查看更多>>摘要：The deep integration of modern information technology and mineral processing, the establishment and application of a database, and fast, efficient and accurate selection of beneficiation technology and flotation reagent system, which is a development trend of modern mineral processing. In this study, the flotation system with hematite, quartz and dodecylamine (DDA) as collector was used as an example to quantify the types and densities of active sites on the surfaces of hematite and quartz, as well as the reaction equilibrium constants of their hydration reactions and the adsorption equilibrium constants of DDA. Protonation and adsorption experiments were simulated using the Surface complexation model (SCM) with single site (equivalent to SiOH or equivalent to FeOH) and monodentate surface complexation. The protonation and adsorption reaction equations were established based on the material and charge equilibrium under experimental conditions, and the equilibrium constants of the surface reactions were obtained by numerical optimization. Results of surface complexation model indicate that the adsorption ability of DDA on the quartz surface is stronger than that of hematite. DDA adsorption can be successfully predicted using SCM in pH and different mineral ratios system. Overall, this work reveals the quantitative expression of the mineral inherent characteristic and the affinity with reagents, forming a model for predicting the adsorption capacity of the reagent and providing an optimal solution for flotation.
查看更多>>摘要：With the decline of gold grades of primary resources in many parts of the world, gold recovery from primary resources may become unprofitable. Therefore, the identification of secondary gold resources (such as mine tailings) to prolong the existence of the gold industry has developed growing interest. Life cycle assessment (LCA) was used to design two process flowsheets (cyanide and thiosulphate) for recovering gold from a hypothetical tailings dam scenario in the West Witwatersrand region of South Africa while reducing environmental impacts of processes. The thiosulphate flowsheet reduced environmental impacts for 18 out of 19 impact categories compared to the cyanide flowsheet, apart from the freshwater consumption. The flowsheets proposed reduced sulphide, uranium, and arsenic in mine tailings by 82%, 75% and 94% respectively. Therefore, the solutions presented reduce environmental impacts associated with acid mine drainage, radionuclides and arsenic while producing gold as a value stream. The LCA model and corresponding sensitivity analysis showed that South Africa's dependency on coal for electricity generation was a major contributor to environmental impacts for both flowsheets and transition to renewable energy can reduce environmental impact of mining operations.
查看更多>>摘要：As the most important method for the separation and purification of rare earth elements, solvent extraction is widely used in industry. HDEHP (Di(2-ethylhexyl) phosphoric acid) has become the most commonly used organic extractant because of its high separation factor for rare earth elements and large processing capacity. However, the large amount of ammonia nitrogen wastewater generated during the extraction process creates huge pressure on the environment. The tartaric acid complexing agent has been added to the aqueous phase to improve the extraction performance of HDEHP without saponification. This can effectively avoid the generation of ammonia nitrogen wastewater, which is more in line with the concept of green production. In this study, the effect of tartaric acid on the separation of Pr and Nd by HDEHP in hydrochloric acid and the corresponding mechanism are investigated. This study showed that the addition of tartaric acid could significantly increase the separation coefficient of HDEHP for Pr and Nd. When the tartaric acid concentration was 0.4 mol/L and the solution pH was 2.5, the separation coefficient reached beta Nd/Pr = 1.85, which was higher than the separation coefficient of HDEHP for Pr and Nd in the saponification system. Combining Fourier-transform infrared spectroscopy, nuclear magnetic spectroscopy other analysis and detection methods, and in-depth exploration of the extraction mechanism, the final extraction of the compound structures was determined.
Guimaraes, L. F.Botelho Junior, A. B.Espinosa, D. C. R.
14页
查看更多>>摘要：One way to obtain critical metals in lithium-ion batteries (LIBs) used in electric cars is to apply hydrometallurgical methods such as acid leaching. Current leaching technologies use reducing agents for cobalt extraction. However, thermodynamics indicates it is not required. In this study, cylindrical NMC 811 batteries (LiNi0.8Mn0.1Co0.1O2 as the active material of the battery's cathode) were ground in a knife mill, sieved, and leached without a reducing agent. A second ground was carried out in a Willey type mill and further sieved to obtain a material concentrated in active materials of the batteries' electrodes (cathode and anode). The leaching agent used for the experiments was sulfuric acid. Parameters such as acid concentration (0.5 mol/L, 0.75 mol/L, 1.0 mol/L and 2.0 mol/L), solid/liquid ratio (1:3, 1:5, 1:10 and 1:25), temperature (25, 50, 75 and 90 C), and time (up to 6 h) were studied. The optimal parameters were a concentration of 1.0 mol/L, a solid/liquid ratio of 1:10, and 90 C (for an isolated temperature experiment). However, in a leaching experiment varying the time parameter at a temperature of 50 C, the extraction of nickel, cobalt, and manganese achieved 90% in 1 h, making it a viable choice instead of the optimal temperature of 90 C found in the experiment isolated from the temperature parameter.
查看更多>>摘要：The leaching behavior of gold from a carbonaceous gold concentrate in copper-tartrate-thiosulfate solutions was studied in this paper. Experimental parameters, including temperature, initial pH, copper, tartrate, and thiosulfate concentration, were systematically investigated. The capability of leaching gold from the carbonaceous gold concentrate by copper-tartrate-thiosulfate solutions is comparable to that in cyanidation or traditional copper-ammonia-thiosulfate systems. The consumption of thiosulfate can be significantly reduced in the presence of tartrate. The mechanism of gold leaching in copper-tartrate-thiosulfate solutions is catalyzed by the mononuclear CuL2H-4-6 complex when the solution pH is beyond 10.5 based on thermodynamic analysis. The stability of the CuL(2)H(-4)(6- )complex increases with an increase in the tartrate content and decreases with increasing copper and thiosulfate concentrations. A moderate increase in solution pH and temperature exhibits less effect on the consumption of thiosulfate or copper-tartrate complex, but a higher temperature may cause a sharp decline in the content of copper-tartrate complex. The recycling of the leaching solutions demonstrates that maintaining a suitable concentration of copper ions and thiosulfate and a suitable solution pH are crucial to obtain a considerable gold leaching rate.
查看更多>>摘要：Indium (In) is commonly found in sphalerite. It is proposed that the increase in In content may be directly dependent on the total iron (Fe) content in sphalerite; however, there is still a lack of theoretical evidence. Using density functional theory (DFT) calculations, the occurrence and relationship of In and Fe in sphalerite and their effects on the crystal structure and electronic structure of sphalerite were studied. The calculation results show that In can incorporate into sphalerite crystal by substituting Zn. Moreover, the presence of Fe-impurity is conducive to incorporating In into the sphalerite crystal, and with the increase of Fe content, In is easier to get into the sphalerite crystal. The presence of Fe is also beneficial for the formation of the In-S bonds in sphalerite, and the crystal structure becomes more stable in the presence of Fe. Band structure calculations suggest that the impurity levels located in the band gap are mainly contributed by the In 5s and Fe 3d orbitals. Spin-polarized calculation suggests that In-Fe sphalerite has half-metallic ferromagnetic property, and the spin density is mainly contributed by the Fe 3d orbital.
查看更多>>摘要：Conventional deposits of rare earth elements (REEs) cannot meet the high demand for REEs globally. Therefore, the prospecting of REEs from alternative sources like high ash coal is vital. In this study, coal discard and "Run of Mine" (ROM) coal were studied to evaluate the abundance and association of REEs in these materials. The TESCAN Integrated Mineral Analyzer (TIMA) and X-ray diffractometer (XRD) techniques were employed to determine the mineralogy of the coal samples. TIMA was further utilized to investigate the REE associations and distributions, whilst the inductively coupled plasma-mass spectrometry (ICP-MS) was used to quantify the amount of REEs in the coal samples. Quantitative analysis results revealed that the total REE content in the coal discard and ROM coal was above 225 ppm. Furthermore, the results show that the dominant REE-bearing minerals in the discard and ROM coal samples were kaolinite, pyrite, and hematite. In addition, the heavy REEs (HREEs) displayed a strong affinity for the organic macerals and were enriched in the ROM coal. The encouraging results of significantly light REEs (LREEs) relative to HREEs in both coals suggest they are viable prospects for REE extraction. Hydrometallurgical leaching is therefore recommended to assess the potential for REE recovery from these sources.
查看更多>>摘要：Nanobubbles are tiny in size but huge in importance for many scientific fields and applications in biology, agriculture, medicine, environment and engineering. Literature on nanobubble science and applications has skyrocketed in recent years and a comprehensive review of nanobubble-related literature is beyond the scope of this paper. This review article is dedicated to the nanobubble science and applications associated with froth flotation, which is the separation process most widely used in mineral processing and wastewater treatment, with the emphasis on the literature published in the most recent five years. Fundamental aspects of bulk and surface nanobubbles regarding their generation, characterization, and stability are described and different theories and research results are analyzed with critical comments. Unique nanobubble properties of the greatest importance to flotation, including microscopic contact angle, size and shape, number density, surface charge and tension, etc. and their controlling factors are discussed in correlation to flotation performance indicators such as recovery, grade, and reagent consumption. A systematic description of widely recognized nanobubble enhancement mechanisms for fine particle flotation is provided based on up-to-date research results. Finally, recent applications of nanobubbles to flotation separation of typical coal and mineral particles are summarized and future nanobubble research needs in fundamental understanding and commercial development are suggested.
查看更多>>摘要：A comprehensive numerical analysis of the fluid flow and dilute particulate flow in the LD9 spiral separator is presented in this work. The air-water flow field on a coal spiral is simulated using the volume of fluid (VOF) coupled with RANS turbulence models. Water depth and flow field predictions by RSM show close agreement with experiments. Stability depth, turbulence intensity was analyzed for entire liquid depths. The discrete phase model is used to model the dilute particulates at different flow rates. Turbulent dispersion of particles using dispersion index and Bagnold force analysis indicate that centrifugal force dominates the separation at increased particle size and water depth level, whereas the fines are significantly affected by turbulence dispersion at the outer trough region. The magnitude of the Bagnold to gravitational force increases from the inner to outer trough region and a dip at the outer edge region due to inherent change of shear rate. Coarse particles experience higher lift than the fines and migrate to the top flowing layers.
查看更多>>摘要：Mining residues have become an important subject for secondary mining and re-processing. They are an inevitable consequence of mining activity with the amount of residues steadily increasing. These residues are heterogeneous bodies, affected by different processes during and after deposition, which might even produce an enrichment of certain valuable elements within parts of the residues. Since geochemistry and mineralogy of the ore can differ heavily due to processing, deposition and weathering within the heaps, the formerly applied processes might be less suitable for re-processing, therefore, these processes should be studied carefully for an effective re-processing. This study examines the fate of molybdenum in the processing of copper ore in a Chilean processing plant. Molybdenum shares the path of Cu from grinding and flotation into the sulfide concentrate. During smelting and converting, the sulfide concentrate is separated gravitationally from the slag. Through the subsequent slag cleaning process, the slag is crushed and submitted to flotation again, but this time the Mo in its oxidized state reports to the tailings and, hence, is deposited on the tailings heap. Drill cores of the heap have been analyzed by X-ray fluorescence spectroscopy revealing a layer of significant Mo enrichment with up to 0.3 wt.-% Mo. From this layer, the minerals within the slag particles were analyzed by more than one thousand electron microprobe analyses. The results show that Molybdenum is enriched mostly in the glassy matrix (median of 0.18 wt.-%), while the spinel phase, which generally incorporates most of the Mo according to literature, contains a smaller fraction of the Mo (median of 0.09 wt.-% Mo). Additionally, within the slag, the glass amount is up to a factor five higher than the magnetite, therefore, the glass poses as the main reservoir for Mo in the heap. Considering the general process, the missing step of Mo-extraction from the sulfide concentrate combined with the slag cleaning process for Cu extraction is responsible for the enrichment of Mo in the slag rich part of the investigated heap.
NSTL
Elsevier