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Öğe Alumina Production from Clay Minerals: Current Reviews(Gazi Univ, 2018) Erdemoglu, Murat; Birinci, Mustafa; Uysal, TuranAlumina (Al2O3), which is a very important material due to its superior physical and technological properties, is widely used in industry and almost all of alumina is obtained from Bayer process using bauxite as a raw material. However, some technical and economical handicaps of alumina production with Bayer process (such as limited or non availability of bauxite reserves in some countries, reduction of high grade bauxite deposits, growing alumina demand for industry etc.) require alternative raw material sources and methods to produce alumina. Therefore, investigations on the alumina production from non-bauxite sources is one of the current studies in related literature as well. Clay minerals are considered to be the best available source of non-bauxite raw material for alumina production. Because clay minerals are abundant and common in the earth crust, they have relatively high grade of aluminum, when compared to other sources, clay mining is easier and require simpler preparation and enrichment processes. There are various processes developed to produce alumina from clays, but among them Acid Leaching Process has become well-known method that could be practiced as a more effective method in alumina production due to some advantages. Moreover, it is seen that there is a consensus on Acid Leaching Process. Besides, there are current studies investigating several technical modifications and improvements on the process steps. The aim of this study prepared by reviewing the studies obtained from literature and current experimental results on production of alumina from clays is to give information particularly to alumina industry and stakeholders and related researchers, and to contribute to scientific studies on this topic.Öğe Aluminum Recovery by Acid Leaching of Variously Enriched Pyrophyllite Ore: Effects of Pre-treatment Methods for Activation(Springer Heidelberg, 2023) Aydogmus, Ramazan; Erdemoglu, Murat; Uysal, TuranEffects of pre-treatment methods such as calcination for thermal activation and intensive milling for mechanical activation on the aluminum (Al) recovery by acid leaching of preliminarily enriched pyrophyllite ore via attrition scrubbing and froth flotation were investigated. XRD patterns of the calcined and the intensively milled samples were compared to determine the changes during the pre-treatment processes. Hot HCl solution was used for dissolution of aluminum to determine the Al recoveries from variously enriched and variously pre-treated pyrophyllite ore samples. Specific thermal and milling energies consumed per unit amount of ore were calculated, and the ideal activation method was suggested by comparing the activation methods in terms of energy consumption. Mechanical activation of the pyrophyllite concentrate obtained by attrition scrubbing rather than froth flotation was suggested for higher recoveries of aluminum from by acidic leaching. It was determined that operating cost (in terms of energy) of the mechanical activation is lower and aluminum recovery is higher than thermal activation. It was concluded that mechanical activation instead of thermal activation is more economical and environmentally friendly method.Öğe Carbothermic reduction of mechanically activated celestite(Elsevier, 2009) Erdemoglu, MuratEffects of dry milling on the carbothermic reduction of celestite were examined. Celestite and coke mixture was milled up to 120 h in a planetary ball mill. Unmilled and milled mixtures and their black ashes from carbothermic reduction were characterized by a combination of X-ray diffraction (XRD) analysis, scanning electron microscope analysis. thermogravimetric analysis, particle size analysis and leaching tests. XRD diffraction peaks for celestite in the milled mixtures are lower and broader than those for the unmilled mixture, mainly due to a disordering of celestite crystal structure. Size of the particles significantly decreased by 1 h of milling, so that d(50) decreased from 79.4 to 6.1 mu m. But, milling for longer periods shifted the particle size distribution to coarse size region. mainly due to the agglomeration of fine particles. By milling the celestite-coke mixture for 1 h, formation temperature of SrS decreased from 957 degrees to 900 degrees C, whereas 24, 72 and 120 h of milling decreased nearly to 700 degrees C. At low roasting temperatures, the mass loss by reduction increased with extending of the milling and the milled mixtures gave a high degree of soluble strontium in the black ash. However, sintering process prevailing at higher temperatures during the roasting of the milled mixtures became active. and the effects of disordering of the celestite structure vanished and subsequently the reduction reaction was retarded. It was concluded that although milling in a planetary ball mill produces more X-ray amorphous SrS, together with SrC2, carbothermic reduction reactions occur at lower temperatures as the milling time increases. (C) 2009 Elsevier B.V. All rights reserved.Öğe Contribution of Mechanical Activation for Obtaining Potassium Chloride from Microcline(Springer Heidelberg, 2023) Alyosif, Bahaa; Uysal, Turan; Aydemir, Muhammet Kuersat; Erdemoglu, MuratThe effect of intensive milling on the conversion of microcline (KAlSi3O8) to potassium chloride (KCl) occurred during the chlorination roasting process for artificial KCl production was investigated. A feldspar ore with 10.89% K2O grade and containing microcline was dry milled by a planetary ball mill for mechanical activation. Milled ore mixed with calcium chloride was roasted at temperatures between 500 and 1000 degrees C to get the chlorination roasting process. The product was then leached in water to dissolve KCl occurring during the roasting, which will be precipitated from the pregnant leach solution by evaporation. Results showed that potassium recovery from the unmilled ore increased rapidly up to 800 degrees C, and dramatically decreased at higher temperatures due to the removal of KCl from the furnace by means of evaporation. A potassium recovery of 31.95% was achieved by the unmilled ore, whereas it was 88.43% when 15 min milled ore was roasted at 750 degrees C. It was concluded that intensive milling caused mechanical activation of microcline to reduce the roasting temperature of the chlorination roasting process.Öğe Copper Enrichment in Solid with Selective Reverse Leaching with Oxalic Acid(Springer, 2020) Turan, M. Deniz; Sari, Zeynel Abidin; Erdemoglu, MuratAs the first part of a novel process proposed for copper extraction, selective dissolution of iron from chalcopyrite in oxalic acid solutions with hydrogen peroxide was studied. Despite the fact that both iron and copper are readily soluble in acidic conditions, it was found that oxalic acid provides altered solubility behaviors for these metals. It should be used to form iron (II) oxalate which has a higher solubility (0.008 g/100 g H2O at 293 K) than copper oxalate (2.16x10(-10) g/100 g H2O at 293 K), while hydrogen peroxide was used to provide an oxidative leaching environment to break the chalcopyrite structure. Under the examined leaching conditions where 100 g/L of H2C2O4, 3 M of H2O2, 318 K of leaching temperature, 120 min of leaching time, 25 mL/g of liquid-solid ratio, and 400 rpm of stirring speed were applied, extraction rates of copper and iron from the chalcopyrite concentrate were almost 1.5% and 70%, respectively. Copper was found as a solid oxalate form in the residue obtained after the leaching process in these conditions.Öğe Effects of intensive grinding on the dissolution of celestite in acidic chloride medium(Pergamon-Elsevier Science Ltd, 2009) Erdemoglu, Murat; Aydogan, Salih; Gock, EberhardEffect of intensive grinding on the dissolution of celestite in acidic barium chloride and sodium chloride solutions was studied by investigating structural changes occurred during milling. Complete dissolution of the celestite was achieved within 25 min by milling in a planetary ball mill in which ball to ore ratio is 10. But, increasing grinding time and ball to ore ratio diminished the dissolution rate. X-ray amorphous phase content and XRD breadths increased and XRD line reflection intensity decreased with increasing of grinding time, and celestite does not undergo a considerable phase transformation during milling. SEM micrographs showed that how prolonged milling results in an increasing degree of agglomeration and a reduced amount of fines. Additionally, the ground samples were heated at elevated temperatures and then re-ground under earlier grinding conditions. Structural, morphological and dissolution characteristics of the samples obtained by each of the three treatments were also evaluated. It was concluded that high energy milling for short times increases the dissolution rate of celestite. But, increase in the particle size due to agglomeration or compactness of the particles as a result of impact stress predominant in planetary ball milling decreased the leaching rate, as grinding time and ball to ore ratio in the mill were increased. (C) 2008 Elsevier Ltd. All rights reserved.Öğe Effects of mechanical activation of colemanite (Ca2B6O11•5H2O) on its thermal transformations(Elsevier, 2016) Uysal, Turan; Mutlu, H. Serdar; Erdemoglu, MuratIn this study, effects of mechanical activation on the thermal characteristics of colemanite (Ca2B6O11 center dot 5H(2)O) were examined with respect to its decrepitation behavior observed during the heating processes. Mechanical activation was achieved by milling (up to 150 min) in a planetary ball mill using tungsten carbide milling media. Crystallinity of the milled colemanite samples was determined by performing X-ray powder diffraction analysis. In this manner, milling conditions at which crystalline colemanite transforms to amorphous structure were obtained. Thermal gravimetric (TG) analyses together with differential thermal (DTA) and differential thermogravimetric (DTG) analysis were performed to determine how prolonged milling affects the thermal behavior of colemanite. It was found by examining the DTA data that intensive milling gives rise to removal of the crystal water from colemanite at low temperatures, which can be attributed to mechanical activation. DTG analysis revealed that mechanical activation decreases the rate of water removal from colemanite structure throughout the heating. It was suggested that mechanical activation eliminates the decrepitation almost completely, so that there is no need for pre-calcining operation which is generally required before manufacturing the colemanite-based high temperature materials. (C) 2016 Elsevier B.V. All rights reserved.Öğe LEACHING OF CHALCOPYRITE CONCENTRATE IN HYDROGEN PEROXIDE SOLUTION(Oficyna Wydawnicza Politechniki Wroclawskiej, 2014) Agacayak, Tevfik; Aras, Ali; Aydogan, Salih; Erdemoglu, MuratThe leaching conditions of chalcopyrite (CuFeS2) concentrate in a hydrogen peroxide medium were investigated by studying the effects of its leaching parameters, such as stirring speed, temperature, hydrogen peroxide concentration and the particle size of the concentrate on Cu extraction. It was found that stirring speed has no effect on the leaching. Copper extraction from chalcopyrite is directly proportional to hydrogen peroxide concentration, but the extraction decreases at temperatures above 60 degrees C. The maximum copper extraction was obtained with the following conditions without stirring: 240 min of leaching time, 3.0 M hydrogen peroxide concentration, 40 degrees C leaching temperature and 53-75. m particle size fraction.Öğe Mechanical activation of pyrophyllite ore for aluminum extraction by acidic leaching(Springer, 2018) Erdemoglu, Murat; Birinci, Mustafa; Uysal, Turan; Tuzer, Esra Porgali; Barry, Thierno SaidouA pyrophyllite [Al2Si4O10(OH)(2)] ore as an alternative source for alumina (Al2O3) was intensively milled for mechanical activation to increase aluminum extraction by acid leaching method. For this purpose, unmilled and milled ore samples were compared to reveal the changes caused by intensive milling. The samples were also leached in HCl solutions to determine whether mechanical activation increased the alumina extraction or not. The milling considerably disrupted XRD peak intensities of the clay minerals found in the ore, except quartz. After milling just for 30 min, peaks of the minerals were not distinguished, suggesting that all are amorphous. Dehydroxylation of the minerals in the unmilled ore was realized to occur at lower temperature ranges and energy consumed for dehydroxylation significantly reduced with prolonged milling. While aluminum recovery by leaching of the unmilled ore was about 12%, it increased to 73.09% as a result of milling the ore for 50 min. It was concluded that as the milling time is extended, energy needed to undergo dehydroxylation due to amorphization continues to decrease and aluminum recovery reaches higher values, suggesting that the clay minerals in the ore can be converted to mechanically activated state.Öğe AN OVERVIEW OF SURFACE ANALYSIS TECHNIQUES FOR CHARACTERIZATION OF MECHANICALLY ACTIVATED MINERALS(Taylor & Francis Inc, 2012) Erdemoglu, Murat; Balaz, PeterSurface characteristics of particles; such as structure, morphology, and chemical composition of surface have a major effect on its response to metallurgical processing operations. In order to understand the characteristics and reactivity of the system, information on the physical topography, the chemical composition, the chemical structure, the atomic structure, the electronic state, and a detailed description of bonding of molecules at the surface are required. Most of the instrumental techniques used for identification of major/minor and bulk/surface characteristics of substances now can be easily utilized as well for the characterization of mechanically activated minerals. This article is concerned with several representative identification techniques which are currently used for characterization of the materials prepared by mechanochemical processes. Fundamental aspects of spectroscopic (Infrared, Raman, and X-ray photoelectron), electron microscopic (Scanning electron microscopy and Transmission electron microscopy), and probe microscopic (Scanning tunneling microscopy and Atomic force microscopy) techniques used for surface characterization of mechanically activated minerals are overviewed.Öğe Production of Aluminum Titanate from Pyrophyllite Ore(Gazi Univ, 2022) Uysal, Turan; Erdemoglu, MuratAluminum titanate (Al2TiO5) is an advanced ceramic material produced artificially from the alumina (Al2O3) and titanium oxide (TiO2) components. In this study, alumina which is produced from pyrophyllite ore and commercial rutile were used to manufacture the aluminum titanate. The alumina used in the study was obtained by roasting the aluminum chloride salt precipitated from the loaded solution obtained by HCl leaching of the pyrophyllite ore. The resulting alumina and commercial rutile mixture is intensively milled, shaped and sintered at different temperatures to produce aluminum titanate. The result of sintering is that aluminum titanate formation is at 1359 degrees C in the milled mixture and at 1367 degrees C in the unmilled mixture. Formation of aluminum titanate at a lower temperature than the unmilled mixture, much less presence of microcracks and lack of pores clearly demonstrate the effect of mechanical activation. As a result, it has been shown that aluminum titanate with high added value can be produced from alumina recovered from pyrophyllite ore by hydrometallurgical processes.Öğe Thermal and Mechanical Activation in Acid Leaching Processes of Non-bauxite Ores Available for Alumina Production-A Review(Springer Heidelberg, 2019) Barry, Thierno Saidou; Uysal, Turan; Birinci, Mustafa; Erdemoglu, MuratThe rapid development of the global alumina and aluminum industry is straight coupled with the demands and the needs of these materials. Nowadays, the only well-known accessible resources to produce alumina and aluminum are bauxite ores. But bauxite ores are limited, and the remaining exploitable reserves do not have high contents in alumina. In countries where there is little or no bauxite reserves or where the recovery of existing bauxite ores to produce alumina with the Bayer process are not economic, alternative resources for alumina have been explored. The most attractive resources for replacing bauxites are aluminosilicate clay minerals and coal fly ash. The important processes developed for the recovery of alumina from these sources are acid leaching and alkaline leaching processes. The acid leaching is known as the most efficient in which thermal and mechanical activation are included for improving the performance of the process. The objective of this review is to give a comprehensive insight on the production of the alumina from thermally or mechanically activated clays and coal fly ash by hydrochloric, sulfuric, and nitric acid leaching processes.Öğe Thermal Behavior of Pyrophyllite Ore during Calcination for Thermal Activation for Aluminum Extraction by Acid Leaching(Springer, 2020) Erdemoglu, Murat; Birinci, Mustaea; Uysal, TuranIn the production of alumina (Al2O3) from clays by acid leaching, thermal activation by calcination is applied widely as a pre-treatment to improve the dissolution of aluminum. Previous studies have focused only on the thermal behavior of high-purity kaolinite and pyrophyllite, individually. However, thermal activation of complex clay ores containing several silicate minerals and their effect on aluminum extraction have not been studied. The purpose of the present study was to characterize the thermal behavior of a clay ore containing mainly pyrophyllite (Al2Si4O10(OH)(2)), kaolinite (Al2Si2O5(OH)(4)), muscovite (KAl2(AlSi3O10)(OH)(2)), quartz (SiO2), and kyanite (Al2SiO5) from the Puturge clay deposits (Malatya, Turkey) for possible use in alumina (Al2O3) production by acid leaching. The ore and its calcination products obtained at various temperatures were characterized with respect to their mineral paragenesis, crystal structure, surface morphology, and thermal, calorimetric, and aluminum dissolution properties in order to understand the changes that occurred. Aluminum recovery in the leach solution increased in direct proportion to the dehydroxylation degree (D-tg) of the ore as the calcination temperature increased to 900 degrees C. A maximum aluminum extraction of 90.57% was achieved by leaching of the product from calcination at 900 degrees C. Aluminum extraction decreased sharply above that temperature, even though D-tg increased a little. By increasing the calcination temperature; the structures of pyrophyllite, kaolinite, and muscovite were destroyed by dehydroxylation, resulting in the exfoliation of the mineral layers, thus, a mixture of dehydroxylated phases formed. Depending mainly on the temperature range at which each of the dehydroxylated phases is durable, aluminum could be leached to some extent. The sharp decrease in the extraction of aluminum, iron, and potassium at higher temperatures was attributed to compaction of previously exfoliated layers of the minerals through re-crystallization to form mullite-like structures which seemed insensitive to acid attack during the leaching.
