查看更多>>摘要：? 2022 Elsevier LtdVanadiferous titanomagnetite deposits are a major resource for processes dedicated to vanadium extraction. Depending on the mineralogical characteristics and the developed unit operations, a titanium bearing waste is produced in mineral processing. The present manuscript deals with the development of an alternative to beneficiate this material to increase the titanium levels and, as consequence, conferring the material an improved composition that might have better acceptance on the market. It seems that a broad thermodynamics simulation regarding the typical roasting methods (e.g., based on sulfates, carbonates, and hydroxides) is scarce, the major contribution is on the development of a systematic approach for process design. The manuscript also covers experiments and a detailed characterization of the involved materials by means of Scanning Electron Microscopy as well as X-Ray Diffraction and Fluorescence. With the selection of NaOH as the most promising roasting reagent, with two subsequent leaching extractions, one in water and the other in acid medium; it was possible to concentrate Ti from 15.69 to 39.22 wt%, with perovskite (CaTiO3) as the main carrier of the element of interest, corresponding to 65.23 wt% of the resulting material mineralogical analysis.
查看更多>>摘要：? 2022 Elsevier LtdTo reduce the amount of ammonia wastewater produced during traditional tungsten metallurgy, a novel method has been developed. Hydrogen peroxide was first used to selectively dissolve tungsten from crude tungstic acid and scheelite hydrochloric acid decomposition residue. Then, the peroxotungstic acid solution obtained was heated to prepare pure tungstic acid through thermal decomposition. The results showed that when the temperature was 40–45 °C, the molar ratio of hydrogen peroxide to tungstic acid was 2:1, and the reaction time was 60 min, more than 96 % of the crude tungstic acid was dissolved. Tungsten was easily leached from the hydrochloric acid decomposition residue under the conditions of a hydrogen peroxide concentration of 1.95 mol/L, 60 min, and 30 °C. The tungsten leaching ratio was 99.4 %. Using a decomposition temperature higher than 95 °C, seed addition amount more than 2.5 g/L, an acid concentration of 1 mol/L, and a reaction time of 120 min, the final W concentration in the mother liquor was 0.5 g/L and the decomposition ratio of peroxotungstic acid was more than 99.6 % with the product being WO3·H2O. This research showed that hydrogen peroxide could dissolve tungstic acid and scheelite hydrochloric acid decomposition residue, and that the peroxotungstic acid obtained was readily decomposed into tungstic acid, which made it possible to leach scheelite cleanly and efficiently.
查看更多>>摘要：? 2022 Elsevier LtdThe third crucial macronutrient required for the development and growth of plants in addition to nitrogen and phosphorous is potassium. The quantity of soluble potassium in soil that could be directly taken up by plants is less and present in the form of evaporite deposits situated in countries lying in the Northern hemisphere such as Canada, Belarus, Israel, USA and Russia. All other countries are dependent on imports from these countries to fulfil their potash requirement. But a major part of potassium exists in insoluble form as silicate minerals abundantly in these countries which can compensate for the potassium deficit. Mostly feldspar and feldspathoid from the tectosilicate group and micaceous minerals from the phyllosilicate group are the common potassium bearing silicates containing 5–15% K2O. Tectosilicates are framework silicates in which potassium is present in the three-dimensional silicate tetrahedra. Phyllosilicates are sheet silicates having a two-dimensional parallel sheet structure and potassium ions are located in the interlayers of the silicate structure. Various processes have been adopted to release the potassium from these silicate resources such as bio-leaching using various algal, bacterial and yeast strains, acid leaching with different acids of varying concentrations, base leaching with diverse strategies and roast-leach studies with alkali and alkaline salts to optimise the recovery. This review summarizes versatile methodologies that have been approached and the scope of various works that could be further accomplished.
查看更多>>摘要：? 2022 Elsevier LtdArsenopyrite exhibits good floatability after copper activation in a high alkaline environment, leading to harder removal of arsenopyrite from concentrate. In this paper, the activation mechanism of copper ion in arsenopyrite flotation was studied using flotation test, surface adsorption experiments, contact angle measurements, X-ray photoelectron spectrometer (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and analysis of Eh-pH diagrams of the FeAsS-H2O system and Cu-FeAsS-H2O system. It can be seen from the results that arsenopyrite participates in the chemical reaction as a reducing agent, the copper formed by Cu2S remained on the mineral surface, and the oxidation state of elements Fe, As and the hydrophilic substance such as arsenate, arsenite and ferric hydroxide was decreased, after activated by copper ions. These phenomenon lead floatability of arsenopyrite activated in alkaline environment.
查看更多>>摘要：? 2022 Elsevier LtdIn this work, a novel surfactant, O,O'-bis(2-butoxyethyl) ammonium dithiophosphate (BEAT), was synthesized and first employed as a collector for the flotation separation of galena from sphalerite. Surface tension measurements elucidated that BEAT possessed a higher surface activity and stronger hydrophobicity than ADD due to the introduction of C–O–C groups. Compared to the conventional collector ammonium dibutyl dithiophosphate (ADD), BEAT exhibited both superior collecting ability and flotation selectivity for galena against sphalerite under approximately neutral or natural pH conditions from the results of micro-flotation and bench-scale flotation. Wettability experiments revealed that BEAT promoted the hydrophobicity of galena surfaces more markedly in comparison with sphalerite. The adsorption mechanism of BEAT on the mineral surface was uncovered by FTIR spectrum and X-ray photoelectron spectroscopy (XPS) measurements. The results of FTIR spectrum demonstrated that BEAT had a much stronger adsorption affinity towards galena than that towards sphalerite. Furthermore, XPS results recommended that BEAT might adsorb on the mineral surface through the reaction of P = S and P–S groups with galena to form metal complexes of P–S–Pb structure. This research provides significant implications for developing novel and efficient industrial chemical reagents for galena flotation.
查看更多>>摘要：? 2022The selectivity of reagents to minerals is extraordinarily important in flotation. However, the selective mechanism of reagents for minerals has not been completely clarified. Similar to other chemical reactions, the surface reaction of minerals is associated with orbital symmetry matching between flotation reagents and surface metals. Nevertheless, no research has been found on this topic. The present work performed density functional theory (DFT) calculations on orbital symmetry matching between flotation reagents and metal ions on sulfide mineral surfaces. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were calculated. The results suggest that the symmetry of xanthate LUMO perfectly matches the symmetry of pyrite Fe HOMO, while the symmetry of dithiophosphate (DTP) LUMO fails to match the symmetry of pyrite Fe HOMO, so xanthate has better collecting ability than DTP for pyrite. Moreover, the symmetry of xanthate LUMO does not match the symmetry of galena Pb HOMO, whereas the symmetry of DTP LUMO matches the symmetry of galena Pb HOMO, so DTP is a stronger collector than xanthate for galena. Copper can activate sphalerite mainly because the symmetry of the Cu HOMO matches the symmetry of the xanthate LUMO. Meanwhile, for pure sphalerite, the Zn HOMO makes no contribution, and the symmetry of the Zn LUMO does not match the symmetry of the xanthate HOMO. In the case of Z-200, the main factor that results in its weak collecting ability for pyrite is the steric hindrance existing between Z-200 and the pyrite surface instead of orbital symmetry matching. For CN– adsorption, both HOMO and LUMO of CN– and those of galena surface Pb do not follow symmetry matching, while the opposite holds for the HOMO and LUMO of CN– and those of pyrite surface Fe, which causes the depressing effect of cyanide on pyrite.
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