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Kurum Dışı Yazarlar Berkant Kayan
169789

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...

169792

Adsorption of Malachite Green on Fe-modified biochar: influencing factors and process optimization

Gözmen, Belgin

Paper sludge and wheat husk biochar was converted to a Fe-composite through a simple coprecipitation process and its adsorption behavior was tested against an emerging pollutant, Malachite Green (MG). Response surface methodology was employed to determine the optimum experimental conditions and the interactions between pH, initial MG concentration, temperature and treatment time. The maximum adsorption percentage obtained experimentally was 97.1%, whereas the Box– Behnken design predicted a maximum adsorption of 98%, at pH 6.16, initial MG concentration of 6.56 ppm, temperature of 34.75°C and treatment time of 22 min. Compared with the original biochar, the Fe-modified sample improved the adsorption of MG by ~34%. The adsorption mechanism followed the Langmuir model (qmax = 172.3 mg/...

169811

Fe-modified sporopollenin as a composite biosorbent for the removal of Pb2+ from aqueous solutions

Gözmen, Belgin

The role of Fe-modified sporopollenin (Fe-Sp) biomass in Pb2+ removal from aqueous solutions was investigated by batch biosorption technique. The prepared biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, and Fourier transform infrared spectroscopy. The influence of pH, contact time, biosorbent dose, and initial concentration on biosorption process were optimized by using a four factor Box–Behnken design combined with response surface methodology. The results indicated a positive adsorption behavior of Fe-Sp and a strong pH dependency of the process. The optimum predicted parameters were determined as follows: biosorbent dosage 0.5 g, pH of 6.75, contact time 104 min, and initial Pb2+ concentration of 25.42 ppm. The Freundlich isotherm mode...

169679

CoFe2O4 nanoparticles decorated onto graphene oxide and graphitic carbon nitride layers as a separable catalyst for ultrasound-assisted photocatalytic degradation of Bisphenol-A

Görmez, Özkan | Gözmen, Belgin | Yakar, Ezgi

The advanced oxidation process (AOP) through ultrasound-assisted photocatalytic degradation has attracted much attention in removing emerging contaminants. Herein, CoFe2O4-GO and CoFe2O4-g-C3N4 nanocomposites were synthesized using the ultrasound-assisted co-precipitation method. TEM, XRD, XPS, EDS, SEM, and FT-IR techniques characterized the structural, morphological, and chemical properties of the synthesized nanocomposites. The analyses showed that CoFe2O4 structure was nano-sized and distributed more homogeneously in graphene oxide (GO) layers with oxygenated functional groups than graphitic carbon nitride (g-C3N4). While the efficiency of composite catalysts, as photocatalysts, for degradation of bisphenol-A (BPA) was low in the visible region in the presence of persulfate, thei...

169669

Adsorption of 2,4-dichlorophenol on paper sludge/wheat husk biochar: Process optimization and comparison with biochars prepared from wood chips, sewage sludge and hog fuel/demolition waste

Gözmen Belgin

The adsorption of 2,4-dichlorophenol, a toxic by-product of triclosan commonly found in wastewater treatment plant effluents, was studied on paper sludge/wheat husks biochar. By using response surface methodology, the optimum conditions and effects of pH, temperature, initial 2,4-DCP concentration and time were determined. The solution pH was found to be the most influential parameter whereas the optimum adsorption conditions were predicted as: C0 = 40.28 mg L−1 , T = 326 K, pH = 2.8, t = 143 min, where a 99.95% adsorption could be achieved. Both Langmuir and Freundlich provided a good fit for the experimental data, indicating a surface and multi-layer adsorption. Kinetically, the process primarily followed the pseudo-second order model (chemisorption). By comparing the adsorption c...

169745

Fe‑modified hydrochar from orange peel as adsorbent of food colorant Brilliant Black: process optimization and kinetic studies

Gözmen, Belgin | Turunç, Ersan

The main aims of this work were to produce and characterize Fe-modified hydrochar from orange peel waste, optimize the adsorption through response surface methodology, investigate the role of treatment time, dye concentration, adsorbent dose and temperature, and determine the dominant mechanisms through kinetics analysis. Orange peel waste was hydrothermally carbonized at 200 °C for 8 h, and the hydrochar was embedded with magnetite nanoparticles. The composite adsorbent was characterized through spectrometric and surface analytical methods. Subsequently, analysis of variance was used to design the experimental runs, propose a polynomial equation describing the adsorption process and finally optimize the adsorption conditions. The results indicated that 99% removal can be theoreticall...

169840

Acid Red 1 and Acid Red 114 decolorization in H2O2-modified subcritical water: process optimization and application on a textile wastewater

Gözmen, Belgin

Solutions of Acid Red 1 and Acid Red 114 were treated in H2 O2 -modified subcritical water in the temperature range of 100°C–200°C for up to 60 min. Response surface methodology based on the Box-Behnken design was used to optimize the process. For Acid Red 1, optimum decolorization of 97% can be achieved at 192°C, 181 mM H2 O2 , 51.3 min treatment time, and 121 mg/L dye concentration. For Acid Red 114, the optimum conditions were 195°C, 157 mM H2 O2 , 38 min treatment time and 110 mg/L dye concentration, where 91% decolorization could be obtained from the proposed model. It was determined that temperature is the most important factor, followed by the oxidant concentration. Degradation was less efficient for AR114 due to the double azo bonds, compared to the single azo bond of A...

169672

Degradation of Acid Red 274 using H2O2 in subcritical water: Application of response surface methodology

Gözmen Belgin

In this research, the degradation of Acid Red 274 (AR 274) was investigated under subcritical water conditions using H2O2, which led to the oxidative degradation of Acid Red 274 up to its 80% of mineralization. The Box–Behnken design matrix and response surface methodology (RSM) were applied in designing the experiments for evaluating the interactive effects of the three most important operating variables. Thus, the interactive effects of temperature (100–250 °C), oxidant (H2O2) concentration (50–250 mM), and time (30–60 min.) on the degradation of AR 274 were investigated. A total of 17 experiments were conducted in this research, and the analysis of variance (ANOVA) indicated that the proposed quadratic model could be used for navigating the design space. The proposed model was essential...

169678

Preparation and application of Fe-modified banana peel in the adsorption of methylene blue: Process optimization using response surface methodology

Gözmen, Belgin | Turunç, Ersan

Banana peel was used as the feedstock for the preparation of a magnetic adsorbent for the adsorption of methylene blue (MB) in aqueous solutions. The Fe-modified banana peel was characterized by surface and spectrometric methods. The Box-Behnken design (BBD) was used for determining the conditions of each experimental run and optimization of adsorption was achieved through response surface methodology. The R2, adjusted R2, and predicted R2 coefficients of the employed BBD model were determined as 0.9820, 0.9686, and 0.9182, respectively, indicating a high level of agreement between the experimental data and the proposed theoretical model. The optimum MB adsorption of 91.89% was achieved at an adsorption time of 50 min, temperature of 45 °C, adsorbent dosage of 2.5 g and MB concentration of...

167242

OXIDATION OF TOLUENES TO AROMATIC ALDEHYDES WITH MOLECULAR OXYGEN IN SUBCRITICAL WATER

Recep Özen, Ahmet M. Gizir & N. Simsek Kus

Oxidations are important transformations in organic synthesis. In general, many oxidations are carried out with a large excess of chromium or manganese reagents. The metal residues are environmentally undesirable and often cause problems during work-up.2 In addition organic oxidations in the chemical industry have traditionally been performed in either aromatic or halogenated solvents.' One of the most attractive oxidants is molecular oxygen? since oxygen is highly soluble in subcritical water. Molecular oxygen has been used as the reagent for the oxidation of alkyl aromatic compounds in the presence of different catalysts, such as MnBr.

169841

Degradation of nitroaromatic compounds in subcritical water: application of response surface methodology

Gözmen, Belgin | Gizir, Ahmet Murat

In this study, subcritical water has been used as a medium for degradation of 2,4-dinitrotoluene (2,4-DNT), 4-nitrotoluene (4-NT) and 2-amino-4-nitrotoluene (2-A-4-NT). The effect of temperature, oxidant concentration and time were studied and the optimal combination of reaction parameters was established using response surface methodology in a Box-Behnken design. Of all the parameters examined, temperature showed the most positive effect on the degradation of the nitroaromatic compounds. Optimal reaction conditions were found to be a temperature of 240°C, 210°C and 236°C, time of 180, 178 and 172 min, oxidant concentration of 100, 99.64 and 99.61 mM for 2,4-DNT, 4-NT and 2-A-4-NT, respectively. Since high-temperature was applied, the possibility of formation of subcritical degradat...