Minerals2016, 6(3), 77; doi:10.3390/min6030077 - published 26 July 2016 Show/Hide Abstract
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 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.
Minerals2016, 6(3), 78; doi:10.3390/min6030078 - published 26 July 2016 Show/Hide Abstract
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 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.
Minerals2016, 6(3), 79; doi:10.3390/min6030079 - published 26 July 2016 Show/Hide Abstract
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, 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.
Minerals2016, 6(3), 75; doi:10.3390/min6030075 - published 21 July 2016 Show/Hide Abstract
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%, 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.
Minerals2016, 6(3), 76; doi:10.3390/min6030076 - published 21 July 2016 Show/Hide Abstract
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. 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.
Minerals2016, 6(3), 74; doi:10.3390/min6030074 - published 19 July 2016 Show/Hide Abstract
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 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.