Yazar "Karagunduz, Ahmet" seçeneğine göre listele

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    Cerium-Doped CuFe-Layered Catalyst for the Enhanced Oxidation of o-Xylene and N,N-Dimethylacetamide: Insights into the Effects of Temperature and Space Velocity
    (Amer Chemical Soc, 2023) Ocal, Zehra Betul; Keyikoglu, Ramazan; Karagunduz, Ahmet; Yoon, Yeojoon; Khataee, Alireza
    Volatile organic compounds (VOCs) are among the most potential pollutant groups that cause air quality degradation because of their toxic effects on human health. Although catalytic oxidation is an effective method for VOC removal, further studies are required to develop more efficient and affordable catalysts. In this study, cerium (Ce) was doped into a CuFe-layered material (Ce-CuFe) to improve the catalytic oxidation efficiencies of N,N-dimethylacetamide (DMAC) and o-xylene. The synthesized catalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. XRD analysis confirmed the successful doping of Ce atoms into the CuFe-layered structure, while in the SEM and TEM images the catalyst appeared as uniformly distributed two-dimensional plate-like particles. The catalytic oxidation performance of the Ce-CuFe was investigated at six temperatures between 200 and 450 degrees C and three space velocities in the range of 31000-155000 mLh(-1)g(-1) for the oxidation of DMAC and o-xylene, which functioned as polar and nonpolar solvents, respectively. At 200 degrees C, the Ce-CuFe catalyst performed 50% greater when oxidizing o-xylene while exhibiting a DMAC oxidation efficiency that was 42% greater than that achieved using undoped CuFe. The Ce-CuFe could remove DMAC and o-xylene with an efficiency higher than 95% at 450 degrees C. Furthermore, Ce-doped CuFe exhibited high resistance against moisture and outstanding reusability performance with only a 5.6% efficiency loss after nine reuse cycles. Overall, the incorporation of Ce into a CuFe-layered material is a promising strategy for the oxidation of various VOCs.
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    Fabrication of PSf nanocomposite membranes incorporated with ZnFe layered double hydroxide for separation and antifouling aspects
    (Elsevier, 2022) Balcik, Cigdem; Ozbey-Unal, Bahar; Cifcioglu-Gozuacik, Bengisu; Keyikoglu, Ramazan; Karagunduz, Ahmet; Khataee, Alireza
    Herein, we report the effect of blending of various concentrations of ZnFe layered double hydroxide (LDH) on the filtration, antifouling, and antibacterial performances of Polysulfone (PSf) nanocomposite membranes for BSA and dye separation. ZnFe LDH with a molar ratio of M2+:M3+=3:1 was synthesized by the co-precipitation method. The PSf-ZnFe LDH nanocomposite membranes exhibited higher hydrophilicity (the lowest contact angle value of 64.42 & nbsp;), porosity (up to 58.7), and mean pore radius compared to the pristine PSf membrane. The water flux of the PSf-ZnFe LDH nanocomposite membrane (LDH content of 2.0 wt% of PSf) was 105 L/m(2)h, which is 2.3 times higher than the flux of pristine PSf membrane of 45 L/m(2)h. The rejection ratios for the fabricated membranes were 93%, 83%, and 16% for BSA, reactive red 198, and methylene blue, respectively. Additionally, 2.0 wt% ZnFe LDH incorporated membrane demonstrated better antifouling performance with a flux recovery ratio (FRR) of 95% compared to the pristine PSf membrane with 42% of FRR. Consequently, a bacterial viability inhibition test was utilized to determine the antibacterial properties, and the ZnFe LDH exhibited a high inhibition capacity. The fabricated PSf-ZnFe LDH nanocomposite membranes exhibited a higher filtration, antifouling, and antimicrobial performance as compared to pristine PSf.
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    Recent advances in boron species removal and recovery using layered double hydroxides
    (Elsevier, 2023) Akdag, Sultan; Keyikoglu, Ramazan; Karagunduz, Ahmet; Keskinler, Bulent; Khataee, Alireza; Yoon, Yeojoon
    Anthropogenic boron discharge threatens ecosystem health and water quality. Although boron is a micronutrient necessary for plants, animals, and humans, excessive concentrations can have toxic effects. Layered double hydroxides (LDH) are two-dimensional anionic clay materials that exhibit intrinsic anion-exchange properties. In this paper, the use of LDH for the removal and recovery of boron species from water is presented. The main factors that affect boron removal, including the LDH dosage, initial boron concentration, solution pH, temperature, and the presence of other anions, are outlined. For boron removal, LDH containing Mg, Fe, Zn, or Ca cations have been mostly used owing to their limited toxicities and abundance in the environment. The boron removal capacity of LDH can be improved by transforming the layered structure into bimetallic oxides through calcination, increasing not only the surface area but also the interaction with anionic species during their regeneration. The main boron-removal mechanism of LDH is ion exchange with intercalated anions or the surface complexation with the surface groups of the LDH. A major advantage of using LDH for boron removal is the possibility of recovering and reusing the extracted boron. LDH synthesized with boron as the interlayer anion showed slow-release fertilizer properties, suggesting the use of boron-loaded LDH as plant growth regulators.
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    Removal of ammonium ions by capacitive deionization and membrane capacitive deionization units
    (Desalination Publ, 2017) Sakar, Hacer; Karataş, Okan; Canbolat, Cigdem Balcik; Keskinler, Bulent; Karagunduz, Ahmet
    In this study, capacitive deionization (CDI) and membrane capacitive deionization (MCDI) unit cells were used to remove NH4+ ions. The influences of operating parameters such as the applied voltage, the initial ammonium concentration and the flow rate on the effectiveness of ammonium removals were investigated. In addition, the effects of different membrane types on MCDI performances were also studied. The results showed that, the electrosorption performances of CDI and MCDI increased by increasing the initial concentration, flow rate and the applied potential. It was observed that the adsorption capacity of MCDI unit was much higher than that of CDI due to the presence of ion-exchange membranes. MCDI technology may provide better advantages on ammonium removal.