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By Matt Kilburn, Liming Lu, Steve Suthers, Alexander Edenton, Rodney Smyth, Matt Adam

"Magnetite concentrate is naturally good for pelletising. However, due to the depletion of reserves of traditional high grade hematite iron ore worldwide, the usage of magnetite concentrate in sintering is expected to increase substantially. Magnetite concentrate is typically high in Fe grade and releases extra heat when oxidised to hematite. This will not only improve the quality of agglomerates produced, but also have a potential beneficial impact on the fuel consumption of the agglomeration process. There are an increasing number of magnetite projects currently being considered and developed. However the concentrates from some of these projects are too coarse as pellet feeds and much finer and denser than normal sinter feeds. Accordingly, special strategies are required in order to utilise the coarse magnetite concentrates at high proportions in pelletising and sintering. This paper discusses various raw material preparation technologies and blending optimization methods demonstrated to be effective for improving the sintering and pelletising performance of coarse magnetite concentrates. Pre-granulation and addition of binders, such as hydrated lime, were found to be particularly efficient in recovering the sintering productivity of sinter blends containing magnetite concentrates. In pelletising, HPGR (High Pressure Grinding Rolls) grinding enabled production of good quality pellets from 100% magnetite concentrates and optimized blends containing up to 70% magnetite concentrates also formed good pellets.INTRODUCTION Magnetite concentrates are often used as feed materials for pellet plants or sinter plants depending on their grades and grain sizes. To achieve the required quality of green and fired pellets, the concentrates often need to be ground very fine (80% passing 38- 45 m), which inevitably consumes a great amount of energy. Therefore, efficient grinding processes are required to reduce the amount of energy consumption needed to achieve the sizing and chemical specification of pellet feeds. The use of magnetite concentrates in sintering has the potential to improve sinter chemistry, which is deteriorating over time due to the slowly decreasing grade of direct shipping iron ores around the world (Yang and Mathews, 1997; Yang and Witchard, 1998, Yang and Davis, 1999; Yang 2005). However, methods are required to allow the utilisation of high levels of concentrates in sintering while maintaining productivity and sinter quality (Han and Lu, 2017)."

Jan 1, 2018

By K. Malysa

Bubble collisions with ore grains and a selective formation of the bubble-grain aggregates are necessary steps for flotation separation of useful and gangue components of an ore. For the attachment of valuable mineral grain to the colliding bubble a liquid film, separating the bubble and the grain needs to rupture during short time of their collision. High hydrophobicity of the grain surface is favorable because stability of the separating (wetting) film is much lower at such surfaces, that is, the film ruptures faster and at greater thickness. Simultaneously, it needs to be kept in mind and taken into consideration that high affinity to air is a typical feature of hydrophobic surfaces. Thus, when the hydrophobic surface is immersed into aqueous phase the air can stay attached to such surfaces and affect kinetics of the bubble attachment. The paper presents results and analysis of dynamic phenomena occurring upon the collision of the rising bubble followed by its attachment to hydrophobic (Teflon) plates of different roughness. The influence of the Teflon surface roughness, solution concentration, bubble size and impact velocity on bouncing of the colliding bubble, time of the three phase contact (TPC) formation and drainage time of the liquid film, formed between the solid and bubble surfaces, is described. High hydrophobicity, as showed earlier (Malysa et al, 2005), does not assure that each collision leads to the TPC formation and attachment of the colliding bubble. Roughness is the parameter of crucial importance for kinetics of the bubble attachment to hydrophobic surfaces (Krasowska and Malysa, 2007; Krasowska et al, 2009; Kosior et al, 2011). Enlarged roughness of the Teflon plate, from ca. 1 to 80µm, results in shortening the time of the TPC formation (bubble attachment) by over an order of magnitude - from 105 to a few milliseconds only. Higher surface roughness means that larger amount of air can be entrapped in bigger scratches and cavities of the Teflon plate during its immersion into aqueous phase. Results documenting importance of the air presence are showed and mechanism of the air facilitated TPC formation and bubble attachment to hydrophobic surfaces is described. Keywords: bubble collisions, hydrophobic surfaces, teflon plate roughness, TPC formation

Sep 1, 2012

By João Queiroz, Cristian Marquez-Sarmiento, Luiz Teixeira

The removal of various metals from process waters and effluents is usually done by precipitation of the corresponding hydroxide. Manganese however is one metal that does not respond efficiently to that approach. It may be seen in its eH X pH diagram that the way of oxidation to Mn IV rather than hydrolytic precipitation of the Mn II ion as its hydroxide, is the way to efficient precipitation of Mn in the pH range 6 to 10. We studied the use of oxidants O2; NaClO; H2O2; Caro´s Acid (H2SO5) and the combinations of O2 or H2O2 with Na2S2O5, and H2O2 with NaClO, for the oxidative precipitation of Mn from synthetic solutions starting with 10 mg/L Mn, at 25 oC. In adequate conditions, which include pH > 8, it is possible to reach final [Mn] less than 0.1 mg/L in 60 minutes of reaction time.

Jan 1, 2014

By Çisem Tuba, Ismail Girgin

"Comparative atmospheric H2SO4 and H2SO4 + H2O2 leaching experiments were performed using a Turkish lateritic nickel ore containing 1.52% Ni. In the leaching tests; acid concentration, temperature and leaching time were considered as main variables and the dissolution behaviour of the ore were studied by Ni, Fe, Co and Mg analyses. The dissolution values in the H2SO4 leaching experiments were observed to increase up to 60% (w/w) acid concentration and a temperature of 95°C. Increase of H2SO4 concentration above 60% at 95°C caused decreases in all the dissolution values and this was attributed to the formation of Fe2(SO4)3 and Fe2(SO4)3•HSO4•H2O type compounds. At the considered optimum H2SO4 leaching conditions ([H2SO4]= 45%, T=95°C, t=45 min); dissolution values reached for Mg, Ni, Fe and Co were determined as 99.12%, 95.58%, 92.63% and 78.37%, respectively. An activation energy of 30.57 kJ/mole was determined for nickel dissolution from the evaluation of the kinetic data obtained for H2SO4 leaching showing that the dissolution was controlled by external diffusion and chemical reactions. Caro’s acid solutions were prepared at H2SO4/H2O2 mole ratio of 3 for varying initial H2SO4 concentrations and leaching tests were performed at 25°C. Co behaved very differently and a dissolution value of 83.94% was obtained even at 5% acid concentration in 60 minutes reaction time. Complete dissolution of Co was obtained after 30 minutes of reaction time at 60% initial H2SO4 concentration and the corresponding dissolution values for Mg, Ni, and Fe were reached to 96.16%, 94.27% and 89.46%, respectively. Although the H2SO4 + H2O2 leaching experiments were conducted at 25°C, it was realized that the temperature of the leaching medium was increased to 122°C after four minutes of reaction time due to probable exothermic reaction(s) at 60% initial acid concentration."

Jan 1, 2014

By Kazutoshi Haga, Batnasan Altansukh, Atsushi Shibayama

Results of flotation process combined with atmospheric leaching and high pressure leaching for recovery of copper from low-grade silicate-copper ore have been presented in this study. The low-grade copper ore contains a small amount of copper (0.42 mass %), iron (4.6 mass %), and silicon (38.3 mass%) and among many other metals (Al, Ca, K, Mg, Na, Ti and S). The main mineralogical constituents of the copper ore are calcium aluminosilicate (Ca(Al2Si2O8), amesite (Mg2Al2SiO5(OH)4) and gypsum (CaSO4×H2O), and quartz (SiO2) as resulted from the alteration of an igneous rock. This study has shown that about 92 % of copper can be recovered with a maximum copper grade of 4.2 mass% in a froth after 15 minutes of flotation at pH 8.5 when used potassium amyl xanthate as a collector, MIBC and Dow-froth 250 as frothers and calcium hydroxide as a pH adjuster. The images of bubbles in the cell during flotation process were recorded using a high-speed camera. The froth concentrate with average copper grade of 2.0 mass% was further processed by atmospheric leaching with a solution of sulphuric acid and hydrochloric acid, respectively and high pressure leaching with sulphuric acid solution. As a result, leaching rate of copper reached about 60 % in an atmospheric leaching with sulphuric and hydrochloric acid respectively, whereas the rate can reach more than 70 % by autoclave leaching at high pressure under the controlled condition. A process to recover of copper from its low-grade ore can be developed by optimization of flotation combined with acid leaching.

Jan 1, 2014

By Ljubisa Obradovic, Baisui Han, Batnasan Altansukh, Zoran Stevanovic, Atsushi Shibayama, Jonovic Radojka, Daizo Ishiyama, Kazutoshi Hag, Radmila Markovic, Ljiljana Avramovic

This paper discussed a combined froth flotation and high pressure leaching (HPL) process to recover copper from mine tailings. At first, froth flotation were carried out using the mine tailings sample under various conditions in the presence of different pH (3.5-10) and sulfurizing reagent value (0-1000 g/t), respectively. As a result, optimum condition (sulfurizing reagent of 1000 g/t, pH of 10, PAX (collector) of 100 g/t and MIBC (frother) of 200 g/t) was found for froth flotation of copper. The effects of sulphuric acid concentration, leaching temperature, total pressure (steam pressure plus oxygen pressure) on high pressure leaching (HPL) of mine tailing were investigated using sulphuric acid solution in the presence of oxygen. The best conditions for HPL were obtained to be sulphuric acid concentration: 0 mol/L (water), leaching temperature: 170 ?, total pressure: 2 MPa, leaching time: 1 hr and pulp density: 100 g/L. The leaching rate of copper reached nearly 99 % and the concentration of copper in pregnant leach solution (PLS) was 0.24 g/L. Finally, copper in the mine tailing was recovered using froth flotation followed by HPL. As a result of a combined froth flotation and HPL, the vast majority of copper (99 %) from the mine tailings was extracted.

Jan 1, 2014

By Nóra Schreithofer, Kari Heiskanen

"INTRODUCTIONThe knowledge of the adhesion forces between particles and bubbles is of key importance in the improvement of flotation models. The development of the Colloidal Interaction Force Measurement Apparatus (CIFMA) opened the possibility to quantify the adhesion forces between particles and bubbles. The aim of this study was to examine the effect of three main variables: the approach velocity, the loading force and the loading time on the adhesion force between an air bubble and a hydrophobized silica particle."

Jan 1, 2003

By James A. Finch, Linda Restrepo, Mitra Mirnezami, Amy Buchanan, Maryam Hashemi

Settling rate studies on slurries from Cu/Zn flotation plants occasionally reveals two aggregation maxima at pH 8-10 and 10-12 (Figure 1). From measurements on sphalerite and silica suspensions the double maxima could be replicated. These maxima correspond to the effects of Zn and Mg ions. The aggregation mechanism of both ions is related to the formation of the corresponding hydroxide precipitate. A combination of chemical and electrostatic bridging by the hydroxides is considered to be the aggregation mechanism.

Jan 1, 2003

By Z. K. Liu

Production of the amines collectors and cation surfactant gives out the liquid waste containing high COD (Chemical Oxygen Demand) and ammonium & nitrogen, which is difficult to be treated with conventional biological method to reach waste water discharge standard. In this paper an engineering practice of treatment on the liquid waste by the technology combined high effective microbe with A/O (Anaerobic& aerobic) process is presented. The quality of treated water comes up to class A national standard for discharging.

Jan 1, 2014

By Christopher Davey, Professor Emeritus, Marian Mazurkiewicz, Peter Kanjorski

The concept of a high pressure liquid jet mill with highly unsteady flow, has been developed and recently patented by Cornerstone Technologies LLC (CsT), for the purpose of micron and sub-micron particle production. The mill accepts feed sizes up to 15mm for some materials and is capable of sub-micron production. Successful material range from precious metals such as silver and palladium to dielectric components and substrates such as Barium Titanate slips, zirconia, titania and silica. The process has also succeeded in adequately reducing the size of materials for both composite and coating uses such as anthracite coal, graphite, chrome metal, wollastonite and more than 100 others. A unique design approach has been taken to highly maximize the energy flux in the mill’s chambers to create extremely high turbulence and destructive cavitation. This is assisted by shock waves, which cause particles to undergo ultra high frequency pressure pulsations, high frequency collisions and then abrasion, shattering, hydro-wedging, and cleaving. Due to these extreme properties the processing occurs in just fractions of a second allowing throughputs up to 1000 kg/h on a machine that would fit inside a 60 cm box. The technical solution and technological advance, as well as the environmental and economic benefits indicate rapid and wide spread acceptance of high-pressure liquid jet milling in modern industry.

Jan 1, 2003

By Yu. Gurevich, M. Teremova, I. Prokopev, A. Razvjaznaya, N. Algebraistova

"The objective of this work is the scientific justification and development of efficient and environmentally-friendly method of bulk concentrate preparation for selection with application of microbiological practices. This research suggests to apply Pseudomonas Japonica bacterial culture to the bulk concentrate before the selection circuit in order to clear the surface of sulphides from the xanthate skin. It is also suggested to apply bacterial consortium Ochrobactrum ?nthropi and Pseudomonas aeruginosa JCM 5962 for desorption of diesel residual concentrations. High-efficient and environmentally friendly method of copper-molybdene and lead-zinc bulk concentrate selection was developed based on theoretical and experimental research work with application of microbiological practices. In comparison with conventional methods (steaming, sodium sulphide washing) the above suggested bio-technological method of bulk concentrate preparation before selection cycle will allow to reduce material and power expenditures, and it is also environmentally friendly. INTRODUCTION High-efficient selection of sulphide bulk concentrate is gained exclusively after collecting agent is removed from mineral surface. Therefore, the problem of bulk concentrate preparing before the selection cycle is acute, since the further technological parameters of the subsequent separation depends on the effectiveness of pulp preparation. Existing traditional ways of bulk concentrate preparation. such as washing or steaming, are characterized by high energy and material costs in industrial conditions [1,2]. The microbiological treatment before separation of the bulk concentrate into different kind of concentrates appear one of perspective processes for treatment of bulk concentrates [3,4]. At the present time, the world practice of processing mineral raw materials demonstrates the wide application of technologies using microorganisms: bacterial leaching and oxidation, purification of industrial wastewater. This is due to the fact that biotechnological methods are environmentally safe, low-cost, and suitable for refining complex ores and raw materials of industrial origin."

Jan 1, 2018

By Kazutoshi Haga, Atsushi Shibayama, Kosuke Nishioka, Yasushi Kihara, Altansukh Batnasan

The aim of this study was to investigate the feasibility studies of seawater in flotation of a 1.5 mass % of copper containing copper sulfide ore. Effects of seawater, various frothers, and different distilled water/seawater ratio on flotation of copper sulfide ore were studied. Surface properties of native copper ore and sea water soaked were examined by using FT-IR spectrometry. Chemical contents of the copper sulfide ore and after flotation were identified using XRD studies. XRD pattern showed that the main constituents of the copper sulfide ore are chalcopyrite (CuFeS2), bornite (Cu5FeS4). Flotation experiments were carried out using mechanical agitation flotation equipment with a mineral separation type flotation cell. Froth flotation experiment was conducted using calcium hydroxide was used as a pH adjuster, using methyl isobutyl carbinol (MIBC), dow froth 250 (DF 250) as frothers and potassium amyl xanthate (PAX) as collector for the copper recovery from the copper sulfide ore containing chalcopyrite and bornite. The results showed that the copper recovery by flotation was dependent on the flotation medium and frother. The main results showed that the copper recovery by flotation was dependent on the process water and frother. The copper recovery reached 97 % and 87 % in the distilled water flotation and seawater flotation with MIBC, respectively. For seawater flotation with DF 250, the Cu recovery achieved near 95 % and grade of Cu in the froth product after 5 min flotation was reached 29.8 mass %.

Jan 1, 2014

By Mingxia Liu, Qi Liu, Tao Jiang

"In addition to physical parameters such as small mass and high specific surface area of fine and ultrafine minerals, chemical parameters such as the adsorption affinity of collectors on the minerals also plays an important role in fine particle flotation. In this study, we have examined collectors with two different ionized groups, carboxylate and hydroxamate, on the flotation of fine niobium oxide (pyrochlore). To facilitate comparison, two hydrocarbon radicals were tested: octyl and oleoyl, which led to four collectors that were studied: octyl hydroxamic acid (OHA), sodium octanoate (C8OONa), oleoyl hydroxamic acid (C18HA), and sodium oleate (NaOl). Small-scale flotation and isothermal microcalorimetric titration measurements were performed to determine the flotation recoveries of different sized pyrochlore and the enthalpic behavior after adsorption of the collectors on pyrochlore. It was found that the flotation performance of the carboxylate-based collectors was generally inferior to hydroxamate-based collectors. Sodium octanoate could not float pyrochlore irrespective of the particle size of the pyrochlore tested. With a longer hydrocarbon chain, sodium oleate was effective to float the relatively coarse pyrochlore (>20 µm) but its collection efficiency dropped sharply for particles smaller than 20 µm. On the other hand, the two hydroxamate-based collectors, octyl hydroxamic acid and oleoyl hydroxamic acid, showed good collecting ability to both the coarse and fine pyrochlore. The isothermal microcalorimetric titration studies indicated a consistent correlation of chain length with floatability of collectors for relatively coarse pyrochlore, as well as a positive relationship between the adsorption affinity and fine pyrochlore flotation recoveries. The key finding of this study was that efficient fine particle flotation could be achieved when strongly chemisorbing collectors were used.INTRODUCTION The first detailed study of the effect of particle size on flotation was made by Gaudin (1931) with sulphide ores. In 1942, Gaudin again demonstrated that (Gaudin et al., 1942) fine particles possess different flotation properties from larger particles. Since then the effect of particle size on froth flotation has been an important research topic by many researchers, e.g., Gaudin (1957), Miettinen et al. (2010), Warren (1976) Jameson (2010), summarizing the behavior of fine particles in terms of their low particle momentum, leading to low rate of collision with bubbles which reduces the chance of adhesion. The suggested remediation methods are mainly based on two approaches: increasing particle size or decreasing bubble size (Warren, 1976). Sand-fine splitting followed by separate flotation treatment of the sand and fines, using deep flotation cells, using starvation quantities of collectors, and using long flotation times, are also strategies to address the problems of fine particle flotation."

Jan 1, 2018

Calcium sulfate whiskers are considered to be a prosperous reinforced material in application due to their high mechanical properties. But the hydration occurs easily at moist atmosphere or in aqueous solution. The surface topographies of the calcium sulfate hemihydrate whiskers and the hydrates were analyzed by on-line observation and using XRD. The results indicated the transformation of the crystal type and shape of calcium sulfate hemihydrate whiskers and the reduction of whiskers? aspect ratio. The hydration process of the calcium sulfate hemihydrate whiskers and the effective parameters were further discussed based on FT-IR measurements. The conclusions were obtained that the hydration of calcium sulfate hemihydrate whiskers can be divided into the three phases, namely, initial hemihydration phase, dehydration phase, and coarsening, dissolving and the re-formation of calcium sulfate dehydrate crystal phase. In addition, it was found that in the hydration process of calcium sulfate hemihydrate whiskers the calcium sulfate dihydrate whiskers are formed at first and then converted into the calcium sulfate dihydrate with different crystal shapes, but in the hydration of gypsum hemihydrate the gypsum dihydrate is formed without transition products. The surface active site-calcium ion which has strong trend to react with H2O, the surface ?OH and the inner channels are considered to play important roles in the hydration process of calcium sulfate hemihydrate whiskers.

Jan 1, 2014

By Alejandro Rubio-Lopetegui, Gonzalo Montes-Atenas

The occurrence of Enargite (Cu3AsS4) in hydrometallurgical plants bears a number of challenges. One question lies on how Copper and Arsenic can be selectively extracted from the solid surface structure when immersed in aqueous solution. The leaching of Enargite in ambient conditions has been extensively studied; nevertheless, challenges regarding the process kinetics and surface structures enabling the extraction process remain ill-understood. Prior knowledge indicates that different conditions of pH, Eh, temperature, speciation of the aqueous phase or variations of these parameters defines the overall rate at which metals and other elements will be transferred to the solution. One aspect that the research studies have seldom addressed involves studying the main features of the surface structures formed during the leaching process at the outmost surface atomic layer. Such structures will mediate between the solid bulk and the solution to undertake subsequent stages of leaching process. The aim of this research work is to critically analyze the state of the art of Enargite electrochemistry from the mediator formation-dissolution mechanisms standpoint occurring at the mineral-solution interface. The most probable mediator species reported in the literature were found to be: Arsenolite and Sulfur (acidic media), Covellite (acidic and alkaline media) and Tenorite (alkaline media). As a result of this analysis, it was observed that the surface speciation was not in full agreement with the previous knowledge suggested to explain Enargite leaching reactions and, therefore, modified Eh-pH diagrams are presented. The acquired insights on the surface structures rising from the Enargite-aqueous solution interactions is further revised to provide new experimental protocols towards selectively separating Copper and Arsenic through hydrometallurgical paths.

Jan 1, 2014

By Ming’an Wei, Chuanyao Sun, Zhenguo Song, Zengwen Dou, Yangge Zhu

"The effects of pH value and dissolved oxygen(DO) in the pulp to the Eh and flotation recovery of pyrite were investigated using potential online detection system. The effects of DO on the Eh and flotation recovery were tested which DO changed from 0.5mg/L to 19.5mg/L in six different pH buffer flotation systems (pH: 4.00, 5.62, 6.86, 9.18, 10.01 and 10.96 respectively). Results of potential detected online demonstrated that the pyrite electrode has nearly the same response to potential as with platinum electrode for the FeS2-xanthate-H2O flotation system under the study conditions. Pulp potential and recovery of pyrite were remarkably influenced by pH, both of them decreased with the increasing of pH and, especially, sharp decreased after pH above 9. As the concentration of DO was increased, the Eh was also increased in all the six different buffer solution, while the flotation recovery was decreased. And the amplitude of variation for Eh was not obvious in acidic and neutral solutions, but on the contrary, the change for flotation recovery was remarkable in neutral and alkaline conditions. This may indicate that the flotation of pyrite will be deteriorated in alkaline and high DO concentration conditions."

Jan 1, 2014

By Gustav Hawlitschek, Henrique Kahn, Carina Ulsen, Renato Contessotto

"The problems related to waste dumping increased with the growth and development of large cities. In the U.K., more than 50% of landfill waste comes from construction use and the U.S. alone produces around 200 to 300 million tons of CDW annually. The exhaustion of natural sand deposits close to large urban centres stimulates the recycling of construction and demolition waste for the production of recycled aggregates as a construction material. This paper presents a flowchart for the production of recycled sand with low porosity and regular shape by the selective removal of the cement paste attached to recycled aggregates. The products characterization was carried out by the determination of the particle size and shape distribution, chemical and mineralogical composition, heavy liquid mineral separation and quantification of all present phases using a scanning electron microscopy with automated image analysis (SEM-MLA). The comminution of CDW by vertical shaft impact crusher made possible the production of a lower porosity recycled sand. The heavy liquid mineral separation showed that the proportion of low porous phases (d>2.5 g/cm3) is very high, exceeding 70% of the weight, encouraging further mineral processing separation to obtain a fine recycled aggregate with less cement paste content. The mineralogical characterization by XRD and SEM indicates that the main phases are tectosilicates, phyllosilicates and calcite which one can be attributed to both calcareous aggregate and cement paste. The precise quantification of cement paste and calcite/dolomite alone is just possible by automated image analysis. The characterization results demonstrated that proportion of phases with no cement paste attached increases progressively in denser products. The results of heavy liquid separations and image analysis are comparable and automated image analysis can be used for the characterization of phase content and their main associations."

Jan 1, 2014

By Georgios N. Anastassakis

"The depletion of the high-grade chromite ores and the inefficiency of the gravimetric methods to process fine particles has shifted the industrial and research interest from gravimetric separation methods to flotation. However, the response of the minerals to various flotation schemes is not clearly established. In this work, the physicochemical behavior of chromite and olivine is studied using a fatty acid collector.The minerals used were from Vourino area (Kozani, Northern Greece). Macroscopically pure samples of chromite and olivine were selected by hand picking, crushed and subsequently ground to the required size. Each sample was then submitted to panning and magnetic separation for the removal of impurities. The mineralogical and chemical analysis of the purified samples revealed the following: a) The purity of chromite was 95% while the minor constituent was mainly magnetite. Its chemical analysis was: 12.50% Fetot, 2.50% SiO2, 54,54% Cr2O3, 9.31% Al2O3, 0.47% CaO, 13.10% MgO. These analyses show that Cr3+ has been substituted by Fe3+ and Al3+ as well as Fe2+ has been significantly substituted by Mg2+. b) Forsterite is the main constituent of olivine either as pure forsterite (Mg2SiO4), which is the prevailing form, or as iron-forsterite [(Mg,Fe)2SiO4] in less amount. Chrysotile, which belongs to the serpentine group, was also detected at a percentage of 10-15%. The chemical analysis of olivine was: 36.90% SiO2, 0,53% Cr2O3, 7,43% Fe2O3, 0.72% Al2O3, 0.91% CaO, 47.00% MgO, 6.02% LOI.The electrokinetic behavior of the minerals was studied in a electrophoretic mass transport equipment Model 1202 of Micromeritics. The reagents used were sodium hexa-metaphosphate of commercial grade and sodium oleate."

Jan 1, 2003

By Ray Everson, Henry Kasaini

"Adsorption of Pd (II) anions on the surface of activated carbon (Norit 0.8) occurred at high proton concentration (0.01 – 2.5M, HCl) in the feed and averaged 27 mg/g. The adsorption process was interpreted in terms of surface ionisation and adsorption model. Enthalpy of adsorption averaged 0.4 kJ/mole indicative of an instantaneous physical adsorption process. We found that the Toth isotherm fit the adsorption data fairly accurately. A combination of the Langmuir and Freundlich equations yields an effective three-parameter Toth equation (1) which is frequently used to describe adsorption on heterogeneous surfaces.Figure 1 shows the comparison between experimental results and the model isotherms. We found that Langmuir isotherms underestimated the adsorption capacity on the porous surface while the Freundlich isotherm overestimated adsorption. Furthermore, the surface coverage at equilibrium was well described by both the Langmuir and Toth isotherms. But, Freundlich isotherm predicted a surface fraction coverage that was higher than unit. Based on better prediction of surface coverage and a reasonable fit to adsorption data, we concluded that the Toth isotherm best described the adsorption data of palladium. The adsorption process was limited by mass transfer resistance through the external film. We estimated the rate constant from equation (2), where e, ?b, and rp are porosity, fluid density and particle radius, respectively"

Jan 1, 2003

By A. Güney, G. Önal

"Karagedik Chromite Concentrator of the ETI Holding Co., which is located in Fethiye (south Turkey), has been producing chromite concentrate assaying 47-48 % Cr2O3 from the chromite ores containing 30-35 % Cr2O3 by using gravity separation methods since 1920. The tailings having 13-14 % Cr2O3, which had been removed from this plant, were accumulated at the stockpiles amounting about 1.2 million tons. In order to recover the ultra fine chromite particles from the Karagedik Concentrator tailings, the new process including Wet High Intensity Magnetic Separation and column flotation, was developed and the Karagedik Research Pilot Plant based on this process was commissioned in 2000. At this plant, the final concentrates assaying 46-48% Cr2O3 were produced and overall plant recoveries are about 60-65%.At the chromite concentrators using gravity separation methods, if their material size is about minus 1.0 mm, chromite particles especially pass to fine fractions according to their mineralogical structures and the ore-genesis (Önal and Güney, 1990). Generally, after crushing and grinding, the shaking tables and spirals are used at the chromite concentrators; therefore fine size chromite particles (-0.038 mm) are removed as tailings. Cr2O3 content of the -0.1 mm size fraction with 52.3% of the total amount is 19.58 % with Cr2O3 distribution of 82.6%.In order to upgrade the minus 0.1 mm size fraction of the tailings, assaying about 20% Cr2O3, Karagedik Research Pilot Plant (KRPP), which includes Wet High Intensity Magnetic Separator (WHIMS) and Column Flotation units, was installed by Istanbul Technical University (ITU), Mineral Processing Section in 2000.Feeding material of the KRPP having 5 tons per hour capacity is obtained from stockpiles amounting 1.2 million tons. After attrition scrubbing, the feed is sent to a screen with aperture of 1.0 mm. The screen overflow, assaying 5-6 % Cr2O3 is removed as tailings. Screen underflow is classified to –1.0+0.1 mm and minus 0.1 mm size fractions by using cyclone and sieve bend. –1.0+0.1 mm size fraction assaying 6-7 % Cr2O3, is sent to existing gravity separation plant. Minus 0.1 mm size fraction is firstly fed to WHIMS for pre-concentration and non-magnetic product assaying 10-11 % Cr2O3 consisting of serpentine, talc and olivine minerals are separated as tailings. Also magnetic product (25-30 % Cr2O3) obtained from WHIMS is fed to the two stages conditioners after dewatered to 30 % solid ratio."

Jan 1, 2003