Minerals2016, 6(2), 40; doi:10.3390/min6020040 - published 27 April 2016 Show/Hide Abstract
Abstract: The Pingshuo Mine is an important coal mine of the Ningwu coalfield in northern Shanxi Province, China. To investigate the mineralogy and geochemistry of Pingshuo coals, core samples from the mineable No. 4 coals were collected. The minerals, major element oxides, and trace elements were analyzed by scanning electron microscopy (SEM), LTA-XRD in combination with Siroquant software, X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS) and ICP-CCT-MS (As and Se). The minerals in the Pennsylvanian coals from the Pingshuo Mine dominantly consist of kaolinite and boehmite, with minor amounts of siderite, anatase, goyazite, calcite, apatite and florencite. Major-element oxides including SiO2 (9.54 wt %), Al2O3 (9.68 wt %), and TiO2 (0.63 wt %), as well as trace elements including Hg (449.63 ng/g), Zr (285.95 μg/g), Cu (36.72 μg/g), Ga (18.47 μg/g), Se (5.99 μg/g), Cd (0.43 μg/g), Hf (7.14 μg/g), and Pb (40.63 μg/g) are enriched in the coal. Lithium and Hg present strong positive correlations with ash yield and SiO2, indicating an inorganic affinity. Elements Sr, Ba, Be, As and Ga have strong positive correlations with CaO and P2O5, indicating that most of these elements may be either associated with phosphates and carbonates or have an inorganic–organic affinity. Some of the Zr and Hf may occur in anatase due to their strong positive correlations with TiO2.
Minerals2016, 6(2), 39; doi:10.3390/min6020039 - published 26 April 2016 Show/Hide Abstract
Abstract: Standard drop weight, SMC, and Bond ball work index tests have been conducted to investigate the comminution circuit of a magnetite ore located in Eastern Hebei, China. In addition, simulations based on JKSimMet and Morrell models have been performed to compare the specific energy consumption of various comminution circuits. According to the desired capacity and the ore communition characteristics observed, a simulation was conducted to determine the size and driving power of the grinding mills. The SMC and Bond ball work index experiments as well as the Morrell model indicated that the order of the specific energy consumption of comminution was “Jaw crusher + HPGR mill + ball mill” < “Jaw crusher + ball mill”< “SAG mill + ball mill”.
Minerals2016, 6(2), 38; doi:10.3390/min6020038 - published 20 April 2016 Show/Hide Abstract
Abstract: In China, direct-reverse flotation is proved to be applicable to most phosphate ores. However, because the ratio of froth product is generally high, current direct-reverse technology faces challenges in terms of high reagent consumptions and cost. A new gravity and flotation combined process has been developed for the recovery of collophanite from sedimentary phosphate ore from the beneficiation plant of Hubei, China. In this process, 53% of the collophanite was firstly recovered by gravity separation, reducing the mass flow to direct flotation. The gravity tailing was the feed for the direct flotation. The flotation concentrate, mixed with gravity concentrate, was then subjected to reverse flotation. A final concentrate with a grade of 30.41% P2O5 at a recovery of 91.5% was produced from the feed analyzing 21.55% P2O5. Compared to the conventional direct-reverse flotation 86.1% recovery at 31.69% P2O5, it was found that pre-recovery of collophanite by spiral separation could significantly reduce the flotation reagent consumption and lead to improved overall collophanite recovery. The benefits of the new process in terms of cost savings were also discussed.
Minerals2016, 6(2), 37; doi:10.3390/min6020037 - published 18 April 2016 Show/Hide Abstract
Abstract: Although there are many studies on biomineralization processes, most of them focus on the role of prokaryotes. As fungi play an important role in different geological and biogeochemical processes, it was considered of interest to evaluate their role in a natural extreme acidic environment, Río Tinto, which has a high level of fungal diversity and a high concentration of metals. In this work we report, for the first time, the generation of iron oxyhydroxide minerals by the fungal community in a specific location of the Tinto basin. Using Transmission Electron Microscopy (TEM) and High Angle Angular Dark Field coupled with Scanning Transmission Electron Microscopy (HAADF-STEM) and Energy-Dispersive X-ray Spectroscopy (EDX), we observed fungal structures involved in the formation of iron oxyhydroxide minerals in mineralized sediment samples from the Río Tinto basin. Although Río Tinto waters are supersaturated in these minerals, they do not precipitate due to their slow precipitation kinetics. The presence of fungi, which simply provide charged surfaces for metal binding, favors the precipitation of Fe oxyhydroxides by overcoming these kinetic barriers. These results prove that the fungal community of Río Tinto participates very actively in the geochemical processes that take place there.
Minerals2016, 6(2), 36; doi:10.3390/min6020036 - published 12 April 2016 Show/Hide Abstract
Abstract: Biochemical reactors (BCRs) using complex organics for bioremediation of mine-influenced water must operate successfully year round. In cold climates, where many mines in Canada are located, survival of the important microorganisms through the winter months is a concern. In this work, broad phylogenetic surveys, using metagenomics, of the microbial populations in pulp mill biosolids used to remediate metal leachate containing As, Zn, Cd and sulfate were performed to see if the types of microorganisms present changed over the seasons of one year (August 2008 to July 2009). Despite temperature variations between 0 and 17 °C the overall structure of the microbial population was fairly consistent. A cyclical pattern in relative abundance was detected in certain taxa. These included fermenter-related groups, which were out of phase with other taxa such as Desulfobulbus that represented potential consumers of fermentation byproducts. Sulfate-reducers in the BCR biosolids were closely related to psychrotolerant species. Temperature was not a factor that shaped the microbial population structure within the BCR biosolids. Kinetics of organic matter degradation by these microbes and the rate of supply of organic carbon to sulfate-reducers would likely affect the metal removal rates at different temperatures.
Minerals2016, 6(2), 35; doi:10.3390/min6020035 - published 6 April 2016 Show/Hide Abstract
Abstract: In this study, a high-sulfur and high-ash yield coal sample obtained from the Yanshan coalfield in Yunnan, China was analyzed. A series of char samples was obtained by pyrolysis at various temperatures (300, 400, 500, 600, 700, 800, and 900 °C) and at a fast heating rate (1000 °C/min). A comprehensive investigation using inductively coupled plasma mass spectrometry (ICP-MS), a mercury analyzer, ion-selective electrode (ISE) measurements, X-ray diffraction (XRD) analysis, and Fourier transform infrared (FTIR) spectroscopy was performed to reveal the effects of the pyrolysis temperature on the transformation behavior of trace elements (TEs) and the change in the mineralogical characteristics and functional groups in the samples. The results show that the TE concentrations in the raw coal are higher than the average contents of Chinese coal. The concentrations of Be, Li, and U in the char samples are higher than those in raw coal, while the opposite was observed for As, Ga, Hg, and Rb. The F and Se concentrations are initially higher but decrease with pyrolysis temperature, which is likely caused by associated fracturing with fluoride and selenide minerals. Uranium shows the highest enrichment degree, and Hg shows the highest volatilization degree compared to the other studied TEs. As the temperature increases, the number of OH groups decreases, and the mineral composition changes; for example, pyrite decomposes, while oldhamite and hematite occur in the chars. It is suggested that the behavior and fate of TEs in coal during fast pyrolysis are synergistically influenced by self-characteristic modes of occurrence and mineralogical characteristics.