查看更多>>摘要：A new metallurgical process via aeration for the decomposition of vanadium slag in concentrated NaOH solution was proposed. The improvement of oxygen mass transfer coefficient when using aeration at different NaOH concentration was studied and the effects of critical reaction parameters on vanadium extraction were systematically investigated. The optimal condition was determined to be: alkali concentration of 60%, reaction temperature of 130 degrees C, alkali-to-ore mass ratio of 6:1, stirring speed of 500 rpm. The yield of vanadium could reach to 97.41% after reacting for 6 h under this reaction condition. The reaction temperature in this new method is 50-270 degrees C lower than the current liquid oxidation methods reported in the literatures, and the medium alkaline concentration declined from 85% to 60%, exhibiting significant advantages in energy consumption as well as reactor design. Kinetics study indicated that the extraction of vanadium was governed by internal diffusion, and the apparent activation energy was calculated to be 17.57 kJ/mol. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Process development for production of lithium carbonate (Li2CO3) from regionally occurring zinnwaldite concentrate (3.0 wt.-% Li2O) was conducted. By acid digestion with mineral acids, preferably hydrochloric acid under re flux (approx. 110 degrees C) and atmospheric pressure, lithium is mobilised up to 94%. In contrast to using sulphuric acid no toxic hydrogen fluoride is released with hydrochloric acid, what is a crucial factor for digestion process design. Separation technologies for recycling of more than 80% of unspent hydrochloric acid, as well as the recovery of associated components, particularly iron hydroxide and potassium/aluminium/fluoride as sodium-potassium-cryolite, are part of the process. After removal of impurities by means of electrodialysis and concentration, technical grade lithium carbonate was obtained by precipitation with soda. Hot water washing furnishes crude-product purities >= 98.0% with a total lithium yield of similar to 70%. (C) 2017 Elsevier B.V. All rights reserved.
Banerjee, P. K.Suresh, NikkamTripathy, Sunil KumarSingh, Veerendra...
16页
查看更多>>摘要：Rare earth roll magnetic separators (RERMS) and induced roll magnetic separators (IRMS) are the simple and efficient dry high-intensity magnetic separators used for upgrading different paramagnetic minerals. These are the most popularly adopted units for separation of mineral sands, but its application for processing of other minerals is scanty. In the present investigation, an effort has been made to understand the role of different process variables of RERMS and IRMS to separate the hematite fines from a low-grade ore. Before magnetic separation studies, detailed characterisation of the material was carried out regarding physical, chemical, mineralogical and magnetic properties which are discussed critically from the magnetic separation point of view. Based on the findings of the characterisation, magnetic separation was conducted using RERMS and IRMS by varying some of the relevant process variables. Further, the effects of each variable on hematite segregation in these units were discussed, and optimum process conditions were derived for the efficient recovery of hematite fines from the low-grade ore. The separation efficiency of these separators is compared with liberation data obtained from QEMSCAN. Finally, the paper concludes stating that RERMS and IRMS can be utilized as a pre-concentrator/ scavenger unit to discard a maximum amount of gangue in a single stage of dry operation which will save energy regarding the fine grinding of the ore for liberation. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Physicochemical changes in a siliceous bauxite ore during attrition milling, and corresponding changes in reactivity are described in this paper. Atrition milling of bauxite has been found to have high milling efficiency. BET Specific surface area has sharply increased in the initial stages, but flattened eventually. Decrease in the enthalpy and temperature of transformation (gibbsite to boehmite) with increase in milling time is a consequence of mechanically induced reactivity. The surface charge, as measured by zeta potential, altered as the milling time is increased; such changes in the surface, surface activation, are also a manifestation of reactivity enhancement with milling. The increase in surface reactivity has been explained in terms of generation of more proton active species (congruent to AIOH) at the surface. Analysis of X-ray diffraction patterns of bauxite milled for different duration shows progressive breakdown of gibbsite structure to an amorphous state - high energy state - with milling. Reactivity enhancement ensuing attrition milling leads to near complete digestion of bauxite (alumina) in Bayer (caustic soda) solution even at ambient pressure. Alumina recovery correlates well with specific surface area and degree of amorphisation; however, amorphisation (mechanical activation) is more relevant than specific surface area for multiphase systems like that of bauxite used in this study. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Leptospirillum ferriphilum (L. ferriphilum) is a widely used microorganism in the commercial biooxidation process. Its ability to adhere to sulfide ores when grown in sulfide mineral substrates is very important for the entire biooxidation process. However, few studies have investigated the ore adhesion properties of L. ferriphilum. In this paper, the effects of temperature, pH and the passive layer of the sulfide ore surface on the ore adherence properties and biooxidation capacities of L. ferriphilum LJ02, which was screened by our laboratory, were investigated. The results of these experiments showed that both the contact and non-contact leaching mechanism were evident during the sulfide biooxidation process. L ferriphilum LJ02 preferred the contact leaching mechanism to the non-contact leaching mechanism. Within the experimental range of temperatures from 36 degrees C to 46 degrees C, the OAR (ore adhesion ratio) of L. ferriphilum LJ02 increased initially and then decreased with the temperature. The optimum OAR was 0.84 at 41 degrees C. Within the experimental pH range of 1.1 to 2.0, the OAR of L. ferriphilum LJ02 decreased with pH. The optimum OAR was 0.87 at pH 1.1. It was also found that the OAR of L. ferriphilum LJ02 could be reduced by the passive layer on the surface of the sulfide ore, which was generated during the biooxidation process. Moreover, it seems that the OAR of L. ferriphilum LJ02 was proportional to the sulfide biooxidation efficiency. (C) 2017 Elsevier B.V. All rights reserved.
Perez, Claudio A.Estevez, Pablo A.Adams, MartinGaldames, Francisco J....
11页
查看更多>>摘要：The determination of hardness and approximate mineral composition of rocks and classifying these lithologies aids in controlling various processes in the plant, such as reducing the grinding process, which accounts for about 50% of its energy consumption. In this paper, a new method for rock lithological classification is presented, based on color as well as 3D laser based features. The method uses color and laser range images, acquired from rocks on a conveyor belt, to compute Gabor and LBP (Local Binary Pattern) features. Various Gabor and LBP features are tested, including rotation invariant features. The images are tessellated into sub images in which the features are computed. The classification is performed in two stages. In the first stage, the sub-images are classified by using a support-vector machine (SVM) classifier. In the second stage, the classification is improved by a voting process among all the sub-images of each rock. The method was tested on a database with five different rock lithologies taken from a copper mine which has been used in previous studies, allowing comparison with our new results. The results show that the classification performance was improved significantly by adding the 3D laser texture features, and using a combination of rotation invariant Gabor and LBP features, achieving a classification accuracy of 99.24% on the database. Using the CMIM (Conditional Mutual Information Maximization) feature selection method showed that only 10% of the total extracted features are required to achieve the maximum correct classification rate and that using the 3D laser features, (for the first time in our rock classification method to the best of our knowledge) is important for maintaining high classification performance. (C) 2017 Elsevier B.V. All rights reserved.
McMaster, Scott A.Ram, RahulFaris, NebealPownceby, Mark I....
10页
查看更多>>摘要：The leaching of uranium from of a synthetic form of the naturally occurring pyrochlore group mineral betafite, was investigated in acid sulfate media. Uranium leaching curves obtained over a range of time, temperature, [H2SO4], [Fe-TOT]and redox potential conditions were similar with each having three discrete segments representing significantly different rates of uranium leaching. The first segment occurred in the initial min and involved extremely rapid leaching. This segment made up for the majority of the overall uranium leaching obtained over the test period (similar to 2.10% U). The high rate of leaching in this segment was demonstrated to be attributed to liberation of surface oxidized uranium from the betafite structure. The second segment between 1 and 120 min was characterised by slow uranium leach rates which could be partially influenced by altering the experimental conditions. Uranium leaching within this period was most likely due to oxidation of uranium by ferric iron which was progressively slowed by the competing diffusion reaction. The uranium leach rate in the third segment was negligible. This negligible leach rate was demonstrated to occur when approximately 2.10% U had leached from the sample and was shown to be due to passivation of the sample surface. Investigations into leaching betafite using various iron salts showed the uranium leaching more than doubling when iron fluoride was substituted for iron sulfate. The additional solubility was attributed to leaching of Nb, Ti, and Ta due to the in-situ formation of HF, where the HF either slowed the formation of a passivating layer or the HF was able to slowly dissolve the passivating layer. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：The objective of this study is to investigate the time-dependent evolution of the yield stress, strength and deformation behaviour of cemented paste backfill (CPB) that contains Portland cement as the binder with different saline concentrations in a sub-zero environment (-6 degrees C). Yield stress measurement with the vane method, uniaxial compressive testing and microstructure analysis have been conducted on various CPB samples with different sodium chloride (salt; NaCI) concentrations and cured in a sub-zero temperature for different times (0, 0.25,1, 2 and 4 h for yield stress measurement; 7, 28 and 90 days for compressive strength testing). The results show that the yield stress decreases with an increase in salinity. The strength of CPB under freezing conditions decreases as the concentration of NaCI is increased. A shift from the strain-softening behaviour of CPB that has no salinity to the strain-hardening behaviour of CPB with high salinity is observed. Additionally, it is also noticed that with curing time, the deformation behaviour of the studied CPB becomes gradually less ductile. The micro- structural analysis results show that the binder hydration products are affected by the salinity. There is strong indication that the absorption of the Na + ions by calcium-silicate-hydrate leads to the decrease of the strength of CPB with different saline concentrations. The results of this investigation provide technical information for the designing of cost-effective, safe and durable CPB structures in sub-zero mining environments. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：The teetered bed separator (TBS) is a gravity concentration device based on the principle of hindered settling velocity, which has been widely applied for the density separation of coarse coal particles. The influences of the teeter water velocity on the density separation of coarse coal particles were investigated based on the slip velocity model and the experimental results. The ash content of clean coal increased as the teeter water velocity decreased initially and increased afterwards according to the relationship between teeter water and minimum fluidization velocity. It was observed that the foreign slime had an effect on the separation of coarse particles, while the effect of the foreign slime was not as significant as that of the teeter water velocity. (C) 2017 Published by Elsevier B.V.
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