Comparative degradation of 5-fluorouracil in aqueous solution by using H2O2-modified subcritical water, photocatalytic oxidation and electro-Fenton processes

Gözmen, Belgin

This study investigated the degradation of the antineoplastic agent 5-fluorouracil (5-FU) widely applied to treat different cancers using different advanced oxidation processes such as electro-Fenton (EF), photocatalysis with TiO2, and H2O2-modified subcritical water oxidation. The treatment with the EF process was the most efficient compared to others. Interestingly, in the EF process, the oxidative degradation of 5-FU behaved differently depending on the anode used. At low currents (20 and 40 mA), Pt and DSA anodes performed better than BDD and Ti4O7 anodes. In contrast, at the higher current of 120 mA, the production of heterogeneous hydroxyl radicals (M(• OH)) became important and contributed significantly to the oxidation of 5-FU in addition to homogeneous • OH generated in th...

Beta-laktam grubu antibiyotik kalıntılarının atıksularda tespiti ve fenton, fotokatalitik, elektro-fenton oksidasyon yöntemleri ile arıtılabilirliğinin incelenmesi

Koyuncu Türkay, Gamze

Efficient removal of insecticide “imidacloprid” from water by electrochemical advanced oxidation processes

Turabik, Meral | Gözmen, Belgin

The oxidative degradation of imidacloprid (ICP) has been carried out by electrochemical advanced oxidation processes (EAOPs), anodic oxidation, and electro-Fenton, in which hydroxyl radicals are generated electrocatalytically. Carbon-felt cathode and platinum or boron-doped diamond (BDD) anodes were used in electrolysis cell. To determine optimum operating conditions, the effects of applied current and catalyst concentration were investigated. The decay of ICP during the oxidative degradation was well fitted to pseudo-first-order reaction kinetics and absolute rate constant of the oxidation of ICP by hydroxyl radicals was found to be kabs(ICP)=1.23×109 L mol−1 s −1 . The results showed that both anodic oxidation and electro-Fenton process with BDD anode exhibited high minera...

Indirect Electrochemical Treatment of Bisphenol A in Water via Electrochemically Generated Fenton's Reagent

Gözmen, Belgin

Bisphenol A (BPA) has been treated with electrochemically generated Fenton's reagent in aqueous medium. Hydroxyl radicals that were formed in Fenton's reagent reacted with the organic substrate producing two different isomers of monohydroxylated product and, upon successive hydroxylation, mainly one dihydroxylated product. Further hydroxylation first degraded one of the aromatic rings, and the side chain thus formed was then cleaved off the other aromatic ring. The second aromatic ring was also degraded upon successive hydroxylations. Small saturated and unsaturated aliphatic acids were the last products prior to mineralization. It was found that use of cuprous/cupric ion pair resulted a faster conversion of BPA and faster mineralization when compared using ferrous/ferric ions, b...

Comparison of the heterogeneous GO-FePO4/electro-Fenton against the homogeneous Fe(II) ion and Fe(III)-oxalate complex/electro-Fenton for the degradation of metronidazole

Gözmen, Belgin | Görmez, Özkan

This study compared the effect of the homogeneous and the heterogeneous electro-Fenton (EF) processes on the degradation of Metronidazole (MTZ). Graphene oxide (GO)-FePO4 synthesized for use in the heterogeneous electro-Fenton process was characterized using FTIR, FE SEM-EDS and XRD analysis. The analyses showed that the amorphous composite structure formed as a result of FePO4 structures dispersed between the GO layers has an average particle size distribution of 141 nm. The activity of the GO-FePO4 catalyst was more effective at pH 3 than pH 5 which is the own pH value of metronidazole. In the heterogeneous EF process, the mineralization percentage was determined as 66% at pH 3, 0.5 g L−1 catalyst dosage after 5 h. No difference was observed in the structure of GO-FePO4, which can be use...

Hydrothermal Synthesis of Siderite and Application as Catalyst in the Electro-Fenton Oxidation of p-Benzoquinone

Görmez, Özkan | Gözmen, Belgin

A weak aspect of the electro-Fenton (EF) oxidation of contaminants is the dependence of the Fenton reaction on acidic pH values. Therefore, the rationale of this work was to develop a novel catalyst capable of promoting the EF oxidation process at near-neutral and basic pH values. In this framework, rhombohedral FeCO3 was synthesized hydrothermally and used as a catalyst in the EF oxidation of p-benzoquinone (BQ). The catalyst was characterized using various surface and spectroscopic methods. Moreover, the effects of applied current (100–500 mA), time (1–9 h), catalyst dosage (0.25–1.00 g L−1 ), and initial concentration of BQ (0.50–1.00 mM) on the total organic carbon removal efficiency were determined. The results indicated that a 400 mA current was sufficient for a 95% total or...

Degradations of model compounds representing some phenolics in olive mill wastewater via electro‐Fenton and photoelectro‐Fenton treatments

Gözmen, Belgin

The electrochemical oxidation of vanillic acid, o‐coumaric acid and protocatechuic acid, three representative toxic phenolics in olive mill wastewater, was studied using carbon felt cathode in the electro‐Fenton system. Results obtained, in the presence or absence of UV support, were compared throughout the degradation processes up to mineralization. It was demonstrated that all three phenolic compounds reacted completely with hydroxyl radicals and degraded efficiently. It was shown in the photoelectro‐Fenton process that the degradation and mineralization efficiency of the phenolic compounds were enhanced by the effect of UV light, especially at the later stages of the degradation processes.

Application and Performance Evaluation of Chemical Coagulation, Electrocoagulation, Electro-Fenton and Anodic Oxidation Processes in the Treatment of Glass Fiber Manufacturing Wastewater

Gözmen, Belgin | Görmez, Özkan

This study investigated the oxidation of wastewater generated during the production of glass fiber manufacturing material, which contains high organic carbon (18.32 g/L) and has a pH of 8.8, by chemical coagulation, electrocoagulation and electroadvanced oxidation techniques. It was determined that the total organic content (TOC) of wastewater was reduced by 53% using the chemical coagulation method. After electrocoagulation with Al/Al electrode pair for 300 minutes at 500 mA, 73% TOC removal was achieved at pH 8.8. While 50% TOC removal was completed in 2 h at 400 mA in electrocoagulation with Fe/Fe electrode pair, 71% TOC removal was obtained in the combined electrocoagulation/electro-Fenton process by adding hydrogen peroxide to the medium under the same conditions. In addition,...

Heterogeneous electro-fenton treatment of clofibric acid with a Fe3O4 loaded bifunctional carbon felt cathode via different anode types

Gözmen, Belgin | Çirmi, Doğan

Pharmaceutical pollutants such as clofibric acid pose significant risks to aquatic environments and human health. In this study, a bifunctional cathode (CF@Fe3O4) was synthesized by anchoring Fe3O4 nanoparticles onto carbon felt via a solvothermal method. The material was characterized using scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The CF@Fe3O4 cathode was then evaluated in a heterogeneous electro-Fenton system for clofibric acid degradation under varying pH and current conditions using platinum and boron doped diamond anodes. Using the CF@Fe3O4/Pt pair, the highest mineralization efficiency (82%) was achieved at pH 3 and 50 mA after 5 h, whereas higher current intensities resulted in decreased mineralization. In contrast, the CF@Fe3...

Carbon felt/CoFe2O4 cathode synthesis and use in the heterogeneous electro-Fenton process for vanillin oxidation

Gözmen, Belgin | Çirmi, Doğan

Synthetic vanillin is widely used in industries such as food and cosmetics, and it isalso produced as a by-product in various processes. This study was conductedto compare the degradation of vanillin using homogeneous and heterogeneouselectro-Fenton (EF) processes. Initially, electrocatalytic characterization was per-formed on a cathode material synthesized by solvothermal deposition of cobalt fer-rite (CoFe 2 O4 ) nanostructures onto a carbon felt (CF) substrate and compared withbare CF. Subsequently, the effectiveness of the CF@CoFe 2O 4 cathode material invanillin oxidation was compared at different pH values and currents with the hetero-geneous electro-Fenton process. The highest vanillin degradation and total organiccarbon (TOC) removal were achieved at pH 3. Following a 3 h heterogen...

Degradation of chloramphenicol and metronidazole by electro-Fenton process using graphene oxide-Fe3O4 as heterogeneous catalyst

Gözmen Belgin | Görmez Özkan

This study investigates the degradation and mineralization of two widely used antibiotics, chloramphenicol and metronidazole, by an electro-Fenton process using graphene oxide-Fe3O4 as a heterogeneous catalyst. The graphene oxide-Fe3O4 composite was typically characterized through conventional spectroscopic and surface analytical methods. The effects of treatment time, pH, catalyst concentration and applied current were examined. In the absence of the graphene oxide-Fe3O4 catalyst (homogeneous environment), the optimum mineralization rates obtained were 57 and 71% at pH 3 and 300 min treatment time for metronidazole and chloramphenicol solutions, respectively. When the optimum graphene oxide-Fe3O4 concentration of 0.5 g L−1 was used, mineralization rates of 73 and 86% were achieved respect...

Indirect electrochemical treatment of bisphenol A in water via electrochemically generated Fenton's reagent
ndirect Electrochemical Treatment of Bisphenol A in Water via Electrochemically Generated Fenton's Reagent

Gözmen Belgin

Bisphenol A (BPA) has been treated with electrochemically generated Fenton's reagent in aqueous medium. Hydroxyl radicals that were formed in Fenton's reagent reacted with the organic substrate producing two different isomers of monohydroxylated product and, upon successive hydroxylation, mainly one dihydroxylated product. Further hydroxylation first degraded one of the aromatic rings, and the side chain thus formed was then cleaved off the other aromatic ring. The second aromatic ring was also degraded upon successive hydroxylations. Small saturated and unsaturated aliphatic acids were the last products prior to mineralization. It was found that use of cuprous/cupric ion pair resulted a faster conversion of BPA and faster mineralization when compared using ferrous/ferric ions, b...