bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactive Oxygen Species Influence Biofilm Formation of Acidophilic Mineral-Oxidizing Bacteria on Pyrite
Authors: Bellenberg Sören , Huynh Dieu , Castro Laura , Boretska Maria , Sand Wolfgang , Vera Mario
Published: December 2015

Reactive oxygen species (ROS), such as hydrogen peroxide (H2O2), superoxide (O2-) and hydroxyl radicals (OH.) are known to be formed on the surface of metal sulfides in aqueous solution under oxic and anoxic conditions. Consequently bacteria which have not been adapted to their presence are metabolically inhibited [1], presumably due to the presence of these ROS. Pyrite-grown cells ofAcidithiobacillus ferrooxidansT, in contrast to iron (II)-grown cells, were able to oxidize iron (II)-ions or pyrite after 24 h starvation and contact with 1 mM externally added H2O2. In this study, similar results were obtained withAcidiferrobactersp. SPIII/3. However,Acidithiobacillus ferrivoransSS3 showed the highest tolerance towards contact with H2O2, whileLeptospirillum ferrooxidansDSM 2391 was most sensitive. Similar results were obtained after exposure to defined doses of gamma radiation, which cleaves water molecules and generates ROS. In this study members of the three aforementioned genera of mineral-oxidizing bacteria were compared regarding their ability to survive, colonize pyrite and to oxidize iron (II)-ions after exposure to different concentrations of H2O2. Pyrite colonization was studied after exposure to endogenous ROS formed on pyrite or after external addition of H2O2using confocal laser scanning microscopy (CLSM).
Microbial & Mineralogical Dynamics during Copper Sulfides Bioleaching, the Search for the Missing Link
Authors: Bobadilla-Fazzini Roberto A. , Piña Patricia , Gautier Veronica , Brunel Karen , Parada Pilar
Published: December 2015

Bioleaching involves a chemical-microbial-driven dynamic process of oxidation and dissolution, as well as precipitation and formation of surface secondary phases that change the copper sulfide exposure/occlusion profiles. This dynamic process determines the kinetics of copper sulfides bioleaching. Former studies have shown the microbiological dynamics of the leaching solutions, and most mineralogical studies have been done with pure copper sulfide species under controlled conditions. In this work we aim to unravel the link between the microbiology and the mineralogy during the bioleaching of a mainly primary copper sulfide ore through the determination of the surface microbial and mineralogical variations in time applying process conditions. The results showed that the microbial dynamics in the leaching solutions is not representative of the bioleaching process since it differs significantly from the one established at the ore surface. Moreover, a major and fast alteration of the primary copper sulfide minerals chalcopyrite (CuFeS2) and bornite (Cu5FeS4) was observed, having as the major bioleaching intermediate the formation of covellite (CuS). When the ore was subjected to a mesophilic inoculation, the microbial dynamics was modified, significantly changing the mineralogical dynamics of these primary sulfides and enhancing the overall kinetics of copper recovery.
Antimicrobial Activity and Hardness of as Cast and as Homogenized Cu-Ti Alloys
Authors: Nurhayani Dinni , Korda Akhmad Ardian
Published: December 2015

Cu-Ti alloy, pure copper, and stainless steel AISI 304 were tested in this study for their microstructure, effect of alloying element to hardness, and antibacterial activity. The antibacterial properties were tested against E. coli suspensions. The titanium in Cu-Ti alloy was varied 1-4 wt. %, and the microstructure was modified by homogenization treatment. The antibacterial susceptibility test was done by inhibition zone measurement and bacterial suspension inoculation methods. Result showed the addition of titanium increased hardness from pure copper (44.93 HV) to 79.68-207.6 HV. No inhibition zone was observed for the stainless steel samples, while the largest inhibition zone diameter was gained by pure copper (12.4 mm). The killing bacteria activity test concluded that the compositions of the alloys were not directly linked to the antibacterial activity.
A Feasibility Study of Arsenopyrite-Bearing Gold Bioleaching and its Characterization
Authors: Hasni Sakinah , Juan Su Xiu , Jian Ma Shao
Published: December 2015

Gold concentrates are mainly composed of arsenopyrite and pyrite. Leptospirillum ferriphilum has been found to be a dominant iron-oxidizing bacterium in the biooxidation of arsenopyrite-bearing gold concentrates. The present study demonstrated the capability of the bacterium Leptospirillum ferriphilum in oxidizing arsenopyrite within 6 days as evidenced by X-ray diffraction (XRD) analyses.
Effect of Phanerochaete chrysosporium on Graphite Degradation during Pre-Treatment of Simulated Gold Preg-Robbing Ore
Authors: Liu Qian , Yang Hong Ying , Tong Lin Lin , Qiao Li Li , Peng Jing , Zhang Zeng Liang , Liu Hai Liang
Published: December 2015

Abstract. In this study, the effect ofPhanerochaete chrysosporiumon graphite was investigated, and graphite was used as a substitute of elemental carbon in carbonaceous gold ores. Under the condition of optimum process, the fungal degradation rate of graphite reached to 13.49%, and the carbon content of graphite was decreased by 5.13%. XRD analysis indicated thatPhanerochaete chrysosporiumcould destroy the crystal structure of graphite. FTIR analysis indicated thatPhanerochaete chrysosporiumcould increase the number of aliphatic structures and oxygen-containing groups. The cyanide leaching gold tests showed thatPhanerochaete chrysosporiumcan decrease the preg-robbing capacity of graphite, about 9.52%. It indicated thatPhanerochaete chrysosporiumis an available microorganism, which was employed to pre-treat carbonaceous matter in carbonaceous gold ores to reduce the interference of gold cyanidation leaching.
Electrochemical Research on N-Type and P-Type Semiconductor Pyrite
Authors: Xu Jia Ning , Yang Hong Ying
Published: December 2015

Studies on cyclic voltammetry, Tafel polarization curve and DFT calculations on N type and P type semiconductor pyrite in or out of bacterial solution were carried out. Cyclic voltammetry showed that the effect of bacterial was not simply in enrich the Fe3+ in the EPS. Tafel polarization curve research showed that bacteria can enhance the oxidation reaction sharply, no matter in the Fe3+ solution and in the bacteria solution, the corrosion current of N type pyrite was much bigger than that of P type pyrite. The DFT calculation shows that containing one Ni or Co atom means a more stable property, containing one As atom meaning a less stable property. However, an energy band around 5eV occurred in N type pyrite (contained Cu or Ni) meaning that N type pyrite is easier to be oxidation than P type pyrite.
Factors Affecting the Selection of BIOX® as the Preferred Technology for the Treatment of a Refractory Gold Concentrate
Authors: van Niekerk Jan
Published: December 2015

The BIOX®process was developed in the late 1980’s for the treatment of refractory gold concentrates. The process has since developed into a commercially proven process with 12 successful installations of which 6 are currently still in operation. During this time development of the technology continued to improve the efficiency of the process, improve the reliability of the equipment used and to reduce the capital and operating cost for the implementation and operation of the process.This paper will look at some critical aspects in the selection of the BIOX as the preferred technology for the treatment of a refractory gold. Process selection will include technical criteria, for example the amenability of a concentrate to biooxidation and process design criteria, but will also include the overall project economic evaluation, a study of the project risks, the impact of the project and technology on the environment and local communities, operability of the process and implementation strategy.It is important that these aspects be taken into consideration in the design of any testwork program, be it fundamental research in the biooxidation field or in the development of a specific project. The impact of decisions taken during the execution of the program must also be tested continuously to gauge the impact on the overall process viability.The selection of biooxidation as the preferred process route for any project, be it gold, copper or any other mineral, will in most cases be based on the overall project economics compared to other processes, rather than technical considerations.
Base Metal Tank Bioleaching: From Laboratory Test Work to Commercialization
Authors: Gericke Mariekie
Published: December 2015

The tank bioleaching of metal sulphides is an established technology. Commercial success started with the treatment of refractory gold concentrates using mesophilic micro-organisms, followed by the development of tank bioleaching processes for the treatment of base metal concentrates. This was initially a mesophilic process treating secondary copper sulphides, pentlandite and cobaltiferous pyrite. There was though limited potential for recovery of copper from chalcopyrite concentrates due to low copper extractions. Over the past decades the optimization of bioleaching processes for the treatment of chalcopyrite ores and concentrates has been the subject of numerous research programmes. The use of bioleaching for the treatment of pure chalcopyrite concentrates has, however, not found commercial application mainly due to competitive smelter prices. With this in mind, Mintek’s base metal bioleaching development over the past few years focused on the treatment of complex polymetallic concentrates containing contaminants such as As, Bi, Pb and Sb as a niche application for tank bioleaching processes. These contaminants pose problems when processed via the smelting route. This paper reviews Mintek’s involvement in the development of base metal tank bioleaching processes for the treatment of chalcopyrite and polymetallic concentrates. Examples of laboratory-scale test work as well as larger scale demonstration and commercialization of the technology are highlighted.
Role of Microbial Activity in Bioleaching of a Pyritic and a Pure Chalcopyrite Concentrate
Authors: Khoshkhoo Mohammad , Dopson Mark , Sandström Åke
Published: December 2015

Leaching of a pyritic and a pure chalcopyrite concentrate was carried out in stirred tank reactors in the absence and presence of a mixed culture of moderately thermophilic microorganisms at 45°C and pH 1.5. To study the effect of microbial activity on copper dissolution, the abiotic experiments were performed under accurately controlled redox potential conditions to reproduce the same oxidising conditions recorded during the bioleaching experiments. X-ray photoelectron spectrometry (XPS) was used to study the surface of chalcopyrite chips leached for different durations. The results showed that the microorganisms in cases of both concentrates did not have any effect in the copper leaching efficiency other than oxidation of ferrous to ferric ions. Biooxidation of elemental sulphur did not improve the leaching efficiency and bulk and surface jarosite had no negative effect on dissolution. A composite layer composed of mainly elemental sulphur and iron-oxy-hydroxide was found to be responsible for the hindered dissolution.
Aspergillus niger PSSG8 Mediated Bioleaching of Monazite for the Recovery of Rare Earth and other Metal Constituents
Authors: Keekan Kishor Kumar , Jalondhara Jayesh C.
Published: December 2015

Aspergillus nigerPSSG8 is assisted bioleaching of monazite to recover the constituent metals were investigated. Bioleaching was carried out using Bromfield (BM1/10P & BM-P) and sucrose media (SM1/10P & SM-P) with different levels of Phosphate under rotary and stationary conditions. The growth of theA. nigerPSSG8 significantly reduced the media pH to acidic. However, the media pH changed later in rotary shake flasks and were stable in roux bottles. A similar trend was observed for ORP. ORP increased as leaching progressed, but in rotary shake flasks ORP started decreasing after 15 days in Bromfield and 30 days in sucrose media. Fungal growth was maximum in SM when comparing to BM. The reduction and the omission of phosphate in both media did not significantly influence the culture parameters including the yield of biomass. ICP-AES analysis of leach liquor showed highest recovery of cerium (Ce) (1419 µg/L in BM-P) and thorium (Th) (182 µg/L in SM1/10P) in rotary conditions when comparing to the stationary conditions (229 µg/L Ce in BM 1/10P & 159 µg/L in SM-P). Reduction in the metal concentration was observed in the rotary shake flasks after 15 days of incubation. It was due to the biosorption of released metals by the fungal mycelium. Uranium was not detected in any of the media tested. SEM studies of the partially bioleached and control mineral particles show no changes in the surface features.
Overcoming the Bacteriostatic Effects of Heavy Metals on A. thiooxidans Direct Bioleaching of Saprolitic Ni Laterite Ores
Authors: Jang Hee Chan , Valix Marjorie
Published: December 2015

In this study, the adaptation of A. thiooxidans to heavy metals leached from saprolitic Ni laterite ores was performed by gradual acclimatisation. The bacteria was cultivated in heavy metals (Ni, Co, Fe, Mg, Cr and Mn) with total concentrations of 2400 to 24000 ppm equivalent to total dissolution of 1 to 10% (w/v) pulp densities of the saprolitic Ni laterite ore. Adaptation evolution mapped from its tolerance index was found to be dependent on metal concentration, acid generation, and period of adaptation. Bio-stimulation of cell growth and acid production was promoted by heavy metal stress on the bacteria. Pre-established heavy metal tolerance of the bacteria improved the leaching rate in its early phase; 20% and 7% increase in Ni and Co metal recoveries were observed in using adapted bacteria. However heavy metal tolerance was also achieved by the bacteria during the leaching process, albeit delayed by a lag phase. These results confirm the robust nature and suitability of A. thiooxidans in direct biomining of Ni ores.
Organic Acid Biogeneration by Aspergillus niger  and its Utilization for Indirect Bioleaching of Nickel Laterite Ore
Authors: Mubarok M. Zaki , Sulistyo Robi S. , Chaerun Siti Khodijah , Minwal W.P.
Published: December 2015

This paper discusses the results of indirect bioleaching test works of nickel laterite ore by the assistance of Aspergillus niger. Series of metabolic acid biogeneration shake-flask experiments were performed to investigate the effects of substrate type, nitrogen and phosphate dosages, the presence of magnesium and manganese salts, as well as aeration of the culture media on the effectiveness of the metabolic acid biogeneration. The investigation results showed that after 16 days of incubation, the solution pH of 1.44 was obtained from the acid biogeneration using cassava starch as carbon source in the presence of 0.1% (w/w) KH2PO4, 1% (w/w) (NH4)2SO4 and 0.25 g/L of MgSO4 under aerated condition. Leaching experiments of limonite and saprolite ore samples were carried out by using the generated metabolic acids at various ore particle size distributions, solid to liquid ratio and temperature. The highest nickel extraction percentage of 88.9% was obtained from the leaching of saprolite ore at 95°C, stirring speed of 400 rpm, particle size distribution of-80+100 mesh, solid to liquid ratio of 4.65 g/mL after 240 minutes, while that of 84.9% was obtained from the leaching of limonite ore at 95°C, stirring speed of 400 rpm, particle size distribution of-80 +100 mesh and solid-liquid ratio of 5.2 g/ml after 1440 minutes. The leaching of saprolite ore by using the biogenerated acids was selective to magnesium, with co-extracted Mg of only 1.5% after 24h of the agitation leaching test.
Influence of Carbonate Solubilisation on Copper Leaching from Kupferschiefer with Organic Acids
Authors: Kostudis Sophia , Bachmann Kai , Kutschke Sabine , Pollmann Katrin , Gutzmer Jens
Published: December 2015

The European Kupferschiefer deposits offer potential for regional resources of base metals such as copper. Because of its chemical and mineralogical complexity the Kupferschiefer ore is still investigated regarding sustainable exploiting strategies such as (bio)leaching with organic acids. The current study examines different processing parameters investigating types of organic acids at pH 4 and 7 in order to reveal the influence of carbonate decomposition onto copper leaching performance. Obtained results show superior leaching performance of organic acids at neutral to alkaline pH range.
Iron Oxidized Acidophiles Distribution and Activities in an Uranium In Situ Bioleaching Site
Authors: Liu Ya Jie , Li Jiang , Zhou Yi Peng , Xu Ling Ling , Xu Wei Yun , Wang Xue Gang , Yang Gou Bin , Liu Jin Hui , Sun Zhan Xue , Liu Jian She
Published: December 2015

Iron oxidized acidophlies are important in uranium extraction for it mainly depends on the indirect mechanism of bioleaching. Taking indirect field In-Situ bioleaching experiment in a uranium deposit as an example, several strains of acidophiles were isolated from the acid leachate. Bacteria compositions of the samples taken different stages were analyzed by 16SrDNA PCR-RFLP method. Results showed that the dominant bacteria in the leachate wereAcidithiobacillus.ferrivorans,At.ferrooxidansandLeptospirrilum. ferrooxidansfrom the beginning to the middle stage of bioleaching process. With the process carried on, ferric ion concentration increased in the oxidation tanks,L. ferrooxidansbecame predominant bacteria. Again confirmed that in this in-situ bioleaching site, iron oxidized bacteria were in dominant.
Metal Recovery and Exploitation of Lignite Ashes by Combined Physicochemical and Biotechnological Approaches
Authors: Kermer René , Hedrich Sabrina , Brett Beate , Schrader Daniel , Räuchle Konstantin , Schönherr Petra , Schippers Axel , Reichel Susan , Glombitza Franz , Janneck Eberhard
Published: December 2015

Ashes from lignite combustion for power generation contain strategic metals, metalloids and rare earth elements and may thus be a potential source of industrially demanded metals. The presented project focuses on the assessment and exploitation of this potential raw material. Lignite ash assessment showed that largest ash amounts for potential exploitation are available in the Lusatia district, Saxony. Mechanical ash pre-treatment in principle provided enriched fractions by different methods but still suffered from low yields of enriched fractions. Thermal ash processing showed multiple significant phase changes compared to original ash. Subsequent chemical leaching using HClaq resulted in high metal extraction. Alternatively, bioleaching was applied using acidophilic Fe (II) and S-oxidizing or Fe (III)-reducing microorganisms (MO) as well as heterotrophic MO. The results indicated likewise high and partly specific metal mobilizations. Industrial ash exploitation was accomplished by direct reaction with acids resulting in Al-Fe-solutions which potentially can be applied in water treatment.
Bioleaching of a Molybdenite Concentrate by Thermophilic Microorganisms in a New RELVA-RBAL 1 AIR LIFT Bio-Reactor
Authors: Rivera Santillan R.E. , Patricio Ramirez F. , Lopez Lopez F.A.
Published: December 2015

In this paper bioleaching of molybdenite concentrate (MoS2) with extreme thermophilic microorganisms at constant temperature (65°C) was studied using a new RELVA-RBAL1 bioreactor, designed at the Faculty of Chemistry of the National Autonomous University of Mexico (UNAM). The equipment keeps homogeneous medium creating physical, chemical and biological conditions that lead to optimal growth of microorganisms, improving its resistance and tolerance to molybdenum significantly, thus achieving high extraction. The RELVA-ARBAL1 AIR LIFT bioreactor allows us the control of necessary conditions for a growth more efficient of the microorganisms. This will allow leach more rapidly the ore, increasing the molybdenum extraction kinetics. The results of extraction from bioleaching molybdenite in an orbital incubator were <1% Mo. The new RELVA-RBAL 1 AIR LIFT bioreactor showed a hight efficiency, 96.84% of molybdenum extracted, most reported, in the shortest time.
Physical Peeling of Passivating Layers on Chalcopyrite Leached with Ferric Ion Using Small Alumina Balls
Authors: Joe Seongjin , Inoue Chihiro , Chida Tadashi
Published: December 2015

Chalcopyrite is the most abundant copper mineral but notorious as its slow dissolution kinetics in hydrometallurgical processes due to the formation of passivating layers on the surface of the mineral. We tried to improve chalcopyrite leaching rate through adding small alumina balls in a shaking flask to peel off physically the passivating layers. Leaching experiments were carried out in shaking flasks at 333 K in anaerobic condition. Each flask contained ferric sulfate solution (pH 0.7), chalcopyrite concentrate, and alumina balls (5-mm diameter). The effects of the alumina ball addition on the chalcopyrite leaching were outstanding. About 97 % copper dissolution was achieved after 30 hours leaching period, while only 12 % of copper was dissolved from the control experiment. In former case, elemental sulfur was detected clearly as a reaction product. These facts indicate that elemental sulfur formed by ferric leaching did not obstruct copper dissolution in case of alumina ball addition in leaching system. Our findings show that the passivating layers on chalcopyrite surface can be peeled off effectively by physical method and high copper extraction can be achieved.
Utilisation of Inorganic Substrates by Alicyclobacillus - Like Strain FP1
Authors: Watling Helen R. , Collinson David M. , Perrot Felicity A. , Shiers Denis W.
Published: December 2015

As Alicyclobacillus-like strain FP1 was isolated from copper heap process water (pH 1.5), this research was directed towards its bioleaching attributes, specifically ferrous ion (Fe (II)) and reduced inorganic sulfur compound (RISC) oxidation, and bioleaching of sulfide minerals. Strain FP1 oxidised iron (II) but not tetrathionate or elemental sulfur in growth media containing yeast extract as growth factor. The addition of tetrathionate (2.5 mM) suppressed iron (II) oxidation. Strain FP1 grew on pyrite, arsenopyrite, chalcopyrite, sphalerite and pentlandite in BSM-YE medium at 30 °C and pH 1.8 (35 days), enhancing Zn, Co (in cobaltiferous pyrite), Fe and As recovery, but not Cu or Ni, relative to abiotic controls.
Study on Bioleaching of Sulfur in Iron Ore by Mixed Culture
Authors: Shang He , Wen Jian Kang , Wu Biao , Mo Xiao Lan
Published: December 2015

Iron ore is the raw material for steel production, in addition to iron and slag major component, still contains sulfur and phosphorus compounds and other harmful elements, is the potential adverse effects of factors constitute the steel product quality and environment. Sulfur in iron ores into the steel products will not only produce "heat brittle" phenomenon, but also in the sintering process by roasting produce sulfur dioxide into the air, causing damage to the atmosphere and ecological environment. A typical of the high sulfur iron ore from Inner Mongolia, China, iron grade of 53.06% and sulfur content is 2.76%, the main metal mineral in the ore is magnetite, followed by magnetic pyrite, pyrite and siderite, otherwise a small amount of copper mineral chalcopyrite, bornite. In this work, a mixed culture composed by Sulfobacillus thermotolerans, Leptospirillum ferriphilum and Ferroplasma acidiphilum was used to leach the sulfur in iron ore samples, we investigated the leaching rate of sulfur under different initial pH, temperature and pulp density conditions. The results showed that under the condition of the initial pH of 1.8, the temperature was 33 °C, and pulp density 15%, after 7 days of oxidation, we got a yield of 80.16% product in which iron grade of 62.31% and sulfur content is 0.17%. Compared with original sample, sulfur content decreased 95.06%, iron grade increased by 9.25%, and iron recovery was 94.13%. From the results it can be concluded that this microbial process for high sulfur iron ore lead to a significant effect of sulfur reduction and substantial increase in iron grade.
Effect of Particle Size on the Column Bioleaching of Tibet Yulong Copper Ore
Authors: Kai Li , Wang Yu Guang , Zhang Li Juan , Zhu Chen , Feng Mao , Zhou Hong Bo
Published: December 2015

This study aimed to investigate the effect of ore particle size on the bioleaching of Yulong copper ore in the bench-scale columns using the mixed culture of moderately thermophilic microorganisms. Bioleaching experiments were carried out on particle sizes of 5-10, 10-15 and 15-25mm in the same kind of column reactors. In the control test of acid leaching, the column reactor was charged with the middle particle size (10-15mm). The results indicated that copper extraction in the column reactor with particle size of 5-10 mm was highest among the three particle sizes. After 110-days leaching, 89% of copper was leached at 5-10 mm particle size while 57% was extracted at 15-25 mm particle size and 80% at 10-15 mm. Under the same particle size (10-15 mm), copper recovery in the column reactor with inoculation of microorganisms was 25% higher in comparison to the control test of acid leaching, while sulfuric acid consumption was 33% less than that.
Study on the Gold Recovery of Double Refractory Gold Ore Concentrate by Biological Oxidation Pretreatment
Authors: Luo Wen Jie , Yang Hong Ying , Jin Zhe Nan
Published: December 2015

In this paper, Bacterial oxidation-cyanide leaching experiments were carried out and the carbonaceous substances composition of carbonaceous gold concentrate was been studied. The elemental composition was 9.73 % iron, 9.66 % sulfur, 4.84 % arsenic and 13.23 % carbon which element carbon and organic carbon was 12.11wt.% and 0.06 wt.% respectively. The main carbonaceous substances were elemental carbon which the morphology was dense and similar to graphite. The removal rates of iron, arsenic and sulfur were achieved to 93.78%, 97.02% and 95.54% respectively by bioleaching, and the gold recovery of oxidation residue reached 92.34% by carbon inhibited cyanide leaching process. The sulfide minerals packing problem could be effectively solved by bacterial oxidation process and greatly increased the gold recovery. So the bacteria oxidation and carbon inhibited leaching process is applicable to the carbonaceous gold ore.
Indium Extraction from Reiche Zeche Sphalerite and Community Analysis of Acidic Mine Water
Authors: Gelhaar Nadja , Schopf Simone , Schlömann Michael
Published: December 2015

During the process of industrialization, the world-wide demand for resources steadily increases. Significant amounts of crucial metals and metalloids remain in low grade mineral deposits, however using conventional metal extraction methods on these minerals is not environmentally feasible. To overcome these problems, biohydrometallurgy has become the focus of recent research. Biohydrometallurgy utilizes the activity of iron-oxidizing bacteria to catalyze the dissolution of sulfide minerals, in our case local sphalerite (ZnS), with the aim of winning zinc and indium. To achieve this enrichment cultures originating from waters of the Reiche Zeche mine in Freiberg, Germany, were used as inoculum for two acidic growth media. To explore the efficiency of the bioleaching process leaching tests have been performed in shaking-flasks under laboratory conditions. Ground ore from Reiche Zeche is mainly comprised of the sulfide minerals sphalerite, galena and pyrite. After the leaching process both the solution and the residue were analyzed either by ICP-MS or XRD.The results clearly show that it is possible to leach indium and zinc from natural sphalerite, but that leaching efficiency is hindered, and dissolved indium removed, by the formation of iron-hydroxy precipitates. Hence, optimal conditions for maximum indium recovery with minimal precipitation have to be determined by variation of physico-chemical parameters. Furthermore, the microbial diversity of Reiche Zeche mine waters were studied with cultivation dependent and independent methods.
Microarray-Based Characterization of Microbial Community Functional Structure and Heterogeneity Associated with Acid Mine Drainages
Authors: Shen Li , Yin Hua Qun , Hu Qi , Liu Xue Duan , Qiu Guan Zhou
Published: December 2015

Acid mine drainage (AMD) presents numerous problems to the aquatic life and surrounding ecosystems. However, little is known about the geographic distribution, diversity, composition, structure and function of AMD microbial communities. In this study, an AMD-specific microarray was used to analyze nine AMD microbial communities, and showed that those nine AMD microbial communities had high variations measured by the number of detected genes, overlapping genes between samples, unique genes, and diversity indices. Statistical analyses indicated that the concentrations of Fe, S, Ca, Mg, Zn, Cu and pH had strong impacts on both phylogenetic and functional diversity, composition, and structure of AMD microbial communities. This study provides insights into our understanding of the geographic distribution, diversity, composition, structure and functional potential of AMD microbial communities and key environmental factors shaping them.
Fluoride Toxicity in Bioleaching of Fluorapatite
Authors: Mäkinen Jarno , Kinnunen Päivi , Arnold Mona , Priha Outi , Sarlin Tuija
Published: December 2015

The use of biohydrometallurgical processes may be restricted by microbial inhibition due to inhibiting fluoride originating from the feed material. In this work, phosphorus bioleaching experiments on fluorapatite ore were conducted in a reactor using Fe-and S-oxidizing bacteria, resulting in 56 % leaching yield for P, despite abundant (800 mg l-1) F in the pregnant leach solution. In further F toxicity experiments it was observed that aluminum had a significant role in decreasing the inhibition caused by F, by producing stable complexes with Al. The bioleached ore contained plenty of Al, explaining why bioleaching was not strongly inhibited.
Bioleaching of Copper Sulphide Ore by a Microbial Consortium Isolated from Acid Mine Drainage: Influence of [Fe2+]
Authors: Salcedo-Mejía Luis , Ramírez-Osco Luis , Cayo-Gonzales Hans , Arias-Arce Vladimir
Published: December 2015

Peru is mining country with a great diversity of mineral resource. The high grade ores are declining, and there is a need to implement new techniques for recycling metals (Cu, Au, Zn, Pb, etc) from low-grade ores. In order to answer this question, the bioleaching of copper from sulphide ore (FeS2 45.30%, CuFeS2 1.90%, ZnS 8.90%, FeAsS 13.12%, PbS 3.69%) was evaluated with different concentrations of Fe2+ using an iron-oxidizing native microbial consortium.The samples were collected from drainage acid mine (4100 m.a.s.l.) located in the south of Huancavelica region and the sample of ore from middle Huaraz region (3200 m.a.s.l.). Microorganisms were isolated in 9k medium at pH 1.8, 22oC. Bioleaching test were performed in two consecutive steps to 150 rpm at 22oC, monitoring pH, ORP (mV). Assays varying the concentration of Fe2+ (0 mM – 53 mM) were performed with a pulp density of 1% and 2% at each step, and with an inoculum 10% (v/v) to a microbial concentration of 108 cel/mL.We isolated a microbial consortium after 8 weeks with presence of bacteria Acidithiobacillus ferrooxidans-like. In assays, copper was solubilized. The microbial concentration in the tests was (2x107- 4x107cel/mL). In the first stage, the test with 21 mM Fe2+ recovered 62% copper. In the next step, with the bacterial concentration of the first step, bioleaching time is reduced by 22% for copper recovery (63%) in absence of Fe2+.With these data, we observed that the addition of iron is not necessary in a stage adaptation when the mineral contain iron.
Bioleaching vs. Chloride Leaching: Real Advantages and Drawbacks for Primary Sulfides
Authors: Bobadilla-Fazzini Roberto A. , Gautier Veronica , Jordan Hector , Parada Pilar
Published: December 2015

Currently the vast majority of the world’s copper is obtained through sulfide mineral processing. Among the copper sulfides, chalcopyrite is the most economically relevant due to its abundance. Therefore, several technologies have been developed in order to achieve an efficient copper extraction from copper sulfides. Among these developments, the hydrometallurgical options of bioleaching as well as chemical chloride leaching are prevailing for secondary copper sulfides due to their good results at lab, pilot and industrial scale. Examples such as the Bacterial Thin-Layer technology developed by Minera Pudahuel in the ́80s (CL Patent 32025), as well as the Cuprochlor® process developed by Minera Michilla (CL Patent 45163), coming to the more recent “Heap leaching method” (US Patent WO2014030048A1) and the mixed version of the “Chloride method for bioleaching” patented by BHP Billiton (US Patent WO2012001501A1), are some examples that are currently being extended to the efficient copper extraction from chalcopyrite. In this work, we have compared at lab-scale BioSigma’s bioleaching technology and the industrial state-of-art chloride leaching for a mainly chalcopyritic copper sulfide ore. The metallurgical and microbial results, and the economical evaluation and comparative analysis clearly show that bioleaching presents several advantages compared to chloride leaching, being the biotechnological option more cost-effective and therefore industrially applicable.
Biooxidation of Carbonaceous Refractory Gold Ores by an Iron-Sulfur-Oxidizing Mixotrophic Bacterium at Neutral pH
Authors: Winarko R. , Mubarok M. Zaki , Rizki I.N. , Chaerun Siti Khodijah
Published: December 2015

The ability of an iron-sulfur-oxidizing mixotrophic bacterium to treat two types of sulfide-rich carbonaceous refractory gold concentrates from Sulawesi and Sumatra in Indonesia was studied in comparison with an acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Over the course of the biooxidation experiments, the pH of the solution tended to rise (pH>5) due to the high content of acid-consuming minerals such as carbonates in both concentrates. Ferric ions were frequently observed to precipitate due to high solution pH. The BIOXskc employed in this study was able to increase the gold extraction from low sulfidic carbonaceous refractory gold concentrates by ~15% higher than that by using At. ferrooxidans. It was also capable of treating carbonaceous matters which causes preg-robbing effect and retaining iron in ionic form due presumably to the production of extracellular polymeric substances (EPS) under high solution pH. Nevertheless, BIOXskc also reduced the gold extraction yield of high sulfidic gold concentrates because of passivation effect. It is suggested that the precipitation of iron and sulfur on the surface of sulfide minerals during biooxidation may prevent cyanide ion contact with gold.
Additions of Pyrite or Chalcopyrite Alters the Microbial Community Diversity, Composition and Function in Sphalerite Bioleaching Systems
Authors: Xiao Yun Hua , Liu Xue Duan , Yin Hua Qun , Dong Wei Ling , Liang Yi Li , Ma Li Yuan , Qiu Guan Zhou
Published: December 2015

Extraction of zinc from sphalerite using bio-hydrometallurgical technologies has become more and more popular. This study used an artificial microbial community with five known microorganisms to examine the relationship among microbial diversity, composition, and function (e.g., zinc extraction rates) in sphalerite bioleaching systems with additional pyrite (SP), chalcopyrite (SC), or both (SPC). Real-time quantitative PCR (qPCR) analysis showed that additional pyrite or chalcopyrite changed the microbial community composition dramatically during the sphalerite bioleaching process. Shannon diversity index, compared with Sphalerite (0.109), showed an increase in SP (0.508), SC (0.536) and SPC (0.289) on day 30, and zinc extraction rates were enhanced by about 12.1%, 4.3% and 9.47%, respectively. Also, additional pyrite or chalcopyrite made ORP and the concentrations of Fe3+, Zn2+ and H+ increased, which were the main factors on shaping the microbial community composition by Mantel test analysis. We developed a unitary model, showing that additional pyrite or chalcopyrite increased the microbial community diversity.
New Technology of Base Metals Precipitation by Hydrogen Sulfide Obtained Using Desulfurella acetivorans and Desulfurella kamchatkenis
Authors: Mikhailova Aleksandra N. , Faiberg A.A. , Gudkov S.S. , Dementev V.Ye.
Published: December 2015

Nowadays, efficient recovery of base metals from the solutions when processing gold ores is a topical issue. In this connection, the focus is on the use of hydrogen sulfide produced in bioreactors using sulfate-reducing (SRB) and sulfur-reducing bacteria. A new technology of biogenic hydrogen sulfide production followed by the precipitation of base metals from the solutions as sulfides was developed. The strains of anaerobic sulfidogenic thermophilic microorganisms: Desulfurellaacetrivans and DesulfurellaKamchatkensis which were obtained at S.N.Vinogradsky Institute of Microbiology RAS, Moscow were used for these tests. They have anaerobic respiration using sodium acetate as an electron donor and elemental sulfur as an electron acceptor. In order to cut costs for biogenic hydrogen sulfide production, the possibility of using acetic acid as an electron donor was studied. Scaled-up test work was conducted in a 1.5L bioreactor at the temperature of 55°C, pH of 5.0, redox of-250mV and using POX solution with the content of C2+=5700.0 mg/L, Fe2+=4890.0 mg/L and Zn2+=1200.0 mg/ L. Selective precipitation of copper (at pH of ≤0.5), zinc (pH=1.0-2.0) and iron (II) (pH≥5.5) was carried out. Recycled gas contacted with the metals solutions (in a series of reactors for the precipitation of metals) coupled with the removal of hydrosulfuric acid from the recycled gas and the recovery of metals from the solution as sulfides. The precipitate was separated from the solutions by filtering. Then the filtrate was directed to the next stage. Carbon dioxide was removed from the recycled gas by filtrating through alkaline solution. After that, about 10% of ultra high purity nitrogen was added from the balloon and the recycled gas was again directed to the bioreactor. The average hydrogen sulfide reactor throughput was 1 g/L per day of culture medium. The total consumption of hydrogen sulfide was 1.28 g/L of the process solution. Results showed that this process can selectively recover metals from POX solutions with generation of high grade copper (50%), zinc (45%) and iron sulfide (45%) concentrates.
Assessment of Surface Properties of Silica-Bacterial Cell Complex: A Potential Application for Silicate Bioflotation Processes
Authors: Sanwani Edy , Wahyuningsih Tri , Chaerun Siti Khodijah
Published: December 2015

The objective of the present work was to assess the surface properties of silica-cell complexes formed by Bacillus pumilus strain SKC-2 for bioflotation purposes. This bacterial strain was employed in this study because it is a Gram-positive, mixotrophic bacterium whose metal binding capacity extends to many different metals and circumstances as well as a biosurfactant producer. The strain was found to promote the formation of silica-cell complexes due to the generation of surface-active agents (i.e., extracellular polymeric substrances (EPS)) as represented by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) observation. Surface properties of the complexes was assessed by water contact angle and surface tension measurements, demonstrating that bacterial cells reduced the surface tension of the solutions and increased the contact angle of the silica surfaces, representing a larger hydrophobic property. Therefore, the findings of this study provide clear evidence for the potential application of the bacterium Bacillus pumilus strain SKC-2 for silicate bioflotation processes (i.e., as frother and collector).
Adsorption Kinetics and Surface Characterization of Microorganisms Grown under Different Conditions
Authors: Wu Zeng Ling , Kong Wei Zhang , Liu Jin Yan , Wu Zhi , Zhong Shui Ping , Zhu Yong Guan
Published: December 2015

The adsorption of bacteria onto minerals is the premise for bioleaching and plays an important role in minerals oxidation. Understanding of the adsorption kinetics onto the surface will give information on the effectiveness of bioleaching. Three kinds of mixed bacteria (Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Sulfobacillus) were cultured in different substrates - copper concentrate, elemental sulfur and ferrous iron and adsorbed onto different solid surface of elemental sulfur, silica and copper concentrate. Adsorption kinetics was examined and surface properties were investigated by Zeta-potential and FT-IR spectroscopy. Bacterial adsorption equilibrium data for bacteria grown on three different substrates were well fitted to Freundlich isotherms, indicating inhomogeneous and selective adsorption. Microorganisms grown on copper concentrate and S0 showed similar adsorption kinetics whereby cell adsorptions proceeded rapidly and reached equilibrium within 30 mins of interaction. With the average KF value of 46.2, most copper concentrate-grown cells were strongly adsorbed to three solid surfaces. Microorganisms grown on copper concentrate and S0 also showed higher hydrophobicity and higher isoelectric point (IEP) (pH 3.4-3.8) as compared to the soluble Fe2+-grown cells (pH 2.1), indicating higher amount of EPS and proteins on the surfaces. The FT-IR spectra indicated the presence of COOH, NH2, OH and PO4 groups on all cell surfaces. However, more proteinaceous compounds were found on cells grown on copper concentrate and S0 substrates.
Biometal Demonstration Plant for the Biological Rehabilitation of Metal Bearing-Wastewaters (Biometal Demo)
Authors: Jimeno Manuel Román , Ballester Antonio , Roig Manuel García , Guibal Eric , Costa Maria Clara
Published: December 2015

Heavy metal pollution is one of the most important environmental problems today even threatening human life. A large number of industries produce and discharge wastes containing different heavy metals into the environment and do not comply with current EU directives. European project BIOMETAL DEMO (www.biometaldemo.eu) aims to demonstrate the feasibility of the application of novel biotechnologies for the treatment of metal polluted wastewaters through the development of three pilot plants to be implemented in metal polluting representative industries.The biotechnologies that have been evaluated in project BIOMETAL DEMO are: metal bioprecipitation by sulphate-reducing bacteria and immobilized phytase biocatalysis, and metal biosorption on agricultural industry by-products and biopolymers such as alginate & chitosan based materials.After the evaluation of these techniques, an optimized bioprocess or a synergy of two integrated bioprocesses will be selected to design and build two demonstration pilot plants for scaling-up the metal removal biotreatment.Finally, an economic, social and technical analysis of the benefits of such biotreatment of metal polluted industrial wastewater will be carried out for the corresponding and related industrial sectors.
Biorecovery of Rare Earth Elements: Potential Application for Mine Water Remediation
Authors: Murray A.J. , Singh Sarah , Tolley M.R. , Macaskie L.E.
Published: December 2015

Rare earth elements (REEs) are highly valuable due to the complex nature of their extraction from primary and secondary sources. A key feature is that REEs often co-occur with uranium and thorium which, being radioactive, increase the hazard and complexity of REE recovery. A bioprocess which utilizes enzymatically-generated inorganic phosphate to precipitate REEs from solution as their phosphate biominerals is highly effective in the recovery of REEs, effecting rapid recovery onto immobilized bacterial biofilm at high flow-through rates. This also bioprecipitates U and Th. The metal recovery process requires addition of an organic phosphate substrate, e.g. glycerol 2-phosphate (G2P), the cleavage of which provides the inorganic phosphate source for REE biomineralization. G2P is expensive, precluding its large scale use, but early work using uranium showed that tributyl phosphate (TBP) can be used as an alternative phosphate donor molecule. The potential for substitution of G2P by TBP for biorecovery of neodymium is described and a new approach is proposed for enhancing the metal selectivity for REEs against uranium.
Diversity of Bioleaching Microorganisms in Interfacial Emulsion of Copper Solvent Extraction
Authors: Liu Xiao Rong , Su Chang , Chi Dao Jie , Zheng Xue Song , Yu Hua Long , Shen Jun Hui
Published: December 2015

In the bioleaching - solvent extraction - electrowinning practices for copper extraction, the solvent extraction process is used to enrich the copper in the leachate to a high lever to make the sequent electrowinning process possible. O/W type of interfacial emulsion always forms at the interface between organic phase and aqueous phase in the solvent extraction practices. Diversified microorganisms were discovered by microscope growing in the interface emulsion of copper solvent extraction. The diversity of them was analyzed by using 16s rRNA gene sequencing. It was indicated that there exist seven categories of bacteria in the interface emulsion, among which common bioleaching bacteria, such as Leptospirillum sp.,Acidithiobacillus ferrooxidans, Metallibacterium sp., are included. The dominant strains are Leptospirillum sp. E4-L9 and Acidithiobacillus ferrooxidans ATCC 23270, which account up to 40.48 % and 38.1 %, respectively. It was uncovered that bioleaching bacteria can be intercepted by interfacial emulsion of solvent extraction to make their population in the raffinate lower and the efficiency of bioleaching decrease consequently.
Metal Removal from Spent Catalyst Using Microbacterium liquefaciens in Solid Culture
Authors: Rojas-Avelizapa Norma G. , Gomez-Ramirez Marlenne , Diana Grecia Alamilla Martínez
Published: December 2015

The purpose of the present study was to investigate the ability ofMicrobacterium liquefaciensstrain MNSH2-PHGII-2, isolated from a Mexican silver mine, for removing Ni and V from spent catalyst at 80% (w/v) pulp density in a glass-column system at laboratory conditions. Firstly, microbial culture was adapted to spent catalyst at 0.1% (w/v) in liquid culture then, it was assayed by its ability to remove Ni and V from a spent catalyst in a glass-column system. Spent catalyst was packed at 80% (w/v) pulp density and inoculated at 20% (3x108CFU/ml); air was supplied at 80 ml/min and then incubated at 30°C during 14 days. Parameters such as microbial growth, pH, Ni and V residual concentrations, in catalyst, were determined at days 7 and 14. The result showed thatMicrobacterium liquefaciensstrain MNSH2-PHGII-2 in the glass-column system was able to remove 1007.4 mg/kg of Ni while V was removed at an extent of 5360.5 mg/kg. Microbial removal for other metals in catalyst was non-significant, that indicated the specificity ofMicrobacterium liquefaciensto remove Ni and V.