查看更多>>摘要：A technological scheme for copper slag processing is proposed. It comprises 5 stages, namely: (i) air oxidation of the copper slag at a temperature above 800 degrees C for 2 h; (ii) hydrothermal treatment of the oxidized slag with sodium hydroxide solution (140 g/l) at 190 degrees C for 3 h; (iii) separation of the solid from the liquid phase by hot filtration; (iv) gel formation through hydrolysis of the liquid silicate phase by changing pH; (v) obtaining of amorphous SiO2 (silica gel) by drying at 80 degrees C. The processes used for slag manipulation were elucidated and optimized for silicon extraction. It was established that the increase in the oxygen partial pressure in the oxidizing gas does not change the mechanism nor significantly intensifies the oxidizing process. A decisive factor for the extraction of SiO2 during hydrothermal treatment was the concentration of NaOH. Its increase from 60 to 140 g/l reduced the amount of residual SiO2 more than half and significantly decreased the formation of analcime (NaAlSi2O6.H2O) in the solid phase. Hydrolysis of the liquid silicate phase by changing pH is an appropriate process for gel formation. (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：The development of mineral phases, analcime, tobermorite and cancrinite, from the valorisation of a waste, is the main objective of this work. The waste considered is a biomass ash (BA) obtained from a fluidized bed forest combustor powered principally by eucalyptus bark residue in a paper company. BA is valorised positively by a hydro thermal treatment (HT)in an alkaline solution. This treatment is an eco-efficient process because it employs low temperatures to activate the BA and implies no emission of CO2 to the atmosphere. Through this HT process, the synthesis of tobermorite is optimized considering the results from different characterization techniques. In addition, the dissolution of chlorides through HT is observed, improving the reutilization of BA in cement-based materials. The results promote the reuse of BA waste and assess its incorporation in cement-based materials due to the high pozzolanic activity shown by the synthesized tobermorite phase (98% of fixed lime at 28 days). (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：Separation of ion-absorbed rare earth elements (REE) by oxalate used as a precipitator is the principal extraction process employed in the mining industry. The oxalic acid precipitator plays the key role in the precipitation process. In this paper, the enhanced effect of a static magnetic treatment applied to the precipitation process of REs was investigated. Compared to the non-magnetization, the results of magnetic processes appeared to be better and its optimal precipitation conditions was obtained at pH value of the precipitation solution at 2,RE2O3: H2C2O4 = 2.5:1, a magnetic strength 400 kA m(-1), a 20 min magnetization time in a magnetized oxalate solution. The dosage of oxalate precipitator is less 5% to that employed in conventional processes conditions with non magnetization while the purity of the rare earth still keeps stable. The electrical conductivity of the oxalate precipitator was increased by magnetization. A possible change in the electron spin of the magnetized precipitator ultimately affected the pace of rare earth precipitation crystallization and growth direction of the rare earth-bearing precipitated crystals. (C) 2016 Published by Elsevier B.V.
查看更多>>摘要：In order to mitigate the effects of climate change, a worldwide effort is being launched to use ultramafic mine waste as feedstock for CO2 sequestration by mineral carbonation. To enhance the rate of mineral carbonation at any specific mine site, it is important to develop individualized methods for use at that specific mine site, and with respect to its particular waste mineralogy. This study examines mechanical activation as the pre-treatment method for ultramafic mine waste containing forsterite and serpentine. Particle size distribution, specific surface area, microstructure and direct aqueous mineral carbonation were measured to test the effects of mechanical activation. The Rietveld method was used to analyze the microstructure of untreated and mechanically-activated material. It was found that, as a result of the grinding energy input on olivine, particle size was decreased, surface area was increased, crystallite size was reduced and micro-strain was accumulated. During the dry mechanical activation of mine waste, serpentine content was partially dehydrated and converted to olivine. The concurrent grinding of serpentine with olivine promoted the formation of new surface area, but it hindered the disordering of the crystal structure of forsterite. Forsterite makes up the majority of the content and contributes to CO2 sequestration under selected carbonation conditions. The CO2 sequestration conversion of mechanically-activated olivine and mine waste are 22.5% and 31.5%, respectively, with 3600 kWh/t specific milling energy input after one hour direct aqueous carbonation. For the purposes of mineral carbonation, the mechanical activation of mine waste is preferable to simply grinding pure olivine. (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：The recovery of valuable base Metals from mining rejects presents an economical alternative to conventional hydrometallurgical processes. The reject of interest investigated in the present work is a nickeliferous, upgraded pyrrhotite tailings produced by Vale Base Metals in the Sudbury Basin of Ontario. A QEMSCAN (TM) analysis of the tailings showed a total Ni content of 1 wt%, with 59% of the total Ni deported to pyrrhotite and 40% associated with pentlandite. The initial part of this study involved the development of a selective dissolution protocol to quantify the differential dissolution extents of the two Ni-bearing minerals. Application of this protocol to the pyrrhotite tailings sample showed that an acidity of 15 wt% HCl, and a temperature of 80 degrees C was adequate to selectively dissolve 96% of pyrrhotite from the tailings. Subsequently, an anoxic acidic leach of the tailings at pH 1.5, and at 5% (w/v) solids loading showed minimal dissolution of Fe and Ni from pentlandite in tests with and without pH control. The extent of Ni dissolution was next evaluated as a function of pH during an oxic add leach. The testing protocol involved leaching the tailings under two pH regimes: fixed and uncontrolled pH. The results showed that operation at a fixed pH increases the extent of Ni dissolution due to the higher concentration of the oxidant Fe(III) in solution. Finally, an oxic ferric leach showed that the terminal dissolution extents of pyrrhotite and pentlandite were comparable at 46% total Ni extraction. (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：This study is focused on the develop of a cost effective physicochemical beneficiation process for low grade ferruginous manganese ores to recover a valuable iron bearing by-product (Fe Oxalate or Mn Ferrite) and manganese ore concentrate. It was found the one molarity solution of oxalic acid can leach five times more Fe than Mn from ferruginous manganese ores during treatment at temperature 333 K for 2 h. Photoreduction of the leached solution with sunlight for four hours provided ferrous oxalate dihydrate of >75 % purity which was further converted into Mn ferrite by roasting it at 773 K for 4 h. Residue samples Were roasted in a controlled atmosphere tubular furnace (temperature: 573 - 973 K; time: 1, 3, 5 h) and muffle furnace (temperature: 523-773 K; time: 2, 4, 12 h) to study the formation of maghemite coating on the surface of iron bearing particles. Chemical analysis, XRD, SEM, magnetometer tests were carried out to characterize the products recovered at different stages of the process. Davis tube magnetic separation tests were conducted using different current intensity (0.5, 1,2 A) to establish grade and yield of the ore concentrate. The proposed process can recover 0.12-0.25 tons of iron oxalate and 033-0.50 tons of manganese ore concentrate (Mn: 42-55 % and Mn/Fe: 2.91-4.5) by processing of one ton of low grade ferruginous manganese ore (Mn: 193-313% and Mn/Fe: 0.48-1.16). (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：In coal preparation, clean coal ash content is a key indicator for evaluating the quality of clean coal. Online ash analysers are employed to rapidly measure the clean ash, and the resulting measurements are monitored for productive process control. However, the ash observations often fluctuate and are disorganized due to random errors and analyser measurement errors, local variations in coal flow, and changing equipment and processes. Thus, this paper attempts to use the Shewhart control chart method to monitor clean ash in a statistical and global manner. From investigations of the coal preparation process, three types of variability can occur in ash process data: random variability, special variability and systemic variability. An effective X-Shewhart control chart can detect all abnormal variations under the condition that the control chart parameters (subgroup and control limits) are properly determined. To achieve this, an error analysis of an ash analyser and the influence of data autocorrelation were considered before structuring a clean ash control chart In phase I, a preliminary dataset was collected from actual ash observations. After an autocorrelation analysis, which excluded abnormal variations, a sampling scheme comparison and the selection of a population standard deviation for the preliminary data, the control chart parameters Were precisely estimated. In phase II, the phase I analysis procedure was broadly used to structure a (X) over bar chart with given standard values for monitoring clean ash. Therefore, an application example is presented, and the results are discussed to demonstrate the positive impact of this method on a coal preparation plant. (C) 2016 Elsevier B.V. All rights reserved.
Abaka-Wood, George BlanksonAddai-Mensah, JonasSkinner, William
8页
查看更多>>摘要：Rare earth element (REE) minerals found in most South Australian ore deposits are in complex association with gangue minerals, typically hematite and quartz. Monazite, a phosphate mineral containing mainly light REEs, is one of the principal minerals found in South Australian REE-bearing deposits. Froth flotation, which exploits the differences in the physicochemical properties of minerals, has proven to be effective in the beneficiation of REE minerals. The physicochemical properties of monazite, hematite, and quartz including zeta potential, contact angle, and floatability were determined in this investigation. Sodium oleate, sodium dodecyl sulphate, and hydroxamic acid were employed as collectors. Electroacoustic zeta potential measurements were used to identify the interaction between monazite, hematite, and quartz and the selected collectors. The capillary rise method was used to determine the contact angle of the three minerals. Single mineral flotation using Denver microflotation cell was carried out to confirm physicochemical properties measured. It is shown that the contact angle of the minerals is dependent on the collector type used. The isoelectric point (IEP) of monazite, hematite, and quartz occurred at pH of 6.5, 6.9, and 2.2, respectively. The zeta potential results also suggest that the collectors chemisorb onto monazite and hematite surfaces With a corresponding change in IEP values. Single mineral flotation results demonstrated that monazite and hematite could be floated by the selected collectors; however, low or no quartz flotation was observed in some cases. Results from electrokinetic and contact angle measurements are consistent with that of the floatability of monazite, hematite, and quartz. (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：Frothers, which are widely used as key reagents in the flotation of ores, are generally alcohols of varying structures. There is abundant experimental data which illustrates that frothers cause changes in froth behavior, bubble size/coalescence and surface tension and that these changes are closely associated with changes in the molecular structure of the frothers. Partial molar Excess Gibbs energy is a thermodynamic property which quantifies the difference between the partial molar value of the Gibbs energy of a species in a real mixture and that for the same species in an ideal mixture and this difference in mixture properties is due to differences in the molecular structures of the constituent species. It is thus reasonable to hypothesize that partial molar Excess Gibbs energy may be a useful parameter to quantify the changes which occur when using frothers of different molecular structures. In this paper it is shown that there is a generally strong relationship between measured characteristics such as froth volume/height, surface tension, hemi-micelle formation and the partial molar Excess Gibbs energy of alcohol frothers and these correlations provide robust evidence that many of the characteristics of frothers are strongly related to their molecular structure which in turn is related to the total surface area, molecular volume, and molar volume of the molecule, the molecular weight of the constituent functional groups and the interaction energies between the species present. (C) 2016 Elsevier B.V. All rights reserved.
查看更多>>摘要：This study presents an evaluation of an innovative technique for the treatment of concrete waste by electrical fragmentation. Scientific arguments are made, indicating that it is possible to strive for the recovery of waste by jointly recycling aggregates and the hydrated cement paste, in order to manufacture new concrete of the same mechanical quality as that produced using raw materials. The results of electrical fragmentation tests on concrete show that i) fragmentation level and selectivity are significantly enhanced when the size of the constituent aggregate in the concrete increases, which is a positive result because the largest proportion of most concrete mixes comprises coarse aggregate (45% of 5/20 mm aggregate); ii) the mineralogical nature of the aggregate has little impact on the electrical fragmentation level and has none on its selectivity, which are positive results demonstrating the robustness of the process in terms of its ability to process aggregate of different origins and iii) aggregate liberation degree depends on neither the energy level applied to the concrete, nor the quality of the process water, which are positive results for industrial applications. The results of this study show that electrical fragmentation has potential for integration as part of a recycling process for concrete waste on an industrial scale. (C) 2016 Elsevier B.V. All rights reserved.
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