查看更多>>摘要：Autogenous grinding (without grinding media) may provide some advantages if satisfactory lixiviation efficiency can be achieved on larger grain sizes. This grinding strategy requires less energy and offers important cost savings and reduction of GHG emissions in the mining industry compared to other commonly used approaches. Two attrition cells (1.2 L, 12 L) were designed to conduct a wet autogenous grinding. The combined grinding and leaching experiments were performed using six Canadian rare earth elements (REEs) ore samples to solubilize the REEs while grinding the ore in a modified attrition mill. Sulfuric, hydrochloric and nitric acids were compared under various operating conditions on three different types of ore samples (carbonatite, sedimentary, peralkaline). The addition of an alkaline step was also investigated. Metals dissolution in the 1.2 L attrition mill with or without NaOH addition (T = 20 degrees C, solid/liquid ratio = 20%, acid concentration [HNO3] = 7.5 M, time = 1 h) was found effective for the carbonatite ore (solubilization efficiencies of 91-99% Th, 29-32% U, 85-91% LREEs, 84-94% HREEs) and the sedimentary ore (solubilization efficiencies of 89-99% Th, 98-99% U, 22-83% LREEs, 48-99% HREEs). Actinide elements often comprise a significant component in REEs ore samples and are considered impurities. Their presence in primary REE mineral resources is problematic from a regulatory and health physics perspective. To overcome these issues, anionic, cationic and chelating resins were tested to remove Th from the nitric leaching liquor. Best separation results were obtained with the impregnated resin Lewatit VPOC 1026. To the best of our knowledge, this is the first time that Lewatit VPOC 1026 was reported in the literature for Th separation from REEs.
Ashkavandi, Rasool AbediAzimi, EbrahimHosseini, Mohammad Raouf
10页
查看更多>>摘要：Employing microorganisms and their metabolites as a potentially low-cost and environmentally friendly alternative for the synthetic compounds in many of the current mineral beneficiation techniques is receiving increasing attention. For the first time, the influence of the Bacillus licheniformis cells and its metabolites for selective flotation of barite from quartz was studied. The maximum adsorption density of 1.33 x 10(10) cells/g was achieved at pH = 3 for barite, six times higher than quartz. Flotation experiments revealed that cell-assisted separation was more effective than metabolite-facilitated flotation, either for single mineral or the mixed sample (barite mixed with quartz). Barite was recovered up to 87% (at pH = 3) in sole-mineral flotation experiments, and flotation of the mixed sample, also, proved a successful selective separation of barite (76% recovery) from quartz at the bio-collector dosage of 6.55 x 10(3) cells/ml. Adsorption kinetics study showed that the pseudo second-order model could represent cell adsorption densities for both minerals, while the Langmuir model simulated adsorption isotherms. Finally, it was shown that B. licheniformis cells could selectively enhance particles hydrophobicity and successfully be utilized as a bio-collector.
查看更多>>摘要：The seawater is purified or pre-treated to obtain the acidic seawater-based media (ASM), which has been gradually utilized in copper hydrometallurgical industries, resulting in desirable copper recovery efficiency. In the chemical/bio leaching of chalcocite, chalcopyrite, and other low-grade copper sulfide minerals, the ASM is proved to have a good catalytic effect and it could potentially intervene the leaching reaction and interface condition. In this regard, to further understand the effects of ASM, this paper critically discussed the pivotal ions (ferric/ferrous ions, cupric/cuprous ions, elemental sulfur, passivation ions, silver catalytic ions, etc.) and its compounds, regeneration behavior in the leaching reaction. The current studies tightly related to the effects of these pivotal ions on the redox potential, reaction activation energy, and leaching kinetics were also comparatively analyzed. The tolerances of microorganisms and reactions to ASM were carefully explored. Relied on the previous studies and reviewing in this paper, it inferred that as an efficient, potential alternative of freshwater, the ASM could provide a good expected possibility to accelerate copper sulfide leaching, especially in areas with scarce water resources.
查看更多>>摘要：In the present study, dithiouracil was employed as the chalcopyrite depressant to selectively change the properties of chalcopyrite surface and separate molybdenite from chalcopyrite. Micro-flotation experiments were carried out to investigate the separation efficiency of dithiouracil on the flotation separation of molybdenite from chalcopyrite. Furthermore, the depression mechanism of dithiouracil was explored at molecular level via zeta potential measurements, fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and time-of flight secondary ion mass spectrometry (ToF-SIMS) analyses. The results showed that dithiouracil strongly depressed chalcopyrite flotation while had less impact on molybdenite flotation, and a satisfactory separation result was acquired by using dithiouracil. Zeta potential measurements and FTIR analyses illustrated that dithiouracil was chemisorbed on chalcopyrite surface. Furthermore, XPS and ToF-SIMS measurements confirmed that dithiouracil could react with Cu atoms on chalcopyrite surface through forming a four membered chelating ring. This paper indicated that dithiouracil can be employed as a high-performance chalcopyrite depressant for the Cu-Mo flotation separation.
查看更多>>摘要：Due to the drawbacks of copper ions used to activate pyrite flotation in gold processing plants where free cyanide occurs in process water and the benefits of lead ions in gold cyanidation, this study investigated the counteraction of lead ions on the negative effects of free cyanide on pyrite flotation in an alkaline condition. Flotation results indicate that 50 ppm (6.8 x 10(-5) mol/L) free cyanide sufficiently depressed pyrite flotation, while 9.5 x 10(-4) mol/L lead ions substantially activated pyrite flotation. It was interesting to find that 9.5 x 10(-4) mol/L lead ions significantly counteracted the depression of 50 ppm free cyanide on pyrite flotation but did not completely restore the flotation of pyrite activated by the same amount of lead ions. Cryogenic X-ray photoelectron spectroscopy was then applied to determine the surface species responsible for pyrite flotation in different conditions. Iron cyanide and thiocyanate formed on pyrite surface were attributed to the depression of free cyanide on pyrite flotation, while lead species, in particular lead hydroxides, adsorbed on pyrite surface were attributed to the activation of lead ions on pyrite flotation. The adsorption of lead ions on pyrite surface was enhanced by the adsorbed cyanide species and lead ions counteracted free cyanide in depressing pyrite flotation through the covering of lead species on the top of iron cyanide and thiocyanate. However, lead species preferentially adsorbed and accumulated on the top of thiocyanate, limiting the capability of lead ions in counteracting free cyanide.
查看更多>>摘要：Static buildup model (SBM) is an analytical approach to predict upstream buildup profile of circular matrix in high-gradient magnetic separation (HGMS). But it was confined to single-wire system in idealized fluid and magnetic field, and was not applicable for more complicated or generalized systems. As better separation performance can be obtained by introducing composite force field or employing novel structural matrices in HGMS, it is necessary to develop models that are more adaptable for predicting particle buildup. In this paper, a simulation model based on SBM was developed to extend its application to complicated situation. The boundary of the buildup was updated by judging whether a particle released from locations near buildup surface would stay or not. And a characterized thickness within boundary layer was proposed to ensure that the released particles were subjected to forces of the same expression as that in SBM. The established model was proved to obtain close results with SBM when HGMS system was in idealized condition. Experimental results testified the model's ability to predict saturated buildup profile of both circular and elliptic matrices in a realistic system. Since fluid and magnetic field information are processed by the simulation software, this model is also believed applicable for more complicated conditions such as multi-wire system and novel structure matrix system, which will be investigated in follow-up studies.
Denzel, MichaelPrenner, MichaelSifferlinger, Nikolaus A.
11页
查看更多>>摘要：Due to mechanical stress during transport, iron ore sinter partly degrades and fines are produced, which have to be re-sintered causing high costs and emissions. Standardized tests for sinter strength are carried out with bulk samples, but for a detailed determination of breakage behavior and discrete element simulations single particle tests are necessary. The great heterogeneity and undefined shape demand a high sample number. In this work a highly automated test rig for rapid single particle impact testing with integrated fragment analysis was developed. The fragment size distributions, return fines production and breakage probability for different size fractions of sinter were investigated and clear trends could be determined. A general return fines production curve could be calculated by introducing a size factor. Contrary to other investigations, it was found that relative return fines generation is not linearly related to specific impact energy input but follows a limited growth trend. Furthermore, a size-independent description of sinter breakage behavior by the well-established tn-modeling concept was performed.
查看更多>>摘要：In this study, the electroflotation of quartz and magnetite with cationic collector dodecylamine (DDA) and anionic collector sodium oleate (NaOL) were investigated to gain a better understanding of the electroflotation process and identify methods to improve it. An interesting phenomenon accompanied with obvious promotion (NaOL is used as collector) and inhibition (DDA-HCl is used as collector) of quartz flotation was observed after electrolysis. The obvious promotion arouse from the supply of the metal cations as active site for the adsorption of negatively charged group and increase active collecting species ionic forms RCOO- and (RCOO)(2)(2-). Conversely, the obvious inhibition originated from the decrease of the active collecting species RNH3+ and (RNH3)(2)(2+). An obvious inhibition phenomenon was observed after the electrolysis for the magnetite. This is because the active collecting species RNH3+, (RNH3)(2)(2+), RNH2 center dot RNH3+ and RCOOH molecule decreased significantly after electrolysis. Furthermore, a comparison test between the regular flotation and electroflotation was conducted in the reverse flotation of magnetic separation concentrate. Compared with the regular flotation process, electroflotation flotation was characterized by simple reagent regime (without pH regulator and activator) and moderate conditions (natural pH), which had mild operation condition superiority. Moreover, the flotation product index of electroflotation can be better through slightly adjusting the reagent regime, and it can be certain that electroflotation is an effective process in the reverse flotation of magnetite. These findings provided a novel perspective for understanding the electroflotation process.
Bhuiyan, MahadiEsmaeili, KamranOrdonez-Calderon, Juan C.
25页
查看更多>>摘要：This paper presents a geometallurgical study for predicting ore grindability at Tasiast Gold Mine. Drill core samples of main gold-bearing lithologies were subjected to three phases of testing for characterization of physicomechanical, geochemical, mineralogical, and textural rock properties. In phase one, a set of physiomechanical and geochemical properties were measured using rapid and portable rock characterization tests. The measured properties include surface rebound hardness (Leeb hardness test), multi-element geochemistry (portable XRF test), acoustic wave velocity, and strength index (Point load test). In the second phase, the rock samples were subjected to more time-consuming and expensive micro-scale tests including mineralogical characterization by XRD and textural classification by petrographic analysis of thin sections. Finally in the third phase, the core samples were used for Bond ball mill work index (BWI) test to assess their grinding behaviour. Geometallurgical associations were identified between grindability and the geometallurgical test predictors using principal components analytics and K-means clustering. These associations were then used for fitting predictive models for BWI using multiple linear regression. Inferential tests were applied to evaluate how well micro-scale (phase 2) and drill core-scale (phase 1) properties can predict BWI behaviour, and how these predictions capture important geometallurgical relationships to BWI. The best BWI predictive model was considered by assessing statistical fit, testing speed, relative cost, and portability and amenability of the testing tool to the field. Accordingly, at the Tasiast mine multi-element geochemistry and lithological textural characteristics are the top two predictors of BWI.
查看更多>>摘要：Recycling of waste printed circuit boards (WPCBs) is desirable to protect the environment and recover the valuable materials. In this regard, dissolution of solder is a key step to recycle the WPCBs. In this work, optimization for maximum dissolution of solder with minimum dissolution of copper is carried out by using Taguchi optimization method. Grey Relational Analysis (GRA) is used for converting multi-response into single response on the basis of Grey Relational Grade (GRG) value. The optimal solution is then achieved by applying Taguchi method on the GRG values achieved from GRA. The results show optimal control factors value of 2.5 mol/l (HBF4), 0.40 mol/l (H2O2), 3.0 % HNO3 and 40 min with maximum Signal/Noise ratio (S/N) -8.31. The treated WPCB with above chemical concentration and time exhibits the complete dissolution of solder and removal of the components without any undesired effect of fading of colour, symbol and characters on the printed circuit board (PCB) surface.
NSTL
Elsevier