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Öğe A comparative evaluation of the response of platinum and mineral electrodes in sulfide mineral pulps(ELSEVIER SCIENCE BV, 2008) Kocabag, Duran; Guler, TakiThe pulp potential of galena, chalcopyrite and pyrite have been measured in parallel with Pt and mineral electrodes by controlling the potential with oxidizing (H2O2 and K2Cr2O7) and reducing (Na2S and Na2S2O4) agents under "free to change conditions" to follow the adaptability of different electrodes to the dynamically changing conditions. It has been determined that while mineral and Pt-electrodes indicated similar potential values in the same environment under acid and reducing conditions, they showed quite different potential values under oxidizing and alkaline conditions. The difference between the measured potentials decreased in the following order: Pt-galena > Pt-chalcopyritc > Pt-pyrite, which is in accordance with the electrochemical activity of minerals. Poisoning of Pt-electrode by Na2S2O4 was observed, whereas no serious poisoning was seen with sulfide ions. (C) 2008 Elsevier B.V. All rights reserved.Öğe Electrochemical study of pyrite-ovalbumin interaction in relation to flotation(ELSEVIER SCIENCE BV, 2013) Guler, Taki; Sahbudak, Kemal; Cetinkaya, Sevil; Akdemir, UnalOvalbumin (OVA), chicken egg albumin, is an environmentally friendly, non-toxic, cheap surface active agent. It has electrochemically active sulfhydryl residues in molecular structure. OVA adsorption on pyrite as an alternative depressant was investigated by cyclic voltammetry, FTIR spectroscopy and flotation. Tests were conducted in a wide potential range in alkaline pH to clarify the role of electrochemical condition on the adsorption mechanisms and the rate of depression. In the absence of OVA, the floatability reached its maxima around slightly oxidizing condition. Beyond the range, it decreased presumably due to the formation of Fe-oxyhydroxides together with the hydrophilic S-containing species. OVA-pyrite interaction occurred in the whole examined potential range. Depressing effect of OVA increased gradually from reducing to slightly oxidizing potential, open circuit potential (OCP) of pyrite, mainly due to weak conformational changes in OVA molecules together with the hydrophobic interaction around OCP. The rate of depression reached its maxima at moderately oxidizing potentials, which was referred to electrostatic attraction. This level was almost kept at higher potentials owing to OVA adsorption as metal-chelates.Öğe IMPACT OF OVALBUMIN ON PYRITE FLOTATION IN THE ABSENCE AND PRESENCE OF METAL IONS(OFICYNA WYDAWNICZA POLITECHNIKI WROCLAWSKIEJ, 2014) Guler, Taki; Sahbudak, Kemal; Akdemir, Unal; Cetinkaya, SevilRecovery of gangue pyrite and its accidental activation are vital issues in flotation of complex sulfide ores. This work was performed by cyclic voltammetry (CV) and flotation tests to elucidate applicability of ovalbumin (OVA) as depressant for pyrite. The synergetic effect of metal ions in addition to its possible use in case of accidental activation by metal ions. CV tests stated that OVA adsorbed irreversibly on pyrite, and restricted electron transfer up to moderately oxidizing potentials due to electrostatic interaction together with weak hydrophobic interactions. At highly oxidizing potentials, adsorption occurred through electrochemical mechanisms through formation of metal-OVA chelates. Rate of pyrite depression with OVA was found to be potential dependent reaching its peak point around moderately oxidizing potentials both in absence and presence of metal ions. Electrochemically active metals display synergetic effect with OVA on pyrite depression, whereas noble metals activate pyrite and reduced depressing potency of OVA.Öğe Phase variation and mechanical properties of waste calcium carbonate to substitute quartz in composite slab production(Wiley, 2023) Bas, Sedanur; Guler, Taki; Ozer, Ali; Akturk, Selcuk; Kriven, Waltraud M.Owing to the fast-emerging nature and rapid advancements in the construction industry, huge volumes of marble dust (MD) are generated as reject during slab cutting in marble processing, causing significant environmental hazards. Nowadays, quartz composite slabs have increasingly been preferred in building works due to their excellent hygienic property and mechanical strength. Composite slab is produced using micronized quartz as filler, the grinding of which is an energy-intensive process. Substitution of micronized quartz with MD at different percentages was investigated in natural form and after roasting. Natural MD offered appreciable physical properties closer to those of a quartz composite slab. Physical properties slightly retrograded by quartz supplementation in the raw form. Roasting the filler led to the formation of rounded Ca-silicate. Wollastonite was the first phase formed after sintering at the lowest MD percentage and shortest roasting times. Larnite became dominating phase first by increasing MD percentage and roasting time, and then calcio-olivine formed. Physical characterization test results demonstrated that hardnesses of new phase and particle shape were the key parameters that improved slabs' mechanical properties of. Hard rounded larnite particles improved mechanical behavior of slabs having the synergic effect of quartz, whereas wollastonite did not show a significant effect.Öğe Statistical evaluation of flotation and entrainment behavior of an artificial ore(ELSEVIER SCIENCE BV, 2012) Guler, Taki; Akdemir, UnalThe role of several parameters on gangue recovery in froth was investigated. Effects of frother type and collector dosage on flotation performance were tested at pH 10. The results were evaluated statistically by two-way analysis of variance without replicates, sample range and sample standard deviation. Hydrophilic mineral was recovered mainly by entrainment through hydrophobization of Ca+2-activated quartz from tap-water in the presence of Na-oleate as collector; entrapment and slime coating were also proposed as recovery mechanisms in minority. Degree of gangue-entrainment in froth product increases by reduction in liberation size. The experimental results state that selectivity would be improved by increasing collector concentration and reducing the flotation time.
