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    Active carbon/graphene hydrogel nanocomposites as a symmetric device for supercapacitors
    (Taylor & Francis Inc, 2016) Ateş, Murat; Çınar, Damla; Çalışkan, Sinan; Gecgel, Unal; Uner, Osman; Bayrak, Yüksel; Candan, İdris
    Activated 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.
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    Diclofenac sodium adsorption in aqueous media by activated carbon obtained from einkorn (Triticum monococcum L.) husk
    (Springer, 2024) Kocabiyik, Baris; Uner, Osman; Gecgel, Uenal
    The 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.