Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 1Citation - Scopus: 1Pressure-Induced Phase Transformations in Amorphous Arsenic(Elsevier Science Bv, 2016-04) Durandurdu, MuratThe atomic structure of amorphous arsenic and its response to high pressure are explored using a constant pressure ab initio molecular dynamics technique. Different analyzing techniques reveal that amorphous arsenic has a local structure close to that of the crystalline phase. The model also presents some twofold and fourfold coordination defects. The existence of a possible amorphous to amorphous phase transition for arsenic is proposed on the bases of the observation of a gradual coordination increase with the application of pressure. Further compression of the amorphous state yields a transformation into a simple cubic crystal. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Liquid and Amorphous States of Boron Subarsenide(Wiley, 2019-08-13) Durandurdu, MuratAb initio molecular dynamics simulations are executed to probe the short-range order and the electrical features of the liquid and amorphous boron subarsenide (B12As2). A drastic volume swelling of similar to 40% is witnessed for the liquid state, relative to the crystal. The density of the melt is found to be close to that of liquid boron. As the temperature applied is gradually decreased, the volume progressively decreases and a glass-transition zone at around 1400 K is observed. About 14% volume expansion is perceived for the amorphous phase. Due to the drastic density (volume) difference between the liquid and amorphous forms, their atomic structure is found to be different from each other. In the liquid phase at 2500 K, the mean coordination number (CN) of B and As atoms is 4.4 and 2.5, correspondingly. During the solidification process, both average CNs steadily increase and reach values of 5.5 (B-atom) and 4.14 (As-atom) at 300 K. The pentagonal pyramid-like motifs barely survive at 2500 K but during the quenching process they develop progressively and some of which lead to the formation of B-12 clusters. In the amorphous state, the chain-like and A7-like As-As clusters are observed. Nonetheless, the noncrystalline state is proposed to be partially similar to the crystalline structure. The liquid state shows a metallic character while the amorphous form presents a semiconducting nature having an energy band gap much smaller than that of the crystalline phase.Conference Object Citation - Scopus: 2Leaching of Yahyali Non-Sulphide Pb-Zn Flotation Tailing Using Organic Acids(Baski, 2019) Hussaini, Shokrullah; Kursunoglu, Sait; Kaya, MuammerThe laboratory scale leaching of Kayseri-Yahyali non-sulphide lead (Pb)-zinc (Zn) flotation tailing using two organic acids was experimentally investigated. The effect of citric and oxalic acid on the dissolution of Zn, Pb, iron (Fe) and arsenic (As) was individually investigated under the following conditions: citric or oxalic acid concentration of 0.5-1.0M, temperature of 60-80°C and leaching time of 30-180 min. at 1/10 solid-to-liquid (S/L) ratio. 90.1% Zn dissolution was achieved using 0.5 M citric acid at 80°C leaching temperature for 180 min leaching time. The Fe, Pb and As dissolutions were determined as less than 20% under the conditions tested. 95.5% Fe and 68.8% As were removed from the flotation tailing along with less than 5% of Zn and Pb using 1.0 M oxalic acid for 180 min. leaching time at 60°C leaching temperature. It was found that citric acid is more prominent than oxalic acid for the selective leaching of zinc from the flotation tailing whereas a substantial amount of iron and arsenic removal can be achived by oxalic acid leaching. The use of NaCl along with citric acid was not useful for higher Zn dissolution. Based on the experimental results, an appropriate process will be improved for the selective leaching of valuable metals from the Pb-Zn non-sulphide flotation tailing in the near future. © 2020 Elsevier B.V., All rights reserved.Article Citation - WoS: 16Citation - Scopus: 16Arsenic Removal by the Micellar-Enhanced Ultrafiltration Using Response Surface Methodology(Iwa Publishing, 2019-12-27) Gokcek, Oznur Begum; Uzal, NigmetThe present research investigates the removal of arsenic (As) from aqueous solutions using micellar-enhanced ultrafiltration (MEUF) by utilizing two different surfactants: benzethonium chloride and dodecyl pyridinium chloride (BCl and DPCl). The impact of the operating variables and maximum removal efficiency were found under different conditions for BCl and DPCl surfactants. The maximum As rejection efficiency for MEUF with BCl and DPCl surfactants is 92.8% and 84.1%, respectively. In addition to this, a statistics-based experimental design with response surface methodology was used for the purpose of examining the impact of operating conditions, including initial pH, initial As concentration (ppb), and surfactant concentration (BCl, mM) in As-removal from aqueous solutions. In the analysis of the experimental data, a second-order polynomial model that was validated by statistical analysis for the BCl surfactant was used. On the basis of the response model created, the removal of As ions was acquired at optimum operating parameters, including the initial As concentration of 150 ppb, surfactant concentration of 5 mM and pH 10 for the BCl surfactant with 92.8% As-removal efficiency.