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Öğe Acid Red 1 and Acid Red 114 decolorization in H2O2-modified subcritical water: process optimization and application on a textile wastewater(Desalination Publications, 2017) Kayan, Berkant; Akay, Sema; Kulaksız, Esra; Gözmen, Belgin; Kalderis, DimitriosSolutions of Acid Red 1 and Acid Red 114 were treated in H2O2-modified subcritical water in the temperature range of 100 degrees C-200 degrees 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 degrees C, 181 mM H2O2, 51.3 min treatment time, and 121 mg/L dye concentration. For Acid Red 114, the optimum conditions were 195 degrees C, 157 mM H2O2, 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 AR1. Application of the optimum treatment conditions on real reactive dye wastewater resulted in 92.7, 79.1 and 20.4% removal of BOD5, COD and TSS, respectively.Öğe 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(Elsevier Ltd., 2017) Kalderis, Dimitrios; Kayan, Berkant; Akay, Sema; Kulaksız, Esra; Gözmen, BelginThe 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: C-0 = 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 capacity at equilibrium of our main biochar (q(e) = 9.28 mg g(-1)) to 3 biochars prepared from different biomasses (q(e) values 1.57-2.96 mg g(-1)), it was concluded that pH-dependent electrostatic interactions and non-covalent pi-electron donor-acceptor mechanisms play the most important role. Finally, there was indication that high concentrations of Ca and K may promote the adsorbate-adsorbent interactions and enhance adsorption.Öğe Adsorption of Malachite Green on Fe-modified biochar: Influencing factors and process optimization(Desalination Publications, 2017) Kulaksız, Esra; Gözmen, Belgin; Kayan, Berkant; Kalderis, DimitriosPaper sludge and wheat husk biochar was converted to a Fe-composite through a simple co-precipitation 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 degrees C and treatment time of 22 min. Compared with the original biochar, the Fe-modified sample improved the adsorption of MG by similar to 34%. The adsorption mechanism followed the Langmuir model (q(max) = 172.3 mg/g, correlation coefficient 0.960) and the kinetics of the process were best described by the pseudo-second-order model (correlation coefficient 0.9818), although boundary layer effects were also observed.Öğe An easily fabricated palladium nanocatalyst on magnetic biochar for Suzuki-Miyaura and aryl halide cyanation reactions(Royal Society of Chemistry, 2021) Turunç, Ersan; Akay, Sema; Baran, Talat; Kalderis, Dimitrios; Tsubota, Toshiki; Kayan, BerkantBiochar is a carbon-rich solid, the surface of which is covered with a high density of functional carbonyl, hydroxyl and carboxylic acid groups. In this work, palladium nanoparticles were embedded on magnetic biochar and a new reusable and environmentally-friendly catalyst was developed and applied for the promotion of Suzuki-Miyaura C-C coupling and cyanation reactions. The high-carbon (77%), low-ash content (5.8%) and the relatively high surface area (266 m(2) g(-1)) of pine tree biochar (PTB) suggested that it might be highly suitable as a catalyst substrate. The Fe3O4-Pd-biochar nanocomposite was successfully characterized using SEM, TEM, EDX, FT-IR, BET and XRD. Its catalytic role was initially evaluated using p-NO2C6H4I as a model reactant (for both types of reactions) and later for the production of biaryls and benzonitriles from a wide range of aryl halides under mild reaction conditions. Biaryls and benzonitriles were characterized using GC-MS. In the case of the Suzuki-Miyaura reaction, the optimum yield of 98% was obtained with a catalyst concentration of 0.04 mol%, microwave irradiation of 400 W, and a residence time of 5 min, using K2CO3 as the base. With respect to the cyanation reaction, dimethylformamide, Na2CO3 and 6 h were the optimum solvent, base and reaction duration, respectively. Subsequently, the nanocatalyst showed excellent catalytic activity in both reactions, achieving >88% yields in most cases, regardless of the aryl iodide or bromide used and the type of substitution.Öğe Assessment of a Pd-Fe3O4-biochar nanocomposite as a heterogeneous catalyst for the solvent-free Suzuki-Miyaura reaction(Elsevier, 2021) Akay, Sema; Baran, Talat; Kayan, Berkant; Kalderis, DimitriosThe objective of this study was the development of a novel, biochar-based Pd nanocatalyst and its evaluation for the promotion of the Suzuki-Miyaura coupling reaction. The Fe3O4-Pd-biochar composite was successfully characterized through a range of spectroscopic and elemental analysis techniques. Its catalytic activity was initially assessed using p-NO2C6H4I as a model reactant and later for the production of biaryls from a wide range of aryl halides, under microwave irradiation and solvent-free conditions. The optimum yield of 99% was obtained at a catalyst dosage of 8 mg, microwave irradiation of 400 W, 6 min residence time, using K2CO3 as the base. Furthermore, the catalyst promoted the Suzuki-Miyaura reaction of aryl iodides and bromides (yields in the range of 88-97 and 86-97%, respectively), but was less successful for aryl chlorides (yields 78-83%). The presence of Fe3O4 allowed for the quick recovery of the catalyst, whereas repeated runs established its recyclability.Öğe Assessment of Orange Peel Hydrochar as a Soil Amendment: Impact on Clay Soil Physical Properties and Potential Phytotoxicity(Springer Netherlands, 2019) Kalderis, Dimitrios; Papameletiou, George; Kayan, BerkantPurpose: The main objectives of this work were the following: (1) to investigate the applicability of orange peel hydrochar as a soil amendment for improving the physical properties of a compacted, clay soil and (2) to study the growth of maize on substrates composed of clay soil and hydrochar and determine any potential phytotoxic effects. Methods: The effect on soil’s bulk density (BD), aeration, water holding capacity (WHC), and hydraulic conductivity were examined with hydrochar additions of 5, 10 and 15% (w/w) and determined by conventional laboratory methods. Potential phytotoxic effects were determined through the Zucconi germination index on fresh, diluted and 4-week old undiluted hydrochar extracts. The effect of hydrochar on maize growth was studied in clay soil (as reference), clay soil with 5% (w/w) fresh hydrochar, clay soil with 5% (w/w) of 4-week-old hydrochar and clay soil with 5% (w/w) biochar (for comparison). Results: At an application rate of 5% (w/w) hydrochar, the bulk density was reduced from 1.35 to 1.22 g/cm3, the air-filled porosity was increased from 33 to 37% and the saturated hydraulic conductivity from 0.96 to 1.01 cm/h. The water holding capacity remained practically unchanged, however it was considerably reduced at higher application rates. The seed germination test indicated strong phytotoxicity of the fresh, undiluted hydrochar extract, which was reduced when the extract was diluted or the hydrochar allowed to mature for 4 weeks. The pot tests indicated that hydrochar did not improve the yield of maize, probably due to the presence of phytotoxic substances. Conclusions: This study demonstrated a new valorization pathway for a significant agricultural waste. Additionally, it proved the applicability of orange peel hydrochar for improving the physical properties of clay soil. However, due to phytotoxic effects, further work is required before a field application is considered. © 2018 Springer Nature B.V.Öğe Comparative degradation of 5-fluorouracil in aqueous solution by using H2O2-modified subcritical water, photocatalytic oxidation and electro-Fenton processes(Elsevier, 2022) Kulaksız, Esra; Kayan, Berkant; Gözmen, Belgin; Kalderis, Dimitrios; Oturan, Nihal; Oturan, Mehmet A.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 the bulk solution. These latter have high O2-evolution overpotential leading to the high amount of physisorbed M(•OH) compared to Pt and DSA. The oxidative degradation of 5-FU was then performed by titanium dioxide-based photocatalytic oxidation and subcritical water oxidation processes, both of which showed a lower degradation efficiency and failed to achieve complete mineralization. Finally, a comparison was performed in laboratory-scale, taking into account the following performance indicators: the degradation efficiency, the mineralization power, the cost of equipment and reagents, and the energy required for the treatment of 5-FU.Öğe Degradation of emerging contaminant coumarin based on anodic oxidation, electro-Fenton and subcritical water oxidation processes(Academic Press Inc., 2022) Görmez, Özkan; Akay, Sema; Gözmen, Belgin; Kayan, Berkant; Kalderis, DimitriosThe degradation of emerging contaminant coumarin was separately investigated in anodic, electro-Fenton and subcritical water oxidation processes. With respect to the anodic and electro-Fenton oxidation, the influence of constant current, treatment time and initial concentration of coumarin was studied. Regarding subcritical water oxidation, the effect of the oxidant concentration, temperature, treatment time and initial coumarin concentration was investigated. In anodic and electro-Fenton oxidation processes, coumarin degradation proceeded in a similar manner, achieving 99% degradation, after 180 min at a constant current of 200 mA. In both set-ups, further increasing the applied current lowered the degradation efficiency due to the formation of by-products and the increasing occurrence of side-reactions. The highest degradation of 88% was achieved in subcritical conditions, specifically at 200 °C, using 150 mM H2O2 and after 37.5 min of treatment. Under subcritical conditions, temperature was the most prominent parameter, followed by the H2O2 concentration. Under all methodologies, increasing treatment time had a small positive effect on coumarin degradation, indicating that time is not the most influential parameter. A comparison of the three methodologies in terms of performance as well as energy consumption and simplicity of operation highlighted the advantages of subcritical water oxidation.Öğe Degradation of nitroaromatic compounds in subcritical water: application of response surface methodology(Desalination Publications, 2017) Kayan, Berkant; Akay, Sema; Gözmen, Belgin; Gizir, A. Murat; Demirel, Muhammet; Kalderis, DimitriosIn 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 degrees C, 210 degrees C and 236 degrees 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 subcriticaldegradation products existed; therefore, total amounts of degraded nitroaromatic compounds and formed intermediate products were determined by gas chromatographic-mass spectrometric analysis.Öğe Degradation, solubility and chromatographic studies of Ibuprofen under high temperature water conditions(Elsevier Ltd, 2021) Akay, Sema; Öztürk, Serpil; Kalderis, Dimitrios; Kayan, BerkantIbuprofen (IBP) is an emerging environmental contaminant having low aqueous solubility which negatively affects the application of advanced oxidation and adsorption processes. It was determined that as the temperature increased to 473 K, the mole fraction solubility increased considerably from 0.02 × 10?3 to 212.88 × 10?3 (10600-fold). Calculation of the thermodynamic properties indicated an endothermic process, ?solH > 0, with relatively high ?solS values. Spectroscopic, thermal and chromatographic analyses established the IBP stability at subcritical conditions. In the second part of the study, the degradation of IBP in H2O2-modified subcritical was studied and the effect of each process variable was investigated. The optimum degradation of 88% was reached at an IBP concentration of 15 mg L?1, temperature of 250 °C, 105 min treatment time and 250 mM H2O2. The process was optimized by response surface methodology and a mathematical model was proposed and validated. Temperature was determined as the most influential parameter, followed by H2O2 concentration. At temperatures higher than 230 °C, a small but noticeable reduction in degradation % suggested that the OH· radicals are consumed at a higher rate than they are produced, through side reactions with other radicals and/or IBP by-products. Finally, potential by-products were determined by gas chromatographic-mass spectrometric analysis and potential by-products were proposed.Öğe Fe-modified hydrochar from orange peel as adsorbent of food colorant Brilliant Black: process optimization and kinetic studies(Springer, 2020) Çatlıoğlu, F. N.; Akay, Sema; Gözmen, Belgin; Turunç, Ersan; Anastopoulos, Loannis; Kayan, Berkant; Kalderis, DimitriosAbstract: 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 theoretically achieved at the following conditions: dye initial concentration of 6.08 mg/L, treatment time of 26.30 min, temperature of 44.79 °C and adsorbent concentration of 2.27 g/L. The dominant factors were the dye and adsorbent concentration, whereas time and temperature variations had a much lesser impact. Among examined models, the Langmuir model showed a better match to the experimental data. The maximum monolayer adsorption capacity was determined as 10.49 mg/g. The mechanism of interaction was largely based on surface chemisorption between the dye and adsorbent. Fe-modified hydrochar exhibited a positive adsorption behavior, and it was shown that a new valorization option for orange peel waste is available. This option may follow other valorization pathways, such as isolation of biologically active molecules, therefore offering a complete solution to this type of waste. Graphic abstract: [Figure not available: see fulltext.]Öğe Fe-modified sporopollenin as a composite biosorbent for the removal of Pb2+ from aqueous solutions(Desalination Publications, 2016) Şener, Murat; Kayan, Berkant; Akay, Sema; Gözmen, Belgin; Kalderis, DimitriosThe 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 model provided a better fit (R-2 = 0.994) for the experimental data, indicating biosorption on a heterogeneous surface. Maximum biosorption capacity (q(max)) was 22.72 mg g(-1) as indicated by the Langmuir isotherm. Kinetically, the adsorption process followed a pseudo-second-order model, indicating that chemisorption was the rate-limiting step.Öğe Microplastics as carriers of hydrophilic pollutants in an aqueous environment(Elsevier B.V., 2022) Anastopoulos, Ioannis; Pashalidis, Ioannis; Kayan, Berkant; Kalderis, DimitriosPlastic materials such as polyethylene (PE), polyvinyl chloride (PVC), and polyamide nylon 6 (PN6) are extensively used worldwide. Significant quantities end up in the environment as waste, which gradually deteriorate and may travel for long distances. In this study, the capacity of these microplastics to sorb RR 120, an anionic dye commonly found in textile wastewaters, was investigated. PN6 showed the highest sorption capacity of 4.80 mg g?1, at a dose of 0.4 g and pH 2, whereas increasing the dose of the microplastic resulted in a gradual decrease of the sorption capacity for all materials. Increasing the dye concentration, resulted in higher sorption capacities. The FTIR analysis of the microplastics before and after sorption of RR 120, indicated no chemical bonding pointing out the absence of covalent bonds with specific surface groups of the microplastics in the sorption of RR 120. A plausible explanation for the highest sorption capacity of PN6 is the presence of N and O, which can readily form H bonds with the hydroxyl groups of RR 120.Öğe Poly(benzoxazine-co-sulfur): An efficient sorbent for mercury removal from aqueous solution(Wiley-Blackwell, 2017) Akay, Sema; Kayan, Berkant; Kalderis, Dimitrios; Arslan, Mustafa; Yağcı, Yusuf; Kıskan, BarışA novel sulfur-rich adsorbent, poly(BA-ala-co-sulfur), was synthesized by reacting allyl functional benzoxazine (BA-ala) and elemental sulfur. Simultaneous inverse vulcanization and ring-opening reactions of benzoxazine generated copolymers in several feed ratios. The adsorption behavior of these copolymers was investigated in aqueous solutions containing Hg2+. A three level Box-Behnken design with four factors was applied in order to examine the interactive effect of Hg2+ concentration (ppm), S % in adsorbent, temperature, and pH. The optimum adsorption conditions were determined as: 10.33 ppm Hg2+, 68% S content, 329 K, and pH 6.3. Common isotherm and kinetic models were applied to the experimental data, where the Langmuir isotherm provided the better fit (q(max)=79.36 mg g(-1)) and the pseudo-second order fit indicated chemisorption as the process-controlling step. (C) 2017 Wiley Periodicals, Inc.Öğe Preparation and application of a hydrochar-based palladium nanocatalyst for the reduction of nitroarenes(MDPI, 2021) Çalışkan, Melike; Akay, Sema; Kayan, Berkant; Baran, Talat; Kalderis, DimitriosIn the present study, a novel heterogeneous catalyst was successfully fabricated through the decoration of palladium nanoparticles on the surface of designed Fe3O4-coffee waste composite (Pd-Fe3O4-CWH) for the catalytic reduction of nitroarenes. Various characterization techniques such as XRD, FE-SEM and EDS were used to establish its nano-sized chemical structure. It was determined that Pd-Fe3O4-CWH is a useful nanocatalyst, which can efficiently reduce various nitroarenes, including 4-nitrobenzoic acid (4-NBA), 4-nitroaniline (4-NA), 4-nitro-o-phenylenediamine (4-NPD), 2-nitroaniline (2-NA) and 3-nitroanisole (3-NAS), using NaBH4 in aqueous media and ambient conditions. Catalytic reactions were monitored with the help of high-performance liquid chromatography. Additionally, Pd-Fe3O4-CWH was proved to be a reusable catalyst by maintaining its catalytic activity through six successive runs. Moreover, the nanocatalyst displayed a superior catalytic performance compared to other catalysts by providing a shorter reaction time to complete the reduction in nitroarenesÖğe Preparation and application of Fe-modified banana peel in the adsorption of methylene blue: Process optimization using response surface methodology(Elsevier B.V., 2021) Çatlıoğlu, Fatmanur; Akay, Sema; Turunç, Ersan; Gözmen, Belgin; Anastopoulos, I.; Kayan, Berkant; Kalderis, DimitriosBanana 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 5 mg L?1. Equilibrium was achieved in 48 min. The most influential process parameter was the adsorbent dosage, whereas the impact of time, MB concentration and temperature was considerably smaller. The Langmuir Qmax value of 28.1 mg g?1 compared favorably to respective values from other published adsorbents.Öğe Sonocatalytic degradation of an anthraquinone dye using TiO2-biochar nanocomposite(ELSEVIER SCIENCE BV, 2017) Khataee, Alireza; Kayan, Berkant; Gholami, Peyman; Kalderis, Dimitrios; Akay, SemaTiO2-biochar (TiO2-BC) nanocomposite was synthesized by sol-gel method. The characteristics of the prepared nanocomposite were examined using X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and N-2 adsorption-desorption analysis. The performance of synthesized TiO2-BC nanocomposite as efficient sonocatalyst was studied for the degradation of Reactive Blue 69 (RB69). Sonocatalytic degradation of RB69 in the presence of TiO2-BC nanocomposite could be explained by the mechanisms of hot spots and sonoluminescence. The optimized values for main operational parameters were determined as pH of 7, TiO2-BC dosage of 1.5 g/L, RB69 initial concentration of 20 mg/L and ultrasonic power of 300 W. Furthermore, the effect of (OH)-O-center dot, h(+) and O-2(center dot-) scavengers on the RB69 degradation efficiency was studied. Gas chromatography-mass spectroscopy analysis was used to identify intermediate compounds formed during the RB69 degradation. The results of repeated applications of TiO2-BC in the sonocatalytic process verified its stability in long-term usage.Öğe Sonocatalytic degradation of Reactive Yellow 39 using synthesized ZrO2 nanoparticles on biochar(ELSEVIER SCIENCE BV, 2017) Khataee, Alireza; Kayan, Berkant; Gholami, Peyman; Kalderis, Dimitrios; Akay, Sema; Dinpazhoh, LalehZrO2-biochar (ZrO2-BC) nanocomposite was prepared by a modified sonochemical/sol-gel method. The physicochemical properties of the prepared nanocomposite were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray fluorescence, Fourier transform infrared spectroscopy and Brtmauer-Emmett-Teller model. The sonocatalytic performance of ZrO2-BC was investigated in sonochemical degradation of Reactive Yellow 39 (RY39). The high observed sonocatalytic activity of the ZrO2-BC sample could be interpreted by the mechanisms of sonoluminescence and hot spots. Parameters including ZrO2-BC dosage, solution pH, initial RY39 concentration and ultrasonic power were selected as the main operational parameters and their influence on RY39 degradation efficiency was examined. A 96.8% degradation efficiency was achieved with a ZrO2-BC dosage of 1.5 g/L, pH of 6, initial RY39 concentration of 20 mg/L and ultrasonic power of 300 W. In the presence of (OH)-O-center dot radical scavengers, RY39 degradation was significantly inhibited, providing evidence for the key role of hydroxyl radicals in the process. The sonodegradation intermediates were identified using gas chromatography-mass spectroscopy and the possible decomposition route was proposed.Öğe Subcritical water treatment of landfill leachate: Application of response surface methodology(Elsevier, 2014) Kirmizakis, Panagiotis; Tsamoutsoglou, C.; Kayan, Berkant; Kalderis, DimitriosContext: Leachate is the liquid formed when waste breaks down in the landfill and water filters through that waste. This liquid is highly toxic and can pollute the land, ground water and water ways. It is mandatory for landfills to protect against leachate in most countries worldwide. Controlling the pollutant loading, means reducing its quantity by containing or treating the waste to comply with certain discharge characteristics which are compatible with the receptor medium. Objective: This paper describes the reduction of the organic load of a mature landfill leachate using a novel experimental set-up that employs hydrogen peroxide under subcritical conditions and aims to establish this method as an effective alternative to currently used options. Response surface methodology was applied to optimize the treatment process and determine which of the following there parameters - temperature, residence time and hydrogen peroxide concentration - played the most important role. Method: The method employed is based on the use of laboratory-scale, stainless steel reactors, filled with the leachate and appropriate quantities of hydrogen peroxide. Under subcritical conditions (temperature in the range of 100-374 degrees C and enough pressure to maintain the liquid state of water), hydrogen peroxide produces hydroxyl radicals which are highly reactive and oxidize the organic molecules of the leachate. Results: The highest COD decrease of 85% was experimentally observed at 300 degrees C, 500 mM H2O2 and 180 min residence time. It was determined that the combination of oxidant concentration and temperature is the rate-determining factor, whereas residence time has a lesser effect on the process. Conclusions: A simple, quick, effective and environmentally-friendly method for the treatment of the organic load of landfill leachate was developed and optimized at laboratory scale. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Synthesis of pumice-TiO2 nanoflakes for sonocatalytic degradation of famotidine(Elsevier Ltd., 2018) Rad, Tannaz Sadeghi; Khataee, Alireza; Kayan, Berkant; Kalderis, Dimitrios; Akay, SemaPumice-TiO2 was synthesized through simple sol-gel method. The successful synthesis of the catalyst was verified by SEM, EDS, XRF, FT-IR and BET techniques. Then, a sonocatalytic process was performed to degrade famotidine in the presence of the synthesized catalyst and under ultrasonic irradiation. The removal efficiency of the sonocatalytic process with pumice TiO2, TiO2, pumice and sonolysis within 70 min was 71.1%, 33.9%, 31.1% and 8.9%, respectively. The main operational parameters which were examined in this study were catalyst dosage, pH, famotidine concentration and ultrasonic power which were optimized as 1.5 g/L, 5, 20 mg/L and 150 W, respectively. Moreover, the addition of radical scavengers (EDTA, Na2SO4 and 1, 4 benzoquinone) and enhancers (H2O2 and K2S2O8) which can affect the removal efficiency were investigated. Diverse degradation by-products were identified using GC-MS analysis. Eventually, the reusability tests confirmed that the synthesized pumice TiO2 catalyst had significant stability after 5 consecutive runs. (C) 2018 Elsevier Ltd. All rights reserved.
