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Minerals, Volume 7, Issue 2 (February 2017)

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Cover Story We show which trace elements are commonly incorporated into natural tetrahedrite-tennantite, at [...] Read more.
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Research

Open AccessArticle Aggregation Mechanism of Particles: Effect of Ca2+ and Polyacrylamide on Coagulation and Flocculation of Coal Slime Water Containing Illite
Minerals 2017, 7(2), 30; doi:10.3390/min7020030
Received: 15 December 2016 / Revised: 14 February 2017 / Accepted: 15 February 2017 / Published: 21 February 2017
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Abstract
Illite is one of the main components in coal slime water and it sometimes makes the water extremely difficult to clarify. In this study, the aggregation mechanism of coal and illite particles was investigated using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and settling experiments
[...] Read more.
Illite is one of the main components in coal slime water and it sometimes makes the water extremely difficult to clarify. In this study, the aggregation mechanism of coal and illite particles was investigated using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and settling experiments of slime water containing coal and illite. The results show that electrostatic energy plays a dominant role and manifests repulsive force in the long-range (>4 nm). However, the leading role becomes a hydrophobic force determined by the polar surface interaction energy in the short-range (<4 nm). A coagulant (Ca2+) can lower the surface electric potential to make all particles easier to coagulate, while the surface hydrophobicity of coal and illite determines whether the particles aggregate. Cationic polyacrylamide (CPAM) can promote the sedimentation of particles flocs effectively and makes the supernatant clearer due to attractive electrostatic forces while anionic polyacrylamide (APAM) flocculates particles through the bridge mechanism. Although the hydration shell on the hydrophilic surface of illite appears to be harmful for either coagulation or flocculation, illite can accelerate sedimentation when it is attached to the coal due to its higher density. Full article
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Open AccessArticle Comparison of Adsorption of Phenol O-O and N-O Chelating Collectors at the Malachite/Water Interface in Flotation
Minerals 2017, 7(2), 20; doi:10.3390/min7020020
Received: 20 December 2016 / Revised: 16 January 2017 / Accepted: 30 January 2017 / Published: 14 February 2017
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Abstract
To separate one base metal mineral from another by flotation, it is indispensable to identify chemical reagents that specifically interact with the surface metal sites of one mineral or a group of minerals. This work studies the interactions of chelating collectors which offer
[...] Read more.
To separate one base metal mineral from another by flotation, it is indispensable to identify chemical reagents that specifically interact with the surface metal sites of one mineral or a group of minerals. This work studies the interactions of chelating collectors which offer the best potential for collecting abilities and mineral specificity with a typical refractory oxide mineral (malachite). Zeta potential, adsorption and Fourier transform infrared (FTIR) measurements are applied to differentiate the interactions of salicylaldoxime and salicyl hydroxamate on the malachite surface. Salicylaldoxime and salicyl hydroxamate are of molecular structures that resemble each other, but with different bond distances in the ligand atoms which result in their unusual adsorption behavior and collecting ability. Thus, the flotation of malachite behaves differently with the two chelating collectors. This study might provide useful clues for designing novel collectors in base metal oxide flotations. Full article
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Open AccessArticle A Novel Comprehensive Detection Method for the Dynamic Characteristics of Coalface Overburden: A Case Study in China
Minerals 2017, 7(2), 21; doi:10.3390/min7020021
Received: 24 November 2016 / Revised: 20 January 2017 / Accepted: 29 January 2017 / Published: 15 February 2017
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Abstract
Accurate and efficient acquisition of information about the dynamic characteristics of coalface overburden can provide an important theoretical basis for green mining in coal producing regions in western China. In this study, a novel method for comprehensively detecting the dynamic behavior of coalface
[...] Read more.
Accurate and efficient acquisition of information about the dynamic characteristics of coalface overburden can provide an important theoretical basis for green mining in coal producing regions in western China. In this study, a novel method for comprehensively detecting the dynamic behavior of coalface overburden is proposed in order to address deficiencies of the existing detection methods. The new method combines surface radon measurement, overburden borehole imaging, and underground pressure observation into a comprehensive detection technology system, resulting in spatial and temporal integration of surface, overburden, and underground detection. To examine the feasibility of the proposed method, a field experiment was carried out at #1103 coalface in the Suancigou Coal Mine, which is operated by the Inner Mongolia Yitai Coal Co. Ltd. The results of the three approaches are largely consistent and they complement one another. But it must be pointed out that this method needs to be further improved by more field experiments. Based on the experimental results, a technique for forced caving by presplit blasting of the overburden was developed and then implemented to #1103 coalface. The practical use of the technique led to good results: it effectively prevented roof-associated accidents by controlling the first weighting step to about 82 m, contributing to safe and efficient mining; coal production was expected to increase about 126 kilotons. Full article
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Open AccessArticle Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies
Minerals 2017, 7(2), 31; doi:10.3390/min7020031
Received: 6 December 2016 / Accepted: 4 February 2017 / Published: 21 February 2017
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Abstract
Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for
[...] Read more.
Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities-1.54 and 1.63 g/cm3-have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively Full article
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Open AccessArticle Effect of Silica Alumina Ratio and Thermal Treatment of Beta Zeolites on the Adsorption of Toluene from Aqueous Solutions
Minerals 2017, 7(2), 22; doi:10.3390/min7020022
Received: 23 December 2016 / Revised: 3 February 2017 / Accepted: 10 February 2017 / Published: 15 February 2017
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Abstract
The adsorption of toluene from aqueous solutions onto hydrophobic zeolites was studied by combining chromatographic, thermal and structural techniques. Three beta zeolites (notated BEAs, since they belong to BEA framework type), with different SiO2/Al2O3 ratios (i.e., 25, 38
[...] Read more.
The adsorption of toluene from aqueous solutions onto hydrophobic zeolites was studied by combining chromatographic, thermal and structural techniques. Three beta zeolites (notated BEAs, since they belong to BEA framework type), with different SiO2/Al2O3 ratios (i.e., 25, 38 and 360), before and after calcination, were tested as adsorbents of toluene from aqueous media. This was performed by measuring the adsorbed quantities of toluene onto zeolites in a wide concentration range of solute. The adsorption data were fitted with isotherms whose models are based on surface heterogeneity of the adsorbent, according to the defective structure of beta zeolites. The thermal treatment considerably increases the adsorption of toluene, in the low concentration range, on all BEAs, probably due to surface and structural modifications induced by calcination. Among the calcined BEAs, the most hydrophobic zeolite (i.e., that with SiO2/Al2O3 ratio of 360) showed the highest binding constant, probably due to its high affinity for an organophilic solute such as toluene. The high sorption capacity was confirmed by thermogravimetric analyses on BEAs, before and after saturation with toluene. Full article
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Open AccessArticle Dissolution and Sorption Processes on the Surface of Calcite in the Presence of High Co2+ Concentration
Minerals 2017, 7(2), 23; doi:10.3390/min7020023
Received: 31 October 2016 / Revised: 26 January 2017 / Accepted: 10 February 2017 / Published: 15 February 2017
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Abstract
The interaction of the calcite surface with Co2+-rich aqueous solutions ([Co2+aq]initial = 1000 ppm, i.e., ca. 17 mM) was investigated by means of macroscopic experiments and surface spectroscopic techniques. In the case of the macroscopic experiments, calcite
[...] Read more.
The interaction of the calcite surface with Co2+-rich aqueous solutions ([Co2+aq]initial = 1000 ppm, i.e., ca. 17 mM) was investigated by means of macroscopic experiments and surface spectroscopic techniques. In the case of the macroscopic experiments, calcite powder and monocrystals were immersed into solutions for different time periods (from 1 min to one month). The Ca concentrations in the filtrates was measured by means of atomic absorption spectrometry (AAS) while the interacted solids were studied using a combination of X-ray photoelectron spectroscopy (XPS) and 12C-rutherford backscattering spectrometry (12C-RBS). The macroscopic data showed a characteristic surface dissolution process, in parallel to the surface sorption processes. Adsorption and co-precipitation were seen for almost the entire immersion period for both calcite powder and monocrystals. The surface study by XPS (analyzed at a depth of approximately 12 nm) suggested that adsorption takes place in the first hour of the interaction, followed by incorporation of Co2+ into calcite surface layers, leading to the formation of a Co2+-bearing surface (co)precipitate, which occurs over a period of hours and days. The 12C-RBS measurements on calcite { 10 1 ¯ 4 } indicated that the thickness of this surface co-precipitate was 270 nm after one day and then stabilized at 320 nm after more than a week. Full article
(This article belongs to the Special Issue Mineral Surface Science and Nanogeoscience)
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Open AccessArticle Selective Separation of Fluorite, Barite and Calcite with Valonea Extract and Sodium Fluosilicate as Depressants
Minerals 2017, 7(2), 24; doi:10.3390/min7020024
Received: 20 December 2016 / Revised: 1 February 2017 / Accepted: 9 February 2017 / Published: 16 February 2017
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Abstract
Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with
[...] Read more.
Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with sodium oleate as the collector. The single mineral flotation results showed that valonea extract displayed the strongest depression on calcite, while sodium fluosilicate displayed the strongest depression on barite. These two depressants allowed selective separation of the three minerals through sequential flotation. The flotation of mixed minerals showed that 94% of the calcite was successfully depressed by the valonea extract, and 95% recovery of the fluorite was achieved in the subsequent flotation with sodium fluosilicate depressing barite. The different depressant–mineral interactions were investigated via electro-kinetic studies and molecular dynamics (MD) simulations using the Materials Studio 6.0 program. The valonea extract exhibited the strongest adsorption on the calcite surface, and sodium fluosilicate exhibited the strongest adsorption on the barite surface, which prevented oleate species from reacting with Ca2+ or Ba2+ surface sites. This study provides useful guidance for how to process fluorite, barite and calcite resources. Full article
(This article belongs to the Special Issue Flotation in Mineral Processing)
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Open AccessArticle Use of Spent Zeolite Sorbents for the Preparation of Lightweight Aggregates Differing in Microstructure
Minerals 2017, 7(2), 25; doi:10.3390/min7020025
Received: 9 January 2017 / Revised: 10 February 2017 / Accepted: 12 February 2017 / Published: 17 February 2017
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Abstract
Lightweight aggregates (LWAs) made by sintering beidellitic clay deposits at high temperatures, with and without the addition of spent zeolitic sorbents (clinoptilolitic tuff and Na-P1 made from fly ash) containing diesel oil, were investigated. Mineral composition of the aggregates determined by X-ray diffraction
[...] Read more.
Lightweight aggregates (LWAs) made by sintering beidellitic clay deposits at high temperatures, with and without the addition of spent zeolitic sorbents (clinoptilolitic tuff and Na-P1 made from fly ash) containing diesel oil, were investigated. Mineral composition of the aggregates determined by X-ray diffraction was highly uniformized in respect of the initial composition of the substrates. The microstructure of the LWAs, which were studied with a combination of mercury porosimetry, microtomography, nitrogen adsorption/desorption isotherms and scanning electron microscopy, was markedly modified by the spent zeolites, which diminished bulk densities, increased porosities and pore radii. The addition of zeolites decreased water absorption and the compressive strength of the LWAs. The spent Na-P1 had a greater effect on the LWAs’ structure than the clinoptilolite. Full article
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Open AccessArticle Strength Reduction of Coal Pillar after CO2 Sequestration in Abandoned Coal Mines
Minerals 2017, 7(2), 26; doi:10.3390/min7020026
Received: 3 November 2016 / Revised: 21 January 2017 / Accepted: 4 February 2017 / Published: 17 February 2017
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Abstract
CO2 geosequestration is currently considered to be the most effective and economical method to dispose of artificial greenhouse gases. There are a large number of coal mines that will be scrapped, and some of them are located in deep formations in China.
[...] Read more.
CO2 geosequestration is currently considered to be the most effective and economical method to dispose of artificial greenhouse gases. There are a large number of coal mines that will be scrapped, and some of them are located in deep formations in China. CO2 storage in abandoned coal mines will be a potential option for greenhouse gas disposal. However, CO2 trapping in deep coal pillars would induce swelling effects of coal matrix. Adsorption-induced swelling not only modifies the volume and permeability of coal mass, but also causes the basic physical and mechanical properties changing, such as elastic modulus and Poisson ratio. It eventually results in some reduction in pillar strength. Based on the fractional swelling as a function of time and different loading pressure steps, the relationship between volumetric stress and adsorption pressure increment is acquired. Eventually, this paper presents a theory model to analyze the pillar strength reduction after CO2 adsorption. The model provides a method to quantitatively describe the interrelation of volumetric strain, swelling stress, and mechanical strength reduction after gas adsorption under the condition of step-by-step pressure loading and the non-Langmuir isothermal model. The model might have a significantly important implication for predicting the swelling stress and mechanical behaviors of coal pillars during CO2 sequestration in abandoned coal mines. Full article
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Open AccessArticle Influence of Temperature on the Formation of Ag Complexed in a S2O32−–O2 System
Minerals 2017, 7(2), 16; doi:10.3390/min7020016
Received: 24 October 2016 / Revised: 11 January 2017 / Accepted: 24 January 2017 / Published: 27 January 2017
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Abstract
Metallic elements of higher economic value, occurring in the mineralogy of Zimapán, are Pb, Zn, Cu, and Fe; said elements are sold as concentrates, which, even after processing, generally include significant concentrations of Mo, Cd, Sb, Ag, and As that can be recovered
[...] Read more.
Metallic elements of higher economic value, occurring in the mineralogy of Zimapán, are Pb, Zn, Cu, and Fe; said elements are sold as concentrates, which, even after processing, generally include significant concentrations of Mo, Cd, Sb, Ag, and As that can be recovered through different leaching methods. In this work, the influence of temperature in the complexation of silver contained in a concentrate of Zn using the technology of thiosulfate with oxygen injection was studied. Chemical and mineralogical characterization of the mineral concentrate from the state of Hidalgo, Mexico confirmed the existence of silver contained in a sulfide of silver arsenic (AgAsS2) by X-ray Diffraction (XRD). The results obtained by Atomic Absorption Spectrophotometry (AAS) reported abundant metallic contents (% w/w) (48% Zn, 10.63% Fe, 1.97% Cu, 0.84% Pb, 0.78% As, and 0.25% Ag). These results corroborate the presence of metallic sulfides such as pyrite, chalcopyrite, and wurtzite; this last species was identified as the matrix of the concentrate by X-ray Diffraction (XRD) and Scanning Electron Microscopy-Energy-Dispersive X-ray Spectroscopy (SEM-EDS). Pourbaix diagrams were constructed for the AgAsS2–S2O32−–O2 system at different temperatures, which allowed the chemical reaction of leaching to be established, in addition to determining Eh-pH conditions in which to obtain silver in solution. The highest recoveries of the precious metal (97% Ag) were obtained at a temperature of 333 K and [S2O32−] = 0.5 M. The formation of silver dithiosulfate complex (Ag(S2O3)23−) was confirmed by the characterization of the leach liquors obtained from the experiments performed in the temperature range of 298 to 333 K using Fourier transform infrared spectroscopy (FTIR). Full article
(This article belongs to the Special Issue Mineral Resources and the Environment)
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Open AccessArticle Hydrometallurgical Process and Kinetics of Leaching Manganese from Semi-Oxidized Manganese Ores with Sucrose
Minerals 2017, 7(2), 27; doi:10.3390/min7020027
Received: 28 November 2016 / Revised: 16 January 2017 / Accepted: 18 January 2017 / Published: 17 February 2017
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Abstract
The extraction of manganese from a semi-oxidized manganese ore was investigated with sucrose as the reducing agent in dilute sulfuric acid medium. The kinetics of leaching manganese from the complex ore containing MnCO3 and MnO2 was also investigated. The effects of
[...] Read more.
The extraction of manganese from a semi-oxidized manganese ore was investigated with sucrose as the reducing agent in dilute sulfuric acid medium. The kinetics of leaching manganese from the complex ore containing MnCO3 and MnO2 was also investigated. The effects of sucrose and sulfuric acid concentrations, leaching temperature and reaction time on the total Mn (TMn), MnO2 and MnCO3 leaching were investigated. Results showed that MnCO3 could more easily react with hydrogen ions than MnO2 in ores, and MnO2 decomposition could be advantageous for MnCO3 leaching. The leaching efficiencies of 91.8% for total Mn, 91.4% for MnO2 and 96.9% for MnCO3 were obtained under the following optimized conditions: 0.035 mol/L sucrose concentration, 5 mol/L sulfuric acid concentration, 60 min of reaction time and 363.2 K of leaching temperature. In addition, it was found that the leaching process of semi-oxidized manganese ore follows the shrinking core model and the leaching rate was controlled by chemical reaction and diffusion. The apparent activation energy of the total manganese, MnO2, and MnCO3 leaching were 40.83, 40.59, and 53.33 kJ·mol−1, respectively. Full article
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Open AccessArticle Minor and Trace Elements in Natural Tetrahedrite-Tennantite: Effects on Element Partitioning among Base Metal Sulphides
Minerals 2017, 7(2), 17; doi:10.3390/min7020017
Received: 21 December 2016 / Revised: 18 January 2017 / Accepted: 23 January 2017 / Published: 29 January 2017
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Abstract
Minerals of the tetrahedrite isotypic series are widespread components of base metal ores, where they co-exist with common base metal sulphides (BMS) such as sphalerite, galena, and chalcopyrite. We used electron probe microanalysis and laser-ablation inductively-coupled plasma mass spectrometry to obtain quantitative multi-trace
[...] Read more.
Minerals of the tetrahedrite isotypic series are widespread components of base metal ores, where they co-exist with common base metal sulphides (BMS) such as sphalerite, galena, and chalcopyrite. We used electron probe microanalysis and laser-ablation inductively-coupled plasma mass spectrometry to obtain quantitative multi-trace element data on tetrahedrite-tennantite in a suite of 37 samples from different deposits with the objective of understanding which trace elements can be incorporated, at what levels of concentration, and how the presence of tetrahedrite-tennantite influences patterns of trace element partitioning in base metal ores. Apart from Fe and Zn, Hg and Pb are the two most abundant divalent cations present in the analysed tetrahedrite-tennantite (up to 10.6 wt % Hg and 4 wt % Pb). Cadmium, Co and Mn are also often present at concentrations exceeding 1000 ppm. Apart from one particularly Te-rich tetrahedrite, most contained very little Te (around 1 ppm), irrespective of prevailing assemblage. Bismuth is a common minor component of tetrahedrite-tennantite (commonly > 1000 ppm). Tetrahedrite-tennantite typically hosts between 0.1 and 1000 ppm Se, while Sn concentrations are typically between 0.01 and 100 ppm. Concentrations of Ni, Ga, Mo, In, Au, and Tl are rarely, if ever, greater than 10 ppm in tetrahedrite-tennantite and measured W concentrations are consistently < 1 ppm. Taking into account the trace element concentrations in co-crystallizing BMS, the results presented allow the partitioning trends between co-crystallized sphalerite, galena, chalcopyrite, and tetrahedrite-tennantite to be defined. In co-crystallizing BMS assemblages, tetrahedrite-tennantite will always be the primary host of Ag, Fe, Cu, Zn, As, and Sb, and will be the secondary host of Cd, Hg, and Bi. In contrast, tetrahedrite-tennantite is a poor host for the critical metals Ga, In, and Sn, all of which prefer to partition to co-crystallizing BMS. This study shows that tetrahedrite-tennantite is a significant carrier of a range of trace elements at concentrations measurable using contemporary instrumentation. This should be recognized when establishing protocols for trace element analysis of tetrahedrite-tennantite, and when assessing the main hosts of trace elements in any given assemblage, e.g., for geometallurgical purposes. Full article
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Open AccessArticle The Influence of the Framework and Extraframework Content on the High Pressure Behavior of the GIS Type Zeolites: The Case of Amicite
Minerals 2017, 7(2), 18; doi:10.3390/min7020018
Received: 30 November 2016 / Revised: 25 January 2017 / Accepted: 29 January 2017 / Published: 5 February 2017
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Abstract
This paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction, of the high pressure behavior of the natural zeolite amicite [K4Na4(Al8Si8O32)·10H2O], the GIS-type phase with ordered (Si, Al) and
[...] Read more.
This paper reports a study, performed by in-situ synchrotron X-ray Powder Diffraction, of the high pressure behavior of the natural zeolite amicite [K4Na4(Al8Si8O32)·10H2O], the GIS-type phase with ordered (Si, Al) and (Na, K) distribution. The experiments were carried out up to 8.13(5) GPa in methanol:ethanol:water = 16:3:1 (m.e.w.) and 8.68(5) GPa in silicone oil (s.o.). The crystal structure refinements of the patterns collected in m.e.w. were performed up to 4.71(5) GPa, while for the patterns collected in s.o. only the unit cell parameters were determined as a function of pressure. The observed framework deformation mechanism—similar to that reported for the other studied phases with GIS topology—is essentially driven by the distortion of the “double crankshaft” chains and the consequent changed shape of the 8-ring channels. The pressure-induced over-hydration observed in the experiment performed in aqueous medium occurs without unit cell volume expansion, and is substantially reversible. A comparison is made with the high pressure behavior of the other GIS-type phases, and the strong influence on compressibility of the chemical composition of both framework and extraframework species is discussed. Full article
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Open AccessArticle The Effects of Calcium Ions on the Flotation of Sillimanite Using Dodecylammonium Chloride
Minerals 2017, 7(2), 28; doi:10.3390/min7020028
Received: 3 November 2016 / Revised: 20 January 2017 / Accepted: 16 February 2017 / Published: 17 February 2017
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Abstract
The effects of Ca2+ ions on the flotation of sillimanite using dodecylammonium chloride as a collector were investigated by micro-flotation tests, zeta potential measurements, solution chemistry analysis and molecular dynamics (MD) simulation. The micro-flotation results indicated that Ca2+ ions remarkably inhibit the flotation
[...] Read more.
The effects of Ca2+ ions on the flotation of sillimanite using dodecylammonium chloride as a collector were investigated by micro-flotation tests, zeta potential measurements, solution chemistry analysis and molecular dynamics (MD) simulation. The micro-flotation results indicated that Ca2+ ions remarkably inhibit the flotation of sillimanite in the pH range of 2.0–9.0. The point of zero charge (PZC) of sillimanite changed from 5.4 to 6.1 with the addition of Ca2+ ions. Meanwhile, the calculated concentration of RNH3+ in the sillimanite interface layer decreased in the presence of Ca2+ ions. The results of MD simulation revealed that Ca2+ ions have strong binding energy with the sillimanite (010) surface, and the binding energy of RNH3+ with sillimanite (010) surface reduced in the presence of Ca2+ ions. The conclusions drawn from the computations are in good agreement with the experimental results. Full article
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Open AccessArticle Application and Mechanism of Anionic Collector Sodium Dodecyl Sulfate (SDS) in Phosphate Beneficiation
Minerals 2017, 7(2), 29; doi:10.3390/min7020029
Received: 22 January 2017 / Revised: 14 February 2017 / Accepted: 16 February 2017 / Published: 20 February 2017
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Abstract
Phosphate ore is a valuable strategic resource. Most phosphate ore in China is collophane. Utilization of mid-low grade collophane is necessary to maintain social sustainable development. The gravity-flotation combination separation process can be utilized to separate mid-low grade collophane, but the process consumes
[...] Read more.
Phosphate ore is a valuable strategic resource. Most phosphate ore in China is collophane. Utilization of mid-low grade collophane is necessary to maintain social sustainable development. The gravity-flotation combination separation process can be utilized to separate mid-low grade collophane, but the process consumes a large quantity of acid in the reverse stage. Sodium dodecyl sulfate (SDS) was used as a dolomite collector in this study to reduce the acid consumption of collophane flotation. SDS effectively removed dolomite from the gravity concentrate when no other reagents were present. Flotation test results showed that, compared to the conventional gravity-flotation process, the proposed SDS-based process reduced phosphoric acid dosage from 6.1 kg/t to 3.9 kg/t with similar separation results. The SDS action mechanisms on dolomite were further investigated by zeta potential analysis, single mineral flotation tests, infrared spectrum detection, and theoretical analysis. The results indicate that the SDS adsorption on dolomite is mainly physical adsorption, and that favorable separation effects between collophane and dolomite may be attributed to physical adsorption and entrainment. In addition, it also indicates that the physical adsorption can be utilized to remove dolomite from phosphate on account of zeta potential differences when the separate feed is coarse. Full article
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Open AccessArticle Investigation on Calcination Behaviors of Coal Gangue by Fluidized Calcination in Comparison with Static Calcination
Minerals 2017, 7(2), 19; doi:10.3390/min7020019
Received: 12 December 2016 / Revised: 10 February 2017 / Accepted: 10 February 2017 / Published: 14 February 2017
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Abstract
In order to comprehensively utilize coal gangue, we present fluidized calcination as a new thermal technology for activating coal gangue and systematical study was conducted in comparison with static calcination. The calcined products obtained by different calcination methods under various temperatures were characterized
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In order to comprehensively utilize coal gangue, we present fluidized calcination as a new thermal technology for activating coal gangue and systematical study was conducted in comparison with static calcination. The calcined products obtained by different calcination methods under various temperatures were characterized by the means of X-ray diffraction (XRD), thermal gravimetry-differential scanning calorimeter (TG-DSC), Fourier transform-infrared spectroscopy (FT-IR) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). Chemical and physical characteristics such as aluminium leaching rate, chemical oxygen demand and whiteness of calcined products were also investigated. The results show that aluminium leaching rate could reach to the maximal value 74.42% at 500 °C by fluidized calcination, while the maximal value of 66.33% could be reached at 600 °C by static calcination. Products by fluidized calcination obtained higher whiteness and lower chemical oxygen demand (COD) under the same calcination temperature. The well-crystallized kaolinite transform to amorphous meta-kaolinite under 600 °C and mullite presence under 1000 °C according to phase transformation, chemical bond variation and microstructure evolution analysis. Fluidized calcination was more efficiently for combustion of carbon/organic matter and dehydroxylation of kaolinite, which might applied in coal gangue industry in future. Full article
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