Nowosielska, Anna M.Nikoloski, Aleksandar N.Parsons, Drew F.
12页
查看更多>>摘要：In this study we have investigated the interactions between coarse and fine galena and quartz particles and their implications for flotation in NaCl solutions. Tested were four different particle systems: (CC) Coarse galena/ Coarse quartz, (CF) Coarse galena/Fine quartz, (FC) Fine galena/Coarse quartz and (FF) Fine galena/Fine quartz. The flotation experiments were carried out on the four particle systems in NaCl concentrations of 10 mM and 100 mM, at pH 9. It was found that the recovery was the highest for the CC particle system, and the lowest for the FF particle system. The experiments also indicated that the recovery improved for the higher NaCl concentration.As part of this study, we calculated the total interaction free energy as a function of separation distance for each pairwise combination of particles and bubbles, for each test condition. It was found that for all particle systems, galena/quartz interactions are dominated by repulsion. The interactions between two galena particles indicated attraction as the dominating force, while the interactions between quartz particles showed repulsion in 10 mM NaCl, which changed to attraction with an increase in NaCl concentration. Galena/air bubble interactions were controlled by repulsive electrostatic interactions in 10 mM NaCl, but these interactions became attractive in 100 mM NaCl salt solutions. On the other hand, the quartz/air bubble interactions were always repulsive, irrespective of the NaCl concentration. Based on these theoretical predictions, we postulate that the stronger repulsion of quartz particles away from the air bubbles could be the driving force for galena recovery.
查看更多>>摘要：In this study, the effect and mechanism of ultrasound on gallium and zinc leaching from corundum flue dust (CFD) were investigated systematically. The conditions for the leaching of valuable metals were optimized while varying the parameters such as leaching time, sulfuric acid concentration and leaching temperature. It was found that under the conditions of a sulfuric acid concentration of 25 wt%, 90 degrees C leaching temperature and 50 min leaching duration, the leaching efficiencies of gallium and zinc can be increased from 62.78% to 82.56% and 94.43% to 99.57% as ultrasound was implemented, respectively. The kinetics analysis indicated that the leaching process of gallium from CFD is controlled by mixed of diffusion and chemical reactions, while the leaching process of zinc is controlled by diffusion. The enhancement of ultrasound on the leaching rate and leaching efficiency was mainly ascribed to that the ultrasound effect causes the agglomerates of particles to break into small pieces or generate cracks, which would augment the diffusion of sulfuric acid and the product layer on the particle surface. On the other hand, the reaction of sulfuric acid with amorphous silicate (or aluminosilicate) is accelerated, so that the gallium in the form of encapsulated can be dissolved.
查看更多>>摘要：Flotation reagents and heavy metal ions always coexist in mineral flotation wastewaters, arousing serious environmental issues or having deleterious effects on mineral flotation. In this work, the steel slag was adopted as a cost-effective adsorbent to synergically remove butyl xanthate (BX), diethyl dithiocarbamate (DDTC), Cu(II) and Pb(II) ions. At the steel slag dosage of 12.0 g/L, Cu(II) and Pb(II) concentrations decreased from 4.0 mg/L to below 10.0 mu g/L, and the removal of COD reached 54.33%. The removal efficiency of COD increased from 11.36% to 57.49% as Cu(II) and Pb(II) concentrations rose from 0 to 8.0 mg/L, revealing the promotion effects of metallic ions on collector adsorption. The maximum uptake capacity of steel slag reached 110.45 and 160.48 mg/g for Cu(II) and Pb(II), respectively. The collector adsorption capacity of steel slag increased nearly two magnitudes after modifying with the uptake of Cu(II) or Pb(II) ions. The SEM/EDS, XPS and FTIR analysis indicated that steel slag could be in-situ modified to generate copper or lead hydroxides and oxides during the removal of Cu(II) and Pb(II) ions. Subsequently, these precipitates acted as reactive sites for chelating BX and DDTC to form indissolvable metal-collector chelates. Owing to in-situ modification of steel slag by uptaking metallic ions, the adsorption was potentially feasible for treating flotation wastewaters.
查看更多>>摘要：In many industrial flotation processes, the operational adjustment is still manual according to individual experience. The adjustment of operational variables is mainly based on the discrimination of feed conditions and the observation of the appearance of flotation froth. Due to the limitation that partial properties of feed ore cannot be monitored online and the individual-level differences in operation experience, it is difficult to control the concentrate grade and recovery in the qualified range for a long time by manual operational adjustment. To resolve this problem, we propose FlotGAIL, an automatic operational adjustment framework based on generative adversarial imitation learning (GAIL) for the flotation circuits. From the perspective of an algorithm, this paper explores a novel way to learn operational adjustment policy. The epistemic uncertainty estimation of feed conditions provided by Bayesian neural networks is used as an additional guidance for the GAIL model to generate flotation operational trajectories, which it is just as an expert considers reducing the risk of process operation and increasing long-term rewards. In FlotGAIL, learning flotation operational adjustment from expert demonstrations is formulated as an imitation learning problem in a Markov decision process, and then the proposed model uses the signal provided by the discriminator as the reward function to guide the policy generator to complete the training process. From the perspective of engineering application, the experiments have verified that the proposed operational adjustment method has a better effect in controlling concentrate grade and recovery up to standard, and FlotGAIL can be used as an effective tool to provide decision support for operators of other similar industrial processes.
查看更多>>摘要：Roasting is often required to convert sulfidic minerals into their sulfate and/or oxide forms with the aim to increase the extractability of targeted metals. In this study, sulfidic tailings of Neves Corvo Cu-Zn-Pb-mine (Portugal) underwent conventional roasting (CR) and microwave-assisted roasting (MR) to compare the effect of both heating technologies on the roasting behavior. Upon roasting in air, transformations of mineral phases in the tailings were studied by different techniques using quantitative X-ray diffraction, mineral liberation analysis, Raman spectroscopy and thermogravimetry-differential scanning calorimetry coupled to mass spectrometry. Also, the leaching behavior of elements from the roasted tailings was assessed in water. It was shown that CR and MR induce different reaction pathways for mineral transformations during roasting. While CR led to indirect pyrite oxidation through intermediate sulfate formation, direct pyrite oxidation was the main transformation pathway during MR. This change in reaction pathway can be attributed to the mineral-selective heating induced by microwaves, which in particular accelerates the oxidation rate of pyrite. In agreement with the proposed roasting mechanism, the leaching behavior in water showed that CR resulted in a higher extraction of Cu, Zn, Pb, As and Fe from the tailings - since their sulfate phases are more abundant - compared to MR at the same roasting temperature. Overall, tailings treated by CR and MR within the temperature ranges of 500 degrees C to 550 degrees C for 1 h gave optimal leaching efficiencies of the studied metals (water leaching at room temperature for 30 min; stirring speed of 600 rpm; solid-to-liquid ratio of 10 mL.g(-1)). Furthermore, thermodynamic equilibrium calculations showed that hydrolysis of soluble Fe(III) species strongly controls the pH of the leachates. In comparison to MR tailings, more acidic leachates were generated for CR tailings because of a more pronounced formation of ferric sulfate.
查看更多>>摘要：The mining and processing of lead-zinc ores produce many lead-zinc ore tailings, which can cause harm by releasing toxic metal ions to the environment. Therefore, the leaching characteristics, acid generation capacity, and fractions of released heavy metals from two Pb-Zn tailings, one from Guangxi designated as F and another from Inner Mongolia designated as YD, have been investigated in this work. Here, sodium diethyl dithiocarbamate functionalized montmorillonite (DDTC-Mt) was synthesized to remediate both F and YD tailings. It was found that YD tailings have a stronger acid generation potential than F tailings, and both of them could be further oxidized and release acid. Moreover, YD showed a certain buffering capacity to acid rain due to its higher calcite content, while the leaching amounts of heavy metals from F was larger than YD resulting from the former's higher weathering degree. DDTC-Mt resulted in a superior stabilization performance to Zn, Mn and Pb from both tailings with optimal stabilization ratios, which are all above 94%. The remediating effect of DDTC-Mt on F was better than that of YD, which could be ascribed to the fact that F contained lower amount of carbonate minerals because of a higher degree of weathering in the latter. The leaching amounts and stabilization ratios of the four elements increased with increasing time and dose of DDTC-Mt, however, temperature and pH showed little or no effect. Mineralogical analysis showed minerals in F and YD before and after leaching were mainly quartz, while the contents of sphalerite and pyrite in F-DDTC-Mt and YD-DDTC-Mt decreased although they were more than those in F and YD without DDTC-Mt after leaching for 72 h. DDTC-Mt could inhibit the release of heavy metals to a certain extent by covering the surface of tailings via complexation and precipitation. Furthermore, DDTC-Mt coating can prevent the oxidation of tailings.
查看更多>>摘要：The key to the lithium extraction from alpha-spodumene is destroying the crystal structure. The conventional commercial process requires high-temperature calcination to transform alpha-spodumene into beta-spodumene. This study aimed at finding an alternative treatment for destroying the structure of alpha-spodumene and extracting the lithium. The results indicated that alpha-spodumene could be directly decomposed by NaOH solution and the Li element in alpha-spodumene was converted into intermediate product Li(2)SiO(3)in the form of solid phase under certain conditions. According to the experiments, the possible reactions during the hydrothermal alkaline treatment were predicted, which were thermodynamically possible by the calculation of Gibbs free energy using HSC Chemistry 10. The total extraction efficiency of Li2O was 87.3%, including the extraction efficiency of Li2O leached into liquid phase, 7.6%, and converted into Li2SiO3, 79.7%, obtained under optimal conditions: stirring speed of 500 rpm, leaching temperature of 250 C, mass ratio of NaOH/ore of 1.5, initial NaOH concentration of 25 wt%, and leaching time of 24 h. Then the Li element in the Li(2)SiO(3 )could be extracted by acid leaching and precipitated using Na2CO3. The mother liquor obtained after hydrothermal alkaline treatment was reused for the subsequent hydrothermal alkaline cyclic leaching under the above conditions. During three cycles of alkaline treatment, the alpha-spodumene decomposition was stable, and the total Li2O extraction efficiency was around 86% (~84% was converted into Li2SiO3). This process avoids high-temperature calcination and concentrated acid roasting, where the acid leaching process is carried out at room temperature.
查看更多>>摘要：The effect of Fe2+ and Mn2+ in the flotation of fine wolframite with octyl hydroxamic acid (OHA) as a collector was studied through a series of experiments. The XPS analysis indicates that Fe2+ and Mn2+ species on the wolframite surface are the active sites to interact with OHA collector. However, microflotation and contact angle tests show that the excess Fe2+ and Mn2+ ions in pulps decrease the flotation recovery and surface hydrophobicity of wolframite, playing inhibition roles on the flotation performance. The zeta potentials of wolframite shift toward positive values in the presence of Fe2+ and Mn2+. Fe(OH)(2(s)) and Mn(OH)(2(s)) precipitates being dominated species preferentially coat onto wolframite surfaces and then hinder the OHA adsorption. The adsorption results further give evidences that the excess Mn2+ and Fe2+ ions in the aqoeous solution also will consume OHA collector. These two processes decrease the adsorption of OHA and the flotation recovery of wolframite.
Mendez, A.Alvarez, M. L.Fidalgo, J. M.Di Stasi, C....
9页
查看更多>>摘要：Chalcopyrite is the resource with the highest amount of Cu content representing around 70-80% of the known reserves in the world. However, chalcopyrite like other copper sulfides, is usually found in deposits with grades around 0.4-0.5% copper. The exploitation of these reserves using traditional flotation methods followed by pyrometallurgical treatment of copper concentrate is at the limit of economic viability. Hydrometallurgical route would be more suitable for treating of these low-graded sulfide ores. However, chalcopyrite is refractory in ferric/sulfuric acid media and shows slow dissolution rates. For this a number of researches were carried out to accelerate the kinetics of leaching by adding pyrite, iron powder, nanosized silica, coal and activated carbon. The main objective of the present work was to study the use of one biomass-derived activated carbon as catalysts in the leaching of copper from chalcopyrite. Sulfuric acid solution of pH 1 with 5 g L-1 of Fe3+ was used as leaching agent. Experiments were performed at 90 C and 250 rpm, during 48 and 96 h. Concentration of Cu, Zn, As, Sb and Co in the liquid phase was determined in order to evaluate their extraction degree, whereas solid residues were characterized by SEM-EDS and XRD. The presence of biomass-derived activated carbon significantly increased the extraction of copper, decreasing the leaching of arsenic. Furthermore, the use of biomass-derived activated carbon led to lower amounts of crystalline sulfur in the final residue.
查看更多>>摘要：Mineral liberation analysis (MLA) is an automated mineral analysis system that identifies minerals in polished two-dimensional (2D) sections of drill or lump cores or particulate mineral matter. MLA allows a wide range of mineral characteristics to be investigated, including fragment size, mineral abundance, and liberation. To date, this analysis has been primarily limited to two-dimensional (2D) section information. In this study, we describe an MLA workflow that enables the extension of MLA into 3D via the utilization of 3D X-ray microcomputed tomography and convolutional neural network (CNN) guided by M4-Tornado micro-X-ray fluorescence (microXRF) data. With the combination of 3D greyscale micro-CT data with several 2D identified element mappings, the state-of-the-art CNN architecture called EfficientU-Net-b3 is trained and tested for multimineral segmentation on both an intact complex iron ore sample and the corresponding crushed fragments. Compared to traditional manual segmentation methods, where only greyscale thresholds are selected by humans, CNN-based segmentation takes the information from unbiased microXRF and extracts not only the greyscale values but also the texture features from the image. After the segmentation of the 3D micro-CT datasets, several mineral liberation analyses are performed in the 3D domain, as well as 2D slices that are uniformly selected from the 3D segmented fragments data. The results from 2D and 3D MLA demonstrate that the 2D analysis results are heterogeneous and significantly different (up to a 14 % difference in the association indicator matrix) from the 3D analysis results. The loss of mineral information from 2D could influence ore body characterization and the proposed mineral processing procedure. Overall, the proposed workflow provides a digital mineral framework for 3D MLA for future ore characterization applications.
NSTL
Elsevier