查看更多>>摘要：? 2021Computational Fluid Dynamics (CFD) modelling of a 1.3 m3 flotation cell fitted with a Wemco 56 mechanism has been performed, backed up by experimental measurements. The flow field, gas dispersion and solids concentration in the flotation cell were studied. Both the PIV measurements and CFD modelling of the cell revealed that the rotor generated a jet stream towards the wall, which induced two strong vortices, one below the rotor level and the other extending from the rotor region to near the free surface. The strong downward flow along the wall of the tank turns horizontally passing underneath the false bottom and up through the draft tube. Inside the draft tube, an average axial velocity of about 0.7 m s?1 with a flow rate of 0.05 m3 s?1 was predicted, in good agreement with experiment. The void fraction was found to vary significantly with height in the cell. The maximum value of void fraction reached 0.55 near the froth interface in the air–water system. In the presence of solids, the air bubbles were able to penetrate further downwards to the bottom of the tank and the void fraction reached a maximum value of 0.35 near the froth interface. The Sauter mean bubble diameter was found to be in the range of 0.3–0.9 mm in the air–water system. The solids concentration was practically uniform throughout the tank except for the region near the surface. CFD simulation results for velocity, bubble size, void fraction and solids concentration are analysed in detail. CFD simulation was then carried out for an industrial-scale Wemco 225 cell (92 m3). Predictions are similar to those for the smaller Wemco 56, though there are differences in detail. Voidage predicted by CFD model of the Wemco 225 cell agrees with plant measurements.
查看更多>>摘要：? 2022 Elsevier LtdEfficient conversion of wolframite in acid solution plays a crucial role in exploration of sustainable technology for ammonium paratungstate (APT) production. In this work, the factors influencing wolframite concentration conversion in HCl solution and the conversion mechanism were investigated to establish a kinetics model for the decomposition process. The results indicated that the conversion rate increased significantly with increasing temperature and HCl concentration and reducing particle size, while it was independent of stirring intensity. Scanning electron microscope (SEM) analysis indicated that layered H2WO3 films were formed on the surface of converted particles, and the experimental data was consistent with the shrinking core model. The conversion process was divided into two stages with a transition point of 30 min, the first stage was a surface reaction controlling process while the second stage was a hybrid controlling process. The kinetic rate equations were established as: 1-(1-x)1/3 = 0.19 × C1.60?D?0.81?exp(?40570/RT)?t for the first stage, and 4 × [1-(1-x)1/3] + [1-2x/3-(1-x)2/3] = 1.41 × C0.75?D?0.31?exp(?38160/RT)?t for the second stage. This work contributes to better understanding of wolframite conversion in HCl solution and the development of a cleaner route for APT production.
查看更多>>摘要：? 2022 Elsevier LtdMetal ions are widely used to achieve selective hydrophobization of different mineral particles. However, the atomic understanding of the roles of metal ions is insufficient due to the limitation of experimental techniques. Herein, the in-situ atomic force microscopy (AFM) force curves and first-principles calculations were combined with the conventional experiments [i.e., batch flotation, zeta potential tests, and X-ray photoelectron spectroscopy (XPS)] to investigate the roles of lead ions (Pb2+) in flotation separation of scheelite and fluorite. The conventional experiments showed that Pb2+ could enhance the flotation recovery of scheelite but suppress fluorite. AFM force curves showed that, due to the presence of Pb2+, the interaction force between benzohydroxamic acid (BHA) and the scheelite surface was a stronger adhesion than the adhesion between BHA and fluorite without lead ions. First-principles calculations revealed that the strong electrostatic attraction resulted in the adsorption of BHA on fluorite surfaces. However, BHA could hardly bond with the scheelite surface with negative charges and hydroxylated Ca sites. The reaction between BHA and Pb2+ was the most favorable. The formed BHA-Pb complexes demonstrated repulsive interactions on fluorite surfaces but attractions on scheelite surfaces. Lead ions played as an inhibitor for fluorite flotation and an on-off switch for scheelite flotation. AFM and first-principles calculations have shown great potential in the analysis of the complicated interface interactions.
查看更多>>摘要：? 2022 Elsevier LtdConventional optimization procedures for Continuous Centrifugal Gravity Concentrators (CCGCs) impose a priori weighting on objectives and results in a single optimum point, thereby failing to exploit the competing grade/recovery relationship. To generate an optimum operating line rather than a conventional optimization approach, a non-dominated recovery/grade line has been developed using a novel multivariate optimization technique code. The goal is to simultaneously maximize both grade and recovery objectives. This optimization has been developed and tested using a Knelson Continuous Variable Discharge concentrator, CVD on flotation tailings of a metallic sulphide ore (0.7 g/t Au), without a priori weighting of the competing objectives. This paper outlines the developed technique, which is an iterative hybrid performance improvement approach that exploits Pareto's non-dominated approach to multi-objective optimization, for determining the operating curve for CCGCs. This work is entirely and directly based on gold metallurgical data (i.e. Au recovery and grades) rather than an indirect proxy to generate the optimum operating line for the Knelson CVD. As a part of the suggested approach, the Artificial Neural Network (ANN) simulation has been effective in predicting the CVD performance: for the experimental and ANN simulated results, correlation coefficients are 0.92 and 0.81 for the Au upgrade ratio and Au recovery, respectively. The prediction level of the Regression Model was acceptable for the Au recovery (R2 = 0.78) and good for the Au upgrade ratio (R2 = 0.88). Based on these, the developed Pareto solution and the hybrid optimization model also enabled significant prediction of CCGC performance: at different operational conditions Au recoveries predicted by the Pareto optimum solution (11–32%) correlated well with experimental results (9–26%). Further, the method enables assessment of the level of influence of operational parameters on the metallurgical outcomes, hence identification of an optimum grade vs. recovery operating line. Overall, the results demonstrate the robustness of the approach in optimization of CCGCs operation despite trace occurrence of Au. Suggested approach is highly reliable for tuning multi operation variables of CCGCs to enable operation of these unique machines to yield successful concentration performance in plant scale.
查看更多>>摘要：? 2022 Elsevier LtdRare earth elements (REEs) are vital for the technology, military, and defense industries. They have been recognized as critical due to potential scarcity, supply constraints, and lack of minable concentrations. Therefore, alternative sources are needed to meet the demand and continue manufacturing rare earth-dependent products. However, the environmental prospect of rare earth mining was not investigated enough, and comprehensive studies are lacking. It demands serious consideration as toxic radionuclides are seen in the same mineralization as rare earths regardless of their primary or secondary sources. The concentration of these hazardous trace elements may be elevated as a result of extraction and beneficiation processes. Unless proper separation and disposal are performed, these radionuclides accumulate on the surface of the soil or integrate with aquatic systems, which consequently raise environmental and health concerns. This review manuscript compiled the environmental impact and aspect of rare earth extraction processes while addressing separation techniques for these radioactive materials from rare earths, emphasizing selective precipitation, solvent extraction, and solid-phase separation.
查看更多>>摘要：? 2022 The AuthorComminution is a major contributor to the Mining Industry's carbon footprint. As most of the world's leading mining companies have formally committed themselves to having net zero scope 3 carbon emissions by at least 2050, the pressure to significantly improve comminution circuit energy efficiency over the next 25–30 years will be intense. High Pressure Grinding Rolls (HPGR) circuits have the potential to reduce the Mining Industry's CO2 emissions by up to 34.5 megatonnes/year, or 43.5% when compared to the established Autogenous (AG)/Semi-Autogenous (SAG)/Ball mill circuit alternatives. However, uptake of HPGR technology has been relatively slow. This may be due in part to the fact that costly and time-consuming pilot testing is still the norm for assessing, selecting and sizing HPGR circuits. This is in contrast to AG/SAG/Ball mill circuits where relatively cheap, fast and effective power-based methodologies are used. To combat this limitation and help accelerate the adoption of this technology a power-based methodology has been developed which can be easily used to assess, size and select HPGR closed circuits in hard rock mining applications. Equations are derived which, on the basis of published data from manufacturers and full-scale operating plants, are demonstrated to accurately reproduce HPGR throughput capacity, installed power and specific energy for a wide range of HPGRs. A number of worked examples are included which demonstrate how the methodology can be applied in practice.
查看更多>>摘要：? 2022The performance of dodecanamide (DDAA) and cetyltrimethylammonium bromide (CTAB) used as the mixed collector on flotation separation of diaspore and kaolinite was investigated in this paper. The results of flotation experiments for single minerals showed that the kaolinite presented a good flotability but diaspore presented a poor flotability by using the mixed reagents of DDAA and CTAB as a collector around pH 5. The results of artificial mixed minerals showed that not only the mass ratio of Al2O3 to SiO2 (A/S) was remarkably increased but also the effective flotation separation of diaspore and kaolinite was carried out by using DDAA and CTAB as a collector. FTIR spectra indicated that DDAA and CTAB were adsorbed on the minerals surface. Zeta potentials analysis, adsorption amounts and XPS analysis illustrated that the difference value of the adsorption amounts of CTAB between diaspore and kaolinite was enlarged due to the addition of DDAA. Moreover, the adsorption mechanism of DDAA and CTAB on the minerals surface by molecular dynamics simulation indicated that DDAA with diaspore exhibited more negative interaction energy while CTAB with kaolinite exhibited more negative interaction energy. The interaction energy difference resulted in the varied relative concentrations of the reagent molecules on the minerals surface. The theoretical calculations supported the experimental results. The enlarged difference was favorable to the increase of the flotation separation performance of minerals.
查看更多>>摘要：? 2022In this study, the potential of tailings generated from hydrometallurgical processing of nickel laterite ores as a source of scandium was investigated. The use of an atmospheric leaching process was proposed and five different lixiviants, namely sulphuric, phosphoric, oxalic, citric and ascorbic acids, were examined systematically to extract the scandium. Characterisation results showed that the nickel laterite residue sample contained about 148 ppm scandium and that the major crystalline phases of the sample were quartz, chromite, magnetite and akaganeite. Results of the leaching experiments suggested that most of the scandium was hosted within the refractory iron-bearing minerals, namely magnetite and chromite, based on the apparent correlation between the scandium dissolution and iron and chromium dissolutions and the composition of crystalline phases in the leached residues. Oxalic acid was found to be the most effective lixiviant to overcome the refractoriness of these minerals and render the scandium accessible for dissolution. To further improve the leaching performance with oxalic acid, the effects of acid concentration, stirring speed, pulp density, temperature and leaching duration on the leaching efficiency were studied. It was found that the scandium dissolution can reach up to 94% in 0.75 mol/L of the acid at a temperature of 95 °C, pulp density of 100 g/L, leaching time of 24 h and stirring speed of 600 rpm. These results demonstrated that the simple, atmospheric leaching process with an organic acid is feasible to extract scandium from nickel laterite residues.
查看更多>>摘要：? 2022 Elsevier LtdIridium (Ir), platinum (Pt), palladium (Pd), rhodium (Rh) and ruthenium (Ru) are five of the six elements known as platinum group metals (PGMs). These, together with gold (Au) are classified as precious metals and make up Sibanye Stillwater's production basket. Substantial price increases for platinum (2,4%), palladium (43,2%) and rhodium (187,2%) in 2020 resulted in an increase in PGM sales despite a drop in PGM production. A UG2 ore was subjected to laboratory scale flotation tests to evaluate elemental grades and recoveries of the individual elements in the production basket. As primary collector, sodium isobutyl xanthate (SIBX) was compared to a novel mass pull enhancer, a fines collector, a coarse ore collector and blends containing the novel reagents. Significant recovery improvements were seen across the whole basket. The grades of palladium and ruthenium showed room for improvement.
查看更多>>摘要：? 2022 Elsevier LtdGlycine and thiosulfate, as alternatives to cyanide, are all considered to be one of the most promising lixiviants for gold. In this paper, a novel copper-catalytic glycine thiosulfate collaborative system of gold leaching was proposed. Based on the available thermodynamic data, a series of Eh-pH and species distribution diagrams for gold/copper-glycine-thiosulfate system under various conditions were constructed using thermodynamic calculations. The analysis results for thermodynamic diagrams indicated that the copper-glycine-thiosulfate system had many potential advantages over the copper-ammonia/citrate-thiosulfate system, such as wider pH range and lower thiosulfate consumption. The electrochemical models for the copper-catalytic mechanism of gold leaching with glycine-thiosulfate were also proposed in this study. Moreover, the relevant results obtained in this study provide a theoretical basis for the optimization of gold leaching with copper-catalytic glycine thiosulfate system.
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