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By M. Kanuchová, J. Briancin, M. Achimovicová

"Faculty of Mining, Ecology, Process Control and Geotechnology, Technical University, Košice, Slovakia An industrial eccentric vibratory mill was used for direct and short-time mechanochemical reduction of ilmenite concentrate (FeTiO3) and anatase (TiO2) with magnesium metal powder in order to reduce Fe and Ti resp. and hereby to convert them to the more soluble phases suitable for further hydrometallurgical processing. X-ray diffraction analysis of FeTiO3 after 60 min of milling with Mg confirmed the presence of Fe0 and Mg2TiO4 phases and for TiO2 after 180 min of milling the new TiO and MgO phases have appeared. X-ray photoelectron spectroscopy has detected Fe0 (metal) and Mg2+ species which are corresponding to the product of FeTiO3 mechanochemical reduction. The product of TiO2 mechanochemical reduction has revealed XPS spectral lines corresponding to Ti2+, Ti4+ and Mg2+ species on its surface. Morphology of mechanochemically reduced samples was studied by scanning electron microscopy analysis. Subsequent leaching of mechanochemically reduced FeTiO3 and TiO2 was performed in dilute HCl and H2SO4 at 80oC and compared with mechanically activated samples. The recovery of Ti has reached 100% for FeTiO3 and 79% for TiO2 after 60 min of leaching. Based on this study the flowsheet for possible processing of natural refractory titanium ores patented by author was adapted and documented. INTRODUCTION Ilmenite (FeTiO3), along with rutile (TiO2) represents the most important titanium resource necessary for titanium industry, for production of titanium metal, alloys and pigment grade TiO2 which are becoming more important and versatile for various industries such as an aircraft and aerospace, navy, chemical, automotive, medical and offshore wind industries, for machine and plant engineering and architecture as well, mainly due to high corrosion resistance. Pigment grade TiO2 is utilizing in pigment, plastic, glass, paper and rubber industries (Zhang, 2011). There are obvious research efforts for development of the potential alternatives to the expensive thermo-chemical commercial processes of titanium raw materials processing. Zhang (2011) has summarized conventional thermo- a electrochemical processes which involved a combination of pyrometallurgical, hydrometallurgical and electrometallurgical technologies and highlighted the improved hydrometallurgical routes promising for commercial application in the future. Such improvement could also be mechanical activation of FeTiO3, TiO2 by high-energy milling which causes their structural disordering, the changes of physical and chemical properties, consequently and has a positive effect on the dissolution kinetics (Achimovicová et al., 2014a, 2017, Baláž, 2008). The various types of mills such as a planetary ball mill, a vertical ball mill, a drum mill, an attritor were used for mechanical activation of FeTiO3 as a pretreatment process for subsequent leaching (Achimovicová et al., 2014)."

Jan 1, 2018

By Osvaldo A. Bascur, J. Pat Kennedy

"The profitability of mining and metallurgical operations continues to lag behind that of other industries despite the technical advances that have occurred in recent years. A primary reason for poor performing in this economic sector is the lack of integration of mining and metallurgical information. The mine cut-off grade can be optimized if mining and metallurgical engineers have the data to optimize milling for the type of ore in hand.Integration of mine transactions, stockpile inventories, process flows and assays is the key to determining the economics for each blast strategy in a mining site. Real-time information from manufacturing assets greatly affects the profitability and flexibility of a company, but gross errors from faulty sensors, inaccurate instrument calibration, or incorrect process models may corrupt actionable information. New software tools can model the process, sift through available data to identify and eliminate gross errors, and use statistical data reconciliation to create materially balanced and consistent readings. The reconciled data is unified for use by both monitoring and decision making processes.Creating a real-time information environment where upgrade and change are allowed is becoming an accepted methodology to accelerate and simplify the integration of applications such as production monitoring, equipment performance management and yield and inventory management.This paper describes the data integration requirements in a mine, concentrator and port for unification of the redundant data. The capture of the mining events, stock pile management and the metallurgical information is the base requirements for a dynamic environment to reduce the overwhelming amount of information to unified set of information. Part of any decision support program should entail these results to continuously improve the measurement system to address the costs in mine and milling the ore."

Jan 1, 2003

By K. Haga

In this study, flotation tests were performed to investigate behavior of enargite and chalcopyrite ores from different sources synthetically mixed for separation of enargite. Flotation parameters including; pH, reagents concentration and type and flotation time were controlled to obtain an enargite concentrate with high As and chalcopyrite concentrate and final tailings with As content below 0.5 mass%. The copper ore bearing enargite mineral contained 5.87 mass% As and 16.50 mass% Cu while the chalcopyrite bearing ore contained 0.32 mass% As and 21.63 mass% Cu. The two ore samples were mixed at 7:3 (enargite: chalcopyrite) by weight ratio to prepare a mixed ore sample with arsenic content at 3.16 mass% and 18.25 mass% Cu for the flotation study. For enargite single ore flotation, the 38?75 µm size fraction showed that over 98% enargite was selectively recovered within 5 min at slurry pH of 4.0 and arsenic content in the final tailings was reduced to 0.22 mass%. In mix ore (enargite+chalcopyrite) flotation, 97% of enargite was first removed at pH 4 followed by chalcopyrite flotation at pH 8, and over 95% recovery was achieved in 15 min flotation time. Arsenic content in the final tailings was reduced to 0.1 mass%.

Sep 1, 2012

By Knut L. Sandvik, Erik Larsen

Crystalline silicon solar cells are the most important solar cells manufactured today. This will most probably remain the situation the next decade. The future silicon feedstock is most likely not reject from the production of electronic-grade silicon. There will probably be a more direct solar-grade silicon route, excluding the electronic-grade silicon "detour". Estimated global solar energy demand in 2001 required approximately 5,500 tons of silicon feedstock. This required 65,000 tons of quartz. If the trend continues, the solar energy demand in 2010 would require approximately 30,000 tons of silicon feedstock and 350,000 tons of quartz, although the need for quartz probably will be lower than this. Quartzite has been regarded as the most suitable primary raw material used in the silicon solar cell production chain. This may change as the raw material requirements for the production of metallurgical-grade silicon are most likely to change. In addition, quartz or other silica-containing minerals from other rocks may be of a higher purity or contain lesser amounts of the most harmful elements. This favours increased beneficiation of primary raw materials in the future solar silicon feedstock production chain.

Jan 1, 2003

By Z. Y. Ma, M. D. Liu, Z. Z. Liu, J. K. Zhou

"An optimization method of microwave assisted leaching of copper anode slime was proposed based on Taguchi method. The results showed that the solid-liquid ratio was the most important factor affecting SNR(signal noise ratio) of the copper, tellurium and selenium leaching efficiencies, and its contributions to the copper, tellurium and selenium leaching efficiencies were 58.34%, 55.54% and 60.74%, respectively. Solid-liquid ratio was a significant factor to SNR(copper, tellurium and selenium). Reaction period was a less significant factor to SNR(copper and tellurium) and concentration of sulphuric acid was a less significant factor to SNR(selenium) while microwave power was an non-significant factor, its contributions to the copper, tellurium and selenium efficiencies were 3.22%, 11.73% and 12.73%, respectively. The optimized parameters of the microwave assisted leaching of copper were as follow: microwave power of 500 W, reaction period of 10 min, solid-liquid ratio of 0.10 g·mL-1 and H2SO4 concentration of 1.0 mol·L-1. The optimized parameters of the microwave assisted leaching of tellurium and selenium were as follow: microwave power of 800 W, reaction period of 15 min, solid-liquid ratio of 0.10 g·mL-1 and H2SO4 concentration of 1.0 mol·L-1. The validation experiments under the optimized conditions has been carried out, the copper, tellurium and selenium leaching efficiencies were 98.66%, 84.32% and 64.54%, respectively. INTRODUCTION As important valuable by-products, copper anode slimes are collected from the bottom of the electrolytic bath in the electrolytic copper refining process(Kilic, 2013). The value of the anode slime is determined by the content of rare metals and precious metals(Liu, 2014). Generally, pretreatment of copper anode slime is the first stage of the whole process. The aim of the pretreatment process is to remove Cu, Te and Se etc and enrich the valuable metals. The methods of pretreatment process can be differentiated into: pyrometallurgical processing and hydrometallurgical processing(Amer, 2003). The hydrometallurgical processes are more promising compared to pyrometallurgical processes in terms of cost effectiveness, low energy consumption and environmental concerns(Ranjbar, 2014). However, the disadvantages of the hydrometallurgy process are evident, such as lengthy processing times and low efficiency. Therefore, it is necessary to develop a highly efficient and environmentally friendly pretreatment method."

Jan 1, 2018

By L. Ya Agapova

Emissions from pyrometallurgical processing of copper concentrates are usually subjected to wet scrubbing. The washing sulphuric acid so produced contains up to 0.2 g/L of rhenium, which is recovered by solvent extraction in the form of crude ammonia permeate (NH4ReO4). The mother liquor, obtained from the sulfuric acid wash, contains up to 35 g/L of rhenium and significant amounts of impurities. Crude rhenium salt is commonly processed by double recrystallization to produce marketable salt. A ton of high grade NH4ReO4 can be produced using 3.0-3.5 m3 of mother liquor. We propose an efficient technology of mother liquor pre-treatment aimed at removal of water-soluble organics with subsequent electrodialysis. Electrodialysis of mother liquor in a multichamber electrodialyzer resulted in the production of pure rhenium acid, from which a marketable NH4ReO4 is precipitated using ammonia solution. Multiple steps of recycling consisting of dissolution of NH4ReO4 salt, rhenium acid production from NH4ReO4 salt by electrodialysis and precipitation of NH4ReO4 from rhenium acid made it possible to upgrade the purity of obtained rhenium compounds by 1-2 orders of magnitude. A rhenium metal powder of 99.997% purity was produced by high-temperature reduction of high-purity NH4ReO4 with gaseous hydrogen. Rhenium metal powder of high purity can be produced from sulfate solutions of NH4ReO4 by non-platinum anode-based membrane electrolysis processes also. Keywords: rhenium, mother liquors, membranes, electrodialysis, rhenium acid, ammonia perrhenate, reduction, powder, electrolysis

Sep 1, 2012

By N. Acarkan

Slags usually contain some quantity of valuable metals. They are actually a secondary resource of metals, rather than an end-waste and have been utilized as a resource material in many areas. In addition, for some applications, slags have comparable or even better properties than their competitors. Leaching is a method for extraction of metals from copper slags. The extraction of metals such as copper and cobalt from the copper slag of Küre-Turkey, was investigated in the past decades. Fayalitic type of these copper slags containing 0.934 % Cu, 0.353 % Co and 50.91% Fe were subjected to the experimental study. As a result of mineralogical analysis of the slag sample, fayalitic type of slag was found to contain hercynite, magnetite, hematite, pyrite, chalcopyrite, covellite, bornite and metallic copper. Direct acid leaching methods were applied on the sample. Effects of leaching time, temperature and acid concentration on Cu and Co leaching recoveries were investigated in the direct acid leaching. The optimum leaching conditions were found as leaching time of 2 hours, solid/liquid ratio of 1/3, H2SO4 concentration of 125 g/L and temperature of 70 °C. At these conditions, 75.5 % of Cu, 95.6 % of Co and 70.9 % Fe were extracted. In the second stage of the leaching experiments, copper in the pregnant solution was precipitated by cementation to produce a Cu concentrate assaying 95.58 % Cu; cobalt was obtained by precipitation with H2S to produce a concentrate containing 62.10 % Co. As a result of this study a process flow sheet has been developed for recovering Cu and Co from these slags to demonstrate its economic and technological benefits.

Jan 1, 2014

By A. V. Nguye, P. A. Harvey

Previous studies have reported that inorganic electrolytes can enhance floatability of coal. The research has shown that the enhancement, if any, is highly dependent on changes in solution pH, type of electrolyte, and electrolyte concentration. The reasons for this are still not clear. In this study the floatability of coal particles in mono and divalent salt solutions was investigated. The zeta potential and hydrophobicity of the coal was measured experimentally, and a modified Hallimond tube was used to determine the floatability of coal particles by single bubbles, where the collision efficiency was equal to unity. The experimental information was used in conjunction with the Hogg-Healy-Fuerstenau equation to quantify the electrical double layer interaction. It was found that for low electrolyte concentration (less than 0.1 M) solutions the flotation recovery of coal particles was less than that for distilled water, and decreased with increase in concentration. Conversely, at electrolyte concentrations above 0.1 M, flotation recovery increased with increasing concentration. Both of these results are consistent with previous observations, but are inconsistent with expectations when considering the possible influence of electrical double layer interaction. A possible mechanism, based on the existence of the pre-existing submicron-sized gas bubbles, known as bubstons (i.e. bubbles stabilized by ions), present in water in close proximity to the hydrophobic coal surfaces is discussed in line with the early observation of flotation improvements by microbubbles “nucleating” on hydrophobic surfaces. In particular, the dependence of the bubble-particle attachment efficiency on electrolyte concentrations supports hypothesis on the salt-dependent and ion-specific existence of bubstons. However, a theoretical explanation of the transition salt concentration (at about 0.1M) is deficient at present. The existence of these submicrobubbles in close proximity to hydrophobic surfaces is not trivial. They can (as can individual gas molecules or other solutes) mediate and extend the range and magnitude of the attraction between hydrophobic macroscopic surfaces. These bubbstons may explain the curious phenomena of the socalled long-ranged hydrophobic attraction measured with the Surface Force Apparatus and Atomic Force Microscopy, and the slippage at hydrophobic surfaces. Finally, the coalescence of bubbstons affects the rupture of liquid films at a very large thickness (over 100 nm), observed, but unexpected, by flotation chemists.

Jan 1, 2003

By X. L. Song

In this paper, ZrSiO4-Cd(S1-xSex) inclusion pigments were synthesized by hydrothermal method. Microstructure, morphology and properties of the powder were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR) and CIE chromaticity, respectively. It shows that, precursors obtained at pH is about 6.0 are sol and products with higher crystallinity, red hues (a*=38.23) and inclusion ratio when hydrothermal synthesis temperature is 180? and holding time is 12h. Hydrothermal reaction mechanism was further analyzed as well. In particular, an ideal model of pigment formation was proposed.

Jan 1, 2014

By B. Friedrich, A. Weyhe, H. Heegn

"Nickel-metal hydride batteries (Ni-MH) are storers of electrochemical energy, which have a higher specific storage capacity than lead or nickel-cadmium batteries. The demand for Nickel-metal hydride batteries is increasing rapidly since their market launch in the early 1990’s. Today there is no suitable and sustainable recycling process to recover nickel, cobalt and rare-earth metals. The discarded batteries are used today in the steel industry as alloy material because they contain nickel. Cobalt and rare-earth metals (RE) are lost; they are non-recycleable.In a German governmental funded research project, IME Aachen, ACCUREC Mühlheim and UVR-FIA Freiberg are cooperating in processing as well as in creating a feasibility study. The target of this project is the development of a new recycling process for metal recovery from Ni-MH-batteries. The proposed process described in this paper consists of a combination of mechanical, pyrometallurgical and hydrometallurgical processing steps. This process is capable of treating all types of Ni-MH-batteries. After comminution steel and organics are separated. The separated Ni-MH is smelted in an electric arc furnace. The products are a nickel-cobalt alloy and a slag phase enriched with rare-earth oxides for further treatment to ‘mischmetal’. Both the Nickel-Cobalt alloy and the ‘mischmetal’ will be directly used in battery production."

Jan 1, 2003

By Mohammad Kor, David Beattie, Agnieszka Mierczynksa-Vasilev

The selectivity of polymer adsorption in mixed mineral systems is the basis for polymer depression of gangue minerals in flotation. Effective polymer depressants not only reduce gangue mineral recovery, they also have minimal effect on the recovery of the value phase, presumably through targeted adsorption on the gangue phase, and minimal uptake on the value phase. Traditionally, polymer depressant design has been guided by single mineral phase adsorption tests, with affinity and maximum adsorbed amount determined for gangue and value phases separately. However, there is a need to determine the actual extent of adsorption on the gangue phase while in the presence of the value phase. In this work, we report on the development of in situ atomic force microscopy (AFM) imaging for determination of polymer depressant coverage and morphology on mixed mineral surfaces. Our group has previously used AFM imaging on single minerals to connect adsorbed layer characteristics with bubble-particle attachment and flotation outcomes. Two sample types were used to test the methodology: (i) a mixture of two crushed/ground minerals encased in resin; and (ii) a composite mineral sample containing macroscopic regions of three different mineral phases. The samples have been used to probe the selective uptake of two modified dextrin polymers (octenyl succinate anhydride dextrin). AFM images acquired in situ (while all surfaces are immersed in the same polymer solution) of each mineral phase have revealed the natural selectivity of the polymer for the mineral surfaces. In all cases, the polymers adsorb on the all mineral surfaces present, but to a varying extent.

Jan 1, 2014

Mineral flotation is effective over a relatively narrow particle size range of approximately 10 µm to 150 µm. If the upper particle size limit can be increased, however, a run-of-mine ore may be coarse ground, and only the middlings are ground further to achieve required grades. This will result in significant energy savings and increased throughput. In this communication, methods of increasing the upper particle size limit will be discussed on the basis of a flotation model that can predict flotation from both hydrodynamic and surface chemical parameters. An example of increasing flotation recovery by control of a chemistry parameter is given.

Jan 1, 2014

By G. Bulut, Ü. Yenial

"Heavy metals contamination in aqueous systems can be found in a variety of industries, in particularly mining, metal processing, finishing and plating. Water containing more than 0.5 ppm heavy metal considered as a toxic due to harmful effects on health. The major techniques employed for heavy metal removal from industrial wastewaters include precipitation, reduction, ion-exchange, and adsorption. Adsorption is a heavy metal removal method for aqueous systems. As a common adsorbent, activated carbon has been used in treatment but it is ineffective on some elements. Thus, there has been a research for developing highly effective and selective adsorbents. In this study the adsorption of lead and arsenic ions on to coal waste and red mud waste was studied. The experimental parameters were determined as pH, equilibrium time and the initial concentrations, activation by heat treatment and the blend of adsorbents. According to their adsorption capabilities, red mud was found to adsorb lead and arsenic ion with high efficiency but coal waste did not adsorb arsenic ion. However the binary adsorptions of these ions were enhanced the adsorption efficiencies. In addition the blend of coal waste and red mud affected the adsorption efficiency. INTRODUCTION As a result of rapidly developing industry and excessive use of water resources, the need of clean water and wastewater management appear as a problem. Wastewater recycling activities and researches come to the fore for an effective use of wastewater. Recycling of wastewater, which contains heavy metals harmful to the environment and human, is a difficult process. Heavy metals are generally divided into three categories: toxic metals, precious metals, radionuclides. Wastewaters from various industries, containing heavy metals, are the main polluters of water and soil. Although their toxic structures, heavy metals are used extensively in industry as they have technological significance. Usually mining industry, metal industry and industrial organizations produce heavy metal containing wastewaters (Volesky 1990, Ting and Lawson 1991, Bishop 2002)."

Jan 1, 2018

By Alireza Javadi Nooshabadi, Kota Hanumantha Rao

Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was examined. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite ((Zn, Fe) S), and galena (PbS) generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids are placed in water immediately after dry grinding. Pyrite produced more H2O2 than other minerals and the order of H2O2 production by the minerals was found to be pyrite > chalcopyrite > sphalerite > galena. The pH of the water influenced the extent of hydrogen peroxide formation with greater amounts of H2O2 produced at highly acidic pH. Furthermore, the effect of mixed sulphide minerals, i.e., pyrite-chalcopyrite, pyrite-galena, chalcopyrite-galena and sphalerite-pyrite, sphalerite-chalcopyrite and sphalerite-galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction. There is clear correlation of the amount of H2O2 production with the rest potential of the sulphide minerals; the greater the rest potential of a mineral the greater the formation of H2O2. This study highlights the necessity of revisiting the electrochemical and/or galvanic interactions between sulphide minerals, and interaction mechanisms between pyrite and other sulphide minerals in terms of their flotation behavior in the context of inevitable H2O2 existence in the pulp liquid.

Jan 1, 2014

By Amir Hajizadeh Omran, Mehdi Irannajad, Sima Mohammadnejad, Fardis Nakhaei

"This study presents an experimental program performed to investigate the effects of flotation variables including gas flow rate, froth depth, slurry solids percent, frother/collector dosage and pH on the froth bubble size during desulfurization of an iron ore. These conditions were varied using a central composite design (CCD). Image analysis techniques have been developed and used successfully to characterize the froth bubble size. Results of the CCD experiments showed that the flotation variables have different effects on the froth bubble size. The froth height, air flowrate, pH and solid content had the most important influence on the froth bubble size. The interaction between the collector-frother, pH-collector, frother-air flowrate, solid content-froth height, pH-froth height and solid content-pH were also significant. Process state can be accurately deduced from the froth surface appearance, providing a convenient way to quantify the parameters as a function of the process control. INTRODUCTION Flotation processes are subjected to a wide variety of process disturbances, some of which are made by the change in mineral features and others to variation in operating procedures. Feed and air flow rates, densities, size distributions and shapes of particles, surface properties, and reagent dosages and compositions can all change, often with significant effect on the performance of the plant (Moolman et al., 1996a). Flotation process efficiency is governed by the wettability of the solid as well as the surface tension at the liquid-gas. Both of these properties are influenced by operational conditions encountering in a flotation process. The structure of froths developed on the pulp surfaces of flotation cells has a remarkable effect on both the grade and recovery of minerals in the concentrate (Shean and Cilliers, 2011)."

Jan 1, 2018

By A. Kamali Moaveni, A. Boehm

"The current research study addresses a physical separation process of basic oxygen furnace slag “BOF-Slag” (also called Linz-Donawitz “LD” slag) for the removal of phosphorous. In order to recycle the LD-Slag into the steelmaking process, the physical dephosphorization methods are considered. The systematic geometallurgical investigation carried out on particle classes of decreasing size, which were further subdivided into susceptibility classes, shows intimate intergrowth beyond 40 µm due to slag´s fast cooling rate. Generally, LD-slag is constituted of oxide and silicate phases, among which di-calcium silicate “C2S” dominates. About 0.5 mass% of phosphorous was detected in the LD- slag, which is exclusively situated in the lattice of the C2S. The comparatively high grinding resistance (Rittinger index 12.9 cm²/J) of the LD-slag reflects the energy demand to liberate the phosphorous carrying phase from the iron containing minerals, while separation efficiency decreases in the very fine particle size range. Hence, the conversion of the phase intergrowth pattern was considered alternatively to re-build the mineral phase structure of the material to a separable interlock pattern. Carbon dioxide, as the most convenient substance in the steelmaking plants, was applied to digest the C2S in the presence of water and to reduce the basicity of the slag slurry. As a result of C2S-CO2 chemical reaction, calcite and calcium silicate are precipitated at the surface of the oxide particles and carried between 25% and 75% of the total phosphorous, respectively. Accordingly, the mobility of the phosphorous content phase to the top of the grains serves the possibility to separate the precipitated layer by mechanical attrition process. This paper is focused on the impact of the intergrowth pattern alteration on the slag´s separability characteristics. Moreover, the operating conditions of the carbonization process, such as temperature and pressure, on the deconstruction kinetics of the C2S and the generated products will be considered. INTRODUCTION The steelmaking BOF-Slag is a stony aggregate waste from the steel manufacturing process. The investigated slag by the current research work was provided by voestalpine steelmaking plant in Linz, Austria. The current legislative situation in Austria restricts the historical application of slag as construction material, due to the high level of heavy metals content and corresponded land-filling and transportation costs of slag, therefore the demand for recycling of BOF-Slag to the steelmaking process has raised, as an alternative application. Statistically, voestalpine steelmaking plant produces about 130 kg BOF-Slag per ton of final steel product, which serves annual BOF-Slag production of 700,000 ton, approximately."

Jan 1, 2018

By Shuji Owada, Shinya Suzuki, Chiharu Tokoro, Daisuke Haraguchi, Sayaka Izawa

"Coprecipitation with ferrihydrite has been one of the major treatment method for As(V) removal from wastewater such as acid mine drainage. We already confirmed coprecipitation of As(V) with ferrihydrite consists of two kinds of mechanism; one is two dimensional As(V) uptake to the surface of ferrihydrite by surface complexation and another is three dimensional As(V) uptake into ferrihydrite by surface precipitation. We also already confirmed As(V) adsorption process by ferrihydrite could be quantitatively evaluated by original surface complexation model with parameter values reported by Dzombak and Morel. However, As(V) coprecipitation process couldn’t quantitatively be represented by only the original model. In this study, construction and calculation using surface precipitation model were attempted for As(V) coprecipitation treatment with ferrihydrite. In the surface precipitation model, precipitation was described by the formation of solid compound between ferrihydrite and ferric arsenate. Activity of these precipitates was determined by surface precipitation ratio of FeAsO4(s) obtained experimentally from XANES analyses. Solubility products of surface precipitation of FeAsO4(s) (Ksp_FeAsO4(suf.)) were determined by fitting to sorption densities and surface precipitation ratio in each condition. The values of Ksp_FeAsO4(suf.) were determined 10-7.7 at pH5 and 10-10.2 at pH7, respectively. Based on the obtained Ksp_FeAsO4(suf.) value, As(V) removal and isotherm were calculated for As(V) co-precipitation treatment using surface precipitation model. Good agreement between experimental and calculated values was observed. These results were suggested that the quantitative prediction of As(V) co-precipitation treatment was possible if Ksp_FeAsO4(suf.) value was estimated experimentally."

Jan 1, 2014

By André Mans, Frans B. Waanders

Current losses of Ferrosilicon (Fe-Si), which is used in the dense medium separation (DMS) of iron ore at Kumba Resources, Sishen, South Africa occur due to adhesion to the separation products and also by being present in the effluent stream, due to abrasion. The losses contribute greatly to the running cost of the plant and the purpose of this project was to determine the characteristics of the unused Fe-Si and then to characterise the changes that occur during storage and the use thereof. A Scanning Electron Microscope (SEM) and Mössbauer Spectroscopy (MS) were used to investigate the characteristics of the fresh and used Fe-Si. It was found that the biggest loss of Fe-Si was due to the abrasion of the particles during the DMS process, which resulted in the liberation of Fe and subsequent formation of an oxihydroxide froth. A possible change in magnetic properties was also observed, leading to further losses that could occur during prolonged use of the medium. No clear changes to the Fe-Si occurred during correct storage methods, as was initially thought.

Jan 1, 2003

By F. S. Niu

With the feature of finely-dissemination particle and complex mineral composition, oolitic hematite is considered to be the ore dressing difficult problem in the world. Series research on refractory oolitic hematite in Zhangjiakou Area are introduced as following: ore properties?technology mineralogy and mineral processing technology. The survey shows: with the fine grinding of the hematite to a fineness of -0.076mm 95%, obtaining iron concentrates grading 62.74% Fe at the recovery of 46.80% by high intensity magnetic separation- reverse flotation flowsheet; under the three stages intensity magnetic separation,four stages grinding and four stages gravity separation, getting the iron concentrates grading 61.09% Fe at the recovery of 45% using high intensity magnetic separation- gravity separation flowsheet; with roasting temperature of 800°C, time for 75~90min and ore-coal ratio of 11, gaining the iron concentrates assaying 62.74% Fe at the recovery of 87% by roasting- magnetic separation flowsheet. At present, this research is still doing for the target of raising the concentration recovery on the base of high grade concentrate. It is in the hope of fully utilizing the existing hematite resources in Zhangjiakou

Jan 1, 2014

By B. McFadzean, S. Geldenhuys

"Dynamic froth stability tests have found widespread application to quantify froth performance. However, little to no attention has been given to scale parameters in the performance of these measurements. One of the most frequently changing scale parameters in the laboratory scale is the column diameter as this directly influences the amount of material needed for testing. Four different column diameters (50, 100, 200 and 300 mm) were used for this study. Column diameter experiments were done on an industrial scale by means of manual tracking of froth growth versus time. An increase in measured dynamic stability was seen with increasing froth column diameter, which reached a limiting value at large column sizes. It is thought that this behaviour is controlled by the differences in drainage rates of the bulk froth compared to froth in contact with the wall. The column diameter required to represent full-scale froth stability is proposed. A ratio of column surface area to total bubble surface area was used to correct for different column diameters.INTRODUCTIONThe froth phase in flotation contributes significantly to the overall performance of the process (Zanin, et al., 2009). Numerous parameters have been investigated to quantify froth performance, most notably froth recovery (Feteris, et al., 1987; Seaman, et al., 2004; Vera, et al., 1999). Experimentally gathering data to determine froth recovery is challenging and for this reason froth stability has been highlighted as a possible alternative.Froth/foam stability is defined as the time of persistence of the froth/foam and is affected by numerous factors, such as: drainage of the liquid in the lamellae (gravitational and capillary), viscosity at the bubble surface, thickness of the electrical double layer and gas diffusion through liquid films caused by pressure differences between bubbles (Aktas, et al., 2008; Beneventi, et al., 2001). It is well documented in both froth and foam literature that froth/foam stability will heavily influence the performance and appearance of the froth/foam phase (Ata, 2012; Farrokhpay, 2011; Weaire, et al., 2005). Experimentally this has been explicitly proven as an increase in froth stability, characterised by water recovery, usually results in an increase in both valuable mineral and solids recovery (Wiese, et al., 2011; Banford, et al., 1998)."

Jan 1, 2018