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    Antibacterial potentials of carbon dots immobilized on chitosan and glass surfaces
    (Elsevier, 2024) Ghaibullah, Yanar Najmalden Ghaibullah; Foto, Egemen; Ozdemir, Naciye; Foto, Fatma Zilifdar; Arslan, Gulsin; Sargin, Idris
    Due to their antibacterial activity, chitosan-carbon dot composites possess great potential for pharmaceuticals, medicine, and food preservation. Conducting a comprehensive study of the interactions between chitosan, carbon dots, and bacteria is crucial to understanding the processes behind applying these composites. This study aimed to immobilize carbon dots (C-dots) synthesized from Elaeagnus angustifolia fruits on chitosan and glass microbeads' surfaces, to characterize the test materials obtained after synthesis and immobilization, and to investigate their antibacterial potentials.C-dot synthesis was carried out from water extract in an acidic medium with the help of microwave irradiation, and their structural and optical properties were characterized by TEM, XRD, FT-IR, UV-vis, Zeta potential, and fluorescence methods. The surface of the glass microbeads was first activated and functionalized with surface amine groups with a silaning agent. C-dots were immobilized on both glass and chitosan microbeads using a crosslinking agent. Antibacterial potentials of nine different test materials, obtained before or after immobilization, were evaluated both qualitatively (MIC and MBC) and quantitatively (GI50) on E. coli, S. typhimurium, B. subtilis, and S. aureus, with the standard broth microdilution method.FT-IR and SEM-EDX analyses showed that C-dots were immobilized on chitosan (<1 mm) and glass (<100 mu m) microbead surfaces. C-dots reduced the cell viability by similar to 25 % on S. typhimurium and B. subtilis (MIC = 25 mg/ mL). It was also found that the highest antibacterial effect was recorded for C-dots-glass microbeads, which had a toxic effect of 43 % on S. aureus. In addition, binding C-dots to glass microbeads increased the antibacterial effect selectively in Gram-positive bacteria, while binding to chitosan microbeads was effective in all bacteria. The study showed that the antibacterial potential of C-dots-chitosan microbeads is more effective than C-dots-glass microbeads. C-dots could be used as carbon-based nanomaterials in antibacterial surface preparation once immobilized.
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    Arsenic(V) removal from underground water by magnetic nanoparticles synthesized from waste red mud
    (Elsevier Science Bv, 2012) Akin, Ilker; Arslan, Gulsin; Tor, Ali; Ersoz, Mustafa; Cengeloglu, Yunus
    In this study waste red mud (bauxite residue) sample obtained from Seydisehir (Konya, Turkey) was evaluated for the synthesis of Fe3O4 nanoparticles (NPs) in ammonia solution that can be used to remove As(V) from both synthetic and natural underground water samples. The synthesized Fe3O4-NPs were characterized by using TEM, VSM, XRD, SAXS,TGA and FT-IR spectroscopy. The Fe3O4-NPs assumed a near-sphere shape with an average size of 9 nm. The results showed that synthesized Fe3O4-NP5 from waste red mud have satisfactory magnetic properties and As(V) sorption capacity, especially at low equilibrium arsenate concentrations. (c) 2012 Elsevier B.V. All rights reserved,
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    Preparation and characterization of novel polysulfone-red mud composite capsules for the removal of fluoride from aqueous solutions
    (Royal Soc Chemistry, 2016) Kazak, Omer; Tor, Ali; Akin, Ilker; Arslan, Gulsin
    This study is the first investigation on the encapsulation of red mud by a polysulfone matrix through a phase inversion process to obtain composite capsules for the removal of fluoride from aqueous solutions. This approach facilitates the use of red mud in batch and column sorption techniques because the polysulfone matrix renders efficient aqueous diffusivity. The produced polysulfone-red mud composite capsules (red mud@ PSF capsules) were characterized by using FT-IR, TGA, SEM and BET. The batch sorption experiments showed that the red mud@ PSF capsules prepared with a mass ratio of red mud to polysulfone (1 : 1, g : g) provided maximum removal at equilibrium pH between 3.2 and 4.7. The batch equilibrium was attained within 30 minutes and sorption behavior was governed by pseudo-second-order kinetics together with intra-particle diffusion. Isotherm analyses showed that the Freundlich and Redlich-Peterson isotherm models better represented the sorption data, which was confirmed by the Chi-square (chi(2)) statistical test. The capsules could be reused for at least two sorption-desorption cycles without significant change in their sorption efficiency. Batch and column experiments on a real mineral water sample fortified with fluoride (final concentration 10 mg L-1) showed that the red mud@ PSF capsules could be applied to real water samples to reduce the fluoride concentration below the limit value (1.5 mg L-1) recommended by the World Health Organization (WHO) for drinking water.
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    Preparation of new polysulfone capsules containing Cyanex 272 and their properties for Co(II) removal from aqueous solution
    (Elsevier Sci Ltd, 2015) Kazak, Omer; Tor, Ali; Akin, Ilker; Arslan, Gulsin
    In this study, new polysulfone capsules containing Cyanex 272 (Cyanex 272@PSF capsules) were prepared by phase inversion technique for the sorption of Co(II) from aqueous solution. The characterization of the Cyanex 272@PSF capsules which were performed by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and thermal gravimetric analysis (TGA) indicated that Cyanex 272 was successfully encapsulated by polysulfone. For the Cyanex 272@PSF capsules having the highest sorption efficiency, the encapsulation efficiency was determined as 7.2%. The batch sorption experiments showed that removal of Co(II) from aqueous solutions occurred through the cation-exchange and chelation mechanisms and maximum removal was achieved at an initial pH of 8.0 (final pH of 5.9). The Cyanex 272@PSF capsules produced with dispersed phase containing 2.0% of Cyanex 272 (by wt.) provided the highest Co(II) removal. The sorption equilibrium time was attained within 120 min. By confirming the non-linear Chi-square (x(2)) statistical test, Langmuir isotherm model was the best fit model. Langmuir sorption capacity (Q(o)) and sorption constant (b) were 2.014 mg/g and 0.281 L/mg, respectively. The regenerated capsules could be used three times with no change in their sorption capacities. Based on the experiments performed at initial pH of 8.0 for other metal ions, including Ni(II), Pb(II) and Cd(II), sorption ability of Cyanex 272@PSF capsules was in the order: Co(II) approximate to Ni(II)>Cd(II)>Pb( II). Consequently, Cyanex 272@PSF capsules have potential for removing Co(II) from aqueous solutions. (C) 2015 Elsevier Ltd. All rights reserved.
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    Preparation of polymer inclusion membrane with sodium diethyldithiocarbamate as a carrier reagent for selective transport of zinc ions
    (Desalination Publ, 2017) Arslan, Gulsin; Yilmaz, Abdurrahman; Tor, Ali; Ersoz, Mustafa
    This study reports the design of a new type of polymer inclusion membrane (PIM) for selective transport of zinc ion. Sodium diethyldithiocarbamate (NaDDTC) was incorporated in the cellulose acetate-based membrane as a carrier for Zn(II) ion. The PIMs were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and contact angle measurements. The effects of parameters, including concentration of Zn(II) in the feed phase, HCl in the stripping phase and amount of NaDDTC incorporated in the membrane, on the transport of Zn(II) ion were studied. For 1 x 10(-4) M of Zn(II) ion in the feed phase at pH 5.04, 96% of Zn(II) ion was transported through the PIMs prepared with 1.0 (wt%) diethyldithiocarbamate via 0.5 M HCl as a stripping phase. The diffusion of Zn(II) ions through the membrane was governed by complex formation between Zn(II) ion and NaDDTC in the membrane. Moreover, selective transport of Zn(II) ion was achieved in the presence of divalent metal ions involving Cu(II), Pb(II) and Ni(II). The prepared PIM provided reproducible transport efficiency, and it can be efficiently used in separation processes.