Bevandic, SreckoBlannin, RosieEscobar, Alexandra GomezBachmann, Kai...
14页
查看更多>>摘要：The exploitation of mine waste materials as secondary resources requires in-depth mineralogical analyses, with metal deportment being of particular relevance for metal recovery. Using a combination of the Scanning Electron Microscope (SEM)-based Mineral Liberation Analyser (MLA) and Electron Probe Micro-Analyser (EPMA) methods, the deportment of lead and zinc in the historic Plombie`res mine site (East Belgium) was investigated. The mine site comprises four different materials: soil, metallurgical waste, brown and yellow tailings. The integration of the MLA and EPMA data allowed the identification and quantification of Pb-and Zn-bearing phases, including minerals present in low abundances as well as slag phases. Different slag types and Pb oxides phases are the main sources of lead in Plombie`res mine waste samples. These phases host 65 to 99 % of the Pb, the rest is distributed between cerussite (0 to 37 %), and/or anglesite (0 to 17 %). Approximately 95 % of Zn is hosted by different types of slags or by fraipontite, with minor amounts contributed by sphalerite (0.1 to 3 %), gahnite (1.0 to 2.4 %), willemite (0.1 to 2.9 %), and bannisterite (0 to 3 %). The MLA/EPMA measurements were validated by comparing calculated Pb and Zn grades with bulk grades measured by X-ray fluorescence spectroscopy. The coefficients of correlation between the measured and calculated values were found to be 0.89 for lead and 0.80 for zinc. Uncertainties on the metal deportments were estimated by bootstrap resampling and are typically low. The highest uncertainties are observed when the metal-bearing phases are present in low abundances, which is particularly noticeable in the yellow tailings. Considering the promising results, the integrated approach applied in this study should be applicable to other metals and waste deposits across the globe.
查看更多>>摘要：Chemical emulsifiers have been used in laboratories to improve the efficiency of oily collectors by reducing their droplet sizes, but their application in flotation plants is limited due to their strong frothing abilities. In this study, recently developed physical emulsification techniques were used to emulsify diesel for coal flotation and diesel emulsions with a droplet size ranging from 12.2 to 0.3 mu m were successfully produced. It was interesting to find an optimal droplet size at which the flotation performance was maximized and beyond which the flotation selectivity deteriorated. A smaller optimal droplet size was identified for the coal sample with a higher degree of surface oxidation. Theoretical modelling showed that the reduction of oil droplet size decreased the collision rate of oil with coal particles, but increased the oil adhesion efficiency on particle surfaces, the opposite effects leading to an optimal droplet size to provide a maximum oil adsorption rate. The decrease of surface hydrophobicity significantly reduced the oil adhesion efficiency and the adsorption rate, and therefore a smaller optimal droplet size was required for coal particles with lower surface hydrophobicity. The results from this study can guide the flotation plants to identify optimal oil droplet sizes for their coal samples and a suitable emulsification technology to produce the optimal oil droplet sizes to maximise the flotation performance.
查看更多>>摘要：Awaruite is a native nickel-iron alloy (Ni3Fe), found in serpentinized ultramafic rocks, that has gained interest as a possible source of nickel. FPX Nickel is advancing a very large awaruite deposit in central British Columbia, Canada, on which this work is based. To date there is limited information available regarding the flotation conditions to selectively concentrate awaruite from gangue minerals in serpentinite ores. The aim of this work was to investigate the floatability of awaruite in different solution conditions with a xanthate collector. Awaruite readily floated in acidic solution with a xanthate collector but not in neutral and alkaline solutions. Voltammograms on awaruite indicated that the alloy shows an active passive transition behaviour in acidic solution and passive behaviour in neutral and alkaline solutions. The passivation layer formed in neutral and alkaline solutions showed to inhibit the interaction between xanthate and awaruite surface. Infrared spectra on awaruite showed the presence of xanthate compounds attached to the surface in acidic condition at potentials higher than the reversible potential of xanthate/dixanthogen. Based on experimental results, it was postulated that xanthate chemisorbs on awaruite and then it oxidizes to form dixanthogen. Also, it was demonstrated that when passivated, awaruite quickly activates in acidic solution, good flotation performance was achieved with 10 min of conditioning, and similar performance was obtained after 30 min of conditioning. This work serves as a confirmation that is possible to float awaruite using xanthate, a well-known collector that offers selectivity over oxides and silicate minerals, which are the main gangue minerals in serpentinite ores.
Marin, Oscar A.Kraslawski, AndrzejCisternas, Luis A.
10页
查看更多>>摘要：The mining industry generates thousands of tons of waste every day. Some types of waste pose environmental risks, while others can be considered important sources of valuable materials. Nowadays, the re-processing of mine tailings starts to be seen as an increasingly more critical operation because of the need to shift from the current linear economy model to the circular one. However, full-scale mine tailings processing is still in the early stages. One of the important factors that could contribute to its spreading would be developing a simple method of preliminary assessment of the profitability of mine tailings processing. Therefore, the aim of this study is to propose a method that could be used to estimate the cost of mine tailings processing for the recovery of valuable elements. The proposed approach deploys dimensional analysis, as well as sensitivity analysis. In order to illustrate the applicability of the proposed method, data from 48 Chilean mining operations were analyzed. Since copper is the element whose concentration in Chilean mine tailings is the highest, and vanadium is the main critical raw material that can be obtained from the same source, both were selected to be recovered. The results show that a plant that processes mine tailings to recover vanadium pentoxide (V2O5) via hydrometallurgical processes would incur a processing cost of 6,218 US$/t of V2O5. On the other hand, a processing cost for a plant engaged in copper recovery would be 2,953 US$/t of Cu. This represents a reduction by 40.87% and 44.20%, respectively, compared to the operating costs of similar mining operations. In addition, the sensitivity analysis determined that the unit price of electricity and electricity consumption are the two variables having the highest impact on the total processing cost. The obtained results are valid for Chilean mines, however, the proposed approach could be widely used to estimate mine tailing processing cost for the recovery of other elements in other countries.
查看更多>>摘要：This paper presents an application of the capsule network to predict the antimony grade of pulp in the roughing cell of an antimony flotation plant in the Hunan Province, China. In this plant, because the chemical testing for analyzing the antimony grade only generated eight data points every day, data could be collected in small amounts and were mixed with some abnormal images. An improved density-based clustering algorithm is introduced to eliminate abnormal images from the training dataset. To use a small amount of data, a capsule network rather than a CNN is adopted to build the recognition model named Froth-CapsNet. Finally, the application of Froth-CapsNet to monitor the working conditions of the antimony flotation process indicates that this model can provide a guide for operators to precisely adjust the dosage of flotation reagents in real-time so that the antimony recovery rate can be improved.
查看更多>>摘要：In developing a geometallurgical characterisation for comminution, the geological information, usually captured from drill core with a resolution of down to micrometre scale, is compared with the results of comminution tests. These tests require several kilograms of material and are empirical tests that do not focus on understanding the effect of ore characteristics separately from the machine functioning. The resultant particles from the comminution process depend upon the operating conditions of the comminution devices (i.e., ball size and load, rotational speed, mill specifications) and the heterogeneity of the rock characteristics (i.e., texture and mineralogy) that influence the mechanical properties of particles which are being reduced in scale from metres to micrometres. A newer approach for comminution modelling and characterisation considers the measurement of the particle strength and minimum required energy to break them at different sizes and its application as a parameter to characterise the breakage behaviour of the ores. However, the relationship between particle strength and minimum energy with the ore characteristics that may link this information to ore' comminution potential has not been explored yet. This study focuses on selecting variables that have been previously identified as relevant for strength at the core scale (i.e., mineralogy, mineral association, grain size, grain shape and porosity) and quantifying their variation as the particle size decreases from 30 to 3 mm. The results show that for a set of ten different rock types, the median value of ore characteristics such as modal mineralogy, mineral association and grain shape does not change with particle size. However, as the particle size is reduced over that size range, these characteristics do become more variable. This behaviour is similar to the variation observed in the strength values of samples, which shows size independence within the studied particle size range, but it is not clear which characteristic has more relevance to the strength results. Detailed geological characterisation information is rarely used to predict how the geological variability may affect the plant's operation. The results from this work indicate that mineralogical and textural features might be controlling the strength of particles formed during comminution. By understanding the physics of the fracture process, these characteristics may be identified. So, a novel link between the detailed mineralogical and textural characterisation at different particle scales and the strength of particles could be developed, which would be helpful in the connection of geological data with the newest developments in comminution research.
查看更多>>摘要：Selective separation of chalcopyrite from sphalerite is a challenge in mineral processing. This study is the first to use the organic compounds in fenugreek gum (FG) as a depressant for sphalerite to aid this separation. The results showed that FG exerts a selectively inhibiting effect on sphalerite in chalcopyrite flotation and thus is a potential sphalerite depressant. The underlying mechanisms were studied by contact-angle measurements, atomic force microscopy (AFM) imaging, Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Overall, FG showed weak adhesion to the chalcopyrite surface and was easily replaced by ethyl xanthate through competitive adsorption. In addition, FG showed greater adsorption capacity for sphalerite and was more stable. According to the detailed mechanism, the Cu and Fe sites on chalcopyrite did not adsorb FG effectively, and the Zn sites on sphalerite were much more active and aided chemical chelation with the C-OH and O-C-O groups of FG. Herein, selective separation of chalcopyrite from sphalerite was achieved using FG as an effective depressant.
查看更多>>摘要：The inevitable presence of metal ions in the slurry significantly impacts the adsorption of organic depressants. In this study, the influence of Fe3+ and Ca2+ on the depression of chalcopyrite by carboxymethyl cellulose (CMC) was investigated. CMC slightly depressed chalcopyrite flotation, and the addition of Ca2+ hardly impact its depression effect. However, the pre-treatment with Fe3+ enhanced its depression effect severely at acid conditions, while this hydrophilic strengthening effect gradually disappeared under alkaline conditions. CMC physically attached to blank chalcopyrite surface, the surface modification with FeCl3 not only increased its adsorption capacity on chalcopyrite surface but also altered it from physical adsorption to chemical adsorption. Cu and Fe sites were not involved in CMC adsorption on blank chalcopyrite surface, and the strongly electrostatic repulsion hindered its adhesion under alkaline conditions. After surface modification with FeCl3, electrostatic repulsion was weakened, and Fe sites participated in the bonding with CMC molecule. Thus, chalcopyrite was strongly depressed. However, the contents of Fe3+, Fe(OH)(2+) and Fe(OH)(2+) on modified chalcopyrite were much less at strong alkaline conditions than acid conditions, which not favored CMC attachment.
查看更多>>摘要：Coal fly ash (CFA) is one of the largest forms of global industrial waste, and continuous accumulation of CFA puts great pressure and poses potential risks to the natural environment. The objective of this study was to evaluate a sustainable process to recycle valuable elements in high-alumina coal fly ash (HACFA). In this study, an efficient and applicable approach was developed to recover Al selectively from HACFA, while most Fe recovery and removal were realized simultaneously in the leaching process. First, the thermodynamic stability of HACFA and the feasibility of Al leaching in HACFA were calculated. Then, HACFA was subjected to nitric acid pressure leaching to selectively extract Al. Under the optimal conditions (temperature of 220 degrees C, nitric acid concentration of 300 g/L, liquid-to-solid ratio of 4 mL/g, and duration of 2 h), 84.24% of the Al was extracted, and the leaching rate of Fe was 6.67%. The concentrations of Al and Fe in the leachate were 46.34 g/L and 0.52 g/L, respectively. The separation of Al and Fe was completed in the leaching process. The leach liquor was purified to further remove impurities, and Al2O3 was obtained after crystallization and pyrolysis of the aluminum-rich leachate. Leach residue was mainly composed of silica and Fe2O3. This process provides a feasible method for the recovery and utilization of valuable components in HACFA.
查看更多>>摘要：The interpretation of core level Synchrotron photoemisison spectra (SPES) collected from a pristine fracture surface of monoclinic pyrrhotite (Fe7S8), as a function of photon energy, has identified the three distinct surface species. The Fe 2p photoemission spectra show the Fe in pyrrhotite is high spin Fe-II in octahedral co-ordination. Comparison of bulk and surface sensitive spectra did not identify any changes due to the broad nature of the high spin Fe 2p spectra. However, the sulfur spectrum shows an undercoordinated monosulfide at 160.8 eV, a disulfide (161.7 eV) and polysulfide species (163.2 eV) at the surface. This indicates stabilisation of the surface involves reconstruction and results in chemical transformation of sulfur species. A high binding energy tail that extends to 167 eV has been attributed to ligand to metal charge transfer satellites (LMCT) and supported by the pre-edge features observed in Fe L(2,3 )and S L-2,L-3 near edge X-ray absorption fine structure (NEXAFS). An accurate fit for the bulk pyrrhotite sulfide spectrum has been estimated by comparing spectra with different surface sensitivities, and thereby an accurate fitting method has been developed for the monoclinic pyrrhotite S 2p spectrum. This method may be used for future photoemission spectra to improve the analysis of similar samples and provide a basis for interpretation of pyrrhotite samples during mineral processing and environmental conditions.
NSTL
Elsevier