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    BARYUM VE MAGNEZYUM İÇEREN KATILARIN KARBONAT YÜKLÜ ÇÖZELTİLERLE ETKİLEŞİMİ
    (2022) Ehsani, İlhan; Ehsani, Arman; Obut, Abdullah
    Bu çalışmada, baryum (Ba(OH)2·8H2O ve BaSO4) veya magnezyum (Mg(OH)2 ve MgSO4·7H2O) içeren katıların, yerel bir simitsonit (ZnCO3) cevher örneğinin sulu sodyum hidroksit çözeltilerinde liçi sonrasında oluşan çözünmüş karbonat yüklü çözeltilerle etkileşimi, bu yüklü çözeltilerdeki çözünmüş karbonatın (BaCO3 veya MgCO3 olarak) uzaklaştırılması amacıyla, X-ışını kırınımı analizleri kullanılarak incelenmiştir. Çözünmüş karbonat yüklü çözeltilerin Ba(OH)2·8H2O ve MgSO4·7H2O katılarıyla etkileşimini takiben, sırasıyla, tek faz olarak BaCO3 ve ana faz olarak Mg(OH)2 içeren katıların oluştuğu gözlenmiştir. Diğer taraftan, BaSO4 ve Mg(OH)2 katılarının yüklü çözeltilerle herhangi bir etkileşime girmediği ve dönüşmeden kaldıkları belirlenmiştir. Bununla birlikte, çalışılan tüm deneysel koşullar altında, baryum veya magnezyum zinkat fazlarına dönüşümün olmadığı da ortaya çıkarılmıştır. Bu çalışma kapsamında, toprak alkali baryum ve magnezyum içerikli katıların çözünmüş karbonat yüklü çözeltilerle etkileştirilmeleri sonrasında ilgili karbonat fazlarına dönüşüm özellikleri, bu katıların çözünürlükleri dikkate alınarak tartışılmıştır. Ayrıca, seçilmiş deneyler sonrasında elde edilen bazı dönüşmüş katıların kızılötesi spektrumları ve taramalı elektron mikroskop görüntüleri de bu çalışma kapsamında sunulmuştur.
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    Direct conversion of alkaline earth metal hydroxides and sulfates to carbonates in ammonia solutions
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Ehsani, Ilhan; Ehsani, Arman; Ucyildiz, Ayse; Obut, Abdullah
    In this study, the direct conversion behaviors of different alkaline earth metal solids (the hydroxides and the sulfates of alkaline earth metals Ca, Sr, Ba and Mg) to their corresponding carbonates in dissolved carbonate-containing pregnant solutions obtained by direct leaching of a smithsonite (ZnCO3) ore sample in aqueous ammonia solutions having different concentrations (4 M, 8 M and 13.3 M NH3) were investigated by using X-ray diffraction analyses at alkaline earth metal to dissolved carbonate mole ratios of 1:1 and 1:2, for revealing the conversion possibilities of dissolved carbonate in the pregnant solutions to solid carbonate by-products. The results of direct conversion experiments showed that Ca(OH)(2), CaSO4 center dot 2H(2)O, Sr(OH)(2)center dot 8H(2)O and Ba(OH)(2)center dot 8H(2)O converted to their corresponding carbonates, SrSO4 partially converted to SrCO3 as observed by the presence of unreacted SrSO4 peaks in X-ray diffraction patterns of the converted solids, and BaSO4 did not convert to BaCO3 because of its lower solubility with respect to BaCO3. On the other hand, it was observed that Mg(OH)(2) did not convert to MgCO3, but MgSO4 center dot 7H(2)O converted dominantly to an uncommon phase, which was tentatively identified as Mg5Zn3(CO3)(2)(OH)(12)center dot H2O. In the study, a complete discussion on the conversion behaviors of alkaline earth metal solids to their corresponding carbonates was given considering the differences between their solubility product constants and the changes in the free energies of the theoretical conversion reactions. In addition, infrared spectra and scanning electron microscope images of some of the converted solids were also presented for characterization purposes.
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    Influence of polyoxometallates as additive on electro-winning of copper
    (Elsevier Science Bv, 2016) Ehsani, Arman; Yazici, Ersin Y.; Deveci, Haci
    In this paper, the electro-winning of copper from synthetic copper sulphate solutions and the pregnant leach solution (PLS) derived from the leaching of e-waste was investigated in an attempt to reduce energy consumption by using a polyoxometallate (POM), ammonium metatungstate hydrate (AMTH) as a novel additive. Effect of addition of AMTH on the current efficiency, rate of copper deposition, deposit quality and morphology was studied. The current efficiency was determined to be 7% lower in the electro-winning of copper from the pregnant leach solution than that from the synthetic solution (84% vs 91%) presumably due to the presence of impurities (e.g. Fe) in the former. The addition of AMTH (50-100-200 mg/L) into the synthetic electrolyte solution was found to increase the current efficiency (by 3-8%) as well as the rate of copper deposition at the current densities tested (150-250-300 A/m(2)). Effect of AMTH on the surface morphology of copper deposit was also examined. Despite its beneficial effect on the current efficiency and rate of copper deposition, the deposit morphology tends to deteriorate (i.e. rough/dendritic texture) with increasing the concentration of AMTH in both PLS and synthetic copper sulphate solution. It can be inferred from the findings that AMTH can be used as an additive for reducing power consumption in electro-winning of copper from sulphate solutions. (C) 2016 Elsevier B.V. All rights reserved.
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    Okyanus ve Deniz Altı Madenciliğinin Kısa Tarihçesi
    (2018) Ehsani, Arman; Sivrikaya, Osman
    Bu çalışmada okyanus ve deniz altı madenciliğinin tarihsel gelişimine kısa ve özet bir şekilde değinilmiştir. Okyanuslar ve denizlerdünyamızın yaklaşık % 71’ini kapsamaktadır. Deniz altı ve okyanus maddeciliğinin gelişimi deniz-okyanus bilimi (oşinografi)çalışmaları kapsamında hayata geçmiştir. Deniz ve deniz altı ile ilgili ilk araştırmalar M.Ö. 2000 yıllarında Giritliler ve Fenikelilertarafından gerçekleştirilmiştir. Oşinografi dalında modern teknikler ile yapılan ilk araştırma, 1855 yılında okyanusların derinliğininölçülmesi (bathymetric) çalışmaları olarak göze çarpmaktadır. British Challenger gemisi ile 1872 yılında 4 yıl süren bir araştırmaseyahatinde Kuzey Kutbu Denizi hariç bütün okyanus ve denizler gezilerek mangan içeren yumrulu yataklar saptanmıştır. 1968 yılındaGolmar Challenger denizaltı aracı, deniz altı ve okyanus tabanı hakkında inceleme çalışmalarına başlamıştır. 2005 yılında ise ilkokyanus-deniz altı madenciliği uygulaması olan Solwara projesinin ilk sondaj çalışmaları Papua Yeni Gine açıklarında başlamıştır.
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    Preparation of different zinc compounds from a smithsonite ore through ammonia leaching and subsequent heat treatment
    (Oficyna Wydawnicza Politechniki Wroclawskiej, 2021) Ehsani, Arman; Ehsani, Ilhan; Obut, Abdullah
    In this study, firstly, the effects of ammonia concentration, leaching time and solid/liquid ratio on the leaching behaviour of zinc from a smithsonite (ZnCO3) ore sample in aqueous ammonia solutions were investigated at room temperature by chemical, X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy analyses. It was found that leaching ratio of zinc steeply increased from 30.1 to 76.2% with increasing ammonia concentration from 1.0 to 4.0 M and maximum zinc leaching ratio of 79.7% was reached after leaching in 13.3 M NH3 solution. The XRD pattern of the residue obtained after leaching in 4.0 M NH3 solution for 90 min at solid/liquid ratio of 0.15 g/mL, the optimum condition, showed that smithsonite phase in the ore sample almost completely dissolved whereas the gangue minerals goethite and calcite remained unaffected, confirming the selectivity of ammonia solution for zinc dissolution. Together with zinc, leaching ratios of cadmium were also determined. In second part of the study, precipitation tests (by complete drying at different temperatures) were conducted on dissolved zinc, carbonate and ammonia containing pregnant solutions obtained after selected leaching experiments. By complete drying of the pregnant solutions at low temperatures, i.e. 50 degrees C, relatively pure solid zinc ammine carbonate (Zn(NH3)CO3) precipitates and at higher temperatures, i.e. 150 degrees C, quite pure solid zinc carbonate hydroxide (Zn-5(CO3)(2)(OH)(6)) precipitates could be prepared. High-temperature heating of Zn(NH3)CO3 and Zn-5(CO3)(2)(OH)(6) precipitates at 450 degrees C yielded single-phase zinc oxide (ZnO). The chemical compositions, FT-IR spectra and scanning electron microscope (SEM) photographs of some of the precipitates were also presented.
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    Recovery of metals from chloride leach solutions of waste of printed circuit boards by adsorption and precipitation
    (Gecamin, 2014) Yazici, Ersin; Deveci, Haci; Ehsani, Arman
    The downstream treatment of chloride leach solutions of WPCB for recovery of base and precious metals by a combination of adsorption and precipitation processes were carried out. A synthetic leach solution (1 M HCl, 116.5 g/L Cl-, 30 g/L Cu2+, 2.5 g/L Fe3+, 5 mg/L Au3+, 10 mg/L Ag+ and 20 mg/L Pd2+), which was prepared based on the composition of the pregnant leach solution obtained in the previous study was used in the tests. The leach solution was initially subjected to activated carbon (AC) adsorption #y(20 g/L AC, 80°C) in which gold was selectively recovered over silver and palladium i.e., 88% Au recovery at 0.5 h (92% at 3.5 h) compared with only 3-6% for Ag/Pd. Copper and iron were also observed to adsorb on AC as indicated by 1.4% and 17% decline, in their respective concentrations. Following the adsorption and filtration stage, metallic copper was added into the gold-barren solution to allow reduction of Cu2+ to Cu+, and to cement Pd on metallic copper. Over the mixing period (1 h), 93% of the Pd was recovered while only 1.4% of silver was cemented onto metallic copper. Subsequently, the leach solution was gradually neutralised by NaOH to pH 4, 7.5 and 9.5 for the precipitation of copper as cuprite (Cu2O). It was found that 41% and 46% of Cu and Ag, respectively, were precipitated at pH 4 at which iron was almost totally (99.8%) removed from solution. Precipitation of copper and silver was increased further at high pHs. At pH 9.5, cumulative recoveries for copper and silver were 91% and 85%, respectively. XRD analysis of the precipitates confirmed the presence of cupric copper oxides/hydroxides and revealed that copper losses occurred at pH 4 was due to the undesired presence of cupric copper in the solution.
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    The Effects of Ball-Mill Grinding Parameters on Lignite Morphology
    (Mdpi, 2023) Guven, Onur; Ehsani, Arman; Kaymakoglu, Burcin
    In recent years, because of the decreasing liberation sizes of the minerals, processes such as grinding need to be evaluated in more detail. As is well known, size reduction processes are very important both in mineral processing and in many industrial applications. However, to increase the efficiency of the processes after size reduction, variations in particle morphology should also be evaluated, along with particle size. Although the effectiveness of grinding media (ball, rod, autogenous) has been shown for different materials, there are very few studies on the effect of the powder/grinding media ratio and grinding time on particle morphology in terms of shape factor and roughness values. This study aims to investigate the variations in the morphology of lignite samples under different grinding conditions such as grinding time and powder/grinding media ratio (U). The results of these analyses showed that while the d80 size of the ground lignite was 1.1 mm after 2 min grinding time, it decreased to 0.5 mm following 15 min grinding time. The roundness values of particles vary in the range of 0.746-0.790 with increasing grinding time. In addition to the grinding time, while the roundness of particles was found to be 0.739 for 0.34 U values (powder/grinding medium rate), it increased to 0.788 when the U value was adjusted to 0.67. The average roughness (Ra) values of particles increased from 60.9 nm to 107.9 nm upon increasing the grinding time from 2 min to 16 min. Due to these findings, it can be suggested that lignite samples became rounder with increasing grinding times, and roughness analyses made in a 10 x 10 & mu;m surface area with an Atomic Force Microscope (AFM) indicated that particle roughness increased in direct proportion to grinding time.