of the genus Sulfobacillus. The results obtained are important for understanding of the regularities of the formation of microbial communities performing technological processes.

Abstract: Previous agglomerate-scale heap bioleaching studies have outlined the variations in cell numbers of the liquid and attached phases during colonisation of sterilised ore by a pure culture. In this study, a mixed mesophilic culture was used in agglomerate-scale columns containing non-sterilised low-grade copper ore. Over a six - month period, columns were harvested at various intervals to provide snapshots of the metal distribution and the quantity, location, and ecological variations of mineral-oxidizing microbes within the ore bed. The initial colonisation period in this experiment was dissimilar to previous work, as the indigenous community was retained within the ore-bed throughout acid agglomeration. The overall colonisation phase lasted for approximately 1,000 hours until cell concentrations stabilised. In each column, less than 0.05% of the total cells were found in the leachate, 15-20% in the interstitial phase and the remaining ~80% were attached to the mineral surface. Once cell numbers had stabilised, interstitial cell concentrations were approximately 2,000× greater than those in the leachate. This difference persisted for the duration of the experiment. Copper concentrations in the two liquid phases generally decreased over time, but were on average 50× higher in the interstitial phase. Iron concentrations were more stable, but again were 30× higher in the interstitial phase. This demonstrates that that the difference in cell concentration between the leachate and interstitial phases cannot be explained through diffusion gradients within the system as it is much greater than those observed for the dissolved metals. It also shows that the specific environmental conditions of the interstitial and attached cells are very different to those inferred through analysis of leachates alone.

Abstract: The use of precious metals and Rare Earth Elements in electronic, medical, and automobile industries is drastically increasing. To meet this demand and to escape the financial pressure of the global metal market, not only mining activities but recently also the recovery of these elements from industrial and urban household waste is in the focus of research. It has been shown that the application of extracting solutions with pH values lower than 4 lead to an economically feasible recovery of industrially precious metals. It is unclear, however, whether and to which extent this abiotic extraction efficiency can potentially be increased by using microorganisms capable of dissolving more stable minerals at low pH. The goal of this project therefore is to first view urban household waste as a resource for metals and evaluate combined abiotic and biotic extraction procedures for an increase in metal extraction efficiency.

Abstract: Sphingomonas sp. is an abundant and novel microbial resource,as for the little awareness of Sphingomonas sp., its ecological and economical values are not well understood. This paper focuses on the bioleaching of phosphorus from hematite with mixed bacteria. When compared with Acidithiobacillus ferrooxidans (At.f), Sphingomonas sp. can increase the leaching rate by 1.5 times,and can also solve the problem of generating higher sulphur content by At.f. Thus Sphingomonas sp. will have an extensive application prospect in biohydrometallurgy.

Abstract: Rio Tinto, a natural extreme acidic environment with a rather constant acidic pH and a high concentration of heavy metals, is the product of the metabolic activity of chemolithotrophic microorganisms thriving in the rich complex sulfides of the Iberian Pyritic Belt. Up to now the microbial characterization has been made mainly in the water column and biofilm samples. Since all ferric reducing activities will not benefit the bioleaching operations, we consider it critical to ascertain the ecology and metabolic properties of the microorganisms inhabiting the anoxic part of the sediments, to facilitate the design and control the operation of heap bioleaching processes, maximizing their efficiency. The implication of these microorganisms in biohydrometallurgical operations is discussed.

Abstract: Bioleaching/minerals biooxidation and bioremediation have been widely used commercially for heap/dump bioleaching of secondary copper sulfide ores, sulfidic-refractory gold concentrates and treatment of acid rock drainage. Technical and commercial challenges, identified in this paper, remain for bioleaching of primary sulfides and complex ores. New frontiers for the technology exist in processing massive sulfides, silicate-locked minerals and in the more distant future in-situ leaching. Decommissioning of cyanide heap leach operations and stabilizing mine wastes using biotechnology are opportunities requiring intensive and focused research, development and engineering efforts.

Abstract: Members of Leptospirillum genus have emerged not only as one of the most representative bacteria in the Río Tinto ecosystem, but also in other acidic environments (AMD), and in biohydrometallurgical operations. The main objective of this work was to study the role of chemolithoautotrophic bacteria of the genus Leptospirillum in the Río Tinto iron cycle (an extreme acidic environment, characterized by its constant low pH) to better understand and control industrial biohydrometallurgical processes. Different strains of Leptospirillum were isolated from the Río Tinto basin and physiologically and genetically characterized. Certain metabolic capabilities, such as pyrite leaching, iron oxidation and nitrogen fixation, were determined for each strain. Complementary molecular ecology techniques (FISH, CARD-FISH and cloning) were used to study the microbial diversity and the distribution of leptospirilli along the iron gradient in the different phases of Río Tinto: water column, anaerobic sediments and biofilms.