Next Issue
Volume 6, December
Previous Issue
Volume 6, June

Table of Contents

Minerals, Volume 6, Issue 3 (September 2016)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Select all
Export citation of selected articles as:
Open AccessArticle
Synthesis of Novel Ether Thionocarbamates and Study on Their Flotation Performance for Chalcopyrite
Minerals 2016, 6(3), 97; https://doi.org/10.3390/min6030097 - 21 Sep 2016
Cited by 8 | Viewed by 1593
Abstract
Novel ether thionocarbamates, O-butoxy isopropyl-N-ethoxycarbonyl thionocarbamate (BIPECTC) and O-(2-butoxy-1-methylethoxy) isopropyl-N-ethoxycarbonyl thionocarbamate (BMIPECTC), were synthesized in this study. Their collecting efficiencies in the flotation of chalcopyrite were investigated using flotation tests, adsorption measurements, ultraviolet spectra (UV) and Fourier transform-infrared spectroscopy (FT-IR) and density functional [...] Read more.
Novel ether thionocarbamates, O-butoxy isopropyl-N-ethoxycarbonyl thionocarbamate (BIPECTC) and O-(2-butoxy-1-methylethoxy) isopropyl-N-ethoxycarbonyl thionocarbamate (BMIPECTC), were synthesized in this study. Their collecting efficiencies in the flotation of chalcopyrite were investigated using flotation tests, adsorption measurements, ultraviolet spectra (UV) and Fourier transform-infrared spectroscopy (FT-IR) and density functional theory (DFT) calculations. The synthesized ether thionocarbamates showed better frothing properties than methyl-isobutyl-carbinol (MIBC) and stronger affinity to chalcopyrite compared with O-isopropyl-N-ethyl thionocarbamate (IPETC) and O-isobutyl-N-ethoxycarbonyl thionocarbamate (IBECTC). UV spectra analysis showed that the ether thionocarbamates react with Cu2+, with the exception of Fe2+, Ni2+, Zn2+ and Pb2+. Additionally, it was further confirmed by FTIR spectra that a chemical reaction occurs between copper ion and BIPECTC and BMIPECTC. The adsorption capacity measurements revealed that chalcopyrite exhibits good adsorption ability for ether thionocarbamates at an approximate pH of 8–10, which agrees with the flotation tests. The quantum chemistry calculation results indicated that the ether thionocarbamates exhibit stronger collecting ability for copper mineral in terms of frontier molecular orbital analysis, binding model simulation with copper ions and the molecular hydrophobicity compared with IPETC and IBECTC. The computational results are in very good agreement with the experimental results. Full article
Show Figures

Figure 1

Open AccessArticle
China’s Rare Earths Supply Forecast in 2025: A Dynamic Computable General Equilibrium Analysis
Minerals 2016, 6(3), 95; https://doi.org/10.3390/min6030095 - 21 Sep 2016
Cited by 15 | Viewed by 2133
Abstract
The supply of rare earths in China has been the focus of significant attention in recent years. Due to changes in regulatory policies and the development of strategic emerging industries, it is critical to investigate the scenario of rare earth supplies in 2025. [...] Read more.
The supply of rare earths in China has been the focus of significant attention in recent years. Due to changes in regulatory policies and the development of strategic emerging industries, it is critical to investigate the scenario of rare earth supplies in 2025. To address this question, this paper constructed a dynamic computable equilibrium (DCGE) model to forecast the production, domestic supply, and export of China’s rare earths in 2025. Based on our analysis, production will increase by 10.8%–12.6% and achieve 116,335–118,260 tons of rare-earth oxide (REO) in 2025, based on recent extraction control during 2011–2016. Moreover, domestic supply and export will be 75,081–76,800 tons REO and 38,797–39,400 tons REO, respectively. The technological improvements on substitution and recycling will significantly decrease the supply and mining activities of rare earths. From a policy perspective, we found that the elimination of export regulations, including export quotas and export taxes, does have a negative impact on China’s future domestic supply of rare earths. The policy conflicts between the increase in investment in strategic emerging industries, and the increase in resource and environmental taxes on rare earths will also affect China’s rare earths supply in the future. Full article
Show Figures

Figure 1

Open AccessArticle
Pb-Isotopic Study of Galena by LA-Q-ICP-MS: Testing a New Methodology with Applications to Base-Metal Sulphide Deposits
Minerals 2016, 6(3), 96; https://doi.org/10.3390/min6030096 - 15 Sep 2016
Cited by 5 | Viewed by 2292
Abstract
In situ laser ablation quadrupole inductively coupled plasma mass spectrometry was used to measure Pb isotopes in galena. Data acquisition was optimized by adjusting spot size, energy density, and ablation time to obtain near steady-state low relative standard deviation (%RSD) signals. Standard-sample bracketing [...] Read more.
In situ laser ablation quadrupole inductively coupled plasma mass spectrometry was used to measure Pb isotopes in galena. Data acquisition was optimized by adjusting spot size, energy density, and ablation time to obtain near steady-state low relative standard deviation (%RSD) signals. Standard-sample bracketing using in-house Broken Hill galena as external reference standard was used and offline data reduction was carried out using VizualAge for Iolite3. Using this methodology, galena grain in polished thin sections from selected massive sulphide deposits of the Bathurst Mining Camp, Canada, were tested and compared to previously published data. Absolute values and errors on the weighted mean of ~20 individual analyses from each sample compared favourably with whole-rock Pb-Pb isotope data. This approach provides a mean to obtain rapid, accurate, and moderately (0.1% 2σ) precise Pb isotope measurements in galena and is particularly well suited for exploratory or reconnaissance studies. Further refinement of this approach may be useful in exploration for volcanogenic massive sulphides deposits and might be a useful vectoring tool when complemented with other conventional exploration techniques. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
Show Figures

Figure 1

Open AccessArticle
Investigation of Platinum-Group Minerals (PGM) from Othrys Chromitites (Greece) Using Superpanning Concentrates
Minerals 2016, 6(3), 94; https://doi.org/10.3390/min6030094 - 12 Sep 2016
Cited by 3 | Viewed by 1582
Abstract
Platinum-group minerals were concentrated using superpanning from two composite chromitite samples, which were collected from two old mines within the Othrys ophiolite. This method allows for the recovery of a broad spectrum of these rare and fine-grained minerals, and helps to better identify [...] Read more.
Platinum-group minerals were concentrated using superpanning from two composite chromitite samples, which were collected from two old mines within the Othrys ophiolite. This method allows for the recovery of a broad spectrum of these rare and fine-grained minerals, and helps to better identify them and interpret their origin. Major differences between the east and west Othrys ophiolites were determined, probably as a result of their different origin and evolution. Primary Os-, Ir-, and Ru-bearing platinum-group minerals (IPGM)-alloys and the Rh-, Pt- and Pd-bearing platinum-group minerals (PPGM) occur only in the east Othrys chromitite, indicating an evolution from initially low fS2 conditions at shallower mantle levels with the subsequent implication of a S-saturated ascending fluid. In contrast, the absence of primary IPGM-alloys in west Othrys chromitite indicates that S saturation had been attained. The presence of erlichmanite suggests that sulphur fugacity eventually increased significantly in both suites. Substantial fluctuations of a fluid phase, likely related to serpentinising fluids, modified the platinum-group minerals (PGM) assemblage of west Othrys, and resulted in a large diversity of secondary PGM minerals. The limited number of secondary species developed in the east Othrys indicate that secondary processes were also different in the two suites. Full article
(This article belongs to the Special Issue Advanced Research on Accessory Minerals)
Show Figures

Figure 1

Open AccessArticle
The Effect of Ca2+ and Mg2+ on the Dispersion and Flocculation Behaviors of Muscovite Particles
Minerals 2016, 6(3), 93; https://doi.org/10.3390/min6030093 - 08 Sep 2016
Cited by 4 | Viewed by 1715
Abstract
The dispersion and flocculation behavior of muscovite suspensions in the presence of Ca2+ and Mg2+ are relevant for industrial processing of pre-concentrated muscovite from stone coal, a primary source of vanadium. In this study, the dispersion and flocculation behavior were investigated [...] Read more.
The dispersion and flocculation behavior of muscovite suspensions in the presence of Ca2+ and Mg2+ are relevant for industrial processing of pre-concentrated muscovite from stone coal, a primary source of vanadium. In this study, the dispersion and flocculation behavior were investigated by means of sedimentation, zeta potential, and ion absorption experiments, as well as the force between particles and ion speciation calculations. The results indicated that the dispersion and flocculation behavior of muscovite particles without excess ions were in qualitative agreement with the classical DLVO theory. The muscovite particles aggregated mainly due to basal surface-edge interactions in acidic suspensions but were dispersed in alkaline suspension by electrostatic repulsion of the total particle surface. In acidic suspensions, the ability of muscovite to form dispersions of muscovite was increased with the decrease in the electrostatic attraction between the basal surface and the edge caused by the compression of the electric double layers withCa2+ and Mg2+. In alkaline suspension, the main adsorption form of Ca2+ and Mg2+ on muscovite surface was the ion-hydroxy complexes. The flocculation behavior of muscovite was affected by the static bridge effect of the ion-hydroxy complexes. Full article
(This article belongs to the Special Issue Mineral Surface Science and Nanogeoscience)
Show Figures

Graphical abstract

Open AccessArticle
The Effect of Chloride Ions on the Activity of Cerussite Surfaces
Minerals 2016, 6(3), 92; https://doi.org/10.3390/min6030092 - 06 Sep 2016
Cited by 9 | Viewed by 1561
Abstract
Chloride ions were found to potentially increase activity of cerussite surfaces. Dissolution experiments, zeta potential measurements, X-ray photoelectron spectroscopy (XPS) studies, and density functional theory (DFT) computation were conducted in this study. Dissolution experiments showed that the lead ion concentrations in the NaCl [...] Read more.
Chloride ions were found to potentially increase activity of cerussite surfaces. Dissolution experiments, zeta potential measurements, X-ray photoelectron spectroscopy (XPS) studies, and density functional theory (DFT) computation were conducted in this study. Dissolution experiments showed that the lead ion concentrations in the NaCl solution system were lower than those in the deionized water system and that the lead ion concentrations in NaCl + Na2S aqueous systems decreased by approximately one order of magnitude compared with that in the Na2S system alone. Results of zeta potential measurements revealed that the pretreatment with chloride ions of cerussite caused a more positive zeta potential than that without chloride ions. XPS analysis results indicated that the number of lead ions on the mineral surface increased after cerussite was treated with chloride ions. Results of DFT computation implied that the number of lead atoms on the mineral surface increased and that the activity improved after PbCl+ was adsorbed onto the cerussite surface. The contribution of chloride ions to the activity on the mineral surface is attributed to the increase in the number of active sites and enhancement in the activity of these sites, resulting in improved sulfidization and flotation performance. Full article
(This article belongs to the Special Issue Mineral Surface Science and Nanogeoscience)
Show Figures

Figure 1

Open AccessArticle
The Cedrolina Chromitite, Goiás State, Brazil: A Metamorphic Puzzle
Minerals 2016, 6(3), 91; https://doi.org/10.3390/min6030091 - 01 Sep 2016
Cited by 5 | Viewed by 2102
Abstract
The Cedrolina chromitite body (Goiás-Brazil) is concordantly emplaced within talc-chlorite schists that correspond to the poly-metamorphic product of ultramafic rocks inserted in the Pilar de Goiás Greenstone Belt (Central Brazil). The chromite ore displays a nodular structure consisting of rounded and ellipsoidal orbs [...] Read more.
The Cedrolina chromitite body (Goiás-Brazil) is concordantly emplaced within talc-chlorite schists that correspond to the poly-metamorphic product of ultramafic rocks inserted in the Pilar de Goiás Greenstone Belt (Central Brazil). The chromite ore displays a nodular structure consisting of rounded and ellipsoidal orbs (up to 1.5 cm in size), often strongly deformed and fractured, immersed in a matrix of silicates (mainly chlorite and talc). Chromite is characterized by high Cr# (0.80–0.86), high Fe2+# (0.70–0.94), and low TiO2 (av. = 0.18 wt %) consistent with variation trends of spinels from metamorphic rocks. The chromitite contains a large suite of accessory phases, but only irarsite and laurite are believed to be relicts of the original igneous assemblage, whereas most accessory minerals are thought to be related to hydrothermal fluids that emanated from a nearby felsic intrusion, metamorphism and weathering. Rutile is one of the most abundant accessory minerals described, showing an unusually high Cr2O3 content (up to 39,200 ppm of Cr) and commonly forming large anhedral grains (>100 µm) that fill fractures (within chromite nodules and in the matrix) or contain micro-inclusions of chromite. Using a trace element geothermometer, the rutile crystallization temperature is estimated at 550–600 °C (at 0.4–0.6 GPa), which is in agreement with P and T conditions proposed for the regional greenschist to low amphibolite facies metamorphic peak of the area. Textural, morphological, and compositional evidence confirm that rutile did not crystallize at high temperatures simultaneously with the host chromitite, but as a secondary metamorphic mineral. Rutile may have been formed as a metamorphic overgrowth product following deformation and regional metamorphic events, filling fractures and incorporating chromite fragments. High Cr contents in rutile very likely are due to Cr remobilization from Cr-spinel during metamorphism and suggest that Ti was remobilized to form rutile. This would imply that the magmatic composition of chromite had originally higher Ti content, pointing to a stratiform origin. Another possible interpretation is that the Ti-enrichment was caused by external metasomatic fluids which lead to crystallization of rutile. If this was the case, the Cedrolina chromitites could be classified as podiform, possibly representing a sliver of tectonically dismembered Paleoproterozoic upper mantle. However, the strong metamorphic overprint that affected the studied chromitites makes it extremely difficult to establish which of the above processes were active, if not both (and to what extent), and, therefore, the chromitite’s original geodynamic setting. Full article
(This article belongs to the Special Issue Advanced Research on Accessory Minerals)
Show Figures

Figure 1

Open AccessArticle
The Flotation of Kyanite and Sillimanite with Sodium Oleate as the Collector
Minerals 2016, 6(3), 90; https://doi.org/10.3390/min6030090 - 31 Aug 2016
Cited by 7 | Viewed by 1893
Abstract
Kyanite and sillimanite are two polymorphic minerals with the same formula of Al2SiO5, but different crystal structures. Despite their high economic values, selectively recovering them by flotation is a challenge. In this study, the flotation behaviors of the two [...] Read more.
Kyanite and sillimanite are two polymorphic minerals with the same formula of Al2SiO5, but different crystal structures. Despite their high economic values, selectively recovering them by flotation is a challenge. In this study, the flotation behaviors of the two minerals with sodium oleate as the collector were examined at different pH conditions. Zeta potential measurement, infrared spectroscopic measurement, chemical speciation and X-ray photoelectron spectroscopy measurement were conducted to identify the underpinning mechanisms. It is found that the flotation behavior of both minerals is different under the same flotation condition. The flotation recovery of sillimanite is much higher than that of kyanite in the presence of the collector sodium oleate. Sodium oleate adsorbs onto the surfaces of kyanite and sillimanite mainly through the chemical interaction of the ionic–molecular dimers with aluminum atoms at pH 8.0. The higher sillimanite flotation recovery between the two minerals is related to the higher electrostatic charge densities of the aluminum atoms in six-fold coordination, which leads to the higher collector adsorption. Full article
(This article belongs to the Special Issue Flotation in Mineral Processing)
Show Figures

Figure 1

Open AccessArticle
The Influence of Impurity Monovalent Cations Adsorption on Reconstructed Chalcopyrite (001)-S Surface in Leaching Process
Minerals 2016, 6(3), 89; https://doi.org/10.3390/min6030089 - 29 Aug 2016
Cited by 6 | Viewed by 1587
Abstract
Hydrometallurgical processing of chalcopyrite is hindered predominantly due to the passivation layers formed on the chalcopyrite surface. However, the effects of impurity cations released from the gangue are not yet well understood. Density functional theory (DFT) calculations were carried out to investigate monovalent [...] Read more.
Hydrometallurgical processing of chalcopyrite is hindered predominantly due to the passivation layers formed on the chalcopyrite surface. However, the effects of impurity cations released from the gangue are not yet well understood. Density functional theory (DFT) calculations were carried out to investigate monovalent cations of Na+ and K+ on chalcopyrite (001)-S surface using Materials Studio. The results show that the 3d orbital of Fe and 3p orbital of S predominantly contribute to their activities during chalcopyrite oxidation and dissolution processes. In addition, SO42− is more likely to be adsorbed on one Fe site in the presence of Na+, while it is preferentially adsorbed on two Fe sites in the presence of K+. However, the adsorption of both Na2SO4 and K2SO4 on the chalcopyrite (001)-S surface contributes to the breakage of S–S bonds, indicating that the impurity cations of Na+ and K+ are beneficial to chalcopyrite leaching in a sulfuric environment. The adsorption energy and partial density of states (PDOS) analyses further indicate that the adsorption of Na2SO4 on chalcopyrite (001)-S surface is favored in both -BB (bidentate binuclear ) and -BM (bidentate mononuclear) modes, compared to the adsorption of K2SO4. Full article
(This article belongs to the Special Issue Mineral Surface Science and Nanogeoscience)
Show Figures

Graphical abstract

Open AccessArticle
Marine Phosphorites as Potential Resources for Heavy Rare Earth Elements and Yttrium
Minerals 2016, 6(3), 88; https://doi.org/10.3390/min6030088 - 29 Aug 2016
Cited by 8 | Viewed by 3044
Abstract
Marine phosphorites are known to concentrate rare earth elements and yttrium (REY) during early diagenetic formation. Much of the REY data available are decades old and incomplete, and there has not been a systematic study of REY distributions in marine phosphorite deposits that [...] Read more.
Marine phosphorites are known to concentrate rare earth elements and yttrium (REY) during early diagenetic formation. Much of the REY data available are decades old and incomplete, and there has not been a systematic study of REY distributions in marine phosphorite deposits that formed over a range of oceanic environments. Consequently, we initiated this study to determine if marine phosphorite deposits found in the global ocean host REY concentrations of high enough grade to be of economic interest. This paper addresses continental-margin (CM) and open-ocean seamount phosphorites. All 75 samples analyzed are composed predominantly of carbonate fluorapatite and minor detrital and authigenic minerals. CM phosphorites have low total REY contents (mean 161 ppm) and high heavy REY (HREY) complements (mean 49%), while seamount phosphorites have 4–6 times higher individual REY contents (except for Ce, which is subequal; mean ΣREY 727 ppm), and very high HREY complements (mean 60%). The predominant causes of higher concentrations and larger HREY complements in seamount phosphorites compared to CM phosphorites are age, changes in seawater REY concentrations over time, water depth of formation, changes in pH and complexing ligands, and differences in organic carbon content in the depositional environments. Potential ore deposits with high HREY complements, like the marine phosphorites analyzed here, could help supply the HREY needed for high-tech and green-tech applications without creating an oversupply of the LREY. Full article
(This article belongs to the Special Issue Marine Minerals: From Genesis to Resources)
Show Figures

Graphical abstract

Open AccessArticle
Restraining Na-Montmorillonite Delamination in Water by Adsorption of Sodium Dodecyl Sulfate or Octadecyl Trimethyl Ammonium Chloride on the Edges
Minerals 2016, 6(3), 87; https://doi.org/10.3390/min6030087 - 23 Aug 2016
Cited by 1 | Viewed by 1749
Abstract
The delamination of montmorillonite in water leads to sliming in ore slurry, which is detrimental to mineral flotation and solid/water separation. In this work, the delamination of Na-montmorillonite (Na-MMT) has been restrained by sodium dodecyl sulfate (SDS) or octadecyl trimethyl ammonium chloride (1831) [...] Read more.
The delamination of montmorillonite in water leads to sliming in ore slurry, which is detrimental to mineral flotation and solid/water separation. In this work, the delamination of Na-montmorillonite (Na-MMT) has been restrained by sodium dodecyl sulfate (SDS) or octadecyl trimethyl ammonium chloride (1831) through the adsorption on the edge of the mineral. The experimental results have shown that the pretreatment by adding SDS and 1831 could greatly reduce the Stokes size percentage of −1.1 µm particles in the aqueous Na-MMT suspension. From the X-ray diffractometer (XRD) results, the interlayer spacing of the MMT pre-treated by SDS and 1831 is smaller than that of original MMT particles. Adsorption position of SDS and 1831 on MMT surfaces was analyzed by the measurements of adsorption capacity of SDS and 1831, inductively-coupled plasma spectra, and zeta potential before and after the plane surface of MMT was covered with tetraethylenepentaminecopper ([Cu(tetren)]2+). The results indicated that SDS and 1831 are adsorbed on the edge and the whole surface of Na-MMT, respectively. Delamination of MMT could be well restrained by the adsorption of SDS and 1831 on the edges of MMT. Full article
(This article belongs to the Special Issue Mineral Surface Science and Nanogeoscience)
Show Figures

Figure 1

Open AccessArticle
Selective Flocculation Enhanced Magnetic Separation of Ultrafine Disseminated Magnetite Ores
Minerals 2016, 6(3), 86; https://doi.org/10.3390/min6030086 - 23 Aug 2016
Cited by 3 | Viewed by 1950
Abstract
Simple magnetic separation for a certain magnetite mine with ultrafine disseminated lean ores has resulted in low performance, as the fine sizes and aggregation of ground mineral particles have caused inefficient recovery of the ultrafine minerals. In this study, we attempt to increase [...] Read more.
Simple magnetic separation for a certain magnetite mine with ultrafine disseminated lean ores has resulted in low performance, as the fine sizes and aggregation of ground mineral particles have caused inefficient recovery of the ultrafine minerals. In this study, we attempt to increase the apparent sizes of target mineral particles, and improve the separation indices, by using a multi-stage grinding-dispersion-selective flocculation-weak magnetic separation process. The results showed that under the conditions of 500 g/t sodium hexametaphospate (SHMP) as dispersant, 750 g/t carboxymethyl starch (CMS) as flocculant, agitating at 400 rpm for 10 min, with slurry pH 11, and final grinding fineness of 93.5% less than 0.03 mm, the obtained concentrate contained 62.82% iron, with recovery of 79.12% after multi-stage magnetic separation. Compared to simple magnetic separation, the concentrate’s iron grade increased by 1.26%, and a recovery rate by 5.08%. Fundamental analysis indicated that, in a dispersed state of dispersion, magnetite particles had weaker negative surface charges than quartz, allowing the adsorption of negative CMS ions via hydrogen bonding. Consequently, the aggregate size of the initial concentrate increased from 24.30 to 38.37 μm, accomplishing the goal of selective flocculation, and increasing the indices of separation. Full article
Show Figures

Graphical abstract

Open AccessArticle
Matrix-Matched Iron-Oxide Laser Ablation ICP-MS U–Pb Geochronology Using Mixed Solution Standards
Minerals 2016, 6(3), 85; https://doi.org/10.3390/min6030085 - 23 Aug 2016
Cited by 26 | Viewed by 2248
Abstract
U–Pb dating of the common iron-oxide hematite (α-Fe2O3), using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS), provides unparalleled insight into the timing and processes of mineral deposit formation. Until now, the full potential of this method has been negatively impacted by the [...] Read more.
U–Pb dating of the common iron-oxide hematite (α-Fe2O3), using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS), provides unparalleled insight into the timing and processes of mineral deposit formation. Until now, the full potential of this method has been negatively impacted by the lack of suitable matrix-matched standards. To achieve matrix-matching, we report an approach in which a U–Pb solution and ablated material from 99.99% synthetic hematite are simultaneously mixed in a nebulizer chamber and introduced to the ICP-MS. The standard solution contains fixed U- and Pb-isotope ratios, calibrated independently, and aspiration of the isotopically homogeneous solution negates the need for a matrix-matched, isotopically homogenous natural iron-oxide standard. An additional advantage of using the solution is that the individual U–Pb concentrations and isotope ratios can be adjusted to approximate that in the unknown, making the method efficient for dating hematite containing low (~10 ppm) to high (>1 wt %) U concentrations. The above-mentioned advantage to this solution method results in reliable datasets, with arguably-better accuracy in measuring U–Pb ratios than using GJ-1 Zircon as the primary standard, which cannot be employed for such low U concentrations. Statistical overlaps between 207Pb/206Pb weighted average ages (using GJ-1 Zircon) and U–Pb upper intercept ages (using the U–Pb mixed solution method) of two samples from iron-oxide copper-gold (IOCG) deposits in South Australia demonstrate that, although fractionation associated with a non-matrix matched standard does occur when using GJ-1 Zircon as the primary standard, it does not impact the 207Pb/206Pb or upper intercept age. Thus, GJ-1 Zircon can be considered reliable for dating hematite using LA-ICP-MS. Downhole fractionation of 206Pb/238U is observed to occur in spot analyses of hematite. The use of rasters in future studies will hopefully minimize this problem, allowing for matrix-matched data. Using the mixed-solution method in this study, we have validated a published hematite Pb–Pb age for Olympic Dam, and provide a new age (1604 ± 11 Ma) for a second deposit in the same province. These ages are further evidence that the IOCG mineralizing event is tied to large igneous province (LIP) magmatism in the region at ~1.6 Ga. Full article
(This article belongs to the Special Issue Advances in Mineral Analytical Techniques)
Show Figures

Graphical abstract

Open AccessArticle
Phytomining for Artisanal Gold Mine Tailings Management
Minerals 2016, 6(3), 84; https://doi.org/10.3390/min6030084 - 15 Aug 2016
Cited by 4 | Viewed by 2491
Abstract
Mine tailings are generally disposed of by artisanal and small scale gold miners in poorly constructed containment areas and this leads to environmental risk. Gold phytomining could be a possible option for tailings management at artisanal and small-scale gold mining (ASGM) locations where [...] Read more.
Mine tailings are generally disposed of by artisanal and small scale gold miners in poorly constructed containment areas and this leads to environmental risk. Gold phytomining could be a possible option for tailings management at artisanal and small-scale gold mining (ASGM) locations where plants accumulate residual gold in their above ground biomass. The value of metal recovered from plants could offset some of the costs of environmental management. Getting gold into plants has been repeatedly demonstrated by many research groups; however, a simple working technology to get gold out of plants is less well described. A field experiment to assess the relevance of the technology to artisanal miners was conducted in Central Lombok, Indonesia between April and June 2015. Tobacco was planted in cyanidation tailings (1 mg/kg gold) and grown for 2.5 months before the entire plot area was irrigated with NaCN to induce metal uptake. Biomass was then harvested (100 kg), air dried, and ashed by miners in equipment currently used to ash activated carbon at the end of a cyanide leach circuit. Borax and silver as a collector metal were added to the tobacco ash and smelted at high temperature to extract metals from the ash. The mass of the final bullion (39 g) was greater than the mass of silver used as a collector (31 g), indicating recovery of metals from the biomass through the smelt process. The gold yield of this trial was low (1.2 mg/kg dry weight biomass concentration), indicating that considerable work must still be done to optimise valuable metal recovery by plants at the field scale. However, the described method to process the biomass was technically feasible, and represents a valid technique that artisanal and small-scale gold miners are willing to adopt if the economic case is good. Full article
(This article belongs to the Special Issue Biotechnologies and Mining)
Show Figures

Graphical abstract

Open AccessArticle
Kinetics and Mechanisms of Chalcopyrite Dissolution at Controlled Redox Potential of 750 mV in Sulfuric Acid Solution
Minerals 2016, 6(3), 83; https://doi.org/10.3390/min6030083 - 10 Aug 2016
Cited by 9 | Viewed by 1683
Abstract
To better understand chalcopyrite leach mechanisms and kinetics, for improved Cu extraction during hydrometallurgical processing, chalcopyrite leaching has been conducted at solution redox potential 750 mV, 35–75 °C, and pH 1.0 with and without aqueous iron addition, and pH 1.5 and 2.0 without [...] Read more.
To better understand chalcopyrite leach mechanisms and kinetics, for improved Cu extraction during hydrometallurgical processing, chalcopyrite leaching has been conducted at solution redox potential 750 mV, 35–75 °C, and pH 1.0 with and without aqueous iron addition, and pH 1.5 and 2.0 without aqueous iron addition. The activation energy (Ea) values derived indicate chalcopyrite dissolution is initially surface chemical reaction controlled, which is associated with the activities of Fe3+ and H+ with reaction orders of 0.12 and −0.28, respectively. A surface diffusion controlled mechanism is proposed for the later leaching stage with correspondingly low Ea values. Surface analyses indicate surface products (predominantly Sn2− and S0) did not inhibit chalcopyrite dissolution, consistent with the increased surface area normalised leach rate during the later stage. The addition of aqueous iron plays an important role in accelerating Cu leaching rates, especially at lower temperature, primarily by reducing the length of time of the initial surface chemical reaction controlled stage. Full article
Show Figures

Graphical abstract

Open AccessArticle
Pre-Concentration of Vanadium from Stone Coal by Gravity Using Fine Mineral Spiral
Minerals 2016, 6(3), 82; https://doi.org/10.3390/min6030082 - 04 Aug 2016
Cited by 4 | Viewed by 2202
Abstract
Due to the low grade of V2O5 in stone coal, the existing vanadium extraction technologies face challenges in terms of large handling capacity, high acid consumption and production cost. The pre-concentration of vanadium from stone coal before the extraction process [...] Read more.
Due to the low grade of V2O5 in stone coal, the existing vanadium extraction technologies face challenges in terms of large handling capacity, high acid consumption and production cost. The pre-concentration of vanadium from stone coal before the extraction process is an effective method to reduce cost. In this study, detailed mineral characterization of stone coal was investigated. It has been confirmed that the vanadium mainly occurs in muscovite and illite. A significant demand for an effective pre-concentration process with simple manipulation for discarding quartz and other gangue minerals is expected. Based on the mineralogical study, a new vanadium pre-concentration process using a fine mineral spiral was investigated. The experimental results showed that the separation process, which was comprised of a rougher and scavenger, could efficiently discard quartz, pyrite and apatite. A final concentrate with V2O5 grade of 1.02% and recovery of 89.6% could be obtained, with 26.9% of the raw ore being discarded as final tailings. Full article
Show Figures

Graphical abstract

Open AccessArticle
Modeling of Geometric Change Influence on Blast-Wave Propagation in Underground Airways Using a 2D-Transient Euler Scheme
Minerals 2016, 6(3), 81; https://doi.org/10.3390/min6030081 - 03 Aug 2016
Viewed by 1446
Abstract
The impact of methane explosions on mining operations can never be over-emphasized. The safety of miners could be threatened and local ventilation facilities are likely to be damaged by the flame and overpressure induced by a methane explosion event, making it essential to [...] Read more.
The impact of methane explosions on mining operations can never be over-emphasized. The safety of miners could be threatened and local ventilation facilities are likely to be damaged by the flame and overpressure induced by a methane explosion event, making it essential to understand the destructiveness and influence range of a specific explosion. In this paper, the attenuation effect of geometric changes, most commonly bends, obstacles, and branches, present in the way of blast-wave propagation and the capability of the selected numerical model were studied. Although some relevant experimental research has been provided, quantitative analysis is insufficient. This paper investigates the attenuation factors of seven bends, three obstacles, and two T-branch scenarios to ascertain a better insight of this potentially devastating event quantitatively. The results suggest that (1) the numerical model used is capable of predicting four of the seven validated scenarios with a relative error less than 12%; (2) the maximum peak overpressure is obtained when the angle equals 50° for bend cases; and (3) the selected numerical scheme would overestimate the obstacle cases by around 15%. Full article
Show Figures

Graphical abstract

Open AccessArticle
Microstructural Control on Perlite Expansibility and Geochemical Balance with a Novel Application of Isocon Analysis: An Example from Milos Island Perlite (Greece)
Minerals 2016, 6(3), 80; https://doi.org/10.3390/min6030080 - 02 Aug 2016
Cited by 3 | Viewed by 2051
Abstract
Representative perlite bulk rock samples from two areas of Milos Island, Greece were collected and the expansion properties of their industrial product were investigated. Coarse crude perlite from Tsigrado exhibits better expansibility, which is assigned to the presence of coarser crystallites in its [...] Read more.
Representative perlite bulk rock samples from two areas of Milos Island, Greece were collected and the expansion properties of their industrial product were investigated. Coarse crude perlite from Tsigrado exhibits better expansibility, which is assigned to the presence of coarser crystallites in its bulk parent rock. During thermal treatment, the finer crystallites of the coarse crude perlite from Trachilas are entrapped in the groundmass and lead to overheating, which inhibits expansion and eventually results in shrinkage. Geochemical modification of the expanded perlites relative to their crude precursors were investigated, using the isocon method. Volatilisation of crystalline water is the main factor controlling mass reduction of the expanded perlites. Other elements, during the adequate expansion of the Tsigrado perlite, can be classified into three categories. The elements that participate preferentially in crystals decrease in the expanded material at amounts higher than the total mass loss of the rock, due to their escape controlled mainly by the removal of the crystalline phases. The elements equally participating in crystals and the groundmass show losses equivalent to the total mass loss of the rocks, as they escaped in the crystalline phases and airborne particles from the groundmass during thermal treatment. Decrease of highly incompatible elements, which mostly participate in the groundmass, in the expanded products is less than the total mass loss, as they escaped mainly in the airborne particles. The inadequate expansion and burst of the Trachilas perlite did not allow for a similar categorisation, due to random and unpredictable escape of the elements. We propose the application of this method to an artificial system to predict unexpandable mineral phases in bulk perlite, as well as elements that are most likely to participate in the amorphous perlite phase, which cannot be determined from a regular industrial production line. This graphical method may also predict environmental pollution of the atmosphere from the release of volatile compounds and airborne particles during thermal treatment of perlite or other processes of mineral treatment. Full article
Show Figures

Graphical abstract

Open AccessArticle
Stability of Naturally Relevant Ternary Phases in the Cu–Sn–S System in Contact with an Aqueous Solution
Minerals 2016, 6(3), 79; https://doi.org/10.3390/min6030079 - 26 Jul 2016
Cited by 4 | Viewed by 1593
Abstract
A relevant research effort is devoted to the synthesis and characterization of phases belonging to the ternary system Cu–Sn–S, mainly for their possible applications in semiconductor technology. Among all ternary phases, kuramite, Cu3SnS4, mohite, Cu2SnS3, [...] Read more.
A relevant research effort is devoted to the synthesis and characterization of phases belonging to the ternary system Cu–Sn–S, mainly for their possible applications in semiconductor technology. Among all ternary phases, kuramite, Cu3SnS4, mohite, Cu2SnS3, and Cu4Sn7S16 have attracted the highest interest. Numerous studies were carried out claiming for the description of new phases in the ternary compositional field. In this study, we revise the existing literature on this ternary system, with a special focus on the phases stable in a temperature range at 25 °C. The only two ternary phases observed in nature are mohite and kuramite. Their occurrence is described as very rare. A numerical modelling of the stable solid phases in contact with a water solution was underwent to define stability relationships of the relevant phases of the system. The numerical modelling of the Eh-pH diagrams was carried out through the phreeqc software with the lnll.dat thermodynamic database. Owing to the complexity of this task, the subsystems Cu–O–H, Sn–O–H, Cu–S–O–H and Sn–S–O–H were firstly considered. The first Pourbaix diagram for the two naturally relevant ternary phases is then proposed. Full article
(This article belongs to the Special Issue Advanced Research on Accessory Minerals)
Show Figures

Graphical abstract

Open AccessArticle
Characterization of Coal Micro-Pore Structure and Simulation on the Seepage Rules of Low-Pressure Water Based on CT Scanning Data
Minerals 2016, 6(3), 78; https://doi.org/10.3390/min6030078 - 26 Jul 2016
Cited by 22 | Viewed by 2518
Abstract
This paper used the X-ray three-dimensional (3D) microscope and acquired, through CT scanning, the 3D data of the long-frame coal sample from the Daliuta Coal Mine. Then, the 3D datacube reconstructed from the coal’s CT scanning data was visualized with the use of [...] Read more.
This paper used the X-ray three-dimensional (3D) microscope and acquired, through CT scanning, the 3D data of the long-frame coal sample from the Daliuta Coal Mine. Then, the 3D datacube reconstructed from the coal’s CT scanning data was visualized with the use of Avizo, an advanced visualization software (FEI, Hillsboro, OR, USA). By means of a gray-scale segmentation technique, the model of the coal’s micro-pore structure was extracted from the object region, and the precise characterization was then conducted. Finally, the numerical simulation on the water seepage characteristics in the coal micro-pores model under the pressure of 3 MPa was performed on the CFX platform. Results show that the seepage of low-pressure water exhibited preference to the channels with large pore radii, short paths, and short distance from the outlet. The seepage pressure of low-pressure water decreased gradually along the seepage direction, while the seepage velocity of low-pressure water decreased gradually along the direction from the pore center to the wall. Regarding the single-channel seepage behaviors, the seepage velocity and mass flow rate of water seepage in the X direction were the largest, followed by the values of the seepage in the Y direction, and the seepage velocity and mass flow rate of water seepage in the Z direction were the smallest. Compared with the results in single-channel seepage, the dual-channel seepage in the direction of (X + Y) and the multi-channel seepage in the direction of (X + Y + Z) exhibited significant increases in the overall seepage velocity. The present study extends the application of 3D CT scanning data and provides a new idea and approach for exploring the seepage rules in coal micro-pore structures. Full article
Show Figures

Graphical abstract

Open AccessArticle
Agates from Kerrouchen (The Atlas Mountains, Morocco): Textural Types and Their Gemmological Characteristics
Minerals 2016, 6(3), 77; https://doi.org/10.3390/min6030077 - 26 Jul 2016
Cited by 2 | Viewed by 2599
Abstract
Agate nodules from Kerrouchen (Khénifra Province, Meknés-Tafilalet Region) in Morocco occur in Triassic basalts and reach up to 30 cm in diameter. Monocentric, banded agates—mainly in pastel pink, grey, white and yellow—with infiltration canals (osculum) are observed. Raman microspectroscopy revealed that [...] Read more.
Agate nodules from Kerrouchen (Khénifra Province, Meknés-Tafilalet Region) in Morocco occur in Triassic basalts and reach up to 30 cm in diameter. Monocentric, banded agates—mainly in pastel pink, grey, white and yellow—with infiltration canals (osculum) are observed. Raman microspectroscopy revealed that the agates mainly consist of low quartz and subordinately moganite with distinctive 460 and 501 cm−1 marker bands, respectively. Linear mapping indicated that moganite mainly concentrates in grey zones of the monocentric agate nodules. The other types, polycentric and pseudostalactitic agates, are usually brown and red and contain minerals such as hematite and goethite. They form both regular and irregular mosaics rich in ornamentation. Occasionally, aggregates of copper sulphides or titanium oxides (rutile) can also be observed. These minerals are sometimes accompanied by carbonaceous material marked by 1320 and 1585 cm−1 Raman bands. It seems that formation of agates from Kerrouchen was induced by Si-rich and Fe-moderate fluids. Copper sulphides, rutile, and carbonates (possibly calcite) were most likely incorporated during post-magmatic processes. The origin of solid bitumen can be the result of hydrothermal or hypergenic processes. Full article
Show Figures

Graphical abstract

Open AccessArticle
Influence of Sulfobacillus thermosulfidooxidans on Initial Attachment and Pyrite Leaching by Thermoacidophilic Archaeon Acidianus sp. DSM 29099
Minerals 2016, 6(3), 76; https://doi.org/10.3390/min6030076 - 21 Jul 2016
Cited by 4 | Viewed by 1617
Abstract
At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. [...] Read more.
At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. Currently, little is known on the influence of pre-colonized mesophiles or moderate thermophiles on the attachment and bioleaching efficiency by thermophiles. The objective of this study was to investigate the interspecies interactions of the moderate thermophile Sulfobacillus thermosulfidooxidans DSM 9293T and the thermophile Acidianus sp. DSM 29099 during initial attachment to and dissolution of pyrite. Our results showed that: (1) Acidianus sp. DSM 29099 interacted with S. thermosulfidooxidansT during initial attachment in mixed cultures. In particular, cell attachment was improved in mixed cultures compared to pure cultures alone; however, no improvement of pyrite leaching in mixed cultures compared with pure cultures was observed; (2) active or inactivated cells of S. thermosulfidooxidansT on pyrite inhibited or showed no influence on the initial attachment of Acidianus sp. DSM 29099, respectively, but both promoted its leaching efficiency; (3) S. thermosulfidooxidansT exudates did not enhance the initial attachment of Acidianus sp. DSM 29099 to pyrite, but greatly facilitated its pyrite dissolution efficiency. Our study provides insights into cell-cell interactions between moderate thermophiles and thermophiles and is helpful for understanding of the microbial interactions in a heap leaching environment. Full article
(This article belongs to the Special Issue Biotechnologies and Mining)
Show Figures

Graphical abstract

Open AccessArticle
Selective Leaching of Vanadium from Roasted Stone Coal by Dilute Sulfuric Acid Dephosphorization-Two-Stage Pressure Acid Leaching
Minerals 2016, 6(3), 75; https://doi.org/10.3390/min6030075 - 21 Jul 2016
Cited by 5 | Viewed by 1886
Abstract
A novel staged leaching process has been reported in this paper to selectively extract vanadium from roasted stone coal and the mechanisms have been clarified. Results showed that the leaching efficiency of V, Al, P and Fe was 80.46%, 12.24%, 0.67% and 3.12%, [...] Read more.
A novel staged leaching process has been reported in this paper to selectively extract vanadium from roasted stone coal and the mechanisms have been clarified. Results showed that the leaching efficiency of V, Al, P and Fe was 80.46%, 12.24%, 0.67% and 3.12%, respectively, under the optimum dilute sulfuric acid dephosphorization (DSAD)-two-stage pressure acid leaching (PAL) conditions. The efficient separation of V from Fe, Al and P was realized. As apatite could be leached more easily than mica, the apatite could completely react with sulfuric acid, while the mica had almost no change in the DSAD process, which was the key aspect in realizing the effective separation of V from P. Similarly, the hydrolyzation of Fe and Al could be initiated more easily than that of V by decreasing the residual acid of leachate. The alunite and iron-sulphate compound generated in the first-stage PAL process resulted in the effective separation of V from Fe and Al. Full article
Show Figures

Graphical abstract

Open AccessArticle
Origin of Minerals and Elements in the Late Permian Coal Seams of the Shiping Mine, Sichuan, Southwestern China
Minerals 2016, 6(3), 74; https://doi.org/10.3390/min6030074 - 19 Jul 2016
Cited by 12 | Viewed by 1914
Abstract
Volcanic layers in coal seams in southwestern China coalfields have received much attention given their significance in coal geology studies and their potential economic value. In this study, the mineralogical and geochemical compositions of C19 and C25 coal seams were examined, and the [...] Read more.
Volcanic layers in coal seams in southwestern China coalfields have received much attention given their significance in coal geology studies and their potential economic value. In this study, the mineralogical and geochemical compositions of C19 and C25 coal seams were examined, and the following findings were obtained. (1) Clay minerals in sample C19-r are argillized, and sedimentary layering is not observed. The acicular idiomorphic crystals of apatite and the phenocrysts of Ti-augite coexisting with magnetite in roof sample C19-r are common minerals in basaltic rock. The rare earth elements (REE) distribution pattern of C19-r, which is characterized by positive Eu anomalies and M-REE enrichment, is the same as that of high-Ti basalt. The concentrations of Ti, V, Co, Cr, Ni, Cu, Zn, Nb, Ta, Zr, and Hf in C19-r are closer to those of high-Ti basalt. In conclusion, roof sample C19-r consists of tuffaceous clay, probably with a high-Ti mafic magma source. (2) The geochemical characteristics of the C25 coals are same as those reported for coal affected by alkali volcanic ash, enrichment in Nb, Ta, Zr, Hf, and REE, causing the C25 minable coal seams to have higher potential value. Such a vertical study of coals and host rocks could provide more information for coal-forming depositional environment analysis, for identification of volcanic eruption time and magma intrusion, and for facilitating stratigraphic subdivision and correlation. Full article
(This article belongs to the Special Issue Minerals in Coal) Printed Edition available
Show Figures

Graphical abstract

Open AccessArticle
N2 and CO2 Adsorption by Soils with High Kaolinite Content from San Juan Amecac, Puebla, México
Minerals 2016, 6(3), 73; https://doi.org/10.3390/min6030073 - 14 Jul 2016
Cited by 5 | Viewed by 2150
Abstract
Carbon dioxide (CO2) is considered one of the most important greenhouse gases in the study of climate change. CO2 adsorption was studied using the gas chromatography technique, while the Freundlich and Langmuir adsorption models were employed for processing isotherm data [...] Read more.
Carbon dioxide (CO2) is considered one of the most important greenhouse gases in the study of climate change. CO2 adsorption was studied using the gas chromatography technique, while the Freundlich and Langmuir adsorption models were employed for processing isotherm data in the temperature range of 473–573 K. The isosteric heat of adsorption was calculated from the Clausius–Clapeyron equation. Moreover, the thermodynamic properties ΔG, ΔU, and ΔS were evaluated from the adsorption isotherms of Langmuir using the Van’t Hoff Equation. The four soil samples were recollected from San Juan Amecac, Puebla, Mexico, and their morphologies were investigated through X-ray diffraction (XRD) and N2 adsorption at 77 K. The SJA4 soil has a crystalline Kaolinite phase, which is one of its non-metallic raw materials, and N2 isotherms allowed for the determination of pore size distributions and specific surface areas of soil samples. The Barrett–Joyner–Halenda (BJH) distribution of pore diameters was bimodal with peaks at 1.04 and 3.7 nm, respectively. CO2 adsorption showed that the SJA1 soil afforded a higher amount of adsorbed CO2 in the temperature range from 453 to 573 K followed by SJA4 and finally SJA2, classifying this process as exothermic physisorption. Full article
(This article belongs to the Special Issue CO2 Sequestration by Mineral Carbonation: Challenges and Advances)
Show Figures

Graphical abstract

Open AccessArticle
Assessment of Excavation Broken Zone around Gateways under Various Geological Conditions: A Case Study in Sichuan Province, China
Minerals 2016, 6(3), 72; https://doi.org/10.3390/min6030072 - 13 Jul 2016
Cited by 3 | Viewed by 1523
Abstract
To study common failure characteristics of gateways, a total of 55 typical gateways at coal mines, in Sichuan Province, China, were selected for investigating the rules of broken widths based on the ground-penetrating radar (GPR) technique and numerical model. Results indicated that the [...] Read more.
To study common failure characteristics of gateways, a total of 55 typical gateways at coal mines, in Sichuan Province, China, were selected for investigating the rules of broken widths based on the ground-penetrating radar (GPR) technique and numerical model. Results indicated that the broken width values around the gateways were larger than 1.5 m, and those in the roof and high side wall were larger than those in the low side wall, as a whole. The width values had close relationships with the thickness of the coal seam and immediate roof, angle of the coal seam, and depth of the gateways. Furthermore, combined with the plastic zone of numerical models in 3-Dimensional Distinct Element Code (3DEC) and the broken width, we obtained the excavation broken zone (EBZ) cross-section diagram for each gateway and determined that the EBZ appeared to have a basically elliptical shape—with the long axis along the seam inclination direction and the short axis along the vertical direction of the rock layer—and that this elliptical shape was only slightly affected by the gateway cross-section shape. It was observed that the failure extent was greater in the seam inclination direction than in the vertical direction of the rock layer. Obviously, the gateways presented asymmetric failure characteristics and implied that an asymmetric support system should be provided when using bolts, cables, and shotcrete combined with steel mesh and steel belts. Such a support system could improve material parameters and form a combined arch structure in surrounding rocks, with arch crown and arch springing thicknesses that are larger in the roof and high side wall. Full article
Show Figures

Graphical abstract

Open AccessArticle
Enhancement of Biofilm Formation on Pyrite by Sulfobacillus thermosulfidooxidans
Minerals 2016, 6(3), 71; https://doi.org/10.3390/min6030071 - 09 Jul 2016
Cited by 11 | Viewed by 2062
Abstract
Bioleaching is the mobilization of metal cations from insoluble ores by microorganisms. Biofilms can enhance this process. Since Sulfobacillus often appears in leaching heaps or reactors, this genus has aroused attention. In this study, biofilm formation and subsequent pyrite dissolution by the Gram-positive, [...] Read more.
Bioleaching is the mobilization of metal cations from insoluble ores by microorganisms. Biofilms can enhance this process. Since Sulfobacillus often appears in leaching heaps or reactors, this genus has aroused attention. In this study, biofilm formation and subsequent pyrite dissolution by the Gram-positive, moderately thermophilic acidophile Sulfobacillus thermosulfidooxidans were investigated. Five strategies, including adjusting initial pH, supplementing an extra energy source or ferric ions, as well as exchanging exhausted medium with fresh medium, were tested for enhancement of its biofilm formation. The results show that regularly exchanging exhausted medium leads to a continuous biofilm development on pyrite. By this way, multiply layered biofilms were observed on pyrite slices, while only monolayer biofilms were visible on pyrite grains. In addition, biofilms were proven to be responsible for pyrite leaching in the early stages. Full article
(This article belongs to the Special Issue Biotechnologies and Mining)
Show Figures

Graphical abstract

Open AccessArticle
The Desulfurization of Magnetite Ore by Flotation with a Mixture of Xanthate and Dixanthogen
Minerals 2016, 6(3), 70; https://doi.org/10.3390/min6030070 - 08 Jul 2016
Cited by 6 | Viewed by 1849
Abstract
The contamination of sulfur emanating from pyrrhotite in magnetite concentrates has been a problem in iron ore processing. This study utilized froth flotation to float pyrrhotite away from magnetite using collectors of xanthate and dixanthogen. It was found that xanthate or dixanthogen alone [...] Read more.
The contamination of sulfur emanating from pyrrhotite in magnetite concentrates has been a problem in iron ore processing. This study utilized froth flotation to float pyrrhotite away from magnetite using collectors of xanthate and dixanthogen. It was found that xanthate or dixanthogen alone could not achieve selective separation between pyrrhotite and magnetite in flotation. A high loss of magnetite was obtained with xanthate, while a low desulfurization degree was obtained with dixanthogen. It was interesting that a high desulfurization ratio was achieved with little loss of magnetite when xanthate was mixed with dixanthogen as the collector. The synergistic effect of the mixed collector on pyrrhotite was studied by electrokinectic studies and FTIR measurements. It was found that xanthate was the anchor on pyrrhotite and determined its selectivity against magnetite, while dixanthogen associated with xanthate, enhancing its hydrophobicity. This study provides new insights into the separation of iron minerals. Full article
Show Figures

Graphical abstract

Open AccessArticle
Preparation of High Purity V2O5 from a Typical Low-Grade Refractory Stone Coal Using a Pyro-Hydrometallurgical Process
Minerals 2016, 6(3), 69; https://doi.org/10.3390/min6030069 - 08 Jul 2016
Cited by 9 | Viewed by 1538
Abstract
The recovery of vanadium from a typical low-grade refractory stone coal was investigated using a pyro-hydrometallurgical process specifically including blank roasting, acid leaching, solvent extraction, and chemical precipitation. The appropriate role of parameters in each process was analyzed in detail. Roasting temperature and [...] Read more.
The recovery of vanadium from a typical low-grade refractory stone coal was investigated using a pyro-hydrometallurgical process specifically including blank roasting, acid leaching, solvent extraction, and chemical precipitation. The appropriate role of parameters in each process was analyzed in detail. Roasting temperature and roasting time during the roasting process showed a significant effect on leaching efficiency of vanadium. Using H2SO4 as a leaching agent, vanadium leaching efficiency can achieve above 90% under the optimum leaching conditions of CaF2 dosage of 5%, sulfuric acid concentration of 4 mol/L, liquid to solid ratio of 2:1 mL/g, leaching time of 2 h, and leaching temperature of 95 °C. 99.10% of vanadium can be extracted from the leaching solution in three stages under the conditions of initial pH of 1.6, trioctylamine (TOA) extractant concentration of 20% (vol), phase ratio (A/O) of 2, and reaction time of 2 min. 1.0 mol/L NaOH was used to strip vanadium from the extracted solvent phase. After purification and precipitation, vanadium can be crystallized as ammonium metavanadate. The V2O5 product with a purity of 99.75% is obtained after ammonium metavanadate thermal decomposition at 550 °C for 2 h. The total vanadium recovery in the whole process is above 88%. This process has advantages of short operation time, high vanadium extraction efficiency, and high purity of the product. Full article
Show Figures

Graphical abstract

Open AccessArticle
Effect of Particle Size and Grinding Time on Gold Dissolution in Cyanide Solution
Minerals 2016, 6(3), 68; https://doi.org/10.3390/min6030068 - 07 Jul 2016
Cited by 2 | Viewed by 1776
Abstract
The recovery of gold by ore leaching is influenced by the size of the particles and the chemical environment. The effect of particle size on the dissolution of gold is usually studied using mono-size particles as the gold in solution comes from the [...] Read more.
The recovery of gold by ore leaching is influenced by the size of the particles and the chemical environment. The effect of particle size on the dissolution of gold is usually studied using mono-size particles as the gold in solution comes from the ore of a unique leached particle size. This paper proposes a method to estimate the gold dissolution as a function of particle size using a bulk ore sample, i.e., with the dissolved gold coming from the various sizes of particles carried by the ore. The results are consistent with the fact that gold dissolution increases with the decreasing particle size but results also indicate that gold dissolution of the ore within a size interval is not significantly affected by the grinding time used for the ore size reduction. Results also show a good dissolution of the gold contained in the fine-size fractions without oxidation and lead nitrate pre-treatment for an ore that is known to require such pre-treatment. Full article
Show Figures

Graphical abstract

Previous Issue
Next Issue
Back to TopTop