Browsing by Author "Yilmaz, Selahattin"
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Article Hydrogel-Biochar Composites for Effective Organic Contaminant Removal From Aqueous Media(Elsevier, 2011) Karakoyun, Necdet; Kubilay, Senol; Aktas, Nahit; Turhan, Omer; Kasimoglu, Murat; Yilmaz, Selahattin; Sahiner, NurettinIn this study, p(acrylamide)-chicken biochar (p(AAm)-CB), p(acrylamide)-wood biochar (p(AAm)-WB), and p(acrylamide)-tire biochar (p(AAm)-TB) hydrogel composites were prepared using acrylamide (AAm) as monomer with the corresponding biochars, with N,N'-methylenebisacrylamide (MBA) as crosslinker and ammonium persulfate (APS) as initiator. P(AAm)-CB, p(AAm)-WB, and p(AAm)-TB were used as adsorbents to remove phenol from aqueous environments. The synthesized p(AAm)-CB, p(AAm)-WB, p(AAm)-TB and p(AAm) hydrogel composites had swelling values of 1112, 1045, 847, and 623%, respectively in distilled water. The prepared hydrogel biochar material compositions were examined using an elemental analyzer. Absorption of phenol into p(AAm)-WB was studied at different pHs to determine the optimum pH for maximum removal of phenol. The ionic strength of the medium was varied between 0.01 and 1 mol L-1 to determine the effect of salt (NaCl) on the absorption characteristics and it was found that the absorption of phenol increased with a decrease in the amount of salt. Langmuir and Freundlich isotherms were applied to describe the absorption characteristics and the Langmuir isotherm describes the absorption phenomena in this study much better than the Freundlich isotherm. Pseudo-first-order and pseudo-second-order kinetic studies were also applied to determine absorption characteristic. (C) 2011 Elsevier B.V. All rights reserved.Article Temperature and Magnetic Field Responsive Hyaluronic Acid Particles With Tunable Physical and Chemical Properties(Elsevier, 2011) Ekici, Sema; Ilgin, Pinar; Yilmaz, Selahattin; Aktas, Nahit; Sahiner, NurettinWe report the preparation and characterization of thiolated-temperature-responsive hyaluronic acid-cysteamine-N-isopropyl acrylamide (HA-CYs-NIPAm) particles and thiolated-magnetic-responsive hyaluronic acid (HA-Fe-CYs) particles. Linear hyaluronic acid (HA) crosslinked with divinyl sulfone as HA particles was prepared using a water-in-oil micro emulsion system which were then oxidized HA-O with NaIO4 to develop aldehyde groups on the particle surface. HA-O hydrogel particles were then reacted with cysteamine (CYs) which interacted with aldehydes on the HA surface to form HA particles with cysteamine (HA-CYs) functionality on the surface. HA-CYs particles were further exposed to radical polymerization with NIPAm to obtain temperature responsive HA-CYs-NIPAm hydrogel particles. To acquire magnetic field responsive HA composites, magnetic iron particles were included in HA to form HA-Fe during HA particle preparation. HA-Fe hydrogel particles were also chemically modified. The prepared HA-CYs-NIPAm demonstrated temperature dependent size variations and phase transition temperature. HA-CYs-NIPAm and HA-Fe-CYs particles can be used as drug delivery vehicles. Sulfamethoxazole (SMZ), an antibacterial drug, was used as a model drug for temperature-induced release studies from these particles. (C) 2010 Elsevier B.V. All rights reserved.