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By G. A. Wierink

This paper discusses a new method to increase flotation recovery. As known from literature, fine and coarse particles have different flotation rate constants, hydrodynamic behaviour and require different reagent regimes. The device discussed allows separate processing of finer and coarser slurry by extraction of a third stream, carrying finer slurry, from the flotation cell. By separate treatment of fine and coarse slurry operational conditions and so flotation recovery for both may be optimized more efficiently. Extraction and classification of the third stream is accomplished by low speed centrifugation and Taylor-Couette flow separation. This Dual Outlet Device (DOD) can be installed in a traditional flotation cell without need for equipment replacement. In order to asses different design options for the DOD a transparent laboratory scale model was built. For this scale model Computational Fluid Dynamics (CFD) simulations using the RANS k-e and LES turbulence models were performed. Essential insight in the dominant flow systems relevant to optimal operation of the DOD was obtained from the CFD simulations and flow visualization tests with the laboratory scale model. Based on these findings a number of configurations were investigated at pilot plant scale in a 5 m3 Outokumpu flotation cell. The results of the pilot plant study show that utilization of the DOD provides a method for in-cell control over particle size distribution in the slurry. Use of the DOD in a flotation cell may enhance flotation recovery and decrease flotation reagent consumption significantly, against marginal investment and operation costs.

Jan 1, 2014

By S. V. Bogdanov, S. I. Grishaev

"The article presents the materials about the appropriateness of the use of rental indices to assess the effectiveness of the use of deposits of rare earth elements (REE). The authors suggest from the standpoint of rent payments to rate for the owner the possibility of using the anticipated rental income as the indicator for the analysis of preferences and economic significance of enrichment of extracted raw materials in the emerging field of rare earth metals (REE). Usually from ore mined at the fields, for flotation technology to produce concentrates with collective REE, then they are subjected to chemical-metallurgical processing of the received products are divided into pure oxides, chemical compounds or isolated from them pure metals and alloys. This commercial product is shipped to the buyer. REE were a non-renewable natural resources, so the calculations for determining differential and specific rent showed that during the development of the technologies of mineral processing of a specific field it is necessary to consider what the expected rental income depends on the magnitude of differential rent is related to the volume of production of REE for the whole planned period of exploitation of natural resources. This income is determined by the amount of stock field. For long-term exploitation of the deposit is observed in almost direct proportional dependence between the annual differential rent and the rental income. The decrease in rents in the long run is determined by the change in the composition of ores included in the extracted raw materials and the balance between light and heavy REE. The largest 70% reduction of the rent projected for ""cerium"" fields, while for ""yttrium"" these losses are considerably smaller. Tomtor, Chuktukon and Katuginskoye Russian deposits are characterized by a level of rent that is comparable to the mastered foreign sources of REE. Thus, the enrichment of minerals with REM in the domestic deposits is quite competitive at the world level. INTRODUCTION Deposits of rare earth metals (REE) are non-renewable resources that should be developed and used so that it would be possible to provide a reduction due to payment of appropriate resources for future generations. This compensation, due to the reduction of natural resources, can be carried out both in natural and in economic terms (1). When analyzing economic compensation options, particular attention should be paid to rental income in assessing the attractiveness of using different REE deposits. It is known that absolute and differential rents are summands when calculating the value of natural rents. The value of the absolute natural rent is proportional to the unit price of the product obtained from mineral raw materials and sold on the commodity market. Limitations, as well as the use in production processes and business, contribute to the gradual reduction of natural resources, which increases their consumer value and affects the price of commodity products from primary raw materials."

Jan 1, 2018

By Hakan Gürsoy, Kemal Bilir, Bahri Öteyaka, Ali Uçar, Oktay Sahbaz

"Jet diffuser flotation column (JDFC) is a flotation device resembles Jameson flotation cell (JFC) in terms of operational principles, but it has significant difference structural points of view. This difference is an essential change in the downcomer to provide an increase of performance of the cell for the coarse particles. By using the hydrodynamic and fluid mechanics principles (Sahbaz et al., 2013) downcomer was changed as a diffuser, therefore turbulence at the end of the downcomer was reduced to provide better aggregate stability and homogeneous dissipation of the bubbles in the separation tank. According to experimental results carried out in pilot scale JDFC, not only higher flotation performance comparing with Jameson cell was obtained specifically for coarse talc particles in a certain condition, but also quiescent froth layer was acquired. In these tests, vertical pipe of JDFC having inlet diameter of 6 cm and outlet diameter of 11.5 cm was used with separation tank having the diameter of 39 cm. By using the data, pilot scale JDFC having 410 cm vertical pipe integrated with separation tank was produced and flotation tests were carried out by using the naturally hydrophobic mineral (talc). Finally, the talc recovery obtained as 94% by the use of JDFC, while Jameson cell has the recovery of 77% for the particle size of 250 µm."

Jan 1, 2014

By Olga D. Khmelnitskaya

The paper presents the results of research on the development of gold recovery technology from oxidized gold-copper ore of one of deposits in Russian Federation. Gold and copper grades in the ore are 9.5 g/t and 0.4%, respectively. Various options of flowsheets, such as direct cyanidation, thiourea leaching, flotation and gravity concentration followed by subsequent cyanidation of con-centration products, were tested. It was established that gravity-cyanidation technology with filtra-tion leaching tails and the use of solutions in the recirculation is the optimal option for ore treatment. The proposed flowsheet provides gold recovery for 91.0% at NaCN consumption 2.5 kg/t ac-cording to the results of pilot testing. Ammonia-cyanide gold leaching was also examined. In comparison with cyanidation, gold leaching solution in system NaCN-NH4OH-(NH4)2CO3 allows NaCN consumption to be reduced three times from 4.5 kg to 1.5 kg per 1 ton of the ore and provides the same gold recovery. Based on the laboratory and pilot plant tests results of gravity-cyanidation technology of gold dissolution, process design criteria were developed.

Jan 1, 2014

By Katsunori Okaya, Toshio Inoue

"Movement of mill charge in the centrifugal mill is essentially dissimilar from that in the vibration mill with circular path despite the apparently similar mode in the motion of mill body. This dissimilarity is the reason for the substantial advantage regarding the comminution intensity of the centrifugal mill over the conventional vibration mill accounting approximately to one order of magnitude.Bradley et al. (1983) developed a math model regarding the mill charge as a lump. This model is presented in a simple equation with which motion of the mill charge can be predicted in terms of the parameters describing the specification and the operation of the centrifugal mill. This equation can be used to explain the power draft of the mill as well as the stability of mill operation. More recently, on the other hand, a numerical simulation technology called discrete element method (DEM) has become a vital vehicle for estimating the motion of the grinding media in the mill. The authors developed a mill simulator called ‘Mill Solver’. Mill Solver is designed to simulate various types of mills including centrifugal and vibration mills. The principle of this simulator is to calculate individual kinetic events of interaction of balls in the mill in a minute time interval, hence the mill performance can be constructed for estimation."

Jan 1, 2003

By G. S. Hansford, G. E. Searby

"Ferrous iron oxidation kinetics was measured in continuous culture at temperatures between 65 and 75ºC, using thermophilic microbes suitable for high temperature bioleaching. The resulting specific oxidation rates were modelled as a function of the ferric/ferrous iron ratio. The results were compared to those obtained by conventional mesophilic microbes.Microbially mediated ferrous iron oxidation is a vital sub-process in the mesophilic bioleaching of sulfide minerals and is expected to be of similar importance at elevated temperatures using thermophilicmicrobes.A thermophilic archaeal culture used in chalcopyrite bioleaching was successfully grown in continuous culture on ferrous sulfate, indicating the capability of the microbes to sustain growth for long periods on the energy provided by the conversion of ferrous iron to ferric iron, the primary leaching agent in sulfide mineral bioleaching.Steady state data was obtained at residence times of between 70 and 10 hours, with washout occurring at residence times between 11 and 9 hours, corresponding to a maximum growth rate (µmax) of between 0.09 and 0.11 hr-1. The reactions were followed by measurements of the solution redox potential, soluble iron concentrations, and offgas analysis of the oxygen and carbon dioxide utilisation rates."

Jan 1, 2003

By S. S. Lu

In sodium oleate and salicylhydroxamic acid systems, sequence of floatability of three sulfate minerals is: barite>celestite>gypsum, in lauryl amine system is: gypsum>celestite>barite. XPS and infrared spectrum analysis are used to find that it is chemical reaction between sodium oleate and three minerals, physical adsorption on the surface of minerals for lauryl amine, and it is chelating reaction between salicylhydroxamic acid and three minerals possibly. Theoretical calculation on chemical bonds in crystal structures of three minerals is carried out, finding that breaking degree of Mn+?O2- in crystal structures of three sulfate minerals is closed related with floatability.

Jan 1, 2014

By Hamid-Reza Manouchehri, Hassna Aitahmed-Ali, Stellan Sundberg

"In flotation practices as the particle size becomes fine, e.g., p<20µm, the process efficiency declines markedly. When flotation of fine particles is necessary, one method to improve the recovery is selective agglomeration of fines. Different agglomerating methods have been introduced and tested; however, one method which has recently received great attention is to aggregate fine particles by magnetic force. A selective aggregation of the fine paramagnetic particles, e.g., sulfide minerals, can be achieved by applying a high intensity magnetic field during flotation conditioning. The method is simple, selective and effective for fines, and has a low operation cost. However, a minimum magnetic susceptibility of fine grains is required for this process. This method has been demonstrated in different sulfide minerals flotation plants. The implementation of the magnetic conditioning device, ProFlote, in both the Cu-Pb and the Zn circuit of Boliden’s Garpenberg plant in Sweden, where a complex massive sulfide ore is treated, is discussed herein. The preliminary results have shown an increase in the recovery of value minerals, in particular Zn and Ag and considerable reduction in Zn deportment to the final tail. Increases in Cu grade and decreases in Pb grade in Cu-con have been achieved as well."

Jan 1, 2014

By Vladimir Vigdergauz, Sergey Kondratiev

The paper reviews the existing criteria of the formation of particle-bubble aggregates during flotation. It is shown that predictions obtained by these criteria do not completely fit to the interaction between mineral particles and air bubbles. Experimental results of the studies into the influence exerted by molecular forms of collectors on the particle-bubble interaction are reported. Rate of dry spot expansion on the surface of pyrite with various combinations of chemically and physically adsorbed xanthate are examined. It is shown that molecular forms of collectors accelerate the rate of dry spot expansion on the mineral surface after the local rupture of the water film between particle and air bubble. The authors come to a conclusion that the molecular forms of collectors remove water from the interlayer between mineral particle and air bubble during their contact. Similarities of the proposed mechanism with the action of ion-molecular associates of fatty acids and amines are discussed. Reagents with high surface pressure and rate of spreading at the water-bubble interface are required for the effective interfacial dewatering. It is concluded that the value of surface pressure can serve as the criterion for efficiency of physically adsorbed reagents. The low surface pressure indicates weak collecting ability but high selectivity of the collector. Therefore, the presence of the molecular forms of collectors in the sorption layer is the necessary condition for formation of particle-bubble aggregates, and comparison of the surface tensions of collectors could be recommended as the estimation criterion of their flotation activity and selectivity.

Jan 1, 2014

By Derek Caizergues, Hurman Eric

The principle of carbothermic reduction has been around for many years. In principle it is a simple process, yet with a multitude of problems. The temperature required to affect reduction is in the region of 2200ºC and results in aluminium oxy-carbide formation rather than metallic aluminium. From a thermodynamic point of view, reducing the temperatures of reaction which would suppress oxy-carbide formation would only be possible by lowering the total pressure of the system. A decrease in thermodynamic activity of product aluminium by dissolving it in another phase would also help preventing the formation of oxy-carbides and would also increase the yield of the reduction reaction. Thus experiments have been conducted at around 1700ºC to determine the possibility of carbothermic reduction of alumina under the presence of a metallic solvent. Total pressure of the system was reduced to around 30kPa and metallic nickel, iron, copper and tin were selected as the solvent. The highest recovery of aluminium was achieved with the nickel solvent followed by iron, copper and tin. This ranking for the first three was also in accord with the extent of negative deviation form ideality in the respective binary solutions of these solvents with aluminium. The tin-aluminium system displays positive deviation form ideality. The rate and extent of reduction was found to be highly dependent on temperature and pressure. The pseudo first order reaction rate was found to be applicable to the process in all the solvents used. Rate constants were calculated and it is also suggested that the reduction was controlled primarily by the chemical reaction rate.

Jan 1, 2003

By J. Gebhardt, D. McBride, M. Cross, S. Gilbert

Heap leaching of ores containing chalcopyrite offers a low cost option to treat low grade complex copper sulfide ore bodies. However, the slow leach kinetics of chalcopyrite at ambient conditions typically results in unacceptably low recoveries. As the mineralogy of new ore deposits becomes more complex and the effects of gangue chemistry exert a greater influence on copper sulfide leach behavior, the control of leach reaction chemistry becomes more critical. Computational fluid dynamics (CFD) technology has been useful in the capture of multi-phase interactions and provides a path to simulate complex fluid flow, gas and liquid phases, through the heap, along with species transport. Coupling the flow models with the reactive mineral dissolution, and the sometimes competing aqueous chemical and solid-liquid reactions, yields a comprehensive model of the heap leach process. The leach kinetics of chalcopyrite dissolution in heap conditions is examined, and the incorporation of chalcopyrite leach kinetics in the CFD model is described. The application of the model to investigate optimization of the heap is discussed.

Jan 1, 2014

By Markus Dammers, Christopher Robben, Hermann Wotruba, Christian Schropp

"In most underground mining processes the entire extracted ore is transported from underground workings to surface processing plants for separation of valuable minerals and gangue material. Most of the transported material consists of barren rock with negligible metal content, especially for low grade deposits, such as in the copper or gold metal ore mining. Increasing mining depths result in higher costs for transportation and hoisting. Therefore, rejecting waste rock as soon as possible from the material stream gains importance. The concept of resource to product integration in the form of earliest waste rejection in combination with subsequent backfilling follows the philosophy of ‚leaving waste underground?. Implementing mineral processing underground can lead to less required mass movement to surface, hence reducing transportation and hoisting costs. At the same time, rejected waste can be used as backfill to increase extraction rates by reducing pillar volumes. In the mill, a stable high grade feed leads to decreased specific operating and investment costs as well as increased productivity and recovery. These effects as a whole have a large potential to reduce cut-off grades so that resources can be turned into reserves. Within the I²Mine (Innovative Technologies and Concepts for the Intelligent Deep Mine of the Future) project of the European FP7, investigations are carried out by the Unit of Mineral Processing of RWTH Aachen University, the Institute of Mining Engineering I and TOMRA Sorting Solutions | Mining. One aim of the cooperation is to develop new concepts for a comprehensive integration of near-to-face processing in combination with backfill into the overall underground mining process. Effects on up-, down- and side-streams are investigated to prove the potential of resource to product integration in comparison to common underground mining systems and processing methods."

Jan 1, 2014

By Yi-jun Cao, Jin-cai Ran, Guo-sheng Li, Jiong-tian Liu, Li-jun Deng, Shu-lei Li

A fly ash sample from a power station in Guangdong province has been characterized by size separation, X-ray diffraction, contact angle measurements and X-ray Fluorescence. The ash sample had a loss-on-ignition (LOI) (%) of 15.54% and a large proportion of the unburned carbon was distributed in the +74 µm and -20 µm fractions. Contact angle measurements suggested that the removal of unburned carbon from the fly ash using flotation would present some challenges. The effects of various operating variables on the removal rate of unburned carbon (RUC) (%) and (LOI) (%) were determined using a cyclonic-static micro bubble flotation column (FCSMC). Within the range studied, the optimum diesel oil dosage was 1200 g/t, abies oil (frother) dosage was 600 g/t, pulp density was 20%, superficial gas velocity was 1.4 cm/s and circulating pressure was 0.20Mpa. Column flotation tests indicated that the FCSMC method a viable and effective separation process for removing the unburned carbon from the fly ash. Under the optimized conditions, a clean ash with 2.13% LOI and 94.21% RUC was obtained.

Jan 1, 2014

By Ersin Yazici, Ahmet Bas, Haci Deveci

Pregnant leach solutions from waste of printed circuit boards (WPCB) leaching contain many impurity metals (Fe in particular) at significant levels. These impurities should be reduced to acceptable levels to avoid problems in downstream recovery processes e.g., low current efficiencies in electro-winning of copper from sulfate solutions in the presence of ferric. In this study, removal of iron in the form of goethite from synthetic (30 g/L Cu2+ and 1 M SO42-) and real leach solutions of WPCB was studied in some detail. The influences of initial concentration of iron (1-4.5 g/L Fe3+), pH (2.5-4.0), temperature (80-90°C) and seeding (23.5 g/L) were investigated over a period of 4 h. A significant increase in the iron precipitation was observed (i.e., from 68% to 96% over 4 h) with rising the pH from 2.5 to 4.0. The addition of seeds had also increased the removal rate over 4 h albeit to a limited extent i.e., from 96% to 99%. For the real leach solutions of sulfate (H2SO4-H2O2) and sulfate/chloride leaching (H2SO4-CuSO4-NaCl), precipitation of iron was found to be 63-73% (pH 2.5) and 93-98% (pH 4.0), respectively. The precipitates were further characterised by SEM-EDS analysis which showed the presence of copper (1-25%) in the precipitates indicating significant copper co-precipitation from the solution. These copper losses can be attributed to the formation of copper compounds such as anthlerite and brochantite within the range of pH (2.5-4.0) tested. This study showed that iron can be readily removed from synthetic/real leach solutions of WPCBs to a large extent (=93%) at the expense of high copper losses particularly at pH 4.0.

Jan 1, 2014

By Dilip. Makhija, Asim. K. Mukherjee, Tamal Ghosh, Abhay Patra

In India around 15-20% of Run of Mine (ROM) from any iron ore deposit reports to slime dams as byproduct of iron ore beneficiation process. The proportion of iron ore slime to ROM will increase in future with higher proportion of lean grade ores in ROM. Furthermore, tonnages of iron ore slime will also increase with increasing demand of iron concentrate. Presently, this slime is stored in the dam in the absence of beneficiation technology. A beneficiation flowsheet has been developed at Tata Steel. This process produced concentrate of 2.2% alumina with 40 % yield from slime of 7-9% alumina. The iron content in the reject will be less than 40% thus adhering to the regulatory norm. Pilot scale study show waste from slime beneficiation is a good raw material for making a variety of building materials. Waste from slime beneficiation also has soil amendment properties. Pilot scale studies show productivity of rice increased when the waste of slime beneficiation process is mixed with soil. On commercialization of this zero waste technology slime generated from the iron ore washing plant will be completely used. In this paper the result of the pilot scale studies on slime beneficiation and utilization processes towards soil making and making of building materials are discussed in detail.

Jan 1, 2014

By A. J. Lynch, L. Ergun, M. Oner

"A research program on modelling cement grinding circuits has been in operation at Hacettepe University, Ankara, for four years. It has concentrated so far on tube mill and air separator grinding circuits for cement clinker, with emphasis on plant sampling surveys, including axial sampling inside the tube mills. The data used for model development have come from 33 surveys in 9 plants.The operating conditions have been:- mill sizes - 3.2 to 4.8 metres diameter and 8.5 to 15 metres long,- mill feed rates - 46 to 158 tonnes per hour,- air flow through mills - 25000 to 125000 cubic metres per hour,- cement clinker work indexes - 10.3 to 18,- separator sizes - 2. to 3.1 metres diameter,- separator feed rates - 132 to 689 tonnes per hour,- separator speeds - 12.3 to 21 metres per second.The ball mill model is Whiten’s perfect mixing model and the separator model is the Tromp curve with a fish-hook. This paper emphasises the importance of calculating the breakage rates and the discharge functions with three case studies at five different circuits which were selected for discussion because they show how particular features of circuit operation can be included in the general models. Size distribution graphs are used to illustrate every aspect of the discussion"

Jan 1, 2003

By Z. Kwela, A. Manhique, W. W. Focke, W. van der Merwe

"The main features of the de Wet improved alkali fusion process for the manufacture of AZST are: Fewer process are steps necessary; radioactivity is removed by leaching rather than by precipitation; fewer waste streams are generated; there is less waste to discard and alkali reagent is recovered in the form of a sodium silicate solution that is essentially free of radioactivity.Here we report on our efforts maximize the alkali recovery in the sodium silicate product stream: Milled zircon, d50 ˜ 9 µm, was fused with caustic soda pearls in open reaction vessels at temperatures between 650°C and 850°C. Fusion times of 1, 2, 4, 24 and 336 hours (with intermittent milling) were investigated. The fusion products were characterized by infrared spectroscopy, X-ray diffraction and by wet chemical analysis.For prolonged fusion times the fusion products approached equilibrium compositions. However, the phases Na2ZrSiO5 and Na4Zr2Si3O12 observed at 850°C did not form at 650°C. Since these compounds do not hydrolyze in water they limit the recovery of alkali in the sodium silicate product stream. For 2-hour fusions a broad spectrum of non-equilibrium reaction-products, that are rich in sodium silicates, is formed."

Jan 1, 2003

By A. Ekrem Yüce, Gülay Bulut, Feridun Boylu, Vecihi Gürkan, Istanbul Technical University, H. MustafaTarkan

"Nickel sulphide ores subjected to this investigation were taken from Orhaneli district where widespread chromite mineralisation can be occurred. Significant amounts of magnetite and chromite have been existed in the ore together with sulphide and oxide type nickel minerals. Ore sample is constituted about 70% magnetite, 15% sulphide minerals, 5% chromite and iron oxides as well as 10% gangue minerals.According to the chemical analysis results, the representative ore sample contains 1.32% Ni, 10.8% SiO2, 78.4% Fe2O3, 1.3 g/t Ag and 1.0 g/t Au. Mineralogical examinations showed that pentlandite (Fe, Ni)9S8, violarite (Ni, Fe)3S4, millerite NiS and asbolane (Co, Ni)MnO2.(OH)2.1-2H2O were the main nickel minerals and magnetite, chromite, chromium spinals, pyrite, pyrhotite, chalcopyrite, cubanite, goethite, hematite, limonite, rutile, chlorite, talc and serpentine group minerals as associated minerals.The aim of this investigation was to produce valuable nickel concentrates by using gravity separation, magnetic separation and flotation methods. As a results of laboratory scale studies, alternative flow sheets for the production of nickel sulphide concentrate were developed. The related experimental results are given in Table 1."

Jan 1, 2003

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisinger

"INTRODUCTIONThe objective of this work was to deport silver into a residue suitable for subsequent extraction without compromising the high base metal extraction during the pressure oxidation.RESULTS AND DISCUSSIONThe complex sulphide from the tailing pond of Cannington mine, Australia, was re-grounded and a bulk concentrate was recovered by flotation. The major economic sulphides are galena and sphalerite. The chemical analyses revealed 17.22% Fe; 4.88% Zn; 8.22% Pb; 9.49% S2- and 422 g/t Ag. The baseline cyanidation yielded 36.60% of silver at high cyanide consumption (24.17 kg/t NaCN). Pressure oxidation at 150°C (in the absence of iodide), followed by cyanidation of the residue yielded 8% silver extraction. Pressure oxidation was carried out at 110-150°C in sulphate media with additions of potassium iodide and the resulting residue was subjected to cyanidation. High recovery of silver was achieved because its incorporation into lead-hydronium jarosite during the pressure oxidation was minimised, while its deportment into the cyanide-soluble silver iodide was favoured (Figure 1). Silver recovery decreased slightly at high temperatures (140° and 150°C) because of the enhanced stability and kinetics of leadhydronium jarosite, but this could be overcome by increasing acidity and iodide concentration of the slurry."

Jan 1, 2003

By G. Granata, C. Tokoro, T. Kato

The rare earth elements (REE) are composed of 17 elements that are 15 elements of lanthanide added scandium and yttrium. REE are divided into light rare earth elements (LREE) and heavy rare earth elements (HREE). Although the supply source of LREE is distributed around the world, the supply sources are unevenly distributed. Thus, the development of a new HREE supply source is required. In this study, we focused on the weathered residual rare earth ore as a new HREE supply source. Since so far this weathered residual rare earth ore could not be treated neither by flotation nor by wet high intensity magnetic separation, it was not considered as HREE resource before. In this study, we investigated the leaching of HREE from the weathered residual rare earth ore and elucidated the effectiveness of planetary milling with sodium hydroxide as a method to enhance their recovery. For this purpose, the weathered residual rare earth ore was first grinded by planetary mill in the presence of sodium hydroxide and then leached by sulfuric acid. The influence of planetary milling on HREE recovery was investigated by assisting the leaching experiments with X-ray absorption fine structure (XAFS) in cerium and yttrium K-edge. Since yttrium was the most contained HREE in the weathered residual rare earth ore used in this study, we focused on yttrium in XAFS analysis. Results clearly showed that the recovery of HREE increased by planetary milling with sodium hydroxide. XAFS analysis revealed that a part of the yttrium in the weathered residual rare earth ore was changed to yttrium hydroxide by planetary milling with sodium hydroxide. It is supposed that all HREE were affected like yttrium due to a similar behavior observed in leaching.

Jan 1, 2018