查看更多>>摘要：? 2022In the traditional process for tungsten recovery from scheelite concentrate, phosphorus is regarded as a harmful impurity that should be strictly controlled. Moreover, the calcium that entered the resideue as Ca(OH)2 or CaCO3 was discarded or landfilled. To date, the residues from the traditional process have been listed as solid hazardous waste in China. A novel method was investigated to realize the comprehensive recovery of tungsten, phosphorus, and calcium. In the leaching process, 96% of scheelite (CaWO4) and 99% of apatite (Ca5(PO4)3F) were digested under the conditions of 3 M HNO3, at a liquid/solid ratio of 10:1, a leaching temperature of 90 °C, and leaching time of 2 h. After extracting tungsten from the leaching solution by solvent extraction, about 70% of Ca2+ in the raffinate was recovered as calcium sulfate whiskers by adding H2SO4. Subsequently, the solution from the calcium removal process was reused to leach scheelite after adding the consumed HNO3. When the P2O5 concentration in the circulating leaching solution was over 30%, it was discharged and neutralized by NH3·H2O, and then used to produce a nitrophosphate fertilizer by spray granulation and drying processes.
查看更多>>摘要：? 2022 Elsevier LtdThe article is devoted to the results of research into the process of sintering, roasting and leaching of oxidized nickel ores, with selection of optimal parameters that include the addition of various reagents, varying the temperature, duration and roasting program, as well as creating the necessary atmosphere in the roasting furnace. It was revealed that only a small part of ferruginous minerals forms iron sulfate during sulfation with sulfuric acid, even at elevated temperatures. It is possible to reduce the loss of nickel binded with oxygen compounds of iron after the roasting at temperatures not exceeding 650 °C, while recrystallization of iron oxides occurs with the formation of α-Fe2O3, and the nickel is released, that can be leached. In general, the sintering and roasting process makes it possible to achieve a higher extraction of nickel and cobalt; it is shown that nickel, being a part of various ore minerals, is available for extraction at different stages of ore processing.
查看更多>>摘要：? 2022 Elsevier LtdWaste printed circuit boards represent one of the most challenging parts of e-waste recycling. The extraction of precious metals (gold, silver, palladium and platinum) from waste printed circuit boards has commonly been done using highly toxic, corrosive, or expensive lixiviants, such as sodium cyanide, aqua regia and iodine/iodide. The present study provides a greener approach to extract precious metals from waste printed circuit boards using alkaline glycine solution in the presence of an oxidant. The common strong oxidant of potassium permanganate and the non-hazardous potassium ferricyanide were investigated and compared in alkaline media. Decrease of the particle size of sample, and the rise of oxidant concentration (0.04–0.16 M) enhanced gold extraction significantly. However, the increase of temperature (～55 °C) and glycine concentration (0.5–1 M), and the staged addition of oxidant did not significantly improve gold extraction. Control of solution Eh could not reduce permanganate consumption whereas the ferricyanide consumption could be reduced by>50% in 72 h. Under the recommended conditions, 86.8% gold, 70.2% silver, 89.3% palladium and 87.9% copper could be extracted using glycine-permanganate leaching system. In comparison, 79.3% gold, 69.0% silver, 68.5% palladium and 83.1% copper could be extracted using glycine-ferricyanide leaching system. These extractions are comparable with what is achievable from cyanide (NaCN)-based leaching systems. Both of the leaching systems showed fairly good selectivity to copper and precious metals. The present study paves a way for the further development of non-NaCN glycine process for e-waste recycling.
查看更多>>摘要：? 2022 Elsevier LtdThe accumulation of large amounts of refractory zinnwaldite in tailings pond in Hunan (China) implies a waste of the rare lithium and rubidium resources and also induces serious environmental problems. In the present study, the microbial pretreatment was introduced prior to the desliming and flotation processes. The silicate bacteria “LM-1”, isolated from deep-sea sediments, was used to decompose and erode the minerals. This procedure will solve the problem of difficult sorting of the tailings in a more efficient and environmentally friendly way. Through flotation tests and mineral surface analysis, we derived the optimum pretreatment and flotation solution and we discuss application processes that will enhance the flotation effectiveness. The test results showed that the pretreatment with “LM-1” caused an enlargement of the cleavage plane {0 0 1} on the surface of the ore grains and an increase of the content of the cleavage plane {0 0 1} throughout the raw ore. Therefore, the adsorption capacity of the collector increased, and the selectivity was enhanced, which largely improved the floatability of the zinnwaldite. A good index of 2.89% Li2O grade with 71.68% recovery and 0.59% Rb2O grade with 80.42% recovery was obtained for the concentrate. Compared to conventional flotation processes, the more efficient release of potassium and desilication through “LM-1” not only avoids the high energy consumption and serious sliming caused by fine grinding of minerals, but also effectively improves the separation results.
查看更多>>摘要：? 2022 Elsevier LtdDown-the-bank grade-recovery data are examined to determine whether the best performance could be correlated with balanced cell-by-cell recovery or balanced cell mass pull. Previous work had shown evidence in support of the former but here we show correlation with balanced mass pull may often be found. Balanced recovery seeks to maximize selectivity against a second floatable mineral while balanced mass pull seeks to maximize selectivity against entrained gangue. The choice, then, would appear to depend on the amount of second floatable mineral relative to entrainable gangue, but the case is made that choosing either balanced recovery or balanced mass pull is better than no choice. Most of the plants examined had forced air mechanical cells and used air rate to manipulate the bank. It is shown that using air further improves performance by controlling water recovery, and hence entrainment. Some observations on banks with self-aerated cells are included.
查看更多>>摘要：? 2022 Elsevier LtdFlotation is a kinetic process designed to separate mineral fines by control of hydrophobicity. In general, both the recovery and selectivity of a flotation process increase with contact angle. It is difficult, however, to model flotation kinetics using the thermodynamic parameter. In the present work, we consider flotation as heterocoagulation so that the bubble-particle interactions occurring in the pulp phase of a flotation cell can be modeled using the hydrophobic force as a kinetic parameter that can represent the role of contact angles in flotation. The pulp-phase model developed in this manner has been combined with a froth-phase model developed earlier by considering the effect of particles in film thinning kinetics and bubble coarsening (Park et al, 2018). The combined model has been used to develop a flotation simulator that can be used to construct grade vs. recovery curves from feed characteristics (e.g., mineral liberation and particle size) and various operating parameters. The simulator has been tested successfully against a set of bench-scale continuous flotation test results reported in the literature (dos Santos and Galery, 2018).
查看更多>>摘要：? 2022 Elsevier LtdAn extensive field test was conducted by Rio Tinto and Eriez to evaluate the operability and metallurgical performance of a StackCell? SC-50 high-intensity flotation machine for recovery of copper and molybdenum from flotation tailings. The field test of the 15-m3 StackCell flotation cell was conducted at Rio Tinto's state-of-the-art tailings recovery demonstration plant located within Kennecott Utah Copper's tailings facility. The metallurgical results demonstrate that the StackCell technology provides a unique solution for recovering metal values from tailings, with excellent selectivity and an order of magnitude increase in flotation kinetics compared to conventional mechanical flotation machines. The metallurgical advantages of the StackCell are particularly pronounced for treating fine tailings, with upgrade ratios >25 achieved at average copper and molybdenum recoveries of 20% and 28%, respectively, within approximately one minute of flotation residence time. Computational fluid dynamics (CFD) simulations were conducted to provide a fundamental explanation of the findings from metallurgical field measurements. The simulations show that maximum levels of turbulent dissipation rates in the StackCell contacting chamber are nearly 5 times that of rotor/stator mechanisms in conventional mechanical flotation machines. Furthermore, the high levels of turbulent dissipation rates in the contacting chamber are favorable for high collisions and attachments rates of fine particles with air bubbles.
查看更多>>摘要：? 2022 Elsevier LtdThe development of new flotation equipment has to address the challenges confronting the minerals industry, the low flotation efficiency of fine and coarse particles and the need to process a higher volume of ores due to the decreased feed grades. By combining a downcomer, a fluidised bed and inclined channels within one equipment, the Reflux Flotation Cell (RFC) offers a general solution to improving fine and coarse particle flotation while maintaining a high throughput. Current research on the RFC has proven its success in coal flotation. Based on the published research work, this paper introduces the history of RFC development, illustrates the unique structure of the RFC and the role of each major component, discusses the flux mechanism formed in the boundary between the fluidised bed and inclined channel section, explains the main theories adapted to characterise the RFC and evaluates the effect of the operating parameters on its performance. This information provides a general picture of the RFC from both theoretical and practical perspectives. This paper also recommends future research on the RFC to expand its application from coal flotation to minerals flotation and also model the bubble motion in inclined channels and the flux mechanism in the boundary area, both of which dictate the performance of the RFC.
查看更多>>摘要：? 2022 Elsevier LtdIn this study, a selective process for separation of vanadium and iron from the steelmaking slag was proposed. The proposed process has a potential to be considered industrially due to its relative simplicity. The process for the separation of vanadium and iron is consisted of three main stages: leaching, cementation, and solvent extraction. The leaching and cementation stage, were designed such that the proper aqueous species of vanadium and iron for the solvent extraction stage got generated. In the solvent extraction experiments, the effect of vanadium and iron aqueous species and the extractant type (extraction through anion and cation exchange reactions) on the separation of these elements were studied. In the solvent extraction stage, D2EHPA (cationic exchange) and Aliquat 336 (anionic exchange) were used. The results, for both extractants, showed that for selective separation of vanadium and iron, conversion of ferric to ferrous is essential. By converting ferrous to ferric ion, almost no iron was extracted through the anion exchange. Through cation exchange, however, ferrous extraction was started at significantly higher pH values comparing to ferric ion. D2EHPA was shown to have the ability to extract vanadium with both oxidation states of +4 and +5. Aliquat 336, however, showed no extraction toward V+4, and only extracted V+5 species. This was found due to the absence of anionic complexes of V+4 in a sulfuric acid solution. The extraction mechanism of vanadium through both anion and cation exchange reactions were studied. The results showed the formation of VO2R(RH) through cationic extraction and VO2SO4R4N for the anionic extraction. Finally, 90% vanadium stripping efficiency from D2EHPA and Aliquat 336 loaded organics were obtained using 2 M H2SO4 and 3 M HCl solutions, respectively.
查看更多>>摘要：? 2022 The Author(s)Froth flotation is an operation currently used for the recovery of Cu from pyrometallurgical smelting slags due its simple operation and relatively low operational costs. While it has been utilized for many decades, it may be necessary to develop strategies that improve Cu recovery from slags, as the unprecedented increase in Cu demand has made industrial waste and side streams economically relevant sources of metals. This study presents a novel chemistry-based approach for the flotation of Cu from smelting slags by utilizing an amphiphilic cellulose-surfactant mixture as a flotation frother, hereby referred to as CellFroth. The present work pursues two main objectives: i) to improve the performance of flotation for the treatment of smelting slags and ii) to accomplish a first proof of concept for frothers produced from renewable sources in the context of industrial waste treatment. The flotation performance of CellFroth was compared with a commercially available additive (i.e., DowFroth250) and hydroxypropyl methyl cellulose (HPMC). The results showed significant advantages in performance for CellFroth. At the highest collector concentration, Cu recovery was higher with CellFroth compared to DowFroth 250 and pure HPMC (73%; 62% and 65% respectively). A 75% reduction in xanthate concentrations had negligible effects on Cu recovery for CellFroth (70%), while recoveries decreased drastically with DowFroth250 (47%) and pure HPMC (50 %). Finally, CellFroth consistently reached comparable concentrate productivity (grade and recovery) as DF250 within significantly shorter flotation times. The use of CellFroth thus offers the possibility of increasing the Cu recovery from flash smelting slags, while reducing the environmental impact of the process by using a frother produced from sustainable sources and simultaneously reducing xanthate consumption.
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