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Minerals, Volume 4, Issue 2 (June 2014), Pages 191-564

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Research

Jump to: Review

Open AccessArticle Field Application of Accelerated Mineral Carbonation
Minerals 2014, 4(2), 191-207; doi:10.3390/min4020191
Received: 11 January 2014 / Revised: 15 March 2014 / Accepted: 18 March 2014 / Published: 26 March 2014
Cited by 2 | PDF Full-text (1405 KB) | HTML Full-text | XML Full-text
Abstract
Globally, coal-fired power plants are the largest industrial source of carbon dioxide (CO2). CO2 emissions from flue gas have potential for direct mineralization with electrostatic precipitator fly ash particles in the field. Demonstration scale accelerated mineral carbonation (AMC) studies were
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Globally, coal-fired power plants are the largest industrial source of carbon dioxide (CO2). CO2 emissions from flue gas have potential for direct mineralization with electrostatic precipitator fly ash particles in the field. Demonstration scale accelerated mineral carbonation (AMC) studies were conducted at the Jim Bridger Power Plant, a large coal fired power plant located in Wyoming, USA. AMC produces kinetically rapid conditions for increased rates of mineralization of CO2, sulfur dioxide (SO2) and mercury (Hg) on fly ash particles. Control and AMC reacted fly ash particles were investigated for: change in carbon (expressed as CaCO3), sulfur (expressed as SO42−), and mercury (Hg) contents; topology and surface chemical composition by scanning electron microscope/energy dispersive X-ray spectroscopy analysis; chemical distribution of trace elements; and aqueous mineral solubility by the toxicity characteristic leaching procedure. Results of the AMC process show an increase in C, S, and Hg on AMC fly ash particles suggesting that multiple pollutants from flue gas can be removed through this direct mineral carbonation process. Results also suggest that the AMC process shifts soluble trace elements in fly ash to less leachable mineral fractions. The results of this study can provide insight into potential successful field implementation of AMC. Full article
(This article belongs to the Special Issue CO2 Sequestration by Mineral Carbonation: Challenges and Advances)
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Open AccessArticle Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations
Minerals 2014, 4(2), 208-240; doi:10.3390/min4020208
Received: 24 December 2013 / Revised: 25 February 2014 / Accepted: 6 March 2014 / Published: 27 March 2014
Cited by 7 | PDF Full-text (2333 KB) | HTML Full-text | XML Full-text
Abstract
A review of the literature about calculating the adsorption properties of arsenic onto mineral models using density functional theory (DFT) is presented. Furthermore, this work presents DFT results that show the effect of model charge, hydration, oxidation state, and DFT method on the
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A review of the literature about calculating the adsorption properties of arsenic onto mineral models using density functional theory (DFT) is presented. Furthermore, this work presents DFT results that show the effect of model charge, hydration, oxidation state, and DFT method on the structures and adsorption energies for AsIII and AsV onto Fe3+-(oxyhydr)oxide cluster models. Calculated interatomic distances from periodic planewave and cluster-model DFT are compared with experimental data for AsIII and AsV adsorbed to Fe3+-(oxyhydr)oxide models. In addition, reaction rates for the adsorption of AsV on α-FeOOH (goethite) (010) and Fe3+ (oxyhydr)oxide cluster models were calculated using planewave and cluster-model DFT methods. Full article
(This article belongs to the Special Issue Advances in Low-temperature Computational Mineralogy)
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Open AccessArticle Effects of the November 2012 Flood Event on the Mobilization of Hg from the Mount Amiata Mining District to the Sediments of the Paglia River Basin
Minerals 2014, 4(2), 241-256; doi:10.3390/min4020241
Received: 28 February 2014 / Revised: 1 April 2014 / Accepted: 2 April 2014 / Published: 9 April 2014
Cited by 5 | PDF Full-text (13391 KB) | HTML Full-text | XML Full-text
Abstract
The Mount Amiata mining district (southern Tuscany, Italy) was, for decades, one of the world’s largest mercury (Hg) producing regions, where mining activity lasted until the 1980s. The Paglia River drains the eastern part of the district and is also the main western
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The Mount Amiata mining district (southern Tuscany, Italy) was, for decades, one of the world’s largest mercury (Hg) producing regions, where mining activity lasted until the 1980s. The Paglia River drains the eastern part of the district and is also the main western tributary of the Tiber River. Recent studies show that, still today, high total Hg contents severely affect the downstream ecosystems of these rivers. In November 2012, a major flood event occurred in the Paglia River basin, which drastically changed the river morphology and, possibly, the Hg concentrations. In the present work, stream sediment was sampled before and after the flood to evaluate possible changes in sediment total Hg concentrations as a consequence of this event. The comparison between pre- and post-flood Hg concentrations shows that Hg content increased up to an order of magnitude after the flood, suggesting that this event triggered Hg mobilization in the basin rather than its dilution. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
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Open AccessArticle Diavik Waste Rock Project: Evolution of Mineral Weathering, Element Release, and Acid Generation and Neutralization during a Five-Year Humidity Cell Experiment
Minerals 2014, 4(2), 257-278; doi:10.3390/min4020257
Received: 30 January 2014 / Revised: 29 March 2014 / Accepted: 1 April 2014 / Published: 10 April 2014
Cited by 8 | PDF Full-text (761 KB) | HTML Full-text | XML Full-text
Abstract
A five-year, humidity-cell experiment was used to study the weathering evolution of a low-sulfide, granitic waste rock at 5 and 22 °C. Only the rock with the highest sulfide content (0.16 wt %) released sufficient acid to overcome a limited carbonate acid-neutralization capacity
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A five-year, humidity-cell experiment was used to study the weathering evolution of a low-sulfide, granitic waste rock at 5 and 22 °C. Only the rock with the highest sulfide content (0.16 wt %) released sufficient acid to overcome a limited carbonate acid-neutralization capacity and produce a substantial decline in pH. Leached SO4 and Ca quickly increased then decreased during the first two years of weathering. Sulfide oxidation continued to release acid and SO4 after carbonate depletion, resulting in an increase in acid-soluble elements, including Cu and Zn. With the dissolution of Al-bearing minerals, the pH stabilized above 4, and sulfide oxidation continued to decline until the end of the experiment. The variation in activation energy of sulfide oxidation correlates with changes in sulfide availability, where the lowest activation energies occurred during the largest releases of SO4. A decrease in sulfide availability was attributed to consumption of sulfide and weathered rims on sulfide grains that reduced the oxidation rate. Varying element release rates due to changing carbonate and sulfide availability provide identifiable geochemical conditions that can be viewed as neutralization sequences and may be extrapolated to the field site for examining the evolution of mineral weathering of the waste rock. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
Open AccessArticle Long-Term Acid-Generating and Metal Leaching Potential of a Sub-Arctic Oil Shale
Minerals 2014, 4(2), 293-312; doi:10.3390/min4020293
Received: 19 February 2014 / Revised: 8 April 2014 / Accepted: 10 April 2014 / Published: 14 April 2014
Cited by 3 | PDF Full-text (835 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Shales are increasingly being exploited for oil and unconventional gas. Exploitation of sub-arctic oil shales requires the creation of gravel pads to elevate workings above the heaving effects of ground ice. These gravel pads can potentially generate acidic leachate, which can enhance the
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Shales are increasingly being exploited for oil and unconventional gas. Exploitation of sub-arctic oil shales requires the creation of gravel pads to elevate workings above the heaving effects of ground ice. These gravel pads can potentially generate acidic leachate, which can enhance the mobility of metals from the shale. To examine this potential, pyrite-bearing shale originating from sub-Arctic gravel pad sites were subjected to leaching tests for 600 days at initial pH values ranging from 2 to 5, to simulate potential real world conditions. At set times over the 600 day experiment, pH, oxidation reduction potential (ORP), dissolved oxygen and temperature were recorded and small liquid samples withdrawn and analysed for elemental concentrations using total reflection X-ray fluorescence spectrometry (TRXRF). Six of eight shale samples were found to be acid generating, with pH declining and ORP becoming increasingly positive after 100 days. Two of the eight shale samples produced increasingly alkaline leachate conditions with relatively low ORP after 100 days, indicating an inbuilt buffering capacity. By 600 days the buffering capacity of all samples had been consumed and all leachate samples were acidic. TRXRF analyses demonstrated significant potential for the leaching of S, Fe, Ni, Cu, Zn and Mn with greatest concentrations found in reaction vessels with most acidic pH and highest ORP. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
Open AccessArticle Mapping Changes in a Recovering Mine Site with Hyperspectral Airborne HyMap Imagery (Sotiel, SW Spain)
Minerals 2014, 4(2), 313-329; doi:10.3390/min4020313
Received: 31 October 2013 / Revised: 2 April 2014 / Accepted: 10 April 2014 / Published: 16 April 2014
Cited by 2 | PDF Full-text (5241 KB) | HTML Full-text | XML Full-text
Abstract
Hyperspectral high spatial resolution HyMap data are used to map mine waste from massive sulfide ore deposits, mostly abandoned, on the Iberian Pyrite Belt (southwest Spain). Mine dams, mill tailings and mine dumps in variable states of pyrite oxidation are recognizable. The interpretation
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Hyperspectral high spatial resolution HyMap data are used to map mine waste from massive sulfide ore deposits, mostly abandoned, on the Iberian Pyrite Belt (southwest Spain). Mine dams, mill tailings and mine dumps in variable states of pyrite oxidation are recognizable. The interpretation of hyperspectral remote sensing requires specific algorithms able to manage high dimensional data compared to multispectral data. The routine of image processing methods used to extract information from hyperspectral data to map geological features is explained, as well as the sequence of algorithms used to produce maps of the mine sites. The mineralogical identification capability of algorithms to produce maps based on archive spectral libraries is discussed. Trends of mineral growth differ spectrally over time according to the geological setting and the recovery state of the mine site. Subtle mineralogical changes are enhanced using the spectral response as indicators of pyrite oxidation intensity of the mine waste piles and pyrite mud tailings. The changes in the surface of the mill tailings deserve a detailed description, as the surfaces are inaccessible to direct observation. Such mineralogical changes respond faithfully to industrial activities or the influence of climate when undisturbed by human influence. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
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Open AccessArticle Characterization of Green Liquor Dregs, Potentially Useful for Prevention of the Formation of Acid Rock Drainage
Minerals 2014, 4(2), 330-344; doi:10.3390/min4020330
Received: 26 February 2014 / Revised: 14 April 2014 / Accepted: 14 April 2014 / Published: 22 April 2014
Cited by 6 | PDF Full-text (1143 KB) | HTML Full-text | XML Full-text
Abstract
Using alternative materials such as residual products from other industries to mitigate the negative effects of acid rock drainage would simultaneously solve two environmental problems. The main residual product still landfilled by sulphate paper mills is the alkaline material green liquor dregs (GLD).
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Using alternative materials such as residual products from other industries to mitigate the negative effects of acid rock drainage would simultaneously solve two environmental problems. The main residual product still landfilled by sulphate paper mills is the alkaline material green liquor dregs (GLD). A physical, mineralogical and chemical characterization of four batches of GLD was carried out to evaluate the potential to use it as a sealing layer in the construction of dry covers on sulphide-bearing mine waste. GLD has relatively low hydraulic conductivity (10−8 to 10−9 m/s), a high water retention capacity (WRC) and small particle size. Whilst the chemical and mineralogical composition varied between the different batches, these variations were not reflected in properties such as hydraulic conductivity and WRC. Due to relatively low trace element concentrations, leaching of contaminants from the GLD is not a concern for the environment. However, GLD is a sticky material, difficult to apply on mine waste deposits and the shear strength is insufficient for engineering applications. Therefore, improving the mechanical properties is necessary. In addition, GLD has a high buffering capacity indicating that it could act as an alkaline barrier. Once engineering technicalities have been overcome, the long-term effectiveness of GLD should be studied, especially the effect of aging and how the sealing layer would be engineered in respect to topography and climatic conditions. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
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Open AccessArticle Precious Metals in Automotive Technology: An Unsolvable Depletion Problem?
Minerals 2014, 4(2), 388-398; doi:10.3390/min4020388
Received: 4 November 2013 / Revised: 24 April 2014 / Accepted: 25 April 2014 / Published: 30 April 2014
Cited by 2 | PDF Full-text (248 KB) | HTML Full-text | XML Full-text
Abstract
Since the second half of the 20th century, various devices have been developed in order to reduce the emissions of harmful substances at the exhaust pipe of combustion engines. In the automotive field, the most diffuse and best known device of this kind
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Since the second half of the 20th century, various devices have been developed in order to reduce the emissions of harmful substances at the exhaust pipe of combustion engines. In the automotive field, the most diffuse and best known device of this kind is the “three way” catalytic converter for engines using the Otto cycle designed to abate the emissions of carbon monoxide, nitrogen oxides and unburnt hydrocarbons. These catalytic converters can function only by means of precious metals (mainly platinum, rhodium and palladium) which exist in a limited supply in economically exploitable ores. The recent increase in prices of all mineral commodities is already making these converters significantly expensive and it is not impossible that the progressive depletion of precious metals will make them too expensive for the market of private cars. The present paper examines how this potential scarcity could affect the technology of road transportation worldwide. We argue that the supply of precious metals for automotive converters is not at risk in the short term, but that in the future it will not be possible to continue using this technology as a result of increasing prices generated by progressive depletion. Mitigation methods such as reducing the amounts of precious metals in catalysts, or recycling them can help but cannot be considered as a definitive solution. We argue that precious metal scarcity is a critical factor that may determine the future development of road transportation in the world. As the problem is basically unsolvable in the long run, we must explore new technologies for road transportation and we conclude that it is likely that the clean engine of the future will be electric and powered by batteries. Full article
Open AccessArticle Evidence for the Multi-Stage Petrogenetic History of the Oka Carbonatite Complex (Québec, Canada) as Recorded by Perovskite and Apatite
Minerals 2014, 4(2), 437-476; doi:10.3390/min4020437
Received: 28 February 2014 / Revised: 7 May 2014 / Accepted: 13 May 2014 / Published: 26 May 2014
Cited by 2 | PDF Full-text (4874 KB) | HTML Full-text | XML Full-text
Abstract
The Oka complex is amongst the youngest carbonatite occurrences in North America and is associated with the Monteregian Igneous Province (MIP; Québec, Canada). The complex consists of both carbonatite and undersaturated silicate rocks (e.g., ijolite, alnöite), and their relative emplacement history is uncertain.
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The Oka complex is amongst the youngest carbonatite occurrences in North America and is associated with the Monteregian Igneous Province (MIP; Québec, Canada). The complex consists of both carbonatite and undersaturated silicate rocks (e.g., ijolite, alnöite), and their relative emplacement history is uncertain. The aim of this study is to decipher the petrogenetic history of Oka via the compositional, isotopic and geochronological investigation of accessory minerals, perovskite and apatite, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The new compositional data for individual perovskite and apatite grains from both carbonatite and associated alkaline silicate rocks are highly variable and indicative of open system behavior. In situ Sr and Nd isotopic compositions for these two minerals are also variable and support the involvement of several mantle sources. U-Pb ages for both perovskite and apatite define a bimodal distribution, and range between 113 and 135 Ma, which overlaps the range of ages reported previously for Oka and the entire MIP. The overall distribution of ages indicates that alnöite was intruded first, followed by okaite and carbonatite, whereas ijolite defines a bimodal emplacement history. The combined chemical, isotopic, and geochronological data is best explained by invoking the periodic generation of small volume, partial melts generated from heterogeneous mantle. Full article
(This article belongs to the Special Issue Advances in Mineral Geochronology)
Open AccessArticle Jarosite versus Soluble Iron-Sulfate Formation and Their Role in Acid Mine Drainage Formation at the Pan de Azúcar Mine Tailings (Zn-Pb-Ag), NW Argentina
Minerals 2014, 4(2), 477-502; doi:10.3390/min4020477
Received: 28 February 2014 / Revised: 12 May 2014 / Accepted: 19 May 2014 / Published: 30 May 2014
Cited by 7 | PDF Full-text (7430 KB) | HTML Full-text | XML Full-text
Abstract
Secondary jarosite and water-soluble iron-sulfate minerals control the composition of acid mine waters formed by the oxidation of sulfide in tailings impoundments at the (Zn-Pb-Ag) Pan de Azúcar mine located in the Pozuelos Lagoon Basin (semi-arid climate) in Northwest (NW) Argentina. In the
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Secondary jarosite and water-soluble iron-sulfate minerals control the composition of acid mine waters formed by the oxidation of sulfide in tailings impoundments at the (Zn-Pb-Ag) Pan de Azúcar mine located in the Pozuelos Lagoon Basin (semi-arid climate) in Northwest (NW) Argentina. In the primary zone of the tailings (9.5 wt % pyrite-marcasite) precipitation of anglesite (PbSO4), wupatkite ((Co,Mg,Ni)Al2(SO4)4) and gypsum retain Pb, Co and Ca, while mainly Fe2+, Zn2+, Al3+, Mg2+, As3+/5+ and Cd2+ migrate downwards, forming a sulfate and metal-rich plume. In the oxidation zone, jarosite (MFe3(TO4)2(OH)6) is the main secondary Fe3+ phase; its most suitable composition is M = K+, Na+, and Pb2+and TO4 = SO42−; AsO42−. During the dry season, iron-sulfate salts precipitate by capillary transport on the tailings and at the foot of DC2 (tailings impoundment DC2) tailings dam where an acid, Fe2+ rich plume outcrops. The most abundant compounds in the acid mine drainage (AMD) are SO42−, Fe2+, Fe3+, Zn2+, Al3+, Mg2+, Cu2+, As3+/5+, Cd2+. These show peak concentrations at the beginning of the wet season, when the soluble salts and jarosite dissolve. The formation of soluble sulfate salts during the dry season and dilution during the wet season conform an annual cycle of rapid metals and acidity transference from the tailings to the downstream environment. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
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Open AccessArticle Chemical Abrasion Applied to LA-ICP-MS U–Pb Zircon Geochronology
Minerals 2014, 4(2), 503-518; doi:10.3390/min4020503
Received: 30 April 2014 / Revised: 19 May 2014 / Accepted: 23 May 2014 / Published: 3 June 2014
Cited by 8 | PDF Full-text (3369 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Zircon (ZrSiO4) is the most commonly used mineral in U–Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion
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Zircon (ZrSiO4) is the most commonly used mineral in U–Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion of zircon involves thermal annealing followed by relatively low temperature partial dissolution in HF acid. It was specifically developed to minimize or eliminate the effects of Pb-loss prior to analysis using Thermal Ionization Mass Spectrometry (TIMS). Here we test the application of chemical abrasion to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) by analyzing zircons from both untreated and chemically abraded samples. Rates of ablation for high alpha-dose non-treated zircons are up to 25% faster than chemically abraded equivalents. Ablation of 91500 zircon reference material demonstrates a ca. 3% greater down-hole fractionation of 206Pb/238U for non-treated zircons. These disparities necessitate using chemical abrasion for both primary reference material and unknowns to avoid applying an incorrect laser induced fractionation correction. All treated samples display a marked increase in the degree of concordance and/or lowering of common Pb, thereby illustrating the effectiveness of chemical abrasion to LA-ICP-MS U–Pb zircon geochronology. Full article
(This article belongs to the Special Issue Advances in Mineral Geochronology)
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Open AccessArticle Evaluation of the Homogeneity of the Uranium Isotope Composition of NIST SRM 610/611 by MC-ICP-MS, MC-TIMS, and SIMS
Minerals 2014, 4(2), 541-552; doi:10.3390/min4020541
Received: 8 March 2014 / Revised: 31 May 2014 / Accepted: 4 June 2014 / Published: 10 June 2014
Cited by 2 | PDF Full-text (1239 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
As analytical and microanalytical applications employing uranium isotope ratios increase, so does the need for reliable reference materials, particularly in the fields of geochemistry, geochronology, and nuclear forensics. We present working values for uranium isotopic data of NIST 610/611 glass, collected by multicollector
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As analytical and microanalytical applications employing uranium isotope ratios increase, so does the need for reliable reference materials, particularly in the fields of geochemistry, geochronology, and nuclear forensics. We present working values for uranium isotopic data of NIST 610/611 glass, collected by multicollector inductively-coupled plasma mass spectrometry (MC-ICP-MS), multicollector thermal ionization mass spectrometry (MC-TIMS), and secondary ion mass spectrometry (SIMS). The presence of depleted U, and, in this case, measureable 236U, makes NIST 610/611 an ideal candidate for a uranium isotopic reference material for nuclear materials. We analyzed multiple chips of three different NIST 611 wafers and found no heterogeneity in 234U/238U, 235U/238U, and 236U/238U within or between the wafers, within analytical uncertainty. We determined working values and uncertainties (using a coverage factor of two) using data from this study and the literature for the following U isotope ratios: 234U/238U = 9.45 × 10−6 ± 5.0 × 10−8; 235U/238U = 2.38555 × 10−3 ± 4.7 × 10−7; and 236U/238U = 4.314 × 10−5 ± 4.0 × 10−8. SIMS data show 235U/238U is reproducible to within 1% (within analytical uncertainty) in a single wafer, at a scale of 25 μm. Multiple studies have demonstrated homogeneity between wafers of NIST 610 and NIST 611, thus the data reported here can be considered representative of NIST 610 as well. Full article
(This article belongs to the Special Issue Advances in Mineral Geochronology)
Open AccessArticle Chemoorganotrophic Bioleaching of Olivine for Nickel Recovery
Minerals 2014, 4(2), 553-564; doi:10.3390/min4020553
Received: 8 May 2014 / Revised: 11 June 2014 / Accepted: 12 June 2014 / Published: 20 June 2014
Cited by 2 | PDF Full-text (1774 KB) | HTML Full-text | XML Full-text
Abstract
Bioleaching of olivine, a natural nickel-containing magnesium-iron-silicate, was conducted by applying chemoorganotrophic bacteria and fungi. The tested fungus, Aspergillus niger, leached substantially more nickel from olivine than the tested bacterium, Paenibacillus mucilaginosus. Aspergillus niger also outperformed two other fungal species: Humicola
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Bioleaching of olivine, a natural nickel-containing magnesium-iron-silicate, was conducted by applying chemoorganotrophic bacteria and fungi. The tested fungus, Aspergillus niger, leached substantially more nickel from olivine than the tested bacterium, Paenibacillus mucilaginosus. Aspergillus niger also outperformed two other fungal species: Humicola grisae and Penicillium chrysogenum. Contrary to traditional acid leaching, the microorganisms leached nickel preferentially over magnesium and iron. An average selectivity factor of 2.2 was achieved for nickel compared to iron. The impact of ultrasonic conditioning on bioleaching was also tested, and it was found to substantially increase nickel extraction by A. niger. This is credited to an enhancement in the fungal growth rate, to the promotion of particle degradation, and to the detachment of the stagnant biofilm around the particles. Furthermore, ultrasonic conditioning enhanced the selectivity of A. niger for nickel over iron to a value of 3.5. Pre-carbonating the olivine mineral, to enhance mineral liberation and change metal speciation, was also attempted, but did not result in improvement as a consequence of the mild pH of chemoorganotrophic bioleaching. Full article
(This article belongs to the Special Issue Advances in Biohydrometallurgy)

Review

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Open AccessReview Recent Developments in Microbiological Approaches for Securing Mine Wastes and for Recovering Metals from Mine Waters
Minerals 2014, 4(2), 279-292; doi:10.3390/min4020279
Received: 11 March 2014 / Revised: 3 April 2014 / Accepted: 10 April 2014 / Published: 14 April 2014
Cited by 11 | PDF Full-text (756 KB) | HTML Full-text | XML Full-text
Abstract
Mining of metals and coals generates solid and liquid wastes that are potentially hazardous to the environment. Traditional methods to reduce the production of pollutants from mining and to treat impacted water courses are mostly physico-chemical in nature, though passive remediation of mine
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Mining of metals and coals generates solid and liquid wastes that are potentially hazardous to the environment. Traditional methods to reduce the production of pollutants from mining and to treat impacted water courses are mostly physico-chemical in nature, though passive remediation of mine waters utilizes reactions that are catalysed by microorganisms. This paper reviews recent advances in biotechnologies that have been proposed both to secure reactive mine tailings and to remediate mine waters. Empirical management of tailings ponds to promote the growth of micro-algae that sustain populations of bacteria that essentially reverse the processes involved in the formation of acid mine drainage has been proposed. Elsewhere, targeted biomineralization has been demonstrated to produce solid products that allow metals present in mine waters to be recovered and recycled, rather than to be disposed of in landfill. Full article
(This article belongs to the Special Issue Mine Waste Characterization, Management and Remediation)
Open AccessReview Computational Redox Potential Predictions: Applications to Inorganic and Organic Aqueous Complexes, and Complexes Adsorbed to Mineral Surfaces
Minerals 2014, 4(2), 345-387; doi:10.3390/min4020345
Received: 11 February 2014 / Revised: 3 April 2014 / Accepted: 13 April 2014 / Published: 24 April 2014
Cited by 14 | PDF Full-text (689 KB) | HTML Full-text | XML Full-text
Abstract
Applications of redox processes range over a number of scientific fields. This review article summarizes the theory behind the calculation of redox potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to
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Applications of redox processes range over a number of scientific fields. This review article summarizes the theory behind the calculation of redox potentials in solution for species such as organic compounds, inorganic complexes, actinides, battery materials, and mineral surface-bound-species. Different computational approaches to predict and determine redox potentials of electron transitions are discussed along with their respective pros and cons for the prediction of redox potentials. Subsequently, recommendations are made for certain necessary computational settings required for accurate calculation of redox potentials. This article reviews the importance of computational parameters, such as basis sets, density functional theory (DFT) functionals, and relativistic approaches and the role that physicochemical processes play on the shift of redox potentials, such as hydration or spin orbit coupling, and will aid in finding suitable combinations of approaches for different chemical and geochemical applications. Identifying cost-effective and credible computational approaches is essential to benchmark redox potential calculations against experiments. Once a good theoretical approach is found to model the chemistry and thermodynamics of the redox and electron transfer process, this knowledge can be incorporated into models of more complex reaction mechanisms that include diffusion in the solute, surface diffusion, and dehydration, to name a few. This knowledge is important to fully understand the nature of redox processes be it a geochemical process that dictates natural redox reactions or one that is being used for the optimization of a chemical process in industry. In addition, it will help identify materials that will be useful to design catalytic redox agents, to come up with materials to be used for batteries and photovoltaic processes, and to identify new and improved remediation strategies in environmental engineering, for example the reduction of actinides and their subsequent immobilization. Highly under-investigated is the role of redox-active semiconducting mineral surfaces as catalysts for promoting natural redox processes. Such knowledge is crucial to derive process-oriented mechanisms, kinetics, and rate laws for inorganic and organic redox processes in nature. In addition, molecular-level details still need to be explored and understood to plan for safer disposal of hazardous materials. In light of this, we include new research on the effect of iron-sulfide mineral surfaces, such as pyrite and mackinawite, on the redox chemistry of actinyl aqua complexes in aqueous solution. Full article
(This article belongs to the Special Issue Advances in Low-temperature Computational Mineralogy)
Open AccessReview Strategizing Carbon-Neutral Mines: A Case for Pilot Projects
Minerals 2014, 4(2), 399-436; doi:10.3390/min4020399
Received: 4 March 2014 / Revised: 22 April 2014 / Accepted: 24 April 2014 / Published: 2 May 2014
Cited by 7 | PDF Full-text (5614 KB) | HTML Full-text | XML Full-text
Abstract
Ultramafic and mafic mine tailings are a valuable feedstock for carbon mineralization that should be used to offset carbon emissions generated by the mining industry. Although passive carbonation is occurring at the abandoned Clinton Creek asbestos mine, and the active Diavik diamond and
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Ultramafic and mafic mine tailings are a valuable feedstock for carbon mineralization that should be used to offset carbon emissions generated by the mining industry. Although passive carbonation is occurring at the abandoned Clinton Creek asbestos mine, and the active Diavik diamond and Mount Keith nickel mines, there remains untapped potential for sequestering CO2 within these mine wastes. There is the potential to accelerate carbonation to create economically viable, large-scale CO2 fixation technologies that can operate at near-surface temperature and atmospheric pressure. We review several relevant acceleration strategies including: bioleaching of magnesium silicates; increasing the supply of CO2 via heterotrophic oxidation of waste organics; and biologically induced carbonate precipitation, as well as enhancing passive carbonation through tailings management practices and use of CO2 point sources. Scenarios for pilot scale projects are proposed with the aim of moving towards carbon-neutral mines. A financial incentive is necessary to encourage the development of these strategies. We recommend the use of a dynamic real options pricing approach, instead of traditional discounted cash-flow approaches, because it reflects the inherent value in managerial flexibility to adapt and capitalize on favorable future opportunities in the highly volatile carbon market. Full article
(This article belongs to the Special Issue CO2 Sequestration by Mineral Carbonation: Challenges and Advances)
Open AccessReview Interaction of Natural Organic Matter with Layered Minerals: Recent Developments in Computational Methods at the Nanoscale
Minerals 2014, 4(2), 519-540; doi:10.3390/min4020519
Received: 5 March 2014 / Revised: 3 May 2014 / Accepted: 14 May 2014 / Published: 6 June 2014
Cited by 11 | PDF Full-text (1331 KB) | HTML Full-text | XML Full-text
Abstract
The role of mineral surfaces in the adsorption, transport, formation, and degradation of natural organic matter (NOM) in the biosphere remains an active research area owing to the difficulties in identifying proper working models of both NOM and mineral phases present in the
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The role of mineral surfaces in the adsorption, transport, formation, and degradation of natural organic matter (NOM) in the biosphere remains an active research area owing to the difficulties in identifying proper working models of both NOM and mineral phases present in the environment. The variety of aqueous chemistries encountered in the subsurface (e.g., oxic vs. anoxic, variable pH) further complicate this field of study. Recently, the advent of nanoscale probes such as X-ray adsorption spectroscopy and surface vibrational spectroscopy applied to study such complicated interfacial systems have enabled new insight into NOM-mineral interfaces. Additionally, due to increasing capabilities in computational chemistry, it is now possible to simulate molecular processes of NOM at multiple scales, from quantum methods for electron transfer to classical methods for folding and adsorption of macroparticles. In this review, we present recent developments in interfacial properties of NOM adsorbed on mineral surfaces from a computational point of view that is informed by recent experiments. Full article
(This article belongs to the Special Issue Advances in Low-temperature Computational Mineralogy)
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