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By William Conger, Greg Schick

Grinding media consumption is a major cost variable in industrial mineral comminution circuits. Specifically, industrial SAG media consumption results from a combination of surface abrasion wear, media breakage, surface spalling and rejection size from the mill. Three main consumption rates; weight of media consumed per time, per kWh and per weight of ore ground are defined and compared. Recent industrial data has provided an opportunity to relate consumption in terms of weight of media consumed to weight of ore ground (g/tonne) and weight of media consumed per kWh of energy consumed (g/kWh) with SAG specific grinding energy consumed (kWh/tonne). Using relationships developed from this data it is possible to project SAG media consumption in future mineral comminution circuits.

Jan 1, 2014

By Cristian Melipichun, Leopoldo Gutierrez

The effect of the presence of fine particles of kaolinite and montmorillonite on the induction time for attachment of bubbles to particles of a copper concentrate rich in chalcopyrite was evaluated in this study. The results obtained from induction time measurements were correlated with data of concentrate recovery achieved from micro-flotation experiments. The effect of the presence of fine clays on the stability of air-water foams was also studied through measurements of the foam volume generated in a glass column under different conditions of air flowrate and MIBC concentrations. The experimental results showed that induction time values increased under the presence of fine clays. These data agreed with results obtained from micro-flotation experiments that showed that copper concentrate recovery decreased when clay particles were added. Although a complete explanation for these results is not available, the fact that experimental observations indicated that fine clay particles tend to adsorb on gas bubbles, suggests that the interactions between fine phyllosilicate particles and air bubbles have to be taken into account when studying the effect of clays on froth flotation. Foamability tests showed that the presence of fine clay particles increased the foam volumes only at high additions of clays and low dosages of MIBC. The results obtained at higher dosages of MIBC showed that the foam volumes decreased with the addition of clays under all the experimental conditions tested.

Jan 1, 2014

By P. Saha, D. M. Chakrabarti, J. P. Srivastavam, P. Bhattacharyya, B. R. Sarkhel, Banerjeem B.

The phosphatic soil deposit at the Sukulu hills region of Uganda contains 10-12% P2O5. The ore occurs as a naturally degraded soil deposit containing a very sticky slime composed of earthy lateritic minerals. Desliming of the ore, which is imperative for its further beneficiation, is an extremely difficult hurdle to overcome for its commercial utilisation. Earlier studies on samples of the same ore at the National Metallurgical Laboratory (NML) and abroad established that it was necessary to pass the ore through a series of three stages of desliming, each consisting of a step of vigorous attrition scrubbing followed by hydrocycloning, for effective elimination of the sticky slime. In the present paper an innovative use of the very strong shear-fields created inside a hydrocyclone has been discussed, that could effectively eliminate the stubborn slime from the ore. The standard design of the hydrocyclone was suitably modified to increase the shearing effect on the slurry. It was possible, through the application of this modified hydrocyclone, to not only totally eliminate all the stages of attrition scrubbing, but also to reduce the subsequent stages of hydrocycloning. The modified technique yielded a concentrate of grade comparable to that obtained by employing the earlier more complex flow sheet, with about 25% higher P2O5 recovery.

Jan 1, 2003

By Magnus Evertsson, Rebecka Stomvall, Josefine Berntsson

"Understanding the effect of particle shape on dry rheology is considered to be an important aspect in order to replace natural sand used in concrete with manufactured sand. Crushed particles from solid rock are normally less rounded and have less equally shaped dimensions compared to natural sand. Thus, the flowability and workability of the concrete will be different. In previous research, it has been demonstrated how different crushing techniques affects the shape of the particles. In many cases it is believed that Vertical Shaft Impact (VSI) technology is a way forward to replace natural sand. To be able to study the effect of VSI at the smaller fractions (63-2000 µm) sufficient measurements methods to determine particle shape are required. Optical tools to analyze the aggregates would make it possible to study a large amount of particles at small fractions. The determination of particle shape of aggregates is challenging since the shape is highly irregular and the size span of particles are very large. This study aim to evaluate one of the available optical tools, the Camsizer, for digital imaging determination of shape and size distribution. The available default shape parameters of the Camsizer are studied to understand the meaning of the parameters and their suitability for determining the quality of manufactured sand. To evaluate the capacity to determine particle shape, tests are made with 35 different materials. The results are compared with the dry rheology measured with the standardized "flow cone" test. Dependence has been previously proven between particle shape and the mass flow rate in the cone. Three different shape parameters, aspect ratio, sphericity and symmetry, are studied with the Camsizer and the results are compared with the mass flow rates in the cone. The results indicate a strong linear relationship between the optical parameters and the flow cone test."

Jan 1, 2014

By Peter J. Scales

The recovery of water for re-use in minerals processing is an important issue in the reduction of water use in mining, as is the dewatering of tailings to reduce the propensity of ?wet? tailings dams. It is common in these dewatering operations to use thickeners whereby polymeric flocculants are combined with the dilute feed to the thickener to aid sedimentation and the subsequent consolidation of particulate materials. Thickeners are the workhorses of water recovery and tailings dewatering and although the basics are well understood, there is still no ability to reliably predict the throughput and underflow density from a thickener based on traditional sedimentation tests and flux analysis. The reasons for the discrepancy between full-scale operations and predictions based on laboratory tests are numerous, including difficulties in mimicking the flocculation conditions experienced in the field and the shear conditions in the thickener. The latter effects are little understood and hard to quantify and include effects due to flocculated aggregate densification, complimentary shear and compressional effects and aggregate break-up. Developing a set of test protocols to quantify the effects of densification, shear in compression effects and aggregate breakup and the subsequent contributions of each to compressional dewatering in a thickening environment has been completed for a simple model polymer flocculated particulate suspension. The data and analysis shows that aggregate densification is a dominant contributor to the difference between observed and predicted behavior based on laboratory tests. A major consideration in the analysis is the fact that common thickener operations are permeability limited and although the various effects are all important, the one that results in the fastest water release is dominant. Of interest also are the shear rate, concentration, and time dependence of the aggregate densification process. A basic model of the process has been developed along with network yielding tests conducted using rheometry. Keywords: compressional dewatering, gravity thickening, rheometry, aggregate densification, raked batch settling

Sep 1, 2012

By Scott C. Brown, Brij M. Moudgil, Ivan U. Vakarelski

The manipulation of the apparent hydrophobicity of particlute surfaces is necessary to achieve optimal selectivity in flotation processes. Previously a number of works have investigated the role of microscale surface and particulate morphologies on chemically modified substrates. These works have suggested that microscale surface asperities lead to an increase in flotation efficiency by assisting in the rupture of wetting films. Yet, in mineral processing the presence of surface asperities may lead to a reduction in flotation. The reason for this may-in part-be due to the presence of nanoscale irregularities at the interface. In this work, it is proposed that the presence of roughness at the nanoscale may have a dominant impact on the apparent hydrophobicity of mineral surfaces during flotation. It is suggested that as inter-asperity seperation distances are reduced capillary effects are enhanced for high energy mineral surfaces leading to the formation of liquid domains, which adversely impact hydrophobicity. In addition, as these distances approach the surfactant headgroup size obstruction of surfactant self-assembly process may occur, thereby further limiting flotation.

Jan 1, 2003

By P. Huang

Chitosan was tested as a depressant in the differential flotation separation of chalcopyrite and galena. The micro-flotation results showed that chitosan selectively depressed chalcopyrite while galena was floated by potassium ethyl xanthate in acidic solutions. With the addition of 0.67 mg/L chitosan (CT) in the slurry of chalcopyrite-galena mixtures at pH 4, the recovery of galena was 95% while that of chalcopyrite was 30%, indicating that chitosan could potentially be used in differential Cu-Pb sulfide separation. Furthermore, the study of chitosan with either low (LCT) or high molecular weight (HCT) in the differential flotation indicated that better separation was achieved by the chitosan with lower molecular weight (LCT). ToF-SIMS was employed to study the distribution of CT on the surface of chalcopyrite-galena mixtures by ion mass spectra analysis and surface imaging, which showed that CT adsorbed heavily on chalcopyrite but barely adsorbed on galena. The positive ion ToF-SIMS spectra provided information on the surface composition of chalcopyrite-galena mixtures after CT treatment. It appears that the selective adsorption of CT on chalcopyrite was originated from the strong interaction between NH3+ and Cu. Keywords: differential flotation, micro-flotation

Sep 1, 2012

By Dietmar Freyhammer

Grinding is the last stage of the comminution process. In the grinding process the particles size are reduced by impact and attrition stresses. The fine grinding of ores is nowadays finding increased application due to depletion of coarse grained, easily processed ore bodies and the increased need to process distributed fine grained deposits, such fine ground iron ore powder is the basis for the pelletisation process. Depending on the ore type and the project environment different approaches to comminution are requested to provide an adequate ground iron ore for the pelletisation process. Currently the ball mill is the most used equipment in grinding iron ore for pellet feed. Based on the various examination and investigation of minerals on grind ability related to the throughput, to the resulting sieve characteristics and necessary energy consumption, the mill circuit can be: Open dry circuit. Closed dry circuit Open wet circuit Closed wet circuit. CEMTEC GmbH is a renowned name worldwide and offers tailor made solutions to cope these issues.

Sep 1, 2012

By David I. Verrelli, Peter T. L. Koh

"Recent experimental measurements of induction time made by direct observation with the ‘Milli-Timer’ indicated that angular particles were able to attach much more rapidly than spherical particles. There was around a tenfold difference in the respective induction periods for particle-bubble attachment. For industrial application, a more holistic comparison is needed, with the induction period for attachment being just one input. Over the years, CSIRO has developed a CFD-flotation model that incorporates both rigorous hydrodynamics, to simulate real industrial cell geometries, and a detailed model of the embedded flotation process, in which the induction period is an important parameter. We conducted transient modelling of batch flotation. First, spherical particles were modelled, as a ‘baseline’, for different particle sizes and levels of hydrophobicity. In the second set of results, the induction period was decreased by a factor of up to ten, simulating flotation of angular particles. Flotation recovery was found to depend upon induction period in a complex manner. For highly hydrophobic or fine particles, the induction period for spheres was already so low that recovery was limited by other factors (e.g. bubble-particle collision frequency). Further decreases in induction period, as for angular particles, did not have a significant effect on recovery in these cases. By contrast, when weakly hydrophobic or coarse particles were modelled, the recovery was predicted to be greatly enhanced for angular particles, in comparison to spheres. For these particles the induction period was limiting recovery, so that the flotation rate constant could be improved directly by reducing the induction period. This is consistent with batch flotation experiments using Ballotini reported earlier. Therefore, when dealing with weakly hydrophobic particles or relatively large particles that are to be floated, an enhancement can be expected for more angular particle shapes. In such cases, judicious specification of the grinding circuit may improve the overall efficiency."

Jan 1, 2014

By S. Gaydardzhiev

Laboratory batch tests having preliminary and orientation character aiming at improvement of the molybdenum flotation at Ellatzite copper processing plant in Bulgaria have been conducted. The following technological parameters have been screened to study their influence on the grade and recovery of copper and molybdenum during the rougher flotation stage: flotation pulp density, pH, addition of secondary collector and replacement of MIBC by pine oil as a frother. The results have shown that slightly better grade/recovery figures could be obtained for both copper and molybdenum at lower flotation pulp densities. The addition of kerosene has improved the recovery of molybdenum however, on the expense of that of copper. The effects from pH variation and the replacement of MIBC by pine oil as a frother have been almost negligible.

Sep 1, 2012

By J. Yianatos

The cleaning circuit operation and its effect on the plant metallurgical performance, was characterized at Los Pelambres concentrator, Chile. Experimental data from columns, scavenger and regrinding stages was evaluated. Each stage was characterized by size fractions, and the interaction between stages (columns, scavenger, regrinding) as well as the effect that circulating loads had. The approach for describing the flotation equipment operation (cells and columns) considered the collection and froth zones separately. This methodology allows for the identification of the impact that particle size distribution has on the actual collection and froth transport processes, independently. In this way the effect of regrinding on flotation recovery and grade can be related to the corresponding operating variables, e.g. pulp flowrate, air flowrate, pulp level and pulp density, among others. The effect of gangue entrainment was considered using an empirical dimensionless correlation. The interaction between the circulating load and the overall performance of cleaning circuit was evaluated. The circulating load was defined as the ratio between the solid flowrate of scavenger concentrate over rougher concentrate. It was found that the overall cleaning flotation circuit (column-scavenger) can operate at a relatively high and constant recovery for a wide range of mineral treatment. This is possible when the scavenger has the capacity for compensating the decrease in column recovery at larger circulating loads. Under the condition of high overall cleaning recovery, the rougher stage closely represents the plant recovery. However, at large mineral treatment conditions, the design characteristics (e.g. concentrate transport channel capacity and transfer boxes) as well as instrumentation, control facilities and operation, became bottle-necked. A simulator was developed using empirical models for each stage (column, scavenger and regrinding) in order to evaluate proper operational strategies for cleaning flotation circuits Keywords: flotation, cleaning, regrinding, Vertimill, simulation.

Sep 1, 2012

By S. A. Vorobyev, Yu. L. Mikhlin, Ye. V. Tomashevich, A. A. Karacharov, M. N. Likhatski1, A. S. Romanchenko, S. V. Saikova

"A set of state-of-the-art methods have been applied to study ultrafine particles and nanoscale species arising on mineral surfaces upon milling, interaction with flotation reagents, and leaching of base metal sulfide ores in order to gain insights into interfacial mechanisms. The fine fractions produced by ball milling of a Pb-Zn Gorevsky ore and four Cu-Ni sulfide ores studied with laser diffraction, dynamic light scattering, zeta-potential measurement, Xray photoelectron spectroscopy (XPS), SEM, TEM and other techniques. The particle size distributions had, aside from the peaks at 20-60 ?m, maxima near 1-2 ?m; the flotation was considerably suppressed when the yield of positively charged ultrafine particles approached tenths % (several kg per ton). High-energy XPS and X-ray absorption spectra revealed that sulfide minerals depleted in metal in air and aqueous solutions were composed of outer “polysulfide” layers, strata with disulfide species, and heavily defective underlayers, and “passivation” was explained by stability of the metal-deficit structures. Dixanthogen at pyrite and copper-activated sphalerite, dixanthogen and then cuprous xanthate on chalcopyrite, and chemisorbed xanthate at galena were specified as the main interfacial products using cryo-XPS of fast-frozen flotation slurries. The particle size, zeta-potential and behavior of colloids of Cu and Pb xanthates and dixanthogens were largely determined by the initial ratio of a cation and collector; the properties of copper xanthate nanoparticles were also affected by incorporated dixanthogen (about 15 wt.%). Submicrometer gas domains of 3-8 nm in height and “hydrophobic” forces upon the probe retraction were found on xanthate-treated minerals using atomic force microscopy and spectroscopy; their impact on flotation is briefly discussed.INTRODUCTIONInterfacial phenomena play a key role in flotation, leaching, water purification and related environmental processes. The mineral processing and extraction of metal from sulfide ores commonly involves milling the ore, which produces, along with the particles of 20 µm to 100 µm, mineral entities ranging from micrometer to submicrometer and nanometer scale. Furthermore, ultrafine particles of flotation reagents, products of metal sulfide oxidation, and so on may form spontaneously and accumulate in production water, flotation froth, deposit on mineral surfaces, affecting the flotation performance, and then enter waste waters, mine and natural drainage, polluting soils, surface- and ground waters (Miettinen et al., 2010; Wang et al., 2014). The efficiency of flotation and hydrometallurgical recovery of values, environmental issues are crucially dependent on the state of mineral surfaces. Particularly, it is generally accepted that the surface non-stoichiometry of sulfide minerals induced by oxidation and leaching should affect their hydrophobicity and reactivity, including so-called “passivation”, but the nature of such surface layers are still a matter of controversy (see, for example, Holmes and Crundwell, 2013). Another phenomenon attracting rapidly growing interest in several areas is low-dimensional gas species (“nanobubbles”) at hydrophobic surfaces that may play a decisive role in particle-bubble attachment in flotation but remains scarcely investigated up to now (Xing et al., 2017). Here, we survey our recent results on the abovementioned problems applying a series of rather new methods and approaches; more details can be found in refs. Karacharov et al., 2016; Mikhlin et al., 2015; 2016; 2016a; 2016b; 2016c; 2016d; 2017; 2017a; Vorobyev et al., 2017."

Jan 1, 2018

By M. Morales, J. Yianatos

"In this work, an alternative approach to evaluate the flotation performance along a flotation rougher row is presented. The collection zone as well as the froth zone performances were separately evaluated. For this purpose, sampling for metallurgical balances along with sampling of top-of-froth (TOF) grades in each cell of a flotation row were employed. The modelling of the rougher circuit consisted of using TOF grades for evaluating the collection zone recovery, because they are a good representation of the bubble loading, which identifies the true flotation process, as shown in previous studies for shallow froths. In addition, the feed characterization, size-by-liberation, allowed the identification of the mineral distribution and its evolution along the circuit. The latter result was obtained by fitting the recovery profiles as well as the TOF grades down the flotation bank. The flotation rates and the maximum recoveries in terms of size-by-liberation (size classes: -45 µm, +45-150 µm, +150 µm, and liberation classes: -20%, +20%-80%, +80%) were then estimated. The results were in good agreement with those reported in literature by other authors and showed the new approach allows flotation kinetics to be characterized in industrial circuits.INTRODUCTIONMineral recovery in industrial flotation circuits is a function of the mineral characteristics, such as particle size distribution and liberation (Trahar, 1981, Jameson, 2012), and operating conditions such as air flowrate, pulp flowrate, solids percent and reagent conditioning (Jameson 1977; Klimpel, 1980; Mehrotra and Kapur, 1974). The cell type and size (self-aerated or forced air) and the circuit arrangement (single cells or banks of cells in series) are also relevant factors. Sampling of circuits (e.g. rougher, cleaner or scavenger) are commonly carried out using standard automatic samplers for metallurgical balance assessment. However, the flotation plants are generally not provided with proper accesses for local streams, which hinders the recovery estimations and the flotation rate characterization."

Jan 1, 2018

By Stoyan N. Groudev, Ioannis Paspaliaris, Irena I. Spasova, Kostas Komnitsas

"Acid mine drainage waters generated in the uranium deposit Curilo, western Bulgaria, were treated by means of a constructed wetland located in the deposit. The waters had a pH in the range of about 2.5 - 4.1 and contained uranium, radium, some heavy metals (iron, manganese, copper, zinc, cadmium, cobalt, nickel, lead), arsenic and sulphates in concentrations much higher than the relevant permissible levels for waters intended for use in the agriculture and/or industry. The wetland covered an area of about 140 m2 and was characterized by an abundant water and emergent vegetation and a diverse microflora. Typha latifolia, Typha angustifolia and Phragmites australis were the prevalent plant species in the wetland but species of the genera Juncus, Eleocharis, Scirpus, Carex and Poa as well as different algae were also well present.The water treatment was started in July 2001 and until now (August 2002) the wetland effluents were characterized by pollutants concentrations decreased below the relevant permissible levels. The water flow rate through the wetland during this period varied in the range of about 0.2 - 1.0 l/s. The water clean-up markedly depended on the temperature but was efficient even in the cold winter months at air and water temperatures close to 0oC. The removal of pollutants was due to different processes but the microbial dissimilatory sulphate reduction and the sorption of pollutants on organic matter (viable and dead plant and microbial biomass) and clay minerals played the main role. Negative effects of the pollutants on the growth and activity of the indigenous plant and microbial communities were not observed."

Jan 1, 2003

By Francesco Vegliò, Luigi Toro, Francesca Pagnanelli

Different hydro-metallurgical processes have been studied in order to recover manganese(II) from oxidised minerals such as MnO2. An innovative acid reductive leaching carried out in mild experimental conditions was here considered using agricultural and industrial wastes containing carbohydrates as reducing agents. The leaching process was investigated from a kinetic and equilibrium point of view in order to optimise the experimental conditions, develop a kinetic model and obtain high purity concentrated MnSO4 solutions. To study the leaching kinetic a Shrinking Core Model (SCM) was modified by a variable activation energy term to take into account both the variable reagent concentrations and the reaction rate change with respect to the manganese dioxide conversion. The influence of the particle size in the kinetic model is discussed with the support of SEM analysis before and after leaching. Manganese extraction yield was maximised (170-190 g/L) using appropriate carbohydrates and acid excesses, while impurity concentrations were kept low (Fe<10ppm and Ca<300ppm) pre-treating the ores, using hydro-alcoholic leaching medium and different combinations of down-stream processes. In particular precipitation, solvent extraction and adsorption onto active carbon were tested to eliminate Fe and Ca from MnSO4 solutions.

Jan 1, 2003

By Erico Tabosa, Kym Runge, Peter Holtham

"The distribution of turbulence in an industrial scale mechanical flotation cell and its effect on flotation kinetics was studied using a fully instrumented 3m³ cell. The cell was operated at a copper concentrator in Australia with different combinations of airflow rates, impeller speeds and sizes and cell aspect ratio providing a wide range of hydrodynamic conditions. An analysis of the overall flotation cell performance showed that the overall copper recoveries were very similar for the conditions tested. However, by decoupling pulp effects from froth effects it was possible to evaluate whether the changes made affected the pulp zone and/or froth zone responses. The analysis showed that the overall recovery has the potential to be up to 7% higher, if not limited by froth recovery. The cell hydrodynamics were characterised by the overall energy dissipation rate and, to understand the distribution of turbulence within the cell, localised measurements were made using a piezoelectric vibration sensor. By comparing the metallurgical performance of the cell with the different hydrodynamic conditions it was found that the collection zone flotation rate constant was not directly related to overall energy dissipation, as is commonly observed at laboratory scale, where energy is usually only changed by varying impeller speed. In this study, energy dissipation rate was varied using not only impeller speed, but also the size of the impeller and the cell aspect ratio. In these circumstances, the best correlation was found to be between the collection zone flotation rate constant and the distribution of turbulence, i.e. the size of the turbulent zone."

Jan 1, 2014

By Gabriel C. Aguilera, Juan Arismendy

"The effect of rheological factors inside of a hydrocyclone is very relevant for the fluid mechanics and for the classification of materials on suspension, since parameters such viscosity and thixotropy are intrinsic variables that depend of the particulate system and the continuous phase; they determine the efficiency of classification. Nevertheless, the exact knowledge of the main characteristics and magnitudes of them inside the hydrocyclone is very difficult because of the geometry of the hydrocyclone, even more if the hydrocyclone is of small diameter. Hence is not possible to make a hydrodynamic study with effects over classification regarding these variables. This work studies the rheological variables inside a small diameter hydrocyclone that works at high pressures, using the information given by a model of Computational Fluid Dynamics (CFD). The model used includes the Reynolds Stress Model (RSM) for the evaluation of turbulence, and the Volume of Fluid (VOF) to study the interaction between water and air, which is very important to obtain regarding the effect of the air core over the performance of the equipment. The validation of the CFD model was done with a kaolin suspension at several conditions of solids contents below the critical volume fraction, without chemical additive aid. These conditions are representative of current work parameters on plant. As result it could be established the ranges of evaluation of rheological variables on specific regions inside the hydrocyclone, and through a rheometric study, based on the mechanic characteristics previously obtained, the main rheological characteristics of the mineral suspensions were determined."

Jan 1, 2014

By L. Muhr, Y. -T. Tang, M. -O. Simonnot, B. Laubie, R. -L. Qui, Z. Chour

"Agromining aims at recovering metals from different secondary resources with hyperaccumulating plants. These natural plants can selectively concentrate metals at very high level and can be transformed to produce commercial compounds. The classical strategy to recover metals from hyperaccumulator plants is based on hydrometallurgy. It consists of: i) burning the plant to obtain ash, which is a very rich bio-ore without organic matter, ii) transferring the target element(s) into aqueous solution by acid leaching and iii) purifying the leach liquor to obtain the target element(s) in the desired form. This method has enabled us to obtain nickel salts, nickel oxide, zinc and cadmium from different plants. However, it is not possible to apply this approach to recover rare earth elements (REEs) from the fern D. dichotoma, growing on mine tailings in South China. Actually, this plant is very rich in silicon: plant burning gives an amorphous ash, very stable despite severe leaching conditions. Therefore, the strategy has been changed and processes are currently developed to extract REEs by direct leaching of the biomass, without burning the plant. Several conditions (i.e. leaching solutions) have been investigated, showing that a good extraction yield was obtained with HNO3 0.5 N (around 84%). This yield was increased to 99% by adding a complexing resin into the leaching solution. After two-steps of elution, results have shown that is possible to recover 75% of the REEs at 81% purity.INTRODUCTION The demand of rare earth elements (REEs) (including 15 lanthanides, yttrium and scandium) has been growing sharply over the past years, because of their industrial applications. REEs are essential elements for emerging technologies, and are used for example in permanent magnets, lamp phosphors or rechargeable batteries. China is the main producer, and the market supply became tense in 2010 when this country decided to limit exports of these elements. Exploitable mineral resources, as well as REE separation capacity are concentrated in a few countries (e.g. USA, Australia, Malaysia, France), which increases the supply risk. Therefore, these elements are considered as critical raw materials (CRM) for many countries and especially for EU (Fortier and Gambogi, 2017)."

Jan 1, 2018

By Kaiwen Liu

Activated carbon is widely used in the removal of organic and/or inorganic contaminants from waste water due to its high surface area, porous structure, and specific surface reactivity. However, in practical applications, it is difficult to recover the activated carbon completely by screening or classification. In this project,we prepared a magnetic form of activated carbon (magnetic activated carbon or M-AC) by precipitation of iron oxides on the surface of activated carbon. The M-AC can be easily separated from effluents by applying an external magnetic field, thus it can be recycled and regenerated for reuse. M-AC was characterized by X-ray diffraction (XRD), specific surface area measurement, and scanning electron microscope (SEM).XRD results show that the major phase of coated iron oxides on activated carbon is magnetite (Fe3O4). The specific surface area of activated carbon was found to be reduced after the impregnation of magnetite particles on the surface. The SEM micrograph shows the aggregation of the iron oxides on the surface of activated carbon. M-ACwas found effective in removing DETA (diethylenetriamine) species and metal ions from solutions. Cu (II) with initial concentrations from 5 ppm to25 ppm in solution is removed by more than 99% with the addition of 0.1 wt.%ofM-AC. For the removal of 25 ppm DETA species from solution, an addition of 0.5 wt.% of M-AC is required due to the larger size of the DETA molecule. Moreover, M-AC showed a good loadingproperty for nickel and gold ions from solutions. M-ACshows a better adsorption capacityover activated carbon and its potential applications in carbon-in-pulp for gold leaching and waste water treatment. Keywords: magnetic activated carbon (M-AC),diethylenetriamine (DETA),metal ion,adsorption

Sep 1, 2012

By Samira Rashidi, Robert Dunne, Raj Rajamani

"High Pressure Grinding Rolls (HPGR) are known for more energy saving, better particle weakening and higher tonnage compared to semi-autogenous/ball mill circuits. These machines are scaled up based on the roll diameter. Therefore, studies in lab-scale HPGRs are always preferred because less weight of feed sample is required to run batch tests. The 50-hp laboratory-scale machine at the University of Utah is the first-ever lab-scale machine designed by late Prof Schönert, the inventor of HPGR. This 200x100 mm [DxL] HPGR is equipped with a robust data acquisition system, which enables running steady state tests using a feed sample as small as 6 kg to 12 kg. This paper presents the HPGR grinding study on two different categories of ores, one hard ore and the other soft. A test series has been performed to evaluate the energy consumption and the relation with size reduction on open multi-pass and locked-cycle HPGR circuits. The effect of feed size distribution and operating conditions has been investigated. Locked-cycle tests result in higher reduction ratio and higher rate of fines (100 mesh, 48 mesh and 28 mesh) generation when compared to open multi-pass tests. Data shows that scale-up trend lines stay consistent even when the circuit configuration and operating conditions are varied."

Jan 1, 2014