bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Nutrient Supplementation on Growth and Leaching Performance of Bioleaching Bacteria
Authors: van Hille Robert P. , Bromfield L.V. , Botha S.S. , Jones Gavin , van Zyl A.W. , Harrison Susan T.L.
Published: September 2009

Heap bioleaching operations are often faced with extended and unpredictable lag periods after inoculation, prior to the establishment of a stable oxidising environment, during which the heap is fully colonised or the inoculum overcomes the sub-optimal conditions resulting from acid agglomeration. Supplementation of laboratory scale (4kg ore) leach columns with soluble nitrogen, particularly as yeast extract, significantly reduced the lag time and promoted bacterial growth, resulting in a 50-95% increase in copper recovery post-inoculation. The effect of yeast extract addition to Acidithiobacillus ferrooxidans in controlled oxidation tests was investigated. Initial exposure of a stock culture to yeast extract resulted in a transient, dose dependent inhibition at concentrations of 0.5 g.l-1 and below. At 1.25 g.l-1 inhibition was complete over the time scale of the experiment. The inhibition phase was characterised by observable changes in cell morphology and ultrastructure. Despite the initial inhibition, the biomass yield at the end of the experiments was equivalent, or higher, in the presence of yeast extract. Cultures were adapted to growth on yeast extract as the sole nitrogen source and adapted cultures showed the highest rates of iron oxidation and cell growth, in the presence of 0.5 and 1 g.l-1 of yeast extract.
Electrochemical Behavior of Massive Bornite Bioleached Electrodes in the Presence of Acidithiobacillus Ferrooxidans and Acidithiobacillus Caldus
Authors: Qin Wen Qing , Wang Jun , Zhang Yan Sheng , Zhen Shi Jie , Shang He , Liu Qian , Shi Hai Bin , Zhang Jian Wen , Qiu Guan Zhou
Published: September 2009

In this work, the monitoring of bacterial and chemical dissolution of massive bornite was performed using cyclic voltammetry (CV); the mineral surface was examined using scanning electron microscopy (SEM) and the elements were indentified by Energy Dispersive X-ray Analysis (EDXA). The electrolyte employed for the electrochemical tests was the medium used for bioleaching the electrodes (3.0 g•dm-3 (NH4)2•SO4, 0.5 g•dm-3K2HPO4, 0.5 g•dm-3 MgSO4•7H2O and 0.1 g•dm-3 Ca(NO3)2).The results showed differences in voltagramms carried out by Acidithiobacillus ferrooxidans and Acidithiobacillus caldus: In bioleached electrodes tested in the presence of Acidithiobacillus ferrooxidans, the anodic and cathodic current signals were larger than with Acidithiobacillus caldus The analysis of CV results allowed attributing the different peaks observed in both the direct and reverse potential scanning to the oxidation of bornite to a secondary copper mineral(chalcocite and covellite) and its reduction via different non stoichiometric copper sulphides intermediaries. Surface evidences were produced by SEM, and chemical elements evidences were also investigated by EDAX.
Leaching of Ni and Cu from Mine Wastes (Tailings and Slags) Using Acid Solutions and A. Ferrooxidans
Authors: Muñoz Alexa , Bevilaqua Denise , Garcia Jr. Oswaldo
Published: September 2009

The objective of this work is to evaluate the acidic and biological leaching of tailings containing Ni/Cu from a flotation and smelting plant. Acidithiobacillus ferrooxidans, strain LR, was used for bioleaching at pH 1.8 and chemical controls were run parallel to that. The acidic leaching was done within 48 hours at pH 0.5 and 1.0. In the slag inoculated flasks the redox potential was high (600 mV), thus indicating oxidative bacterial activity, however, the obtained results after 15 days showed only around 13% Ni and 8% Cu extractions, which were not different to those of the controls. For the flotation tailings bioleaching extractions were approximately 45% for Ni and 16% for Cu while differing figures were obtained for the chemical controls. These were 30% and 12% respectively. Here we could observe that the presence of bacterial activity led to a higher solubility of Ni. Acid leaching of slag showed higher nickel and copper extractions: 56% and 24% respectively at pH 0.5 and 21% and 11% at pH 1.0. However, the acid consumption was 320 and 150 Kg/ton of slag, respectively, both much higher than in bacterial assays. These results indicated that Ni and Cu solubilization from the slag is acid dependent no matter the redox potential or ferric iron concentration of the leaching solution. For flotation tailings, acid treatment showed extractions of 23% for Ni and 16% for copper at pH 0.5 and 22% and 28%, respectively at pH 1.0. The acid consumption was also higher: 220 and 120 Kg/ton, at pH 0.5 and 1.0, respectively. Based on own findings we could observe that acid leaching is found to be more effective for slag, though the acid consumption is much higher, while for the flotation tailings, bacterial leaching seems to be the best alternative.
Thermodynamic Simulation of Sulphide Mineral Leaching
Authors: Ahonen Lasse , Nurmi Pauliina , Tuovinen Olli H.
Published: September 2009

Geochemical modeling program PHREEQC was used to simulate generic bioleaching processes. Carbonate minerals (e.g., calcite) dissolve in acid solution, increasing the solution pH and Ca concentration while the concentration of CO2 may be controlled by the equilibrium with the atmospheric CO2. Non-oxidative dissolution of Fe-monosulphides was demonstrated to release H2S and increase the pH. In the absence of ferric iron precipitation (goethite), the oxidation of pyrite decreased the solution pH from 2 to ~1.4, while the oxidation of Fe-monosulphide and chalcopyrite increased the solution pH to ~3.2-3.4. Assuming equilibrium precipitation of goethite, oxidative leaching decreased the solution pH for all three minerals from pH ~2 to ~0.9-1.2. Adjustment of the solution pH to 1.8 or 2.0 with KOH with concurrent equilibrium precipitation of K-jarosite resulted in low dissolved iron concentrations.
Thermodynamic Modelling of Phosphate and Chloride Effects on Solid and Solution Phase Ferric Iron Speciation
Authors: Tuovinen Olli H. , Nurmi Pauliina , Ahonen Lasse
Published: September 2009

The purpose of this study was to model, based on thermodynamic equilibrium constants, the effects of chloride and phosphate ion on the speciation of ferric iron in solution and on Fe(III)-precipitates. The thermodynamic modelling was based on the geochemical modelling code PHREEQC and the thermodynamic database WATEQ4F. Increasing phosphate levels (g per L range) increase the complexation of ferric ion with phosphate (FeH2PO42+) with a parallel decrease in ferric sulphate complex (FeSO4+) and release of sulphate as SO42- in solution. Chloride ion at comparable levels and under otherwise similar conditions had negligible effects on the speciation of soluble iron species. In the solid phase analysis, jarosite and goethite species declined with increasing phosphate levels, whereas chloride did not affect the relative proportions of secondary Fe(III) minerals in the solid phase. Saturation index values for jarosites and goethite were dependent on the temperature with the range of phosphate levels (0–20 g/L) examine in this study.
Adhesion of Acidithiobacillus Caldus and Leptospirillum Ferriphilum on Pyrite and their Effect on Surface Properties of Sulfide Minerals
Authors: Gu G. , Su Li Jun , Qiu Guan Zhou , Hu Y.
Published: September 2009

Acidithiobacillus caldus and Leptospirillum ferriphilum cells grown in different energy substances (ferrous ion, sulfur and pyrite) were used. The adhesion of A. caldus and L. ferriphilum cells on pyrite and their effect on pyrite surface properties were studied by adsorption, zeta-potential and FT-IR methods, and the corrosion images of pyrite interaction with bacteria were examined using atomic force microscopy. Research showed that pyrite isoelectric point (IEP) after interaction with bacterial cells shifted towards cells isoelectric point, and the shift degree in case of interaction with A. caldus was observed to be much more pronounced than for interaction with L. ferriphilum, which can be due to higher affinity of A. caldus towards pyrite. The FT-IR spectra of pyrite treated with bacterial cells revealed the presence of the cell functional groups signifying cells adsorption. Although the adsorption density of A. caldus on pyrite was higher than that of L. ferriphilum, L. ferriphilum with strong ability to oxidize ferrous ion showed better leaching efficiency than A. caldus with strong ability to oxidize sulfur for pyrite leaching. The results demonstrated that more important of indirect action (L. ferriphilum) than direct action (A. caldus) on pyrite.Introduction Bacterial adsorption to minerals is an initial step in bacterial leaching for metal recovery [1]. It has been reported that bacterial adhesion is dependent not only on the biochemical properties of the organism but also on the interfacial properties of the various interfaces existing in a bioleaching system[2].The bacteria-mineral interactions result in the changes of their surface properties. The elucidation of their alternate will be beneficial for bioleaching processes. Both Acidithiobacillus caldus and Leptospirillum ferriphilum are known for their ability to inhabit acidic environments and derive energy from oxidation of inorganic substances with natural occurrence in ore deposits and acid mine drainage and high affinity towards sulfide minerals [3-5]. In this work, the alterations of surface properties of pyrite after interaction with L. ferriphilum and A. caldus are studied, and the changes in surface properties caused by bacterial adsorption are discussed with reference to bioleaching behavior of pyrite.
Precipitation of Iron Oxyhydroxides and Basic Sulphates from Bioleach Liquors Generated by Thermophilic Micro-Organisms
Authors: Mchibwa K.A. , Ndlovu Sehliselo , Iyuke S.
Published: September 2009

Thermophilic micro-organisms are known to oxidise pyrite and other iron sulphide minerals resulting in the production of acidic ferric sulphate solutions. In this study, the leach liquors generated from such bacterial oxidation were aged through a forced hydrolysis process to yield various iron oxyhydroxides and sulphates. The forced hydrolysis was carried out under a pH range of 1.9 to 9.0. Upon completion of aging, the precipitates generated were characterised using powder X-Ray diffractrometry. The XRD analyses revealed a production of a variety of iron oxyhydroxides and basic iron sulphates. The nature of these precipitates was influenced by the pH conditions used during aging. Jarosite compounds were precipitated under acidic conditions, whilst aging under more basic conditions led to the precipitation of iron oxyhydroxides. These findings may find application in forecasting the phase boundary conditions for Fe(III) precipitation in biogeochemical processes and provide an insight into the tackling of problems associated with the treatment and management of acid mine drainage.
New Biox® Agitator Concept Testwork
Authors: Van Deventer J.R. , Gigas Bernie
Published: September 2009

The paper describes the evaluation of a new mixer system developed in conjunction with SPX Process Equipment for the BIOX® process. Five different impeller combinations were tested with a Lightnin A315 A340 combination given the best results. With this combination the overall power per unit were reduced and less air were injected into the test reactors and still obtain the same and even better oxygen mass transfer compared to the commercially used A315 impeller.
Recent Advances in the BIOX® Technology
Authors: van Niekerk Jan A.
Published: September 2009

The past number of years has seen a sharp rise in the gold price. This has led to renewed activity in the gold sector and especially in refractory ore-bodies that are not economically feasible at lower gold prices.
There have, historically, been a total of eleven BIOX® plants commissioned world wide with eight currently in operation. The most recent plants to be commissioned were Bogoso and Jinfeng in 2007 and Kokpatas in Uzbekistan in 2008.
Design of the Bogoso BIOX® plant was started by Minproc in 2005. The design throughput of the sulphide BIOX® circuit is 820 tpd concentrate at a feed sulphide sulphur grade of 20 %. The Bogoso BIOX® plant has the largest biooxidation reactors with a live capacity of 1,500 m3 each.
Plant design on the Jinfeng project started in 2005 and the engineering was performed jointly by Ausenco and Nerin. The BIOX® plant has a design capacity of 790 tpd concentrate at 9.4 % sulphide sulphur.
The Kokpatas plant will be the largest BIOX® plant in the world with a Phase 1 design concentrate treatment capacity of 1,069 tpd at 20 % sulphide sulphur. The throughput will be doubled during Phase 2. Interestingly, unlike other BIOX® Plant, this plant will use a resin-in-pulp circuit for gold recovery, but the design will allow the plant to be converted to Carbon-in-pulp if required.
There are currently three BIOX® projects in various stages of design or construction. This includes two expansions to existing BIOX® operations and one new BIOX® project.
There are a number of major R&D projects currently under investigation with some very positive results. Most R&D is focussed on the main capital and operating cost items in the process, but there are also projects focussed purely on process optimisation and improvement.
The Influence of Disimilatory Fe(III) Reducers on Iron Ore Dissolution
Authors: García-Balboa C. , Cautivo Dina , Blázquez M. Luisa , González F. , Muñoz J.A. , Ballester Antonio
Published: September 2009

The biological reduction rate of Fe(III) was studied using dissimilatory ferric reducing bacterial cultures (FeRB) in an attempt to establish a biotechnological via for the metallurgical treatment of iron ores. Enrichment cultures of dissimilatory ferric reducers were obtained from samples collected from a flooded acidic open pit in an abandoned Pb and Zn sulphide mining site nearby La Unión (Murcia, Spain). Adapted cultures were able to reduce 3 g/L of soluble Fe(III) with 100 efficiency in 36 hours. The growth of mixed cultures was also tested in solids. Ferrihydrite and ammonium jarosite served as electron acceptors in cultures where lactate acted as electron donor. Bacterial growth was also positive in both cases. This result represents an effective alternative to the chemical reduction of ferric minerals that avoids extreme temperatures when pyrometallurgical reactors are used. In addition, three species of FeRB were isolated and identified as Serratia fonticola, Aeromonas hydrophila and Clostridium celerecrescens. One of them, Aeromonas hydrophila, results of particular interest and, at the present moment, is being studied in depth. The particular significance of Aeromonas hydrophila is related to the characteristics of its exhausted cultures, where ferrous iron remains solved at pH values next to 7. At the present moment, the identification and characterization of the Fe(II) soluble complex is being account.
Microbially Induced Flotation of Galena and Quartz from Pyrite
Authors: Sarvamangala H. , Natarajan K.A.
Published: September 2009

Selective separation of pyrite from galena and quartz was achieved through microbiologically induced flotation in presence of Bacillus subtilis. B. subtilis functions as a depressant for pyrite while it promotes the flotation of galena and quartz. Bacterial extracellular protein (EP) was isolated and the protein profile of bacterial cells grown in presence and absence of minerals established.
Today’s Wastes, Tomorrow’s Materials for Environmental Protection
Authors: Macaskie Lynne E. , Mikheenko I.P. , Yong P. , Deplanche K. , Murray Angela J. , Paterson-Beedle M. , Coker Vicky S. , Pearce Carolyn I. , Pattrick Richard A.D. , Vaughan David , van der Laan Gerrit , Lloyd John R.
Published: September 2009

Over the past 30 years the literature has burgeoned with bioremediation approaches to heavy metal removal from wastes. The price of base and precious metals has dramatically increased. With the resurgence of nuclear energy uranium has become a strategic resource. Other ‘non-carbon energy’ technologies are driven by the need to reduce CO2 emissions. The ‘New Biohydrometallurgy’ we describe unites these drivers by the concept of conversion of wastes into new materials for environmental applications. The new materials, fashioned, bottom-up, into nanomaterials under biocontrol, can be termed ‘Functional Bionanomaterials’. This new discipline, encompassing waste treatment along with nanocatalysis or other applications, can be summarized as ‘Environmental Bionanotechnology’. Several case histories illustrate the scope and potential of this concept.
Isolation of Mesophilic Sulphate-Reducing Bacteria from a Microbial Community: Comparative Study of the Effect of pH and Dissolved Heavy Metals on the Reduction of Sulphate
Authors: Kikot P. , Viera M. , Mignone C. , Donati Edgardo R.
Published: September 2009

Metallurgical processes and mining are the main source of heavy metal contamination of water sources, rivers and lakes. There are a large number of physicochemical processes that can be applied for the immobilization of heavy metals from a liquid matrix. However, many of them are not particularly desirable because their low selectivity and inefficiency when high volumes of low metal concentration liquids must be treated. In such conditions, alternative biological processes have shown to be more useful than traditional physicochemical processes. One of those processes, bioprecipitation of metal sulphides is relevant due to the possibility of forming stable solids (very low solubility) with small volumes compared with other solids. This process is mediated by a broad group of organisms called sulphate reducers that are able to catalyze, under anaerobic conditions, the reduction of sulphate with organic compounds as electron donors. In this paper, we study the effect of the presence of various heavy metals and the pH on the ability to reduce sulphate by sulphate-reducing bacteria. We compare the reduction of sulphate by a microbial community obtained from the effluent of a tannery with a strain isolated from that community. Our results showed that sulphate reduction was significantly affected by pH changes whereas the presence of heavy metals did not show a significant effect. In addition, metal precipitation by the isolated strain was similar than that produced by the community.
Microbial Diversity and Genetic Response to Stress Conditions of Extremophilic Bacteria Isolated from the Escondida Copper Mine
Authors: Galleguillos Pedro Antonio , Hallberg Kevin B. , Johnson D. Barrie
Published: September 2009

The Escondida mine, located in northern Chile, is the largest copper producing mine in the world. It has an abundant low-grade (ca. 0.5% Cu) sulfide copper ore reservoir, which is processed in large heap bioreactors at the mine. To understand better how microorganisms adapt to heap leaching environments, we have isolated and identified acidophiles from pregnant leach solution (PLS) from the heaps. Six bacteria and one archaeon were isolated directly on solid overlay media, and identified by phylogenetic analyses of their 16S rRNA genes as strains of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferriphilum, Acidiphilium cryptum and Ferroplasma acidiphilum. The sequences of the 16S rRNA genes from isolated strains showed high similarity with those detected previously by culture-independent analyses performed on samples from a pilot plant for this process.
Of the three known species of Leptospirillum, only L. ferriphilum has been detected in Escondida PLS. Tolerance of the Escondida isolate (coded IESL-25) to copper and some other transition metals such as zinc, nickel and silver was compared with several other strains of both L. ferriphilum and Leptospirillum ferrooxidans. It was noted that all L. ferriphilum strains (including IESL-25) displayed far greater tolerance to both copper and silver than strains of L. ferrooxidans, though tolerance to zinc and nickel was similar among isolates of both species.
Micro-representational-difference analysis (MRDA) was used to study the genetic response of L. ferriphilum IESL-25 to high copper concentration. Gene sequences obtained by MRDA were analyzed using available genomic information for L. ferriphilum and one copper-induced gene identified appears to be involved in lipopolysaccharide biosynthesis.
Heavy Metals Immobilization in Contaminated Smelter Soils Using Microbial Sulphate Reduction
Authors: Almendras Maylin , Wiertz J.V. , Chamy R.
Published: September 2009

The main environmental problems associated with the mining activities are related to the production of large amounts of wastes; Different pathways are responsible for heavy metals dispersion, by air due to wind action, by water mediated by acid mine drainage and erosion, and the metals could be mobilized in the soil by different transport mechanisms. Different remediation alternatives have been studied and reported in literature. In situ stabilization is a cheaper method. The heavy metals stabilization enables the decrease of metal mobility, reactivity and toxicity in the soil, decreasing heavy metals availability and phytoavailability. Sulphate reducing bacteria (SRB) have been successfully utilized in groundwater bioprecipitation of heavy metals. In this study, this biological agent has been used in the immobilization of heavy metal in the subsurface of the soil due to its dissimilative metabolism. SRB produces hydrogen sulfide that reacts with soluble metals present in the media, generating as final product low soluble metal compounds (metal sulfides). The bio-stabilization was studied at pilot scale to determine the stabilization efficiency using biological agent, SRB. The metals studied were Fe, Cu, Pb and Zn in the contaminated smelter soil. Bioaugmentation and biomagnification were applied. After 4 months, the metal stabilization efficiency was determined by leaching with acid solution at different pH to stimulate the metal mobility. The remediation pilot scale system showed that copper, lead and iron were much more stable at pH 3.0, with only 3.7% and 1% of total metal eluted, and compared with the system without biological agent. In the case of zinc, the elution was similar with or without remediation. The metal stabilization using biological agent was successful in the contaminated smelter soil and these results are promising antecedents for full scale in situ remediation strategy.
Waste Biomass from Marine Environment as Arsenic and Lead Biosorbent
Authors: Beolchini F. , Pennesi C. , Testaferri B. , Totti C. , De Michelis I. , Vegliò Francesco
Published: September 2009

This paper deals with arsenic and lead biosorption by different waste biomasses coming from the marine environment. Shoreline seaweeds and seagrasses were used to adsorb metals from aqueous solutions, under different pH. Experimental tests were performed in order to study the equilibrium of biosorption with suspended biomass. The obtained results confirmed the possibility of using marine macrophyte biomass for heavy metal biosorption and evidenced a strong dependence of lead and arsenic uptake on the macrophyte structure. Brown algae were found to be the best sorbents for lead with a maximum observed lead uptake of 140 mg/g; green algae showed a maximum lead uptake in the range 50-70 mg/g; red algae were the worst lead sorbent, in the investigated experimental conditions, with a maximum lead uptake in the range 10-40 mg/g. As concerns arsenic, the macrophytes had in general good sorption abilities when compared with those of activated carbon. Furthermore red algae, that for lead were not effective, resulted to be the best sorbents for arsenic. This was explained by a different speciation in aqueous solution of lead (II), that is cationic with respect to arsenic(V), that is anionic.
Bioaccumulation of Metals in Different Parts of Weed Species at Proposed Bauxite Mines
Authors: Chandra R. , Azeez P.A.
Published: September 2009

We investigated and evaluated metal up-take in three common dominant plants namely Ageratina adenophora, Eupatorium odoratum and Phoenix acaulis from three proposed bauxite mine sites in Araku valley, Vishakhapatnam, India. The concentrations of Cr, Cu, Pb and Zn varied from 14.41 to 87.73 mg/kg, 3.39 to 25.09 mg/kg, 2.48 to 17.39 mg/kg and 5.77 to 50.81 mg/kg, respectively. The variables studied showed significant spatial heterogeneity (General Linear Model, ANOVA, P < 0.05) among sites and metals. Transportation index (Ti) for Zn was >1 for all the species. The pH seemed to have the greatest effect on the solubility / retention of metals in soils thus, enhancing accumulation of metals.
Biorecovery of Uranium from Minewaters into Pure Mineral Product at the Expense of Plant Wastes
Authors: Paterson-Beedle M. , Macaskie Lynne E. , Readman J.E. , Hriljac J.A.
Published: September 2009

Perceived environmental problems of nuclear fuel fabrication, use and treatment limit the acceptability of nuclear power as an alternative to fossil fuels. This applies to nuclear fuel processing and reprocessing but contamination also occurs at source via run-offs from current and historic mining activities. The price of uranium (U3O8) in the1990s was US$10/lb but is currently US$ 58/lb, peaking in 2007 at US$135/lb. With the potential global expansion of nuclear power as an alternative to fossil fuels the market and strategic values of U will rise. A new biotechnology was demonstrated for efficient recovery of U from minewaters as pure hydrogen uranyl phosphate (HUP) but an economic assessment (discounting the value of U) showed that the limitation as a waste treatment process was the cost of the phosphate feed supplement which contained 1 mol/mol phosphate. We describe the use of phytic acid (inositol phosphate; 6 mol phosphate/mol), a ubiquitous plant waste, to support the removal of uranium as HUP by an immobilised cell reactor and shift the focus from away bioremediation to value product manufacturing from wastes, and resource efficiency.
Sequenced Bioleaching and Bioaccumulation of Phosphorus from Sludge Combustion – A New Way of Resource Reclaiming
Authors: Zimmermann Jennifer , Dott Wolgang
Published: September 2009

The recovery of phosphorus from sewage sludge incineration ash as well as the separation of heavy metals from ash was investigated by using the biotechnological process of bioleaching and bioaccumulation of released phosphorus by newly developed population of bioleaching bacteria, Acidithiobacillus sp. strains, and polyphosphate (poly-P) accumulating bacteria, the AEDS-population (Acidithiobacillus sp. enriched digested sludge). The biologically performed solubilization of phosphorus from sewage sludge incineration ash is accompanied by the release of toxic metals. Therefore a combined process to separate phosphorus from heavy metals by achieving a plant available phosphorus-enriched product and a metal depleted ash was designed. Leaching experiments were conducted in laboratory scaled leaching reactor containing a bacterial stock culture of Acidithiobacillus sp.. Next step was the enhancement of P-recovery in combining bioleaching with simultaneous bio-P-accumulation by AEDS-population. The uptake of phosphorus in biomass reaches up to 66 % of the mobilized phosphorus by bioleaching. The combined biologically performed technology of phosphorus leaching and separation from toxic metals by simultaneous bioaccumulation developed in this study is a promising process for economical and ecological recovery of phosphorus from waste solids.
Selective Sorption of Ce3+ over La3+ Ions on Biogenic Manganese Oxides
Authors: Sasaki Keiko , Kaseyama T. , Hirajima Tsuyoshi
Published: September 2009

Unique properties of biogenic Mn oxides were applied to a fundamental study of separation and recovery of rare earth elements. Selective sorption of Ce3+ over La3+ ions was achieved at neutral pH values using biogenic Mn oxides produced by Paraconiothyrium sp. WL-2 strain. The selective coefficient for Ce3+ (αCe) was much greater with biogenic and synthetic Mn oxides than those for La3+ (αLa). Ce3+ ions were oxidized to CeO2 by Mn(III, IV) in Mn oxides under anaerobic conditions resulting in the release of Mn2+ ions, while La3+ ions were sorbed without a redox reaction. With an increase in coexisting La3+ ions, sorption of Ce3+ on both Mn oxides was significantly suppressed, especially with synthetic Mn oxides. The edges of the structure are competitive sites because of fewer numbers of vacant sites in synthetic Mn oxide layers. The preferential sorption on the edge sites of Mn oxides is in the order of La3+ > Ce3+. These phenomena can be expanded to separation and recovery of other rare earth elements from natural and anthropogenic sources.
Microbial Aspects of Acid Generation and Bioremediation with Relevance to Indian Mining
Authors: Natarajan K.A.
Published: September 2009

The role of Acidithiobacillus group of bacteria in acid generation and heavy metal dissolution was studied with relevance to some Indian mines. Microorganisms implicated in acid generation such as Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans were isolated from abandoned mines, waste rocks and tailing dumps. Arsenite oxidizing Thiomonas and Bacillus group of bacteria were isolated and their ability to oxidize As (III) to As (V) established. Mine isolated Sulfate reducing bacteria were used to remove dissolved copper, zinc, iron and arsenic from solutions.
Reduction of Heavy-Metal Content in Overburden Material by Bacterial Action
Authors: Hernández Díaz Ianeya , Galizia Federico , Coto Pérez Orquidea , Donati Edgardo R.
Published: September 2009

In previous studies it has been showed that bacterially produced sulphuric acid is a good leaching agent for laterite tailings. In this work we evaluated heavy metals leaching from low grade laterite ore for cobalt and nickel extraction using sulphuric acid produced in situ by Acidithiobacillus thiooxidans under different culture conditions. In studies where that material was initially added to the cultures, considerable percentages of metals were leached (100 % Mn, 70 % Co, 7.5 % Ni, less than 5 % of Cr and Fe) after 18 days of incubation at low pulp densities (1 % and 2.5 %) of overburden. The maximum percentages were reached when cultures pH was approximately or below than 1.5. At higher pulp densities material was added to the cultures after different pre-cultivating times; also higher sulphur amounts were assayed; in such way about 100 % Mn, 60 % Co, 9 % Ni and Fe and 2.5 % Cr were leached. Although toxic metals were not completely leached, sequential extractions results indicate that these metals are not readily available. All studies finally suggest that bioleaching is a suitable technology for recovery of valuable metals as Co and remediation of mining residues by extraction of heavy metals.
Acidianus Brierleyi is the Dominant Thermoacidophile in a Bioleaching Community Processing Chalcopyrite Containing Concentrates at 70°C
Authors: Dinkla Inez J.T. , Gericke Mariekie , Geurkink B.K. , Hallberg Kevin B.
Published: September 2009

Bioleaching test work was performed in continuously operated multi-stage reactor systems at 70°C using a thermophilic culture treating an Aguablanca Ni-Cu concentrate from Spain and a blend of Cu concentrates from Bor, Serbia. The copper in both these concentrates occurs as chalcopyrite and therefore the use of thermophiles was applied, which resulted in copper recoveries of over 95%. Qualitative assessment of the microbial community in the bioreactors was performed by terminal restriction enzyme fragment length polymorphism (T-RFLP) and clone library analysis of the 16S rRNA genes amplified by PCR. T-RFLP analysis revealed that only archaea were present, and that the communities in both the Aguablanca and Bor systems consisted of two different microorganisms. A 16S rRNA gene clone library using DNA from the Aguablanca system was constructed and screened. Again, two archaea were detected in similar relative abundance in the population as found by T-RFLP analyses. The sequences of these two cloned genes revealed that the dominant archaeon (up to 98% of the total archaea detected) was Acidianus brierleyi, and the other was Metallosphaera sedula. Quantitative assessment of the microbial community was performed by Q-PCR and confirmed the dominance of archaea in the system with Acidianus being the dominant strain (98-99% of the total population) and a minor part of the population (1-2%) consisted of Metallosphaera. Additionally, very small amounts of Sulfolobus spp. were detected. This study, along with other recent studies on the diversity of thermoacidophiles involved in the solubilization of copper from chalcopyrite concentrates, revealed that a wider variety of thermoacidophiles are involved in bioprocessing of metal sulfides, and showed that A. brierleyi should be considered an important biomining acidophile.
Biological Solubilisation of Metals from Solid Waste Materials from Copper, Steel and Recycling Industries
Authors: Vestola Elina A. , Kuusenaho M.K. , Närhi H.M. , Tuovinen Olli H. , Puhakka Jaakko A. , Plumb Jason J. , Kaksonen Anna H.
Published: September 2009

The aim of the present work was to study the feasibility of using bioleaching for the solubilisation of metals from solid waste streams and by-products of copper, steel and recycling industries. Optimal process conditions were tested using iron and sulphur oxidising acidophiles in shake flasks at 25°C. The effects of inoculum, ferrous iron, sulphur, chloride ion, pH, and the type of waste material on metal solubilisation were evaluated. Solubilisation of metals was mainly achieved through acid attack due to the formation of sulphuric acid by sulphur oxidising bacteria. Addition of ferrous iron and chloride ion did not enhance solubilisation.
Preliminary Study of Neutralization and Inhibition of Chemolitotrophic Bacteria in an Acid Mine Drainage from Rio Tinto Site
Authors: Carnicero D. , Díaz E. , Escolano O. , Rubinos D. , Ballesteros O. , Barral M.T. , Amils R. , García Frutos F.J.
Published: September 2009

Limestone is commonly used for neutralization of acid mine drainage (AMD). Its main advantages are its lower price, sustained generation of alkalinity and production of low sludge volumes. Nevertheless, armouring of limestone by ferric hydroxides is a problem in oxic limestone drains and in active limestone treatment systems, reducing the efficiency of the process. Due to these disadvantages, there is a permanent search for cheaper and more effective neutralization agents. Many alkaline industrial wastes are gaining importance in the treatment of AMD.
The possibilities to use two different industrial by-products, red mud from a bauxite exploitation and low grade magnesium hydroxide from a magnesite mine, as neutralizing and bacterial inhibiting agents, and the comparison with conventional limestone treatment has been studied in this paper. An AMD from Rio Tinto mine site with an initial pH of 2.4 and a ferric concentration of 1 g/L was used. Comparative test were done percolating the AMD in a continuous form with a peristaltic pump through three different columns filled with limestone, red mud and low grade magnesite, during one month and in same conditions of flow rate and amount of each compound used to fill the columns. The evolution of pH, iron and heavy metals, sulphates and microbial populations in the percolate were monitored at different times.
The results showed that the best neutralization capacity was obtained with low grade magnesite during the month treatment. By contraire limestone and red mud loosed their neutralization capacity after 10 and 13 days respectively. The control of microbial populations showed that there is an inhibition of chemolithotropic bacteria as long as the materials maintain their neutralization capacity, reverting to the initial conditions when this capacity was loosed.
Inhibition of Iron Oxidizing Bacteria Involved in the Generation of Acid Mine Drainage
Authors: Cruz Viggi Carolina , Pagnanelli Francesca , Sabattini Matteo , Toro Luigi
Published: September 2009

Obligate autotrophic and acidophilic characteristics of iron oxidizing bacteria were exploited to prevent or attenuate the generation of AMD. Inhibition of iron oxidizing bacteria growth was performed by variation of growth medium by increasing pyrite concentration (substrate inhibition), by addition of limestone (inhibition by pH increase) and olive pomace (inhibition by organic compounds). Preliminary pyrite bioleaching tests showed the ability of the available inoculum to oxidize the mineral. Inhibition tests of batch growth were performed according to full factorial design with three factors (pyrite, limestone and olive pomace). Experimental data denoted a strong inhibition in all the operating conditions, except the case when larger pyrite concentrations were used. In particular, limestone is a strong inhibitor and inhibition by olive pomace may be related to the antioxidant properties of polyphenols. Interactions among operating conditions were specifically assessed by analysis of variance.
Process Decisions Focused on the Prevention of AMD Formation on Beneficiating Sulfide Minerals
Authors: Harrison Susan T.L. , Hesketh Alexander H. , van Hille Robert P. , Broadhurst Jennifer L.
Published: September 2009

Acid Mine Drainage (AMD) from voluminous sulfide-bearing wastes contributes to the environmental burden of mineral processing. To diminish burden and its time frame of risk, the disposal of sulfidic waste materials is re-examined through the valuable distinction between reactive or active gangue materials contributing to AMD generation and largely unreactive passive gangue. In an example process for disposal of tails from mineral sulfide beneficiation, a proof of concept is provided for inclusion of a non-selective sulfide float preceding or following selective separation of the desired mineral sulfide. The environmental benefit of subsequent reduction of sulfide in the tailings from 3.7 to 0.2% on AMD generation potential is quantified through a combination of methodologies including MPA, ANC, NAPP, NAG and microbial testing. Sulfide reduction from 4 to 1% reduces AMD generation. Further reduction below 1% S yields diminishing returns. The environmental benefit of separating ‘active’ and ‘passive’ gangue material prior to disposal is shown, and the reduced active gangue fraction determined through material balance.
Competition between Lactate Oxidisers and Fermenters under Biosulphidogenic Conditions: Implications in the Biological Treatment of AMD
Authors: Oyekola Oyekanmi O. , van Hille Robert P. , Harrison Susan T.L.
Published: September 2009

This study investigated the influence of culture conditions on the dominant metabolic pathways and resultant reaction stoichiometry, using chemostat cultures. The kinetic properties (max and Ks) under conditions dominated by either lactate oxidation or lactate fermentation were determined. These properties were used to simulate the competition between lactate fermentation and oxidation. Sulphate reduction and lactate utilisation were determined across residence times of 1 to 5 d and feed sulphate concentrations of 1.0 to 10.0 g l-1. Assuming lactate limitation, results revealed a lower maximal growth rate max of 0.2 h-1 and a higher affinity for lactate characterised by Ks of 0.6 g l-1 for the lactate oxidisers (SRB) than the lactate fermenters. The latter were characterised by a max of 0.3 h-1 and Ks of 3.3 g l-1. Modelling of the competition between lactate fermenters and lactate oxidisers illustrated that lactate oxidisers compete more effectively for lactate under conditions of low lactate concentration (≤5 g l-1) and high sulphide concentration (0.5 g l-1). On the other hand lactate fermenters outcompete the oxidisers under conditions of higher lactate concentration (>5 g l-1). Findings from this study show that in order to optimise BSR system, an understanding of the impact of physicochemical conditions on the metabolic dominance is critical.
Phytoremediation as an Alternative Way for the Treatment of Large, Low Heavy Metal Contaminated Sites: Application at a Former Uranium Mining Area
Authors: Willscher Sabine , Wittig J. , Bergmann Hans , Büchel Georg , Merten Dirk , Werner Peter
Published: September 2009

Large sites with a low contamination of metall(oid)s were in the past a problem for remediation measures – the “traditional” processes were too expensive for an application on such expanded areas. Phytoremediation can be an alternative for such low contamination problems. In Germany, a research project is performed on this subject, in cooperation of the University of Jena and the TU Dresden. The field site is a former U mining area. Until 1991, a low grade U ore dump for sulfuric acid leaching was located on this site. After the close-down of the U mining in East Germany in 1991, the dump material was removed. Now, a phytoremediation test field is constructed on top of this site for the capture of the remained contaminants coming up by capillary forces. The paper pictures the phytoremediation in general, the research project and gives some first preliminary results.
Biological Production of Selenium Nanoparticles from Waste Waters
Authors: Lenz Markus , van Aelst A.C. , Smit M. , Corvini P.F.X. , Lens Piet N.L.
Published: September 2009

Due to the photoelectric, semi-conducting and X-ray-sensing properties, selenium is an element of great economic potential. Since nanomaterials display special properties compared to bulk particles, the production of selenium nanostructures (wires, rods or spherical particles) has attracted much attention. In this study, alternative approaches to classical synthesis were investigated, producing selenium nanospheres biologically during treatment of contaminated water.
Biomineralised Palladium is an Effective Hydrogenation Catalyst
Authors: Mikheenko I.P. , Bennett J.A. , Shannon I.J. , Wood J. , Macaskie Lynne E.
Published: September 2009

This study was aimed at the development of a new heterogeneous Pd catalyst based on biologically mineralised palladium (Bio-Pd). Desulfovibrio desulfuricans was used to reduce Pd(II) to nanocrystalline Pd embedded in the bacterial surface. In this way the biomass provides support and prevents coalescence of the palladium nanoparticles. Palladised biomass exhibits catalytic activity, which was demonstrated in a range of applications including reduction, oxidation and hydrogenation reactions. Preparation of Bio-Pd under various conditions leads to the formation of a supported palladium catalyst with potentially different catalytic properties according to the preparation method.
Biorecovery of Precious Metals from Wastes and Conversion into Fuel Cell Catalyst for Electricity Production
Authors: Yong P. , Mikheenko I.P. , Deplanche K. , Sargent F. , Macaskie Lynne E.
Published: September 2009

Bio-manufacturing of nano-scale palladium was achieved using bacterial cells. Highly active Pd-catalyst (Bio-Pd) produced by an E. coli mutant gave power output in a fuel cell. Up to ~115% of the maximum power generation was achieved by electrodes of Bio-Pd catalysts from Escherichia coli, compared to that from a commercial-Pd electrode (~0.099 W). A bio-precious-metals (Bio-PM) catalyst made directly from an industrial reprocessing solution by the E. coli was also made into fuel cell electrodes and ~0.06W of maximum power generation was observed.
Chitosan-Based Hydrogels for the Recovery of Precious Metals
Authors: Sicupira D. , Campos Karol , Vincent Thierry , Leao Versiane Albis , Guibal Eric
Published: September 2009

Chitosan (an aminopolysaccharide), cross-linked with glutaraldehyde, is very efficient for Pd(II) and Pt(IV) recovery from acidic solutions (pH 2). Due to poorly porous properties, it is necessary to condition the biopolymer as hydrogels. The uncontrolled drying of hydrogels depreciates the diffusion properties of original materials. A different method (to the acidic dissolving/alkaline neutralization procedure) has been used: after chitosan dissolving in acetic acid solution, the viscous solution was dropped into an ionotropic gelling solution (polyphosphate and glutaraldehyde to form stable gel beads with improved porosity. The restriction of diffusion properties due to drying step was less drastic with the modified procedure: a few hours were sufficient for reaching equilibrium while more than two days were required for standard material
Electron Paramagnetic Resonance Analysis of Active Bio-Pd-Based Electrodes for Fuel Cells
Authors: Pinto de Carvalho Regina , Yong P. , Mikheenko I.P. , Paterson-Beedle M. , Macaskie Lynne E.
Published: September 2009

Nanoparticles of palladium were obtained with the help of hydrogen-oxidising, metal- reducing bacteria and used for the production of electricity in a proton exchange membrane (PEM) fuel cell. Earlier works have shown that palladised cells of Escherichia coli and Desulfovibrio desulfuricans (Bio-PdE.coli and Bio-PdD.desulfuricans, respectively) appeared similar by electron microscopy and were comparably active in a chemical test reaction. When tested in a PEM fuel cell they produced 0.018 and 0.108 W, respectively. Electron paramagnetic resonance analysis of Bio-PdE.coli mixed with activated carbon showed paramagnetic activity. However, Bio-PdD.desulfuricans under the same conditions quenched the intrinsic EPR signal. This quenching is indicative of the magnetic properties of the particles. The magnetic behaviour of Pd nanoparticles was theoretically predicted for particles between 10 and 20 nm in diameter and can be experimentally confirmed by EPR measurements.
A Study of Biofilm and Non-Line-of-Sight Bio-Hydroxyapatite Coatings Using a Serratia sp.
Authors: Yong P. , Paterson-Beedle M. , Liu W. , Zhang Z. , Beauregard D.A. , Johns M.L. , Macaskie Lynne E.
Published: September 2009

This study describes biofilm formation as a non line-of-sight coating method on support materials such as polyurethane foam, porous glass, polypropylene (PP) and titanium alloy, using a Serratia sp., which can manufacture extracellular nanoscale scaffolded hydroxyapatite (HA) crystals via enzymatic cleavage of glycerol 2-phosphate (G2P) in the presence of CaCl2. Various microscopies and non-invasive magnetic resonance imaging were used to visualize the biofilm coating on the support surface. A novel micromanipulation technique was used to estimate the adhesive strength of native and HA-mineralized biofilms. The biofilm with HA was up to forty times stronger than that without HA. A coating of nano-HA (> 80 m) onto a biofilm-Ti disc was achieved.
Acidophilic Microorganisms from Geothermal Copahue Volcano System. Assessment of Biotechnological Applications
Authors: Chiacchiarini P. , Lavalle L. , Giaveno Alejandra , Donati Edgardo R.
Published: September 2009

This work presents an overview of the physicochemical and biological studies carried out along Rio Agrio and in different hot springs belonging to the geothermal Copahue volcano system, in Neuquén Argentina. This is an extreme environment characterized by wide ranges of temperature, pH (<1 to 8) and heavy metals concentration. In these extreme conditions chemolitho-autotrophic bacteria, archaea, heterotrophic bacteria, yeasts and filamentous fungi were detected. Members of Leptospirillum ferrooxidans, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidianus spp., among others, were successfully cultivated and physiological properties of different isolates were determined. Additionally, bioleaching and biooxidation of regional ores were carried out using mixed native cultures.