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Öğe Active carbon/graphene hydrogel nanocomposites as a symmetric device for supercapacitors(Taylor & Francis Inc, 2016) Ates, Murat; Cinar, Damla; Caliskan, Sinan; Gecgel, Unal; Uner, Osman; Bayrak, Yuksel; Candan, IdrisActivated carbons (ACs) are successfully synthesized from Elaeagnus grain by a simple chemical synthesis methodology and demonstrated as novel, suitable supercapacitor electrode materials for graphene hydrogel (GH)/AC nanocomposites. GH/AC nanocomposites are synthesized via hydrothermal process at temperature of 180 degrees C. The low-temperature thermal exfoliation approach is convenient for mass production of graphene hydrogel (GH) at low cost and it can be used as electrode material for energy storage applications. The GH/AC nanocomposites exhibit better electrochemical performances than the pure GH. Electrochemical performance of the electrodes is studied by cyclic voltammetry, and galvanostatic charge-discharge measurements in 1.0 M H2SO4 solution. A remarkable specific capacitance of 602.36 Fg(1) (based on GH/AC nanocomposites for 0.4 g AC) is obtained at a scan rate of 1 mVs(1) in 1 M H2SO4 solution and 155.78 Fg(1) for GH. The specific capacitance was increased 3.87 times for GH/AC compared to GH electrodes. Moreover, the GH/AC nanocomposites for 0.2 g AC present excellent long cycle life with 99.8% specific capacitance retained after 1000 charge/discharge processes. Herein, ACs prepared from Elaeagnus grain are synthesized GH and AC supercapacitor device for high-performance electrical energy storage devices as a promising substitute to conventional electrode materials for EDLCs.Öğe ADSORPTION OF BOVINE SERUM ALBUMIN ONTO ACTIVATED CARBON PREPARED FROM ELAEAGNUS STONE(Chem Soc Ethiopia, 2018) Gecgel, Unal; Uner, OsmanIn this study, the adsorption of bovine serum albumin was studied using the activated carbon prepared from Elaeagnus stone with chemical activation. Elaeagnus stone activated carbon was characterized using the point of zero charge, Fourier transform infrared spectra, Brunauer-Emmet-Teller method, scanning electron microscopy, and elemental analysis. The BET surface area of Elaeagnus stone activated carbon obtained by using 30% ZnCl2 (w/w) was determined to be 1588 m(2)/g. The effects of adsorbent dosages, contact time, initial bovine serum albumin concentrations, temperature and pH on the adsorption were investigated. The optimum values of adsorbent dosage, pH, and contact time were determined to be 1 mg/mL, 5, and 160 min for 500 mg/L BSA concentration, respectively. Additionally, the studies of adsorption equilibrium and kinetics were performed. The best fitting model from the experimental data was determined to be Langmuir model and the adsorption follows a pseudo-first-order kinetic model.Öğe Adsorption of cationic dyes on activated carbon obtained from waste Elaeagnus stone(Sage Publications Inc, 2016) Gecgel, Unal; Uner, Osman; Goekara, Gueney; Bayrak, YuekselActivated carbon was obtained from waste Elaeagnus stone by a chemical activation method utilizing ZnCl2. The resultant Elaeagnus activated carbon (EAC) with a high activated specific surface area of 1588m(2)/g was characterized using Brunauer-Emmett-Teller method, Fourier transform infrared spectra, point of zero charge, and scanning electron microscopy. The removals of cationic dyes, i.e., malachite green (MG), rhodamine B (RB), and methylene blue (MB) from aqueous solutions via EAC adsorption were characterized by investigating the effects of adsorbent concentration, contact time, initial dye concentration, and temperature. Langmuir model provided the most appropriate fit for all EAC dye adsorption processes, and the adsorption capacities for MB, RB, and MG at 25? were calculated to be 288.18, 281.69, and 432.90mg/g, respectively. The EAC adsorption curves of MB, RB, and MG follow a pseudo second-order kinetic model, and the calculated thermodynamic parameters, i.e., G degrees, H degrees, and S degrees revealed that the synthetic dye adsorptions from aqueous solution were endothermic and spontaneous.Öğe Adsorption of Methylene Blue by an Efficient Activated Carbon Prepared from Citrullus lanatus Rind: Kinetic, Isotherm, Thermodynamic, and Mechanism Analysis(Springer International Publishing Ag, 2016) Uner, Osman; Gecgel, Unal; Bayrak, YukselBy using the activated carbon obtained from Citrullus lanatus rind by zinc chloride activation, methylene blue (MB) removal from aqueous solutions was studied, and the adsorption mechanism was solved through Weber-Morris intraparticle diffusion model, Bangham model, Boyd model, Fourier transform infrared spectra, and scanning electron microscopy. The effects of adsorption parameters (adsorbent concentration, temperature, initial dye concentration, and pH) were investigated. The equilibrium data of MB adsorption were described by applying the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The obtained results from adsorption isotherms indicated that Langmuir model is the best-fitted model with the maximum adsorption capacities of 231.48, 243.90, 244.50, and 259.74 mg/g at 25, 35, 45, and 55 degrees C, respectively. The analysis of the kinetic data by pseudo-first-order, pseudo-second-order, and Elovich models displayed that MB adsorption followed pseudo-second-order model. Also, the date obtained from intraparticle diffusion model, Bangham model, and Boyd model presented that intraparticle diffusion, pore diffusion, and film diffusion played significant role in MB adsorption. The thermodynamic studies demonstrated that MB adsorption onto the activated carbon obtained from C. lanatus rind was physical, spontaneous, feasible, and endothermic. Thus, the activated carbon prepared from C. lanatus rind has been an efficient adsorbent for MB removal from an aqueous solution.Öğe Adsorptive removal of diclofenac sodium from aqueous solution onto sycamore ball activated carbon - isotherms, kinetics, and thermodynamic study(Elsevier, 2021) Avcu, Tarik; Uner, Osman; Gecgel, UnalThis study reports the analysis data of diclofenac sodium adsorption on sycamore ball activated carbon surface, in which various parameters such as adsorbent dosage, initial diclofenac sodium concentration, temperature, and pH were analyzed. At 25 degrees C, adsorbent dosage was used the range from 2.5 mg/50mL to 30 mg/50mL, and initial diclofenac concentration was taken from 10 mg/L to 50 mg/L. For adsorption temperature effect, adsorption temperature was investigated from 25 degrees C to 45 degrees C by holding adsorbent dosage constant (10 mg/50mL). By holding constant adsorbent dosage of 10 mg/50mL, contact time effect from 0 to 210 min was investigated with initial DS concentrations of 10, 20, 30, 40, and 50 mg/L. To examine pH effect, pH parameters were adjusted from 2.84 to 10.20. Besides, adsorption isotherm model, kinetic and thermodynamic studies carried out in this study are given. Langmuir isotherm model was determined to be the best fitting isotherm model for diclofenac sodium adsorption on sycamore ball activated carbon. Also, the maximum sodium diclofenac adsorption on sycamore ball activated carbon was calculated 178.89 mg/g at 25 degrees C, and kinetic data displayed that this adsorption occurred quite fast. Pseudo-first and pseudo-second order models were applied for sodium diclofenac adsorption on sycamore ball activated carbon, and the correlation coefficient values of 1.000-0.998 indicate that this adsorption was well fitting with pseudo-second order model. Moreover, from the thermodynamic study, sodium diclofenac adsorption on sycamore ball activated carbon was found to be exothermic, spontaneous, and feasible. Thus, the results obtained from this study confirmed that sycamore ball activated carbon is an economically suitable and effective adsorbent for sodium diclofenac adsorption.Öğe Adsorptive Removal of Methylene Blue from Aqueous Solution by the Activated Carbon Obtained from the Fruit of Catalpa bignonioides(Springer International Publishing Ag, 2015) Gecgel, Unal; Kocabiyik, Baris; Uner, OsmanIn this study, the fruit of Catalpa bignonioides was used as the raw material to obtain low-cost activated carbon. The activation process was carried out by using chemical activation method with zinc chloride. Catalpa activated carbon (CAC) was characterized using elemental analyzer, Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and the point of zero charge (pHZPC). The BET surface area of CAC prepared by the impregnation ratio of 30% ZnCl2 (w/w) was found to be 896.02 m(2)/g. The efficiency in the process of the removal of methylene blue (MB) from aqueous solution by CAC was searched with different factors, such as temperature, pH, adsorbent concentration, dye concentration, and contact time. From the experimental data obtained, the studies related to adsorption isotherm, kinetics, and thermodynamics were performed. Langmuir model provided the best fit, and the adsorption capacity for the removal of methylene blue from aqueous solution by CAC was calculated to be 271.00 mg/g at 25 degrees C. The adsorption follows a pseudo-second-order kinetic model. Moreover, the thermodynamic parameters such as Delta G degrees, Delta H degrees, and Delta S degrees presented that the adsorption was spontaneous and endothermic.Öğe Adsorptive Removal of Rhodamine B with Activated Carbon Obtained from Okra Wastes(Taylor & Francis Inc, 2017) Uner, Osman; Gecgel, UEnal; Kolancilar, Hakan; Bayrak, YukselThis study aimed at preparing and optimizing an activated carbon (OAC) obtained from dry okra wastes by chemical activation with zinc chloride. Also, Rhodamine B removal performance from aqueous solution was analyzed by using this optimized activated carbon. The characterization of the resultant activated carbon, with a high surface area of 1044m(2)/g, was carried out using thermogravimetric analysis, Brunauer-Emmett-Teller model, t-plot, N-2 adsorption/desorption isotherms, density functional theory, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and the point of zero charge. Furthermore, the effects of operating conditions (contact time, initial concentration, adsorbent dosage, temperature, and pH) on Rhodamine B adsorption onto OAC were investigated. Langmuir model was determined to be the best adsorption process, and the maximum adsorption capacity was calculated to be 321.50mg/g at 25 degrees C. Also, the intraparticle diffusion and boundary layer diffusion were involved in RhB adsorption onto OAC. Moreover, OAC adsorption curves of Rhodamine B followed pseudo second-order model. At 25 degrees C, Gibbs free energy, enthalpy, and entropy obtained from thermodynamic studies were determined to be -27.87kJ/mol, 13.03kJ/mol, and 0.15kJ/mol K, respectively. These thermodynamic values revealed that Rhodamine B adsorption onto OAC was feasible, endothermic, physical, and spontaneous.Öğe Comparisons of activated carbons produced from sycamore balls, ripe black locust seed pods, and Nerium oleander fruits and also their H2 storage studies(Springer Japan Kk, 2021) Uner, Osman; Gecgel, Unal; Avcu, TarikStarting materials are very significant to produce activated carbons because every starting material has a different chemical structure; hence they affect the surface functional groups and surface morphologies of obtained activated carbons. In this study, sycamore balls, ripe black locust seed pods, and Nerium oleander fruits have been used as starting materials by ZnCl2 chemical activations for the first time. Firstly, activated carbons were obtained from these starting materials with ZnCl2 chemical activation by changing production conditions (carbonization time, carbonization temperature, and impregnation ratio) also affecting the structural and textural properties of the resultant activated carbons. Then, the starting materials and resultant activated carbons were characterized by utilizing diverse analysis techniques, such as TGA, elemental analysis, proximate analysis, BET surface areas, pore volumes, pore size distributions, N-2 adsorption-desorption isotherms, SEM, FTIR spectra, and H-2 adsorption isotherms. The highest surface areas were determined to be 1492.89, 1564.84, and 1375.47 m(2)/g for the activated carbons obtained from sycamore balls, ripe black locust seed pods, and N. oleander fruits, respectively. The yields of these activated carbons with the highest surface areas were calculated to be around 40%. As the carbonization temperature increased with sufficient ZnCl2 amount, N-2 adsorption-desorption isotherms began to turn into Type IV isotherms given by mesoporous adsorbents with its hysteresis loops. Also, their hysteresis loops resembled Type H4 loop generally associated with narrow slit-like pores. Moreover, hydrogen uptakes under 750 mmHg at 77 K were determined to be 1.31, 1.48, and 1.24 wt% for the activated carbons with the maximum surface areas produced from sycamore balls, ripe black locust seed pods, and N. oleander fruits, respectively. As a result, the highest surface areas of the activated carbons with different structural properties produced in this study were obtained with different production conditions.Öğe Diclofenac sodium adsorption in aqueous media by activated carbon obtained from einkorn (Triticum monococcum L.) husk(Springer, 2024) Kocabiyik, Baris; Uner, Osman; Gecgel, UenalThe uncontrolled release of waste diclofenac with low biodegradability is considered to be a potential threat for the environment and creatures. To find effective solution for this issue, this study reports the adsorption performance of diclofenac sodium salt (DCF) by using activated carbon (EHAC) obtained from einkorn (Triticum monococcum L.) husk in aqueous solution under various circumstances. It was found that DCF adsorption on EHAC was highly solution pH dependent, and DCF adsorption by EHAC decreased with increasing adsorption temperature. Equilibrium data showed that fitted isotherm model with the experiment results of DCF adsorption on EHAC followed the order of Langmuir > Temkin > Freundlich > Dubinin-Radushkevich. Adsorption capacity of EHAC for DCF adsorption in aqueous solution was calculated to be 147.06 mg/g at 25 degrees C. The adsorption kinetic of DCF adsorption on EHAC was determined to obey the pseudo-second-order kinetic model. By utilizing FTIR and pH data obtained from DCF adsorption on EHAC, DCF adsorption mechanisms with some interactions such as pi-pi stacking, electrostatic interactions, and hydrogen bonding were suggested at diverse pH values. Additionally, intraparticle diffusion model was applied to kinetic results to further recognize the kinetic mechanism of DCF adsorption on EHAC. Furthermore, thermodynamic parameters for DCF adsorption on EHAC were calculated and evaluated, in which DCF adsorption process by EHAC was determined to be exothermic, spontaneous, and feasible.Öğe The effect of carbonization temperature, carbonization time and impregnation ratio on the properties of activated carbon produced from Arundo donax(ELSEVIER SCIENCE BV, 2018) Uner, Osman; Bayrak, YukselActivated carbons from Arundo donax were obtained by varying impregnation ratio, carbonization time, and carbonization temperature via chemical activation method. By operating impregnation ratio as 1.5 and carbonization temperature as 400 degrees C, the activated carbons with the highest surface areas were produced. Under this operating condition, the surface areas were measured to be 1784, 1781, and 1785 m(2)/g when the carbonization times were 60, 90, and 120 min, respectively. N, adsorption-desorption isotherms are generally Type I and Type IV isotherm mixtures, but when sufficient thermal energy at carbonization process is given and the chemical activation ratio is increased, N-2 adsorption-desorption isotherms are more likely to resemble Type IV isotherms. Also, H4 type hysteresis in the N-2 adsorption-desorption isotherms proves that activated carbons have micromesopore structures, and the pore shapes are usually cylindrical. Moreover, the resultant activated carbons were characterized by using pore size distributions, elemental analysis, SEM and FTIR.Öğe Preparation and characterization of mesoporous activated carbons from waste watermelon rind by using the chemical activation method with zinc chloride(Elsevier, 2019) Uner, Osman; Gecgel, Unal; Bayrak, YukselWaste watermelon rind was analyzed as a precursor for preparing activated carbons by using a one-step chemical activation process by zinc chloride. The effects of activation parameters, i.e., carbonization temperature, impregnation ratio, and impregnation time on the properties of the final products were tested in detail. The resultant activated carbons were characterized using elemental analysis, the Brunauer-Emmet-Teller method, pore property analysis, N-2 adsorption/ desorption isotherms, Fourier transform infrared spectroscopy, the point of zero charge, Boehm titration method and scanning electron microscopy. The maximal Brunauer-Emmett-Teller surface area of the resultant activated carbon, produced by using the impregnation (ZnCl2/dried watermelon rind) ratio of 2/1 at the carbonization temperature of 700 degrees C with the residence time of 60 min, was 1156 m(2)/g. Upon using the impregnation ratio of 3/1 at the carbonization temperature of 600 degrees C with the residence time of 60 min, the maximal total pore volume, which also contains the highest mesopore volume, was 1.41 cm(3)/g. (C) 2015 The Authors. Published by Elsevier B.V. on behalf of King Saud University.
