Electrochemical Process Engineering in Biohydrometallurgical Metal Recovery from Mineral Sulfides

2017 ◽  
Vol 262 ◽  
pp. 118-121
Author(s):  
Christoph Tanne ◽  
Axel Schippers
Keyword(s):  
Iron Reduction ◽  
Ferric Iron ◽  
Electrochemical Techniques ◽  
Iron Oxidation ◽  
Dissolution Kinetics ◽  
Electrode System ◽  
Electrochemical Process ◽  
Mineral Dissolution ◽  
Redox Active ◽  
First Results

Primary copper sulfides are recalcitrant to bioleaching, probably due to semi-conductivity or passivation effects which result in slow dissolution kinetics. The mineral dissolution strongly depends on redox reactions and, consequently, electrochemical techniques are recommendable for analyzing and processing of redox-active minerals. For this reason we installed a three electrode system into a conventional bioreactor. Electrolytic bioleaching was applied to a copper concentrate from black shale ore. First results verified the operational capability of ferric iron reduction during electrochemical leaching and that bioleaching is not hindered by the physical presence of the electrochemical setup. Although the working electrode was able to reduce ferric iron and to regenerate it as electron supply for ferrous iron oxidizing microorganisms, the electron input into the bioleaching process has to be further increased to keep up with fast biocatalytical iron oxidation.

scholarly journals Ferric Iron Reduction in Extreme Acidophiles

2022 ◽  
Vol 12 ◽  
Author(s):  
Luise Malik ◽  
Sabrina Hedrich
Keyword(s):  
Iron Reduction ◽  
Ferric Iron ◽  
Hydrogen Oxidation ◽  
Iron Oxidation ◽  
Minor Role ◽  
Microbial Conversion ◽  
Dissimilatory Iron Reduction ◽  
Alternative Scenarios ◽  
A Minor ◽  
Life On Earth

Biochemical processes are a key element of natural cycles occurring in the environment and enabling life on earth. With regard to microbially catalyzed iron transformation, research predominantly has focused on iron oxidation in acidophiles, whereas iron reduction played a minor role. Microbial conversion of ferric to ferrous iron has however become more relevant in recent years. While there are several reviews on neutrophilic iron reducers, this article summarizes the research on extreme acidophilic iron reducers. After the first reports of dissimilatory iron reduction by acidophilic, chemolithoautotrophic Acidithiobacillus strains and heterotrophic Acidiphilium species, many other prokaryotes were shown to reduce iron as part of their metabolism. Still, little is known about the exact mechanisms of iron reduction in extreme acidophiles. Initially, hypotheses and postulations for the occurring mechanisms relied on observations of growth behavior or predictions based on the genome. By comparing genomes of well-studied neutrophilic with acidophilic iron reducers (e.g., Ferroglobus placidus and Sulfolobus spp.), it became clear that the electron transport for iron reduction proceeds differently in acidophiles. Moreover, transcriptomic investigations indicated an enzymatically-mediated process in Acidithiobacillus ferrooxidans using respiratory chain components of the iron oxidation in reverse. Depending on the strain of At. ferrooxidans, further mechanisms were postulated, e.g., indirect iron reduction by hydrogen sulfide, which may form by disproportionation of elemental sulfur. Alternative scenarios include Hip, a high potential iron-sulfur protein, and further cytochromes. Apart from the anaerobic iron reduction mechanisms, sulfur-oxidizing acidithiobacilli have been shown to mediate iron reduction at low pH (< 1.3) under aerobic conditions. This presumably non-enzymatic process may be attributed to intermediates formed during sulfur/tetrathionate and/or hydrogen oxidation and has already been successfully applied for the reductive bioleaching of laterites. The aim of this review is to provide an up-to-date overview on ferric iron reduction by acidophiles. The importance of this process in anaerobic habitats will be demonstrated as well as its potential for application.

Introduction to geomicrobiology

2018 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Fossil Fuels ◽  
Solid Phase ◽  
Direct Reduction ◽  
Iron Oxidation ◽  
Mineral Dissolution ◽  
Precipitation Process ◽  
Soluble Ions ◽  
Chemolithoautotrophic Bacteria ◽  
The Impact

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.

Biological iron oxidation-reduction and the effects on sulfur oxidation-reduction, denitrification and poly-P accumulation in an anaerobic-oxic activated sludge

2002 ◽  
Vol 46 (1-2) ◽  
pp. 55-60 ◽  
Author(s):  
R. Yamamoto-Ikemoto ◽  
T. Komori ◽  
S. Matsui
Keyword(s):  
Activated Sludge ◽  
Sulfate Reduction ◽  
Iron Reduction ◽  
Iron Oxidation ◽  
Sulfur Oxidation ◽  
Monod Equation ◽  
Oxidation Rates ◽  
Oxidation Reduction ◽  
Initial Iron ◽  
P Accumulation

Iron oxidation and reduction were examined using the activated sludge from a municipal plant. Iron contents of the activated sludge were 1–2%. Iron oxidation rates were correlated with the initial iron concentrations. Iron reducing rates could be described by the Monod equation. The effects of iron reducing bacteria on sulfate reduction, denitrification and poly-P accumulation were examined. Iron reduction suppressed sulfate reduction by competing with hydrogen produced from protein. Denitrification was outcompeted with iron reduction and sulfate reduction. These phenomena could be explained thermodynamically. Poly-P accumulation was also suppressed by denitrification. The activity of iron reduction was relatively high.

scholarly journals Reviews and syntheses: Weathering of silicate minerals in soils and watersheds: Parameterization of the weathering kinetics module in the PROFILE and ForSAFE models

2019 ◽  
Author(s):  
Harald Ulrik Sverdrup ◽  
Eric Oelkers ◽  
Martin Erlandsson Lampa ◽  
Salim Belyazid ◽  
Daniel Kurz ◽  
...  
Keyword(s):  
Mineral Water ◽  
Dissolution Kinetics ◽  
Base Cation ◽  
Mineral Dissolution ◽  
Soil Evolution ◽  
Groundwater Systems ◽  
Level Model ◽  
Kinetic Expression ◽  
Improved Model ◽  
Mineral Dissolution Kinetics

Abstract. The PROFILE model, now incorporated in the ForSAFE model can accurately reproduce the chemical and mineralogical evolution of the soil unsaturated zone. However, in deeper soil layers and in groundwater systems, it appears to overestimate weathering rates. This overestimation has been corrected by improving the kinetic expression describing mineral dissolution by adding or upgrading breaking functions. The base cation and aluminium brakes have been strengthened, and an additional silicate brake has been developed, improving the ability to describe mineral-water reactions in deeper soils. These brakes are developed from a molecular-level model of the dissolution mechanisms. Equations, parameters and constants describing mineral dissolution kinetics have now been obtained for 102 different minerals from 12 major structural groups, comprising all types of minerals encountered in most soils. The PROFILE and ForSAFE weathering sub-model was extended to cover two-dimensional catchments, both in the vertical and the horizontal direction, including the hydrology. Comparisons between this improved model and field observations is available in Erlandsson Lampa et al. (2019, This special issue). The results showed that the incorporation of a braking effect of silica concentrations was necessary and helps obtain more accurate descriptions of soil evolution rates at greater depths and within the saturated zone.

Latent disciplinal clashes concerning the batch dissolution of minerals, and their wider implications

2018 ◽  
Vol 15 (2) ◽  
pp. 113 ◽  
Author(s):  
Victor W. Truesdale ◽  
Jim Greenwood
Keyword(s):  
Large Scale ◽  
Dissolution Kinetics ◽  
Mineral Dissolution ◽  
Atomic Scale ◽  
Rate Equations ◽  
Silicate Mineral ◽  
Waste Products ◽  
Calcite Dissolution ◽  
Macro Scale ◽  
Made In

Environmental contextMineral dissolution kinetics are important to understand natural processes including those increasingly used to store waste carbon dioxide and highly radio-active nuclides, and those involved in the amelioration of climate change and sea-level rise. We highlight a mistake made in the fundamental science that has retarded progress in the field for over 40 years. Its removal suggests improved ways to approach dissolution studies. AbstractMineral dissolution kinetics are fundamental to biogeochemistry, and to the application of science to reduce the deleterious effects of humanity’s waste products, e.g. CO2 and radio-nuclides. However, a mistake made in the selection of the rate equation appropriate for use at the macro-scale of the aquatic environment has stymied growth in major aspects of the subject for some 40 years. This paper identifies the mistake, shows how it represents a latent disciplinal clash between two rate equations, and explores the misunderstandings that resulted from it. The paper also briefly explores other disciplinal clashes. Using the example of calcite dissolution, the paper also shows how the phenomenon of ‘non-ideal’ dissolution, which is prevalent in alumino-silicate mineral dissolution, as well as with calcite, has obscured the clash. The paper provides new information on plausible mechanisms, the absence of which has contributed to the problem. Finally, it argues that disciplinal clashes need to be minimised so that a rigorous description of dissolution at the large scale can be matched to findings at the atomic, or near-atomic, scale.

scholarly journals A Flexible Platform of Electrochemically Functionalized Carbon Nanotubes for NADH Sensors

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 518 ◽  
Author(s):  
Aranzazu Heras ◽  
Fabio Vulcano ◽  
Jesus Garoz-Ruiz ◽  
Nicola Porcelli ◽  
Fabio Terzi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Direct Evidence ◽  
Electrode System ◽  
Electrochemical Process ◽  
Organic Residues ◽  
Flexible Electrode ◽  
Functionalized Carbon Nanotubes ◽  
Solution Interface ◽  
Sensor Platform ◽  
Walled Carbon Nanotubes

A flexible electrode system entirely constituted by single-walled carbon nanotubes (SWCNTs) has been proposed as the sensor platform for β-nicotinamide adenine dinucleotide (NADH) detection. The performance of the device, in terms of potential at which the electrochemical process takes place, significantly improves by electrochemical functionalization of the carbon-based material with a molecule possessing an o-hydroquinone residue, namely caffeic acid. Both the processes of SWCNT functionalization and NADH detection have been studied by combining electrochemical and spectroelectrochemical experiments, in order to achieve direct evidence of the electrode modification by the organic residues and to study the electrocatalytic activity of the resulting material in respect to functional groups present at the electrode/solution interface. Electrochemical measurements performed at the fixed potential of +0.30 V let us envision the possible use of the device as an amperometric sensor for NADH detection. Spectroelectrochemistry also demonstrates the effectiveness of the device in acting as a voltabsorptometric sensor for the detection of this same analyte by exploiting this different transduction mechanism, potentially less prone to the possible presence of interfering species.

Reduction of Soluble and Solid Ferric Iron by Acidiphilium SJH

2007 ◽  
Vol 20-21 ◽  
pp. 497-500 ◽  
Author(s):  
Alexandra Vašková ◽  
Daniel Kupka
Keyword(s):  
Iron Reduction ◽  
Consumption Rate ◽  
Ferric Iron ◽  
Oxygen Transfer Rate ◽  
Oxygen Limitation ◽  
Co2 Production ◽  
Anaerobic Conditions ◽  
Terminal Electron Acceptor ◽  
Aerobic Conditions ◽  
Microaerobic Conditions

Facultative Fe(III)-reducing bacterium Acidiphilium SJH was incubated in media with ferric iron under various conditions with respect to oxygen availability for the growing cells. The bacteria oxidized organic substratum to carbon dioxide using oxygen and ferric iron as terminal electron acceptors. Ferric iron reduction was observed in all incubation modes. The distribution of reducing equivalents from the oxidation of organic carbon for the reduction of both O2 and Fe(III) was evaluated from CO2 production rate and O2 consumption rate. In fully aerobic conditions approximately 10 % of CO2 produced was coupled with reduction of Fe(III) as terminal electron acceptor. Under aerobic conditions, the ratio of CO2 produced to O2 consumed remained unaffected in a broad concentration range of dissolved oxygen. In the course of oxygen limitation (microaerobic conditions) the molar CO2 to O2 ratio increased from approx. 1 to 2 and even much more with respect to oxygen transfer rate during incubation. On the other hand no bacterial growth and extremely slow iron reduction was observed in obligatory anaerobic conditions in a reactor purged with either pure or CO2-enriched nitrogen.

scholarly journals Ferric Iron Reduction by Bacteria Associated with the Roots of Freshwater and Marine Macrophytes

1999 ◽  
Vol 65 (10) ◽  
pp. 4393-4398 ◽  
Author(s):  
G. M. King ◽  
Meredith A. Garey
Keyword(s):  
Iron Reduction ◽  
Ferric Iron ◽  
Sodium Molybdate ◽  
Dry Weight ◽  
Root Activity ◽  
In Vitro Assays ◽  
Freshwater Macrophytes ◽  
Marine Macrophytes ◽  
Marine Isolate

ABSTRACT In vitro assays of washed, excised roots revealed maximum potential ferric iron reduction rates of >100 μmol g (dry weight)−1 day−1 for three freshwater macrophytes and rates between 15 and 83 μmol (dry weight)−1 day−1 for two marine species. The rates varied with root morphology but not consistently (fine root activity exceeded smooth root activity in some but not all cases). Sodium molybdate added at final concentrations of 0.2 to 20 mM did not inhibit iron reduction by roots of marine macrophytes (Spartina alterniflora and Zostera marina). Roots of a freshwater macrophyte, Sparganium eurycarpum, that were incubated with an analog of humic acid precursors, anthroquinone disulfate (AQDS), reduced freshly precipitated iron oxyhydroxide contained in dialysis bags that excluded solutes with molecular weights of >1,000; no reduction occurred in the absence of AQDS. Bacterial enrichment cultures and isolates from freshwater and marine roots used a variety of carbon and energy sources (e.g., acetate, ethanol, succinate, toluene, and yeast extract) and ferric oxyhydroxide, ferric citrate, uranate, and AQDS as terminal electron acceptors. The temperature optima for a freshwater isolate and a marine isolate were equivalent (approximately 32°C). However, iron reduction by the freshwater isolate decreased with increasing salinity, while reduction by the marine isolate displayed a relatively broad optimum salinity between 20 and 35 ppt. Our results suggest that by participating in an active iron cycle and perhaps by reducing humic acids, iron reducers in the rhizoplane of aquatic macrophytes limit organic availability to other heterotrophs (including methanogens) in the rhizosphere and bulk sediments.

scholarly journals Vibrio cholerae VciB Mediates Iron Reduction

2017 ◽  
Vol 199 (12) ◽  
Author(s):  
Eric D. Peng ◽  
Shelley M. Payne
Keyword(s):  
Electron Transport ◽  
Vibrio Cholerae ◽  
Ferrous Iron ◽  
Electron Transport Chain ◽  
Iron Reduction ◽  
Iron Transport ◽  
Ferric Iron ◽  
Transport Systems ◽  
Content Type ◽  
Transport Chain

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. V. cholerae thrives within the human host, where it replicates to high numbers, but it also persists within the aquatic environments of ocean and brackish water. To survive within these nutritionally diverse environments, V. cholerae must encode the necessary tools to acquire the essential nutrient iron in all forms it may encounter. A prior study of systems involved in iron transport in V. cholerae revealed the existence of vciB, which, while unable to directly transport iron, stimulates the transport of iron through ferrous (Fe2+) iron transport systems. We demonstrate here a role for VciB in V. cholerae in which VciB stimulates the reduction of Fe3+ to Fe2+, which can be subsequently transported into the cell with the ferrous iron transporter Feo. Iron reduction is independent of functional iron transport but is associated with the electron transport chain. Comparative analysis of VciB orthologs suggests a similar role for other proteins in the VciB family. Our data indicate that VciB is a dimer located in the inner membrane with three transmembrane segments and a large periplasmic loop. Directed mutagenesis of the protein reveals two highly conserved histidine residues required for function. Taken together, our results support a model whereby VciB reduces ferric iron using energy from the electron transport chain. IMPORTANCE Vibrio cholerae is a prolific human pathogen and environmental organism. The acquisition of essential nutrients such as iron is critical for replication, and V. cholerae encodes a number of mechanisms to use iron from diverse environments. Here, we describe the V. cholerae protein VciB that increases the reduction of oxidized ferric iron (Fe3+) to the ferrous form (Fe2+), thus promoting iron acquisition through ferrous iron transporters. Analysis of VciB orthologs in Burkholderia and Aeromonas spp. suggest that they have a similar activity, allowing a functional assignment for this previously uncharacterized protein family. This study builds upon our understanding of proteins known to mediate iron reduction in bacteria.

Reduction and Complexation of Copper in a Novel Bioreduction System Developed to Recover Base Metals from Mine Process Waters

2013 ◽  
Vol 825 ◽  
pp. 483-486 ◽  
Author(s):  
Sabrina Hedrich ◽  
Chris du Plessis ◽  
Nelson Mora ◽  
D. Barrie Johnson
Keyword(s):  
Copper Sulfide ◽  
Iron Reduction ◽  
Elemental Sulfur ◽  
Ferric Iron ◽  
Sodium Sulfide ◽  
Base Metals ◽  
Processing Scheme ◽  
Step Process ◽  
Potential Alternative ◽  
Axenic Cultures

An integrated bio-processing scheme was devised and tested in the laboratory for recovering copper, or other base metals, from pregnant leach solutions (PLS) using a two-step process involving both iron-reduction, and sulfate-reduction for H2S generation and sulfide precipitation, as a potential alternative to conventional SX-EW. Reduction of ferric iron in the PLS was achieved using iron-reducingAcidithiobacillusspp. andSulfobacillus thermosulfidooxidansin column reactors containing elemental sulfur as electron donor. Analysis of the column reactor effluents showed not only that most of the ferric iron was reduced to ferrous, but also that all of the copper (II) had been reduced to copper (I), i.e. cuprous copper. This copper (I) appeared to be complexed as it was not oxidized when exposed to ferric iron nor precipitated as a copper-sulfide when exposed to either sodium sulfide or H2S. The data suggested that copper (II) was reduced and the resulting copper (I) complexed, with both reactions probably mediated by sulfur oxy-anions produced indirectly by the bacteria, in the anoxic sulfur column bioreactors. It was also noted that copper (I) produced chemically by reduction of copper (II) by hydroxylamine was more toxic to axenic cultures ofAcidithiobacillusspp. andSb. thermosulfidooxidansthan was the copper (I) in the column effluent liquors.

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