bluuebunny/crossref_metadata_2025 huggingface dataset:
Microorganisms in Bioflotation and Bioflocculation: Potential Application and Research Needs
Authors: Hanumantha Rao K. , Vilinska Annamaria , Chernyshova I.V.
Published: September 2009

Conventionally, physico-chemical methods are used in mineral processing for recovering value minerals from ores. The ageing of ore processing tailings and waste rocks, and mining tailings contamination by chemical reagents constitute a major threat to the environment. It is imperative to develop novel economically more efficient and environmentally benign methods of flotation and waste processing, exploiting the intriguing and exciting ability of bacteria to selectively modify the surface properties of solids. Microorganisms have not only facilitate hydrometallurgical leaching operations but have also show a great promise in mineral beneficiation processes such as flotation and flocculation. Several laboratory investigations revealed that microorganisms could function similar to traditional reagents. Microorganisms have a tremendous influence on their environment through the transfer of energy, charge, and materials across a complex biotic mineral-solution interface. The bio-modification of mineral surfaces involves the complex action of microorganism on the mineral surface. The manner, in which bacteria affect the surface reactivity and the mechanism of bacteria adsorption, is still unknown and accumulation of the primary data in this area is only starting. The bio-flotation and bio-flocculation processes concern the mineral response to the bacterium presence, which is essentially interplay between microorganism and the physicochemical properties of the mineral surface, such as the atomic and electronic structure, the net charge/potential, acid-base properties, and wettability of the surface. There is an urgent need for developing basic knowledge that would underpin biotechnological innovations in the natural resource (re)processing technologies that deliver competitive solutions.
Attachment Behavior of Leaching Bacteria to Metal Sulfides Elucidated by Combined Atomic Force and Epifluorescence Microscopy
Authors: Florian Bianca M. , Noël Nanni , Bellenberg Soeren , Huergo J. , Rohwerder Thore , Sand Wolfgang
Published: September 2009

The aim of the study was to quantify and to visualize colonization of metal sulfides by pure and mixed cultures. Strains of the genera Acidithiobacillus and Leptospirillum were tested. Sessile and planktonic cells were visualized by fluorescence microscopy using 4',6-diamidino-2-phenylindole (DAPI) and FISH. Additionally, atomic force microscopy was used for the investigations on cell morphology, spatial arrangement of cells on metal sulfides and mineral surface topography. It was shown that the morphology of sessile cells was totally different as compared with planktonic ones. Interactions of different species resulted in increased production of extracellular polymeric substances (EPS) or caused negligible-attaching bacteria to be incorporated into a biofilm by the good attaching ones. Consequently, biofilm formation was furthered.
Studies on Thermophilic Bioleaching of Chalcopyrite toward Heap Application
Authors: Vilcáez Javier , Suto Koichi , Inoue Chihiro
Published: September 2009

In a series of studies, various aspects of thermophilic bioleaching of chalcopyrite minerals and concentrates have been analyzed. Although the main objective was the elucidation of the catalytic effect of thermophiles in leaching chalcopyrite, various other new findings contributed to a better understanding of interactions among chemical, physicochemical and biological factors, which influence the bioleaching of chalcopyrite with thermophiles. Additionally, in order to bridge laboratory results and field applications, novel mathematical models as well as an alternative method to efficiently leach chalcopyrite without thermophiles are the contributions of this research.
Impacts of Mineralogy on the Chemistry and Microbiology of Heap Bioleaching
Authors: Watling Helen R. , Elliot Alexander D. , Perrot Felicity A. , Shiers Denis W.
Published: September 2009

The microbial microenvironment in heaps is strongly influenced by ore mineralogy. While laboratory studies on microbial activity under controlled conditions provide a good understanding how bioleaching organisms might assist in metal extraction, examination of the ore, its mineralogy and leaching chemistry offer additional valuable insights. Some examples are discussed and illustrated with data for a copper-nickel sulfide ore.
Geomicrobiology of Sulfidic Mine Dumps: A Short Review
Authors: Schippers Axel , Kock Dagmar
Published: September 2009

The geomicrobiology of sulfidic mine dumps is reviewed. More than 30 microbiological studies of sulfidic mine dumps have been published. Mainly culturing approaches such as most probable number (MPN) or agar plates were used to study the microbial communities. More recently, molecular biological techniques such as FISH, CARD-FISH, Q-PCR, T-RFLP, DGGE, or cloning have been applied to quantify microorganisms and to investigate the microbial diversity. Aerobic Fe(II)- and sulfur compound oxidizing microorganisms oxidize pyrite, pyrrhotite and other metal sulfides and play an important role in the formation of acid mine drainage (AMD). Anaerobic microorganisms such as Fe(III)-reducing microorganisms dissolve Fe(III)(hydr)oxides and may thereby release adsorbed or precipitated metals. Sulfate-reducing microorganisms precipitate and immobilize metals. In addition to the microbial communities several biogeochemical processes have been analyzed in mine dumps. Pyrite or pyrrhotite oxidation rates have been measured by different techniques: Column experiments, humidity cells, microcalorimetry, or oxygen consumption measurements. Analyses of stable isotopes of iron, oxygen and sulfur have yielded valuable information on biogeochemical reactions. The microbiology and the biogeochemical processes in sulfidic mine dumps have to be understood for control and prevention of AMD generation and to provide different possibilities for remediation concepts. Today, remediation measures, e.g. under water storage of the waste or covering of the dumps, focus on the inhibition of pyrite oxidation to keep the toxic compounds inside the mine waste dumps. As an alternative to the inhibition of pyrite oxidation, metals which also have economic value could be extracted from mine dumps by the application of different metal extraction technologies including bioleaching.
Oxidation of Chalcopyrite (CuFeS2) by Acidithiobacillus Ferrooxidans and a Mixed Culture of Acidithiobacillus Ferrooxidans and Acidithiobacillus Thiooxidans Like Bacterium in Shake Flasks
Authors: Mejía E.R. , Ospina J.D. , Márquez M.A. , Morales A.L.
Published: September 2009

Chalcopyrite bioleaching process using Acidithiobacillus ferrooxidans and a mixed culture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans like bacterium was carried out. Two mineral particle sizes were evaluated, 200 and 325 Tyler mesh. The strains were adapted by gradually decreasing of the main energy sources and increasing in the mineral content. The experiments were performed in absence of ferrous sulphate and elemental sulfur. When the mixed culture was used, pH values were always over 2,1, indicating a probable passivation of Acidithiobacillus thiooxidans in the consortium. For both cultures, the Cu2+ dissolution occurred at relatively low redox potential values, around 400mV–450mV, while at high redox potential values, 550mV, chalcopyrite dissolution was inhibited. Copper lixiviation was around 40% for both tests. The Fourier Transform-Infrared spectra showed that the main oxidation phase is jarosite. The results showed that chalcopyrite oxidation is more dependent on the redox potential than particle size or type of culture used.
The Effect of Chloride Ions and A. Ferrooxidans on the Oxidative Dissolution of the Chalcopyrite Evaluated by Electrochemical Noise Analysis (ENA)
Authors: Horta Daniela G. , Acciari Heloísa A. , Bevilaqua Denise , Benedetti Assis Vicente , Garcia Jr. Oswaldo
Published: September 2009

It is believed that the dissolution of chalcopyrite (CuFeS2) in acid medium can be accelerated by the addition of Cl- ions, which modify the electrochemical reactions in the leaching system. Electrochemical noise analysis (ENA) was utilized to evaluate the effect of the Cl- ions and Acidithiobacillus ferrooxidans on the oxidative dissolution of a CPE-chalcopyrite (carbon paste electrode modified with chalcopyrite) in acid medium. The emphasis was on the analysis of the admittance plots (Ac) calculated by ENA. In general, a stable passive behavior was observed, mainly during the initial stages of CPE-chalcopyrite immersion, characterized by a low passive current and a low dispersion of the Ac plots, mainly after bacteria addition. This can be explained by the adhesion of bacterial cells on the CPE-chalcopyrite surface acting as a physical barrier. The greater dispersions in the Ac plots occurred immediately after the Cl- ions addition, in the absence of bacteria characterizing an active-state. In the presence of bacteria the addition of Cl- ions only produced some effect after some time due to the barrier effect caused by bacteria adhesion.
Effect of Flotation and Solvent Extraction Reagents on the Bioleaching of a Copper Concentrate with Sulfolobus Metallicus
Authors: Escobar B. , Quiroz L. , Vargas T.
Published: September 2009

The effect of two flotation reagents: isopropyl- and ethyl-xanthates and two solvent extraction reagents (SX): Lix 984 and Lix 860IC on the bioleaching of a copper concentrate with Sulfolobus metallicus was analyzed. The experiments were performed in 250 ml shake flasks with 100 ml basal medium with an initial pH of 1.6, inoculated with a pure culture of S. metallicus and 0.5 % copper concentrate (38% of Cu) at 70oC. In the bioleaching flasks 0, 50 or 500 μg/mL of flotation reagent and 0, 10 or 100μg/mL of SX reagents was added. All organic reagents caused a strong inhibition of ferrous iron oxidation and growth of planktonic cells of S. metallicus. However, bioleaching in presence of 50 μg/mL of isopropyl-xanthate or 10 μg/mL of Lix 984 reached copper dissolutions of 70% and 72% respectively after 200 hours, compared with 98% in the process without organic reagents. These results suggest that isopropyl-xanthate and Lix 984 at the lowest concentrations used in this study would not affect the mechanism of bioleaching by contact of S. metallicus on the sulphide, however it strongly affected the indirect mechanism. Ethyl-xanthates and Lix 860IC, beginning with 50μg/mL and 10μg/mL respectively, generated a total inhibitory effect on the oxidation activity of S. metallicus on the sulphides.
Bacterial Oxidation of Ferrous Iron and RISCs at Low Temperatures: Their Effect on Acid Mine Drainage and Bioleaching of Sulphide Minerals
Authors: Escobar B. , Buccicardi S. , Morales G. , Wiertz J.V.
Published: September 2009

Chilean copper production has been growing in the last 20 years reaching an annual production of 5,557,000 tons of Cu in 2007. For each ton of copper produced, about 200 tons of sterile and low grade ore and 100 tons of tailings are discharged in the environment. Most of these wastes contain significant amounts of sulphide minerals, mainly pyrite, and once submitted to weathering, may produce acid mine drainage. On the other hand, the high price of copper raised the interest for processing by leaching the low grade ore deposited in large dumps. An important part of these mining wastes and low grade ores is located in the Andes, where the mean temperature is usually ~5°C or less. The rate at which bioleaching reactions occur is directly related to the temperature at which the microorganisms (bacteria and archaea) develop. A temperature decrease causes both a decrease of the rate of the involved chemical reactions and a decrease or inhibition of microbial growth. In this work we present the results of the isolation of microorganisms from an old tailing deposit, exposed at low temperatures (5oC) during most of the winter. The isolated microorganisms initially showed a low capacity to oxidize 3g/L Fe(II) sulfate at pH 1.6, and tetrathionate 0.01 M, with an initial pH 4 both at 5oC. However, after successive cultures, microorganisms showed a slow capacity to oxidize both substrates, as well as the sulphide contained in the tailings samples. The terminal Restriction Fragment Length Polymorphism (tRFLP) of the isolated cells grown in basal medium containing Fe(II) showed a nearly pure culture of Acidithiobacillus ferrooxidans. The present study indicates that, even at very low temperatures, microorganisms play an important role in the generation of acid mine drainage and in the oxidation and leaching of sulphide ores.
Bioleaching of Uranium Ore by a Novel Acidophilic Consortium at Different Acid Concentrations
Authors: Liu Ya Jie , Li Jiang , Li Xue Li , Shi Wei Jun , Sun Zhan Xue , Xu Ling Ling , Liu Jin Hui , Gao Feng
Published: September 2009

This study examined bioleaching of uranium ore at different acid concentrations by a novel consortium culture combined with both mesophilic and moderately thermophilic acidophiles containing 4 species of bacteria and 1 species of fungus. Four plastic buckets were set up with uranium minerals at room temperature (about 27-32°C) at different acid concentration (6g/l and 15g/l) for acidification and initial pH of 1.6, 1.8 and 2.1 for bioleaching, respectively. Results showed that from a point of application in commercial uranium bioleaching, higher acidified concentrations of acid can shorten the duration and working cycles of uranium recovery, and a higher initial pH in bioleaching stage can reduce the usage of acid.
Biooxidation of Refractory Gold Ores by Mixed Moderate Thermophiles in Airlift Bioreactor
Authors: Xie Xue Hui , Xiao Sheng Mu , Wang Hua Tai , Liu Jian She
Published: September 2009

Bacterial preoxidation of refractory gold ore has showed many advantages, such as lower operation cost and environmental friendly. In this paper, biooxidation of refractory gold ore by mixed moderate thermophiles culture in airlift bioreactor has been well studied. Firstly, a laboratory scale airlift bioreactor unit has been designed for bacterial preoxidation of refractory gold ore, a mixed moderate thermophilic culture was incubated. The orthogonal experiment was performed to investigate the effects of particle size, pulp density, aeration rate and initial pH. The results showed that when particle size 37micrometer，pulp density 5%，aeration rate 4 dm3•s-1 and initial pH 1.2, the arsenic leaching rate achieved to 93.5%. On the base of the airlift bioreactor unit, a continuous airlift bioreactor was designed. The preoxidation of refractory gold ore by a mixed culture of moderately thermophilic bacteria also was investigated in this equipment. The results showed that, under the conditions of pulp density 8% and stay time 60h, it can deal with 0.256 kg refractory gold ore per day, and the arsenic leaching rate can reach to 95.25%. During the experiment, some leaching liquor has been sampled from the second sect the fourth column of the continuous airlift bioreactor. The composition of microbial communities in this sample has been investigated using culture-independent 16S rDNA based cloning approach- restriction fragment length polymorphism. The phylogenetic analysis revealed that Leptospirillum ferriphilum and Acidithiobacillus caldus are the main organisms in this system. Both of them are moderate thermphilic bacteria and can resist relatively high concentration of arsenic ion.
Diversity of Iron Oxidizing Bacteria from Various Sulfidic Mine Waste Dumps
Authors: Breuker Anja , Blazejak Anna , Bosecker Klaus , Schippers Axel
Published: September 2009

More than 100 cultures of acidophilic Fe(II)- and/or sulfur-oxidizing microorganisms from mine waste dumps in 10 different countries all over the world have been maintained in liquid media in the BGR-strain collection for many years. Our 16S rDNA analysis showed that most of the cultivated Fe(II)-oxidizers belong to four genera: Acidithiobacillus, Acidimicrobium, “Ferrimicrobium” and Leptospirillum. All analyzed Acidithiobacillus strains were identified as At. ferrooxidans. The Leptospirillum strains were affiliated with L. ferriphilum or L. ferrooxidans. The Gram-positive strains related to Acidimicrobium or ”Ferrimicrobium” were phylogenetically more diverse than the strains of the genera Acidithiobacillus and Leptospirillum and fell into three separate clusters. While several strains could be identified as syngeneic (16S rDNA) with “Ferrimicrobium acidiphilum”, two other 16S rDNA clusters were distantly related and might represent new species or even new genera. In addition, one new Sulfobacillus strain and one new Alicyclobacillus strain could be identified. Furthermore several strains related to Acidiphilium acidophilum have been detected and form one 16S rDNA cluster.
Mineralogical Characterization of a Polymetallic Concentrate Portovelo Mining District. Bioleaching by a Native Bacterial Consortium
Authors: Gordillo F. , Suarez J.P. , Sanmartín Vasan , Aguirre P. , Gentina J.C. , Donati Edgardo R.
Published: September 2009

The mining district of Zaruma-Portovelo of southern Ecuador is a deposit of polymetallic sulfides worked since 1908. Currently the small traditional mining operation processes 1800 tons of ore a day, generating environmental waste that is accumulated and systematically discharged into the Calera and Amarillo Rivers. In this watershed area of Puyango-Tumbes, where samples were taken and subjected to gravimetric concentration, a mineralogical analysis of the concentrate was made. Samples of sediments taken from areas of weathered mining shafts were used to isolate native microorganisms for subsequent molecular and physiological characterization. The mineral concentrate contains 66.63 % of pyrite, 175 ppm Ag and 6.9 ppm Au (with 80 % of refractory gold). This mineral was subjected to biooxidation by the isolated native organisms. In experiments with pulp density of 10%, the solubility of the sulfides was very significant, reaching concentrations of Fe3 + 30 g/L and sulfate 60 g/L.
Bioleaching of Enargite by Arsenic-Tolerant Acidithiobacillus Ferrooxidans
Authors: Sasaki Keiko , Takatsugi Koichiro , Hirajima Tsuyoshi , Kozai Naofumi , Ohnuki Toshihiko , Tuovinen Olli H.
Published: September 2009

Acidithiobacillus ferrooxidans was acclimatized to 1000 mg/L arsenic(V) and then used
for the bioleaching of enargite (Cu3AsS4) at pH 2. Secondary minerals formed during the
bioleaching of enargite were characterized by X-ray diffraction, FT- infrared spectroscopy, Raman
spectroscopy and X-ray photoelectron spectroscopy. Oxidative dissolution of enargite resulted in
the formation of elemental sulfur, arsenate and oxidized sulfur species including jarosites and
possibly also schwertmannite at pH 2.
The Microbial Assisted Leaching of Nickel Laterites Using a Mixed Culture of Chemolithotrophic Microorganisms
Authors: Ndlovu Sehliselo , Simate Geoffrey S. , Gericke Mariekie
Published: September 2009

Nickel laterite contains metal values but is not capable of participating in the primary chemolithotrophic bacterial oxidation because it contains neither Fe2+ iron nor substantial amount of reduced sulphur. Its metal value can, however, be recovered by allowing the primary oxidation of FeS2, or similar iron/sulphur minerals to provide H2SO4 acid solutions, which solubilise the metal content. This study investigated the possibility of treating nickel laterites using chemolithotrophic microorganisms. Preliminary studies conducted using H2SO4 acid, citric acid and acidified Fe2(SO4)3 gave an insight on the use of chemolithotrophic bacteria in this process,. Results showed that H2SO4 acid performed better, in terms of nickel recovery, than citric acid or acidified Fe2(SO4)3. In the bacterial leaching test works, mixed cultures of Acidithiobacillus ferrooxidans, Acidithiobacillus caldus and Leptospirillum ferrooxidans were used in the presence of elemental sulphur and FeS2 as energy sources. The sulphur substrate exhibited better effects in terms of bacterial growth, acidification and nickel recovery than the FeS2 substrate. Using response surface methodology, the theoretical optimum conditions for maximum nickel recovery (79.8%) within the conditions studied was an initial pH of 2.0, 63μm particle size and 2.6% pulp density.
In Situ Application of Bioleaching for Improving the Quality of Quartz Sand
Authors: Štyriaková Iveta , Jablonovská Katarína , Mockovčiaková A.
Published: September 2009

Quartz sands contain various iron and clay minerals which coat silicate grains or are impregnated in silicate matrix. Treatment by basin water bioleaching in combination with electromagnetic separation can substantially improve the quality of quartz sands. The purpose of this in-situ study was to evaluate the feasibility of using a biological basin treatment process to improve the quality of quartz sands. The environmental conditions involved the changes of climate temperature, using fresh surface water without disinfection, inhibition of algae and fungi, and promoting bacteria. Analyses of the solution phase were used to monitor the dissolution of iron during the bioleaching of the quartz sands and to optimize the in-situ conditions for the bacterial activity. The rate of iron dissolution varied with environmental conditions, with the addition of nitriloacetic acid (NTA)/l and organic feedstock in the form of molasses. Bacterial removal of clay and iron minerals can be used to expose the white surfaces of quartz grains. The quartz sands from the Šaštín deposit (Slovakia) were used in glass industry after decreasing the Fe content.
Bacterial Removal of Iron from Bauxite Ores: A Comparative Study Using Three Dissimilatory Iron Reducing Microorganisms
Authors: Papassiopi N. , Vaxevanidou K. , Kontogianni A.
Published: September 2009

Bio-beneficiation of ores through iron removal is a common technique, but not yet tested for the case of bauxite. In this study we compared the iron reducing ability of three bacterial species with and without the chelating action of EDTA. Tests were carried out using a diasporic bauxite sample containing 19.3% Fe2Ο3 in the form of hematite, goethite and chamosite. Reductive dissolution was attempted using three neutrophilic, dissimilatory Fe(III) respirators, i.e. the facultative anaerobes Shewanella putrefaciens and Ferrimonas balearica and the strict anaerobe Desulfuromonas palmitatis. Almost 25% of Fe was reduced by D. palmitatis and S. putrefaciens and 30% by F. balearica in bauxite samples. In the case of S. putrefaciens and F. balearica, Fe(III) reduction took place without addition of EDTA, but most of the biologically produced Fe(II) reprecipitated. The addition of EDTA proved to hinder the bioreduction potential for both S. putrefaciens and F. balearica. On the contrary, D. palmitatis was able to reduce Fe(III) oxides only in the presence of EDTA. Moreover, the presence of EDTA helped maintain biogenic ferrous iron in solution.
Status of Coal Biotechnology in Pakistan
Authors: Ghauri M. Afzal , Anwar M.A. , Akhtar N. , Haider R. , Tawab A.
Published: September 2009

Pakistan is endued with 185 billion tons colossal reserves of coal, but only 7.89 % of the country total energy requirements are met by coal. Most of the Pakistani coal reserves are sub-bituminous or lignitic in nature and contain 3-12 % sulphur. Existence of sulphur compounds in coal limits its industrial application due to environmental as well as technical problems. However, coal biotechnology can emerge as panacea for upgrading the huge reserves of coal in Pakistan. In general, coal biotechnology refers to biodesulphurization, biosolubilization and biogasification of coal. NIBGE has long term interests in the field of coal bioprocessing for tapping prime resources of indigenous coal. In NIBGE, lab scale experiments for coal biodesulphurization led to 90% efficiency in sulphur removal. Heap leaching was also carried out at the level of 10 and 20 tons coal heaps with 60% sulphur removal efficiency. Furthermore, a prototype of 300 tons coal heap was set up with a local cement industry and 75% microbial desulphurization was achieved. The league of indigenously isolated chemolithotrophic bacteria was involved in coal desulphurization. On the other side, for making the best use of 175 billion tons of low rank coal reserves, coal biosolubilization and subsequent biogasification is being projected. Consequently, beneficiated coal through biotechnology is supposed to contribute in energy mix of Pakistan for providing electricity requirements of the country and saving huge oil import bills.
Interaction of Chitosan with Metal Ions: From Environmental Applications to the Elaboration of New Materials
Authors: Guibal Eric , Vincent Thierry , Roussy Jean
Published: September 2009

Chitosan is an emblematic example of biopolymer that can be obtained from renewable resources (fungal biomass, crustacean shells…) and that can be used for binding a number of metal ions through different mechanisms (complexation, electrostatic attraction, ion pair formation). Chitosan was used for the sorption of various transition metals, from toxic (Hg(II), Cd(II), U(VI), Mo(VI), V(IV) and V(V) …) to strategic and valuable metals (Pd(II), Pt(IV), Au(III) …). However, the interactions of chitosan with metal ions are not strictly limited to environmental applications. Hence, the binding of metal ions on the biopolymer can be used for designing new materials or new applications. Some examples are reported below.
Metal - Microbes Interactions: beyond Environmental Protection
Authors: Tsezos Marios
Published: September 2009

Bioremediation can be applied for the treatment of metal/metalloid and radionuclide bearing water streams in order to immobilize the targeted species. Interactions of microbial cells with soluble targeted species may occur during the microbial metabolism and result to the reduction of their mobility and toxicity. The most important metabolically mediated immobilization processes for metal/metalloid and radionuclide species are bioprecipitation and bioreduction. Bioprecipitation includes the transformation of soluble species to insoluble hydroxides, carbonates, phosphates and sulfides as a result of the microbial metabolism. In the case of biological reduction, the cells use the species as terminal electron acceptors in anoxic environments to produce energy and/or reduce the toxicity of the cells microenvironment. These processes can be the basis of technologies for the rehabilitation of contaminated sites both for surface and groundwater aquifers, soils and industrial water streams. Such technologies are recently developed and applied both in pilot and full scale, although the related mechanisms are complicated and not always fully understood.
In Situ Bioremediation of Contaminated Soils in Uranium Deposits
Authors: Groudev Stoyan N. , Spasova Irena , Nicolova Marina , Georgiev Plamen S.
Published: September 2009

Experimental plots consisting of acidic and alkaline soils heavily contaminated with radionuclides (mainly U and Ra) and non-ferrous metals (mainly Cu, Zn, Cd, Pb) were treated in situ under real field conditions using the activity of the indigenous soil microflora. This activity was enhanced by suitable changes of some essential environmental factors such as pH and water, oxygen and nutrient contents of the soil. The treatment was connected with solubilization and removal of contaminants from the top soil layers (horizon A) due to the joint action of the soil microorganisms and leach solutions used to irrigate the soils (mainly acidophilic chemolothotrophic bacteria and diluted sulphuric acid in the acidic soil, and various heterotrophs and bicarbonate and soluble organics in the alkaline soil). The dissolved contaminants were removed from the soil profile through the drainage soil effluents or were transferred to the deeply located soil subhorizon B2 where they were precipitated as the relevant insoluble forms (uranium as uraninite, and the non-ferrous metals as the relevant sulphides) as a result of the activity of the sulphate-reducing bacteria inhabiting this soil subhorizon.
Sulphate Reducing Bacteria for the Treatment of Heavy Metals Contaminated Waters in Permeable Reactive Barriers
Authors: Cruz Viggi Carolina , Pagnanelli Francesca , Cibati Alessio , Berteletti C. , Toro Luigi
Published: September 2009

The aim of the work was the comparison between a selected reactive mixture containing organic matter for SRB and other electron donors, such as ethanol and polysaccharides. The comparison was performed in order to select the best operating conditions in terms of organic sources for SRB. A continuously operating fixed-bed column was filled with a batch-optimised solid reactive mixture (6% leaves, 9% compost, 3% zero valent iron, 30% silica sand, 30% perlite, 22% limestone) and inoculated by SRB. At steady state 50±10% sulphate abatement was reached and metals were totally removed. Batch tests with ethanol showed the ability of SRB to grow on this substrate efficiently. Experimentation using ethanol was performed using two different column reactors filled with perlite, one inoculated by SRB and the other used as blank. Sulphate abatements of the inoculated column were 70±10% against 10±5% of the blank column. Preliminary batch tests with polysaccharides showed the ability of bacteria to grow on these substrates.
Testing of Different Substrate Materials for Sulphate Reducing Reactive Barrier to Treat Acid Mine Drainage
Authors: Vestola Elina A.
Published: September 2009

The aim of this study was to find cheap, solid substrate material for sulphate reducing bacteria (SRB) to be used in permeable reactive barrier (PRB) and infiltration beds to treat acidic, nickel-, copper- and iron-rich mine drainage. Laboratory experiments were carried out to examine the reactivity and utilisation of different substrate materials. The materials of interest were peat, sawdust, cucumber compost and cellulose. Limestone, phosphorus and nitrogen were added to the mixture to create optimum growth conditions for SRB. Based on a batch tests, cucumber compost was chosen to be examined in larger-scale column tests. Results from the column tests were promising. Nickel (43 mg L-1), copper (24 mg L-1) and iron (95 mg L-1) were precipitated almost completely and the concentration of sulphate was decreased approximately 20 %. pH values increased from 2.7 to 8. Based on laboratory tests results it appears that cucumber compost was suitable substrate material for SRB in PRBs and infiltration beds treating AMD.
Bioprecipitation of Arsenic Sulphide at Low pH
Authors: Battaglia-Brunet F. , Morin Dominique H.R. , Coulon S. , Joulian Catherine
Published: September 2009

A process for the precipitation of trivalent arsenic sulphide in sulphate-reducing condition at low pH would be very attractive due to the high arsenic content (60%) in the final precipitate. A bacterial consortium able to reduce sulphate at pH 4.5 served to inoculate column bioreactors that were continuously fed with As(V) or As(III), glycerol and/or hydrogen, at pH values between 2 and 5. The diversity, functionality and evolution of the consortium colonizing the bioreactors were characterized by means of biomolecular tools, in relation with operating parameters (pH, As, sulphide, acetate). The highest As removal rate obtained during these experiments was close to 3 mg.l-1.h-1 using As(V) as the initial arsenic form, while precipitation rates were improved using As(III). When glycerol was replaced by hydrogen in a bioreactor containing a mature biofilm, sulphate-reducing activity increased roughly. Organisms related to Desulfosporosinus were the only sulphate-reducing bacterium (SRB) detected in the bioreactor. arrA genes, involved in As(V) dissimilatory reduction, were also detected and suggested that As(V) was reduced by a Desulfosporosinus-like organism. Molecular fingerprints evidenced an evolution of the bacterial population structure according to changes in operating conditions.
Biosorption of Mercury(II) with Different Marine Algae
Authors: Reategui Mariana , Maldonado Holger , Ly M. , Guibal Eric
Published: September 2009

Five species of algae (Lessonia nigrescens Bory, Prionitis decipiens, Grateloupia doryphora, Lessonia trabeculata and Macrocystis integrifolia) collected from Peruvian coast have been tested for mercury recovery from synthetic solutions. Preliminary experiments showed that optimum sorption occurred at pH 6-7 and that Lessonia algae were the most efficient sorbents for Hg(II). The biomass was cross-linked with calcium chloride. Stabilized biosorbent showed sorption capacity as high as 267 mg g-1 at pH 6. The sorption isotherm was described by the Langmuir equation, while the pseudo-second order equation was used for modeling uptake kinetics. Salt addition strongly affected mercury sorption following the sequence: NaNO3 << Na2SO4 <<< NaCl.
Characterization of Sargassum sp. from Brazil and Evaluation of Cu2+ and Ni2+ Biosorption
Authors: Kleinübing S.J. , Guibal Eric , da Silva Meuris Gurgel Carlos
Published: September 2009

Fundamental investigation on adsorption of Cu2+ and Ni2+ ions on Sargassum
sp. was performed in fixed-bed column. The Langmuir isotherm fitted well the biosorption
equilibrium and the maximum Cu2+ and Ni2+ uptake capacities were 1.35 and 1.06 mmolg-
1, respectively. Mappings of copper and nickel in the algae surface using energy
dispersive X-ray spectroscopy indicated a homogeneous distribution of Cu- and Niadsorbent
sites. Fourier-transform infrared analysis revealed that the main chemical
groups involved in the copper and nickel biosorption were carboxyl, ether, alcoholic,
amino, and sulphonic groups.
Cr (VI) Ion Uptake by the Yeast S. Cerevisiae UCM Y-1968 and its Protoplasts
Authors: Mameeva Olag G. , Podgorsky V.S.
Published: September 2009

The present study is focused on the investigation of hexavalent chromium uptake by the yeast S. cerevisiae UCM Y–1968 and its protoplasts. For the first time the ability of S. cerevisiae protoplasts to accumulate Cr (VI) ions was shown. Under the influence of various concentrations of Cr (VI) ions, the proportion of the surviving yeast cells and protoplasts decreased as treatment time extended. During 0.5 – 1h of treatment, yeast protoplasts demonstrated a significant level of Cr (IV) ion accumulation, 44 – 47 % of the supplied Cr ions, whereas the initial strain S. cerevisiae UCM Y-1968 accumulated 9 – 10 %. The isotherms for S. cerevisiae UCM Y-1968 were related to L2 types and for yeast protoplasts isotherms were related to L3 types. Cr (VI) sorption/uptake parameters (Qmax, b) for living cells were found for S. cerevisiae UCM Y–1968 (Qmax = 890 μmol/g) and its protoplasts (Qmax = 1335 μmol/g) at the initial Cr (VI) ions concentration of 25 mg/l. The results showed that hexavalent chromium uptake by living yeasts biomass mainly depended on intracellular accumulation. Chromium uptake by protoplasts cells was characterized by simultaneous metabolism-dependent bioaccumulation with prevalence of the intracellular accumulation of Cr (VI) ions.
Study of Biosorption of Rare Earth Metals (La, Nd, Eu, Gd) by Sargassum sp. Biomass in Batch Systems: Physicochemical Evaluation of Kinetics and Adsorption Models
Authors: Oliveira R.C. , Garcia Jr. Oswaldo
Published: September 2009

This work evaluated kinetic and adsorption physicochemical models for the biosorption process of lanthanum, neodymium, europium, and gadolinium by Sargassum sp. in batch systems. The results showed: (a) the pseudo-second order kinetic model was the best approximation for the experimental data with the metal adsorption initial velocity parameter in 0.042-0.055 mmol.g-1.min-1 (La < Nd < Gd < Eu); (b) the Langmuir adsorption model presented adequate correlation with maximum metal uptake at 0.60-0.70 mmol g-1 (Eu < La < Gd < Nd) and the metal-biomass affinity parameter showed distinct values (Gd < Nd < Eu < La: 183.1, 192.5, 678.3, and 837.3 L g-1, respectively); and (c) preliminarily, the kinetics and adsorption evaluation did not reveal a well-defined metal selectivity behavior for the RE biosorption in Sargassum sp., but they indicate a possible partition among RE studied.
X-Ray Absorption Spectroscopy Applied to Metal Accumulation
Authors: Pinto de Carvalho Regina , Silva G.C. , Dantas M. Sylvia S. , Vasconcelos I.F. , Ciminelli Virgínia S.T.
Published: September 2009

X-Rays Absorption Fine Structure Spectroscopy (XAFS) is an analytical technique that can be used as a probe to characterize almost all elements, even if they appear in diluted or non-crystalline systems. This is due to the fact that the absorption probability of X-rays has a unique feature for each element, and is modulated by the chemical and physical state of that element, as well as by its neighborhood. This paper presents a brief description of the X-rays absorption phenomenon and the analytical technique involving this phenomenon, as well as the application of XAFS in biosorption studies. For more details on XAFS theory, refer to [1].
Nickel and Cobalt Removal Capacities of Native Metal-Resistant Bacteria
Authors: Marrero Jeannette , Diaz A. , Valle Antonio , Cantero Domingo , Gómez José Manuel , Coto Orquidea
Published: September 2009

Genetic determinants for heavy metal resistance could be exploited in the design of bioprocesses for environmental cleanup. The removal of Ni(II), Co(II), Cr(VI) and Mn(II) was investigated using Serratia marcescens strains C-1, C4, 16 and Kluyvera sp. Nic3 isolated from nickel deposits in Moa, Holguín (Cuba). The high nickel and cobalt resistance of S. marcescens C-1 is based on the NreB- genetic determinant ncrABC, which encodes histidine-rich proteins, NcrA, NcrB and NcrC. NcrC is a Ni(II)/Co(II) uptake protein. In this work the presence of ncrAB fragment in S. marcescens C4, 16 and Kluyvera sp. Nic3 was determined by PCR. ncrAB fragment was efficiently amplified from genomic DNA of the strains C4 and 16 but not from strain Nic3. Strains C4, 16 and C-1 showed the highest resistance to Ni(II) and Co(II). The Ni(II)/Co(II) removal capacities of C4, 16 and C-1 strains were two times higher than that by Nic3 (12.88 mg of Ni(II)/g of biomass and 9.77 mg of Co(II)/g of biomass). Uptake of Cr(VI) and Mn(II) was not observed for any of these strains. pH value has an important influence on the Ni(II) and Co(II) removal capacity of S. marcescens C-1. Additional studies are currently in progress aimed to check the metal removal efficiency of strain C1 in batch reactors.
Arsenic Immobilization by Biological Scorodite Crystallization: Effect of High Ferric Concentration and Foreign Seeds
Authors: González Contreras Paula , Weijma Jan , Buisman Cees N.J.
Published: September 2009

Biological scorodite is produced at 80°C and 1g L-1 As5+, using iron oxidizing bacteria Acidianus Sulfidivorans, with a molar ratio Fe/As of 1 and without the use of seeds. We investigated the effect of high ferrous concentration, Fe/As higher than 1, and the use of foreign seeds (gypsum) on biological scorodite crystallization. The use of high ferrous concentrations resulted in a retardation of the time of crystallization due to the high concentration of ferric produced by a high biological oxidation. However, ferrous biological oxidation might be controlled to avoid this effect. The use of seeds did not improve the kinetics of crystallization. Nonetheless, a high arsenic removal rate was observed in the presence of seeds probably as a result of the formation of less stable scorodite.
Comparison between the Bacterial Populations from Solutions and Minerals in 1 m Test Columns and the Industrial Low Grade Copper Sulphide Bioleaching Process in the Escondida Mine, Chile
Authors: Zepeda V. , Galleguillos F. , Urtuvia V. , Molina J. , Demergasso Cecilia
Published: September 2009

The study of microbial populations of biohydrometallurgic processes is generally more focused on the solutions involved than on the minerals. This is mainly due to complexity and costs associated with taking mineral samples during the leaching cycle. The present study compares the microorganisms in the solutions and the minerals in 1 m test columns and in samples taken from two strips of an industrial heap from the Escondida Copper Mine in Chile. The column test was carried out in six 1 m columns that were operated with similar parameters than the industrial heap. The industrial heap is divided into strips, and samples were collected from Strip 1 (after the end of the operation) and from Strip 9 (during the irrigation period). To analyze the bacterial population Real-Time PCR and CARD-FISH techniques were used. From the results of the column leaching tests a slightly greater cellular density was observed for the mineral than the solution, when the total bacterial count was considered. In both types of samples the predominant microorganisms were Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans D2 and Leptospirillum ferriphilum. In the samples from the industrial heap A. ferrooxidans predominated at the start of operation and A.thiooxidans at the end of the leach cycle.
Mercury Reduction by Bacteria Isolated from Informal Mining Zones
Authors: Sánchez Dávila J. , Hurtado Custodio J.
Published: September 2009

The aim of this research was the selection of bacterial strains resistant to mercury, as well as to demonstrate their capacity to reduce mercury in solution when they are inoculated in pure and mixed cultures. Samples of soil from informal mining gold sites in Peru were collected and fifteen mercury resistant bacteria were isolated. Strains RM6, RM7, RM9, RM11, RM12 and RM13 were selected for their capacity to reduce mercury in solution. The six bacterial strains belong to the genus Pseudomonas. Inoculated in pure cultures, these strains reduce mercury in solution although in different percentages: RM9, RM11 an RM12 reduce 93% to 97% of the mercury, while strains RM6, RM7 y RM13 reduce 80% to 85%. The consortium of all six bacterial strains showed a mercury reduction of 84%. Approximately 91% of mercury in solution was reduced in 1 hour and this reaction was not associated to bacterial growth. Using specific primers, the merA gene was amplified from genomic DNA of the bacterial strains, which would suggest the activity of the mer operon as a mechanism of mercury resistance. Due to their ability to reduce mercury in solution, it is advisable to carry out more research on the selected strains since they could be useful in future bioremediation processes.
Recovery of Nickel and Zinc Using Biogenerated Sulphuric Acid
Authors: Yagnentkovsky Nadia , Viera M. , Donati Edgardo R.
Published: September 2009

Sludge generated in automotive and related industries often contains heavy metals. Bioleaching is an attractive alternative for the treatment of metal containing solids. Bacteria of the genus Acidithiobacillus are the most important microorganisms applied to metal solubilisation. These microorganisms are able to produce sulphuric acid from the aerobic oxidation of elemental sulphur. The biogenerated sulphuric acid can be applied to the solubilisation of metals from a solid matrix. In this paper we present the results of our experiments aimed at the removal of nickel and zinc from sludge generated in the water treatment plant of an automotive industry. Acidithiobacillus thiooxidans cells were immobilised on sulphur pearls in a column reactor. The effects of sulphur pulp density and the dilution rate on the production of sulphuric acid were studied. In a second stage, sulphuric acid was used to solubilise the nickel and zinc from the sludge. The effects of different sludge pulp densities and initial acid pH were studied. High recoveries of zinc and nickel were obtained when the pH value of the sulphuric acid solution was lower than 2.0 for 1 and 2 % of pulp density.
Bioleaching of Nickel, Vanadium and Molybdenum from Spent Refinery Catalysts
Authors: Beolchini F. , Fonti V. , Ferella Francesco , Centofanti Marcello , Vegliò Francesco
Published: September 2009

Spent catalysts represent a large amount of refinery solid waste. In particular, hydro-processing catalysts contain base valuable metals, such as nickel, vanadium and molybdenum and, for their toxic component, these wastes have been classified as hazardous by the Environmental Protection Agency in the USA. The development of an innovative eco-sustainable process for the valorisation of such wastes would undoubtedly give significant advantages also taking into account primary resources preservation. This paper deals with bioleaching of metals from hazardous spent hydro-processing catalyst by means of iron/sulphur oxidizing bacteria. The exhaust catalyst was rich in nickel (45 mg/g), vanadium (44 mg/g) and molybdenum (94 mg/g). Before bioleaching, the solid was washed by means of a mixture of Tween 80 and ethyl alcohol, for hydrocarbon removal. The effects of elemental sulphur, ferrous iron and actions contrasting a possible metal toxicity (either the presence of powdered activated charcoal or the simulation of a cross current process by means of filtration stages in series) was investigated. Ferrous iron resulted to be essential for metal extraction and for bacteria adaptation. Nickel and vanadium were successfully bioleached in the presence of iron, reaching extraction yields of 83% and 90%, respectively; on the other hand extractions around 50% for nickel and vanadium were observed both in biological systems in the absence of iron and in the chemical controls with iron. As concerns molybdenum, the highest extraction yields experimentally observed was about 50%, after 26 days bioleaching in the presence of iron, while a maximum extraction of 25 % was observed in the other treatments. In conclusion, a bio-oxidative attack with iron could successfully extract nickel, vanadium and partially molybdenum. Further actions aimed at contrasting a possible metal toxicity resulted not to be effective.
Gold Bioleaching of Electronic Waste by Cyanogenic Bacteria and its Enhancement with Bio-Oxidation
Authors: Pham V.A. , Ting Yen Peng
Published: September 2009

This work compares gold bioleaching from e-waste containing gold and copper by Chromobacterium violaceum and Pseudomonas fluorescens. The effect of pulp density (ranging from 0.5 to 8%w/v) was examined. Although C. violaceum produced more cyanide than P. fluorescens in the absence of e-waste, P. fluorescens showed higher growth rate, cyanide production and gold leaching efficiency at all pulp densities. Pretreatment with biooxidation of the e-waste using Acidithiobacillus ferrooxidans resulted in the removal in excess of 80% of the copper present in the waste, and increased the gold/copper ratio in the residual solid. Bioleaching the biooxidised e-waste significantly improved gold recovery, especially by C. violaceum, particularly at high pulp density. For example, at pulp densities of 2 and 4% w/v, gold recovery from non-biooxidzed e-waste was 0.22 and 0.14% respectively. Higher gold recovery, at 8%, was obtained for bioleaching of the biooxidised e-waste at both these pulp densities. The ratio of gold/copper in leachates after bioleaching of the biooxidized e-waste was also found to be increased.
Fungal Bioleaching of Spent Hydroprocessing Catalyst: Effect of Decoking and Particle Size
Authors: Islam M. , Ting Yen Peng
Published: September 2009

. This work reports on the bioleaching of spent NiMo catalyst using Aspergillus niger. As-received and decoked catalysts of various sizes (as-received, 180-120 µm, 120-45 µm and <45 µm) were examined. Chemical analysis of the spent catalyst confirmed the presence of heavy metals including Al (38.2%), Ni (3.36%), and Mo (12.9%). SEM-EDX analysis revealed a change in the metal distribution within the spent catalyst following the decoking process. In one-step bioleaching where the fungus was inoculated together with the catalyst, fungal growth was not observed. In 2-step bioleaching where the catalyst was added three days after the start of the fungal incubation, the highest Mo (87.3%) and Al (17.20%) leaching efficiencies were obtained from the catalyst of smallest particle size (i.e. decoked grounded; <45µm) while the highest Ni leaching efficiency (94%) was achieved from the as-received spent catalyst.