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    Electro-oxidation of cytostatic drugs: Experimental and theoretical identification of by-products and evaluation of ecotoxicological effects
    (Elsevier Science Sa, 2018) Barışçı, Sibel; Türkay, Özge; Ulusoy, Ebru; Şeker, Mine Gül; Yüksel, Ebubekir; Dimoglo, Anatoli
    Methotrexate (MTX) and Capecitabine (CPC) as mostly used cytostatic drugs were degraded by electro-oxidation process in this study. Ti/IrO2-RuO2 electrode was used to provide anodic oxidation. The effect of change of current density, initial pH of the solution and supporting electrolyte concentration on electro-oxidation of cytostatic drugs was evaluated. Current density of 30 mA/cm(2), neutral pH and supporting electrolyte concentration of 200 mg L-1 were determined as optimum operational parameters. After oxidation process, the transformation by-products of cytostatic drugs were identified by LC-MS-MS analysis. Density functional theory (DFT) modelling was performed and the calculations were given in harmony with analytic results. In addition, toxicity evaluation on the electro-oxidation was assessed due to the possible toxic effect of the metabolites after treatment process. Indeed, the transformation by-products of MTX showed toxic effects after treatment, however; the metabolites CPC did not cause toxicity although lower removal efficiency.
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    Electrochemical Reduction of X-ray Contrast Iohexol at Mixed Metal Oxide Electrodes: Process Optimization and By-product Identification
    (Springer International Publishing Ag, 2018) Türkay, Özge; Barışçı, Sibel; Ulusoy, Ebru; Dimoglo, Anatoli
    The reduction of commonly used X-ray contrast iohexol (IOX) by the electrooxidation process is presented in this study. To begin with, the effect of anode material was examined, and different mixed metal oxide electrodes (MMOs) such as Ti/RuO2, Ti/Pt, Ti/IrO2-RuO2, Ti/IrO2-Ta2O5, Ti/Ta2O5-SnO2-IrO2, and Pt/SnO2 were used. To assess experimental conditions at Ti/RuO2 anode, provided the highest removal efficiency, the response surface method was applied and the key influencing parameter was the process time. The determined optimal conditions were triplicated with real wastewater samples, and the average degradation efficiency of IOX was found to be 99%. By-products of the IOX degradation on the Ti/RuO2 anode have been identified using density functional theory and LC/MS-MS analysis. The results showed that IOX degradation opened with OH group detachment and resulted in the formation of a by-product with a molecular mass of 804 g mol(-1). Further degradation mechanism took place due to the breakup of C-4-C-10 and C-5-I-7 bonds with a by-product formed as 603 g mol(-1). Iodide atom replacement by OH groups caused the formation of a molecular fragment with 375 g mol(-1) molecular weight. The further disintegration of C-2-C-11 and C-6-N-16 sigma- bonds led to the formation of molecular masses of 133, 126, and 119 g mol(-1), respectively.
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    Electrochemical treatment of anti-cancer drug carboplatin on mixed-metal oxides and boron doped diamond electrodes: Density functional theory modelling and toxicity evaluation
    (Elsevier Science Bv, 2018) Barışçı, Sibel; Türkay, Özge; Ulusoy, Ebru; Soydemir, Gülfem; Şeker, Mine Gül; Dimoglo, Anatoli
    This study represents the electrooxidation of anti-cancer drug carboplatin (CrbPt) with different mixed metal oxide (MMO) and boron doped diamond (BDD) electrodes. The most effective anode was found as Ti/RuO2 with the complete degradation of CrbPt in just 5 min. The effect of applied current density, pH and electrolyte concentration on CrbPt degradation has been studied. The degradation of CrbPt significantly increased at the initial stages of the process with increasing current density. However, further increase in current density did not affect the degradation rate. While complete degradation of CrbPt was provided at pH 7, the degradation rates were 49% and 75% at pH 9 and 4, respectively. Besides, increasing supporting electrolyte (Na2SO4) concentration provided higher degradation rate but further increase in Na2SO4 concentration did not provide higher degradation rate due to excess amount of SO4-2 According to the DFT calculations, the formation of [Pt(NH3)(2) (H2O)(2)](2+) and [Pt(NH3)(2) (OH)(2)] takes place with molecular weights of 265 and 263 gmol(-1), respectively. Toxicity of treated samples at BDD and Ti/RuO2 electrodes has been also evaluated in this study. The results showed that Ti/RuO2 anode provided zero toxicity at the end of the process. (C) 2017 Elsevier B.V. All rights reserved.