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11 pages, 3069 KiB

Open AccessArticle

Effect of Extracellular Polymeric Substances on Surface Properties and Attachment Behavior of Acidithiobacillus ferrooxidans

by Qian Li, Qianfen Wang, Jianyu Zhu, Shuang Zhou, Min Gan, Hao Jiang and Wolfgang Sand

Minerals 2016, 6(4), 100; https://doi.org/10.3390/min6040100 - 28 Sep 2016

Cited by 30 | Viewed by 6243

Abstract

Bacterial contact leaching of ores is more effective than non-contact leaching. Adhesion is the first step for leaching bacteria to form a biofilm on a mineral surface. Extracellular polymeric substances (EPS) are pivotal for mediating bacterial adhesion to a substratum. In order to [...] Read more.

Bacterial contact leaching of ores is more effective than non-contact leaching. Adhesion is the first step for leaching bacteria to form a biofilm on a mineral surface. Extracellular polymeric substances (EPS) are pivotal for mediating bacterial adhesion to a substratum. In order to clarify the role of EPS, we measured the adhesion forces between chalcopyrite-, sulfur- or FeSO₄·7H₂O-grown cells of Acidithiobacillus ferrooxidans and chalcopyrite by an atomic force microscope (AFM) before and after EPS removal. Surface properties of these cells were assessed by measurements of the contact angle, zeta potential, Fourier transform infrared spectroscopy (FTIR) and acid-base titration. Bacterial attachment to chalcopyrite was monitored for 140 min. The results indicate that the EPS control the surface properties of the cells. In addition, the surface properties are decisive for adhesion. The adhesion forces and the amounts of attached cells decreased dramatically after removing EPS, which was not dependent on the preculture. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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11 pages, 6428 KiB

Open AccessArticle

Phytomining for Artisanal Gold Mine Tailings Management

by Baiq Dewi Krisnayanti, Christopher W.N. Anderson, S. Sukartono, Yusrin Afandi, Herman Suheri and Ardiana Ekawanti

Minerals 2016, 6(3), 84; https://doi.org/10.3390/min6030084 - 15 Aug 2016

Cited by 28 | Viewed by 11443

Abstract

Mine tailings are generally disposed of by artisanal and small scale gold miners in poorly constructed containment areas and this leads to environmental risk. Gold phytomining could be a possible option for tailings management at artisanal and small-scale gold mining (ASGM) locations where [...] Read more.

Mine tailings are generally disposed of by artisanal and small scale gold miners in poorly constructed containment areas and this leads to environmental risk. Gold phytomining could be a possible option for tailings management at artisanal and small-scale gold mining (ASGM) locations where plants accumulate residual gold in their above ground biomass. The value of metal recovered from plants could offset some of the costs of environmental management. Getting gold into plants has been repeatedly demonstrated by many research groups; however, a simple working technology to get gold out of plants is less well described. A field experiment to assess the relevance of the technology to artisanal miners was conducted in Central Lombok, Indonesia between April and June 2015. Tobacco was planted in cyanidation tailings (1 mg/kg gold) and grown for 2.5 months before the entire plot area was irrigated with NaCN to induce metal uptake. Biomass was then harvested (100 kg), air dried, and ashed by miners in equipment currently used to ash activated carbon at the end of a cyanide leach circuit. Borax and silver as a collector metal were added to the tobacco ash and smelted at high temperature to extract metals from the ash. The mass of the final bullion (39 g) was greater than the mass of silver used as a collector (31 g), indicating recovery of metals from the biomass through the smelt process. The gold yield of this trial was low (1.2 mg/kg dry weight biomass concentration), indicating that considerable work must still be done to optimise valuable metal recovery by plants at the field scale. However, the described method to process the biomass was technically feasible, and represents a valid technique that artisanal and small-scale gold miners are willing to adopt if the economic case is good. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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15 pages, 3762 KiB

Open AccessArticle

Influence of Sulfobacillus thermosulfidooxidans on Initial Attachment and Pyrite Leaching by Thermoacidophilic Archaeon Acidianus sp. DSM 29099

by Jing Liu, Qian Li, Wolfgang Sand and Ruiyong Zhang

Minerals 2016, 6(3), 76; https://doi.org/10.3390/min6030076 - 21 Jul 2016

Cited by 13 | Viewed by 5339

Abstract

At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. [...] Read more.

At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. Currently, little is known on the influence of pre-colonized mesophiles or moderate thermophiles on the attachment and bioleaching efficiency by thermophiles. The objective of this study was to investigate the interspecies interactions of the moderate thermophile Sulfobacillus thermosulfidooxidans DSM 9293^T and the thermophile Acidianus sp. DSM 29099 during initial attachment to and dissolution of pyrite. Our results showed that: (1) Acidianus sp. DSM 29099 interacted with S. thermosulfidooxidans^T during initial attachment in mixed cultures. In particular, cell attachment was improved in mixed cultures compared to pure cultures alone; however, no improvement of pyrite leaching in mixed cultures compared with pure cultures was observed; (2) active or inactivated cells of S. thermosulfidooxidans^T on pyrite inhibited or showed no influence on the initial attachment of Acidianus sp. DSM 29099, respectively, but both promoted its leaching efficiency; (3) S. thermosulfidooxidans^T exudates did not enhance the initial attachment of Acidianus sp. DSM 29099 to pyrite, but greatly facilitated its pyrite dissolution efficiency. Our study provides insights into cell-cell interactions between moderate thermophiles and thermophiles and is helpful for understanding of the microbial interactions in a heap leaching environment. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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10 pages, 10268 KiB

Open AccessArticle

Enhancement of Biofilm Formation on Pyrite by Sulfobacillus thermosulfidooxidans

by Qian Li, Wolfgang Sand and Ruiyong Zhang

Minerals 2016, 6(3), 71; https://doi.org/10.3390/min6030071 - 9 Jul 2016

Cited by 27 | Viewed by 7950

Abstract

Bioleaching is the mobilization of metal cations from insoluble ores by microorganisms. Biofilms can enhance this process. Since Sulfobacillus often appears in leaching heaps or reactors, this genus has aroused attention. In this study, biofilm formation and subsequent pyrite dissolution by the Gram-positive, [...] Read more.

Bioleaching is the mobilization of metal cations from insoluble ores by microorganisms. Biofilms can enhance this process. Since Sulfobacillus often appears in leaching heaps or reactors, this genus has aroused attention. In this study, biofilm formation and subsequent pyrite dissolution by the Gram-positive, moderately thermophilic acidophile Sulfobacillus thermosulfidooxidans were investigated. Five strategies, including adjusting initial pH, supplementing an extra energy source or ferric ions, as well as exchanging exhausted medium with fresh medium, were tested for enhancement of its biofilm formation. The results show that regularly exchanging exhausted medium leads to a continuous biofilm development on pyrite. By this way, multiply layered biofilms were observed on pyrite slices, while only monolayer biofilms were visible on pyrite grains. In addition, biofilms were proven to be responsible for pyrite leaching in the early stages. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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11 pages, 3230 KiB

Open AccessArticle

Recovery of Cobalt as Cobalt Oxalate from Cobalt Tailings Using Moderately Thermophilic Bioleaching Technology and Selective Sequential Extraction

by Guobao Chen, Hongying Yang, Haijun Li and Linlin Tong

Minerals 2016, 6(3), 67; https://doi.org/10.3390/min6030067 - 5 Jul 2016

Cited by 21 | Viewed by 8934

Abstract

Cobalt is a very important metal which is widely applied in various critical areas, however, it is difficult to recover cobalt from minerals since there is a lack of independent cobalt deposits in nature. This work is to provide a complete process to [...] Read more.

Cobalt is a very important metal which is widely applied in various critical areas, however, it is difficult to recover cobalt from minerals since there is a lack of independent cobalt deposits in nature. This work is to provide a complete process to recover cobalt from cobalt tailings using the moderately thermophilic bioleaching technology and selective sequential extraction. It is found that 96.51% Co and 26.32% Cu were extracted after bioleaching for four days at 10% pulp density. The mean compositions of the leach solutions contain 0.98 g·L⁻¹ of Co, 6.52 g·L⁻¹ of Cu, and 24.57 g·L⁻¹ of Fe (III). The copper ion was then recovered by a solvent extraction process and the ferric ions were selectively removed by applying a goethite deironization process. The technological conditions of the above purification procedures were deliberately discussed. Over 98.6% of copper and 99.9% of ferric ions were eliminated from the leaching liquor. Cobalt was finally produced as cobalt oxalate and its overall recovery during the whole process was greater than 95%. The present bioleaching process of cobalt is worth using for reference to deal with low-grade cobalt ores. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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17 pages, 1268 KiB

Open AccessArticle

Seasonal Microbial Population Shifts in a Bioremediation System Treating Metal and Sulfate-Rich Seepage

by Susan A. Baldwin, Al Mattes, Maryam Rezadehbashi and Jon Taylor

Minerals 2016, 6(2), 36; https://doi.org/10.3390/min6020036 - 12 Apr 2016

Cited by 19 | Viewed by 5673

Abstract

Biochemical reactors (BCRs) using complex organics for bioremediation of mine-influenced water must operate successfully year round. In cold climates, where many mines in Canada are located, survival of the important microorganisms through the winter months is a concern. In this work, broad phylogenetic [...] Read more.

Biochemical reactors (BCRs) using complex organics for bioremediation of mine-influenced water must operate successfully year round. In cold climates, where many mines in Canada are located, survival of the important microorganisms through the winter months is a concern. In this work, broad phylogenetic surveys, using metagenomics, of the microbial populations in pulp mill biosolids used to remediate metal leachate containing As, Zn, Cd and sulfate were performed to see if the types of microorganisms present changed over the seasons of one year (August 2008 to July 2009). Despite temperature variations between 0 and 17 °C the overall structure of the microbial population was fairly consistent. A cyclical pattern in relative abundance was detected in certain taxa. These included fermenter-related groups, which were out of phase with other taxa such as Desulfobulbus that represented potential consumers of fermentation byproducts. Sulfate-reducers in the BCR biosolids were closely related to psychrotolerant species. Temperature was not a factor that shaped the microbial population structure within the BCR biosolids. Kinetics of organic matter degradation by these microbes and the rate of supply of organic carbon to sulfate-reducers would likely affect the metal removal rates at different temperatures. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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Review

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13 pages, 707 KiB

Open AccessReview

Novel Biotechnological Approaches for the Recovery of Metals from Primary and Secondary Resources

by Katrin Pollmann, Sabine Kutschke, Sabine Matys, Sophias Kostudis, Stefanie Hopfe and Johannes Raff

Minerals 2016, 6(2), 54; https://doi.org/10.3390/min6020054 - 13 Jun 2016

Cited by 38 | Viewed by 7609

Abstract

Microorganisms have developed various mechanisms to deal with metals, thus providing numerous tools that can be used in biohydrometallurgical processes. “Biomining” processes—including bioleaching and biooxidation processes—facilitate the degradation of minerals, accompanied by a release of metals. These processes are especially attractive for low-grade [...] Read more.

Microorganisms have developed various mechanisms to deal with metals, thus providing numerous tools that can be used in biohydrometallurgical processes. “Biomining” processes—including bioleaching and biooxidation processes—facilitate the degradation of minerals, accompanied by a release of metals. These processes are especially attractive for low-grade ores and are used on an industrial scale mainly for sulfidic ores. In biosorption processes, biomass or certain biomolecules are used to bind and concentrate selected ions or other molecules from aqueous solutions. Biosorptive materials can be an environmentally friendly and efficient alternative to conventional materials, such as ion exchange resins. Other interesting mechanisms are bioaccumulation, bioflotation, bioprecipitation, and biomineralisation. Although these processes are well-known and have been studied in detail during the last decades, the recent strong progress of biotechnologies (e.g., genetic engineering and molecule design), as well as their combination with novel developments in material sciences (e.g., nanotechnologies) facilitate new strategies for the application of biotechnologies in mineral processing. The article gives a summary of current activities in this field that are being performed in our group. Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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19 pages, 1520 KiB

Open AccessReview

Microbiological Advances in Biohydrometallurgy

by Helen Watling

Minerals 2016, 6(2), 49; https://doi.org/10.3390/min6020049 - 25 May 2016

Cited by 72 | Viewed by 9556

Abstract

The most exciting advances in biohydrometallurgy are occurring in the field of microbiology. The two main technologies employed in biohydrometallurgy, agitated tanks for the processing of refractory concentrates and heaps and dumps for the processing of low-grade ores, are technologically sound and widely [...] Read more.

The most exciting advances in biohydrometallurgy are occurring in the field of microbiology. The two main technologies employed in biohydrometallurgy, agitated tanks for the processing of refractory concentrates and heaps and dumps for the processing of low-grade ores, are technologically sound and widely practised at commercial scale, but their development began at a time when very little was known of the microorganisms that assisted metals extraction from sulfide ores. During and subsequent to those developments it has been shown that microbial communities in metals extraction are more diverse than originally thought, and extremely robust and adaptable to different and variable environments. Recent advances in genomics and proteomics, exploiting hugely increased computing power and speed, have made it possible to describe not only which microorganisms are present in bioleaching systems, but also what physiological functions are being exercised. The body of knowledge being acquired through the application of molecular biology methods will be used increasingly to monitor microbial behaviour, optimise conditions for more appropriate microbiological activity and/or infer the “microbiological health” of bioreactors (tanks and heaps). Full article

(This article belongs to the Special Issue Biotechnologies and Mining)

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