查看更多>>摘要：This work aims to establish the quantitative relationship between the surface oxidation state of pyrite and flotation performance. In this paper, an efficient method was proposed to prepare pyrite with different oxidation degrees. Flotation tests show that the floatability of pyrite decreased with prolonging the oxidation time. TofSIMS results reveal that the main component on the oxidized pyrite surface is Fe hydroxides or oxides. XPS analysis confirms that Fe(OH)2 and FeOOH are the main formula of Fe species, and the ratio of Fe2+/Total Fe agrees well with the floatability of pyrite with different oxidation degrees, which can be taken as an index to develop the flotation performance of pyrite. DFT simulation calculation further demonstrates the reliability of Fe (OH)2 as the active site. This study provides essential surface chemistry evidence for correlating the surface species with the floatability of pyrite with different oxidation states through quantitative analysis of various intermediate products.
查看更多>>摘要：Removal of pre-adsorbed xanthate is a crucial step to the further separation of chalcopyrite from other sulfide minerals possessing similar floatability. Traditionally, adding excess sodium sulfide (Na2S) suffers from a series of environmental problems. Herein, to seek more effective alternatives, inorganic oxidizers i.e., KMnO4, H(2)O(2 )and Ca(ClO)(2) were employed. Comparative effects of inorganic oxidizers and Na2S on removal of sodium butyl xanthate (NaBX) on chalcopyrite surface were investigated. Results showed that the adsorption of NaBX on chalcopyrite surface followed Langmuir isotherm, and the product was Cu(BX)(2) at pH 8. Xanthate removal performance of different additives followed: KMnO4 > H2O2 > Ca(ClO)(2) > Na2S, and 0.5 mmol/L of KMnO4 could get the same effect as 2.73 mmol/L of Na2S. FT-IR studies revealed that oxidation products of Cu(BX)2 with different oxidizers included dixanthogen (ROCSS)(2), perxanthate ROCSSO- and thiocarbonate ROCOS-, while Na2S removed NaBX from the mineral surface via the competitive adsorption which was non-specifical ion exchange. Furthermore, surface analysis confirmed that KMnO4 treatment rendered the mineral surface less hydrophobic owing to the formation of FeOOH and Fe-2(SO4)(3), and the formed cupric oxide prevented the re adsorption of xanthate or its reaction product, consequently decreasing the chalcopyrite floatability from 86% to 12%. These findings indicated that KMnO4 might be a promising alternative to Na2S in separation chalcopyrite from molybdenite which are both pre-floated by xanthate.
查看更多>>摘要：The catalytic effect of Pb2+ adsorption on gold surface in gold thiosulfate leaching was investigated by electrochemical methods. Open circuit potential (OCP), cyclic voltammetry (CV) and polarization tests showed that 50 and 100 mg/L Pb2+ addition to thiosulfate solution increased the OCP from  0.136 V to  0.110 and  0.105 V, respectively, due to adsorbed Pb on the gold surface. The Pb2+ addition also increased corrosion rate of gold as well as the anodic current densities. Chronoamperometry was used to determine the interaction between Pb2+ and Au during the anodic polarization at  0.1, 0.0, and +0.1 V. A concentration of 100 mg/L Pb2+ accelerated the gold oxidation rate relative to the Pb2+-free condition, particularly at higher anodic potentials, which resulted in higher dissolved gold concentrations (from near 0 to 2 mg/L). Analysis of the electrode surface with scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy showed that gold oxidation in the thiosulfate solution in the presence of 100 mg/L Pb2+ follows a two-step process: (1) formation of an AuPb2 layer on the gold surface, which improved gold oxidation by inhibiting gold surface passivation; and (2) dissolution of the AuPb2 layer assisted by the applied anodic potential. Addition of 50 and 100 mg/L Pb2+ clearly improved gold oxidation kinetics and efficiency during thiosulfate gold leaching.
查看更多>>摘要：Secondary aluminum dross (SAD) is a hazardous solid waste due to containing aluminum nitride (AlN). In this work, AlN was used to reduce heavy metals in pickling sludge by pyrometallurgy. Reduction extent of Fe, Cr and Ni was up to 97, 91 and 100%. However, it was found that some AlN was oxidized by oxygen. AlN oxidization could be decreased by shortening melting process. The AlN oxidization would be restricted after aluminosilicate was melted. Reduction extent of heavy metals increased from 51% to 86%, when treatment temperature was increased from 1350 to 1400 degrees C. Meanwhile, AlN oxidization could be exacerbated by increasing CaF2 and soda. The CaF2 and soda could corrode the alumina protective layer on AlN and promote AlN oxidization. Reduction extent of heavy metals decreased from 48% to 19% after adding soda. The AlN oxidization could be restrained by cutting down the air during melting process. After covering the crucible, reduction extent of heavy metals was increased from 48% to 92%, and reduction extent of Fe, Cr and Ni was increased from 58, 18 and 83% to 97, 91 and 100%. After evaluating environment benefit of AlN reducing heavy metals, it was found that utilizing a ton SAD replacing carbon to reduce heavy metals in pickling sludge could reduce carbon emissions of 279 kg. In addition, SAD could be used as reductant to replace Al for chromium metallurgy. Using a ton SAD to replace Al for chromium metallurgy could reduce carbon emission of 3961 kg.
查看更多>>摘要：During froth flotation, fine gangue particles are difficult to reject as they are easily entrained, leading to a poor quality of concentrates, especially in saline water. In this study, the focus was on the selective reduction of kaolinite entrainment using anionic polyacrylamide (PAM) MF1011 during chalcopyrite flotation in saline water. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was employed to understand the adsorption of MF1011 and potassium amyl xanthate (PAX) on mineral surfaces while Focused Beam Reflectance Measurement (FBRM) was used to monitor in-situ particles aggregation and subsequent size fluctuations during agitated flotation. It was found that the adsorption of MF1011 was strong on kaolinite but weak on chalcopyrite. Meanwhile, MF1011 potentially targeted kaolinite rather than chalcopyrite during the particles aggregation and size changes. The selective adsorption and aggregation of MF1011 in the kaolinite-chalcopyrite mineral system were attributed to the selective reduction of kaolinite entrainment by MF1011 during chalcopyrite flotation.
查看更多>>摘要：The microstructures of mineral materials determine their mineral processing characteristics. Realistic microstructure models are a precondition for simulations of various mineral processing steps. For this reason, a model for simulating the microstructure of minerals that consists of densely packed grains of various phases is presented. It is based on geometrical information and image analysis of planar sections of samples of the material of interest. This includes grain size characteristics, frequencies of mineral components, and information on the spatial distribution of phases. The simulation is carried out by a sequential algorithm, which adds stepwise new grains to an incomplete microstructure. The final result is a tessellation of irregular non-convex grains of spatially variable components. The application of the model is demonstrated for a sample of granite material. A goodness of-fit test shows that in this case the model is indeed realistic.
查看更多>>摘要：Based on the chemical affinity with sulfur, and solubility and volatility differences of the sulfurized transformed phases, sulfidation treatment of refractory hazardous solid waste can effectively recover valuable metals. In this work, a technically reasonable and efficient treatment of hazardous electrolytic manganese anode slime (EMAS) for rapid and synchronous manganese (Mn), lead (Pb), tin (Sn), and selenium (Se) separation via sulfidation transformation and leaching was proposed. After sulfidation, the valuable elements in EMAS were selectively separated in which the Mn and Sn were converted to soluble salts, whereas Pb was transformed to insoluble sulfate and most Se was volatilized. 70% Se was collected from the volatile dust, 98.1% Mn and 80.5% Sn were transferred to the leachate, while 99% Pb was kept in the leaching residual as the EMAS was treated after sulfidation transformation followed by sulfuric acid leaching under the optimized conditions: roasting with a sulfur/EMAS mass ratio of 1:1 at 400 degrees C for 10 min, followed by leaching under a sulfuric acid concentration of 8%, a liquid/solid ratio of 10:1, and a stirring rate of 100 r/min at 25 degrees C for 5 min. Sulfidation kinetics indicated that the sulfidation of manganese oxides was controlled by the interfacial chemical reaction with an activation energy of 35.367 kJ/mol. In terms of efficiency, the low-temperature sulfidation roasting within 10 min and dilute sulfuric acid leaching within 5 min for synchronous separation indicated that the proposed process was reasonable and efficient for hazardous EMAS treatment. For environmental protection, the detrimental SO2 byproduct can be returned to the sulfidation roasting process to reduce the tetravalent manganese or used to make sulfuric acid. The sulfidation and leaching mechanisms for Mn, Pb, Sn, and Se separation were also discussed in detail in this work.
查看更多>>摘要：The recovery of rare earth elements (REEs) from secondary resources, particularly coal-based materials, has recently received attention due to supply and demand imbalance. Research reported to date indicates that a high REE recovery can be realized when treating bituminous coal sources using strong acid solutions of approximately100 g/L or higher. This study introduces an approach to enhance the total rare earth recovery (TREE), especially for heavy rare earth elements (HREEs), from these coal sources at significantly lower acid concentrations. Based on the presence of REE minerals like monazite and xenotime, a detailed investigation was undertaken to quantify three pre-leach treatment methods, i.e., 1) roasting, 2) direct acid baking, and 3) acid baking after roasting. Roasting tests at 600 degrees C revealed that the recovery of light REEs (LREEs) was enhanced while the recovery of HREEs remained relatively unaffected. LREE and HREE recovery values of 38.3% and 21.3%, respectively, were achieved using a 50 g/L (0.5 M) sulfuric acid solution at 5% solid concentration and a solution temperature of 75 degrees C for 2 h. Comparatively, direct acid baking at 250 degrees C provided substantial increases in LREE and HREE recovery values to approximately 49.4% and 53.0%, respectively, using an equivalent acid dosage. Recoveries were maximized to 77.0% and 79.6% for LREE and HREE, respectively, by roasting followed by acid baking. Similar results were obtained from the treatment of a second bituminous coal source. Due to strong correlations between REE and Al recovery values, tests were performed on kaolinite and illite, which were prominent clay minerals within the source coals. These experiments revealed that the REE recovery improvements were likely a result of dehydroxylation of clays and subsequent release and decomposition of REE-bearing minerals such as monazite, xenotime and zircon.
查看更多>>摘要：The new three-phase fluidized bed flotation column (TFC) hydrodynamics characteristics, such as gas holdup, bubble diameter and bubble surface area flux have been carried out, and this study focuses on bed fluid hydrodynamic parameters of the TFC. The bed hydrodynamic characteristics viz., bed fluctuation ratio (r), bed expansion ratio (R) and bed voidage (epsilon) of the TFC have been studied using air as the discontinuous phase and water as the continuous phase, respectively. The effects of the system parameters studied include superficial gas, liquid velocities and initial static bed height (H-0). Experimental studies based on the Response surface methodology (RSM) have been made to investigate the mathematical model of hydrodynamic parameters (r, R, epsilon) and bubble diameter (D-b) of the TFC. The results show that the models which were established by operating variables can predict the r, R, epsilon and D-b of the TFC well. Based on the previous investigation of the optimization of bubble performance parameters which has been caned out by Liu et al. (2020), the correlation of D-b has been carried out, and the result shows that H-0 is the boundary condition that determines the variation of D-b. The optimization of D-b by RSM shows that relatively small bubbles can be obtained when H-0 is greater than 0.290 m within the range of parameters studied. The values of the experiment have been compared with those predicted by the proposed models and have been found to agree well.
查看更多>>摘要：Rare earth metals (REM) have applications in multitudinous fields such as the medicinal industry, nuclear technology, and agricultural implementations. Recently, this has caused considerable interest within the community due to its growing demand which leads scientists to explore effective, economical, and safer ways of extraction from primary and secondary sources. This review is of pivotal importance as it summarizes the requirements of REM worldwide, leaching of REM from ores, recycling of REM from scrap materials, end-life products, and industrial wastes. This represents an important topic to explore as it demonstrates existing REM production and effective recovery pathways, and highlights the critical challenges such as the harsh harmful leaching technologies used to recover REM from primary and secondary sources. A comprehensive classification of REM, hydrometallurgical extraction, bioleaching, separation techniques, and sustainable approaches to supporting a circular economy has been extensively discussed. This factual and comprehensive overview of past, present and future aspects of REM recovery technologies will be helpful to researchers in developing efficient leaching pathways for REM recovery.
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Elsevier