Browsing by Author "Kar, Yakup"

Now showing 1 - 2 of 2

Citation - WoS: 18
Citation - Scopus: 24
Adsorption of Cr(vi) Onto Cross-Linked Chitosan-Almond Shell Biochars: Equilibrium, Kinetic, and Thermodynamic Studies
(SPRINGER INTERNATIONAL PUBLISHING AG, 2021) Altun, Türkan; Ecevit, Hüseyin; Kar, Yakup; Çiftçi, Birsen
In this study, to remove Cr(VI) from the solution environment by adsorption, the almond shell was pyrolyzed at 400 and 500 degrees C and turned into biochar (ASC400 and ASC500) and composite adsorbents were obtained by coating these biochars with chitosan (Ch-ASC400 and Ch-ASC500). The resulting biochars and composite adsorbents were characterized using Fourier transform infrared (FTIR) spectroscopy; Brunauer, Emmett, and Teller (BET) surface area; scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX); and the point of zero charge pH (pH(pzc)) analyses. The parameters affecting the adsorption were examined with batch adsorption experiments and the optimum parameters for the efficient adsorption of Cr(VI) in 55 mg L-1 solution were determined as follows; adsorbent dosages: 5 g L-1 for biochars, 1.5 g L-1 for composite adsorbents, contact time: 120 min, pH: 1.5. It was seen that the temperature did not affect the adsorption much. Under optimum conditions, Cr(VI) adsorption capacities of ASC400, ASC500, Ch-ASC400, and Ch-ASC500 adsorbents are 11.33, 11.58, 37.48, and 36.65 mg g(-1), respectively, and their adsorption percentages are 95.2%, 97.5%, 94.3%, and 94.0%, respectively. Adsorption data were applied to Langmuir, Freundlich, Scatchard, Dubinin-Radushkevic, and Temkin isotherms and pseudo-first-order kinetic model, pseudo-second-order kinetic model, intra-particle diffusion model, and film diffusion model. The adsorption data fitted well to the Langmuir isotherm and pseudo-second-order kinetic models. From these results, it was determined that chemical adsorption is the dominant mechanism. Also, both intra-particle diffusion and film diffusion is effective in the adsorption rate. For all adsorbents, the Langmuir isotherm proved to be the most appropriate model for adsorption. The maximum monolayer adsorption capacities calculated from this model are 24.15 mg g(-1), 27.38 mg g(-1), 54.95 mg g(-1), and 87.86 mg g(-1) for ASC400, ASC500, Ch-ASC400, and Ch-ASC500, respectively. The enthalpy change, entropy change, and free energy changes during the adsorption process were calculated and the adsorption was also examined thermodynamically. As a result, adsorption occurs spontaneously for all adsorbents.
Citation - WoS: 5
Citation - Scopus: 7
Biochar Produced From Co-Pyrolysis of Olive Pomace & Crude Oil as an Adsorbent for Cr (vi) Removal From Aqueous Solutions
(Iranian Institute of Research and Development in Chemical Industries, 2022) Almezgagi, Maha; Kaya Güzel, Gülcihan; Kar, Yakup; Deveci, Hüseyin
This study investigated aqueous solution treatment to remove Cr (VI) using a biochar-based adsorbent. Olive pomace and crude oil were used to synthesize the biochar adsorbent via co-pyrolysis for the first time. The biochar properties were examined with Fourier Transform Infra-Red (FT-IR) spectroscopy, scanning electron microscopy (SEM), and Energy Dispersive X-ray (EDX) analyses before and after adsorption. The adsorption experiments were carried out in a batch process under different experimental conditions. The optimum adsorption efficiency was experimentally found to be at pH of 1.5, contact time of 15 min, Cr (VI) initial concentration of 20 mg/L, adsorbent dose of 0.4 g, and 303 K. Langmuir and Freundlich isotherms were used to evaluating the adsorption performance of biochar, and the Langmuir isotherm model was well fitted to experimental data with a maximum adsorption capacity of 9 mg/g. Kinetic experimental data was best described using a pseudo-second-order kinetic model. The thermodynamic parameters of the adsorption process were examined in detail, and the process was exothermic and spontaneous in nature. It is concluded that biochar can be successfully used as an adsorbent for the treatment of Cr (VI) contaminated water. Additionally, the evaluation of olive pomace provided not only a decrease in waste accumulation in the olive production industry but also the synthesis of an inexpensive and environmentally friendly adsorbent. © 2022, Iranian Institute of Research and Development in Chemical Industries. All rights reserved.