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...
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/...
Valorization of loquat seeds by hydrothermal carbonization for the production of hydrochars and aqueous phases as added-value products
Gözmen, Belgin | Görmez, Özkan | Saçlı, Barış | Çalhan Doğan, Selda
In the framework of circular bio-economy, waste loquat seeds were utilized for the production of two addedvalue products. The seeds were hydrothermally carbonized at a temperature range of 150–250 ◦C and time range 2–6 h and the resultant hydrochars and aqueous phases were characterized using various methods. The optimum higher heating value of 30.64 MJ kg− 1 , ash content of 1.99 wt % and alkali index of 0.05 were achieved for the hydrochar prepared at 250 ◦C and 6 h, establishing its suitability for energy-related applications. The aqueous phase obtained at 250 ◦C and 6 h achieved 90% scavenging of the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical and had a IC50 value of 43.71 μg mL− 1 . Principal component analysis showed that the production of phenols, ketones, alkenes a...
A dual purpose aluminum-based metal organic framework for the removal of chloramphenicol from wastewater
Gözmen, Belgin | Geçgel, Cihan | Görmez, Özkan | Turabik, Meral
The presence of antibiotics in the aquatic environment can cause significant environmental and human health problems even at trace concentrations. Conventional treatment systems alone are ineffective in removing these resistant antibiotics. To address this problem, oxidation and adsorption techniques were used to explore the removal of recalcitrant antibiotic chloramphenicol (CAP). An aluminum-based metal-organic framework (AlMIL) with high surface area and extended porosity, was prepared and used both as adsorbent and catalyst for the oxidation of CAP. Characterization of the Al-MIL revealed a large surface area of 1137 m2 g− 1 , a homogeneous microporous structure, good crystallinity, and particle size in the range of 200–400 nm. Adsorption of CAP on AlMIL achieved equilibrium afte...
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...
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...
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...
Evaluation of sewage sludge biochar and modified derivatives as novel SPE adsorbents for monitoring of bisphenol A
Gözmen, Belgin | Sönmez, Özgür
Sewage sludge is abundant biomass, the sustainable management of which remains a big issue worldwide. It was demonstrated that pyrolysis of sewage sludge using simple and cost-effective apparatus can produce biochars, suitable for solid-phase extraction applications of hydrophobic analytes. Detailed characterization showed that modification lead to three more hydrophobic and one more hydrophilic sample, compared to the original biochar. All samples were evaluated in the solid-phase extraction of the emerging contaminant Bisphenol A from aqueous solutions. KOH-SSB and KOH/MeOH-SSB exhibited the most promising behavior, with the latter achieving recoveries of 88.1%, at a quantity of 0.1 g at the natural pH of the BPA solution (6.5). The effect of solution pH was insignificant in the range of...
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...
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...
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...
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...