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Öğe Adsorption behaviour of methylene blue from aqueous solution on poly(ethylene terephthalate)-g-4-vinylpyridine/2-hydroxyethylmethacrylate fibers(Walter De Gruyter Gmbh, 2007) Yigitoğlu, Mustafa; Arslan, MetinIn this study, a novel fibrous adsorbent obtained by grafting 4-vinyl pyridine (4-VP)/2-hydroxyethylmethacrylate ( HEMA) comonomers onto poly ( ethylene terephthalate) ( PET) fibers was used for removal of methylene blue (MB) from aqueous solutions through a batch equilibration technique. The Influence of treatment time, pH of the solution, dye concentration, reaction temperature and percent graft yield on adsorbed amount were investigated. 300 min. of adsorption time was found sufficient to reach adsorption equilibrium for MB. It was found that the adsorption isotherm of MB fitted to Langmuir type isotherm. The highest adsorption capacity was found to be 55.33 mg MB per gram adsorbent. The adsorbed amount of MB was much higher on the comonomers grafted PET fibers than on the ungrafted PET fibers. MB was removed by 98 % while the initial dye concentration was at 5 mg L-1 and by 88% at 300 mg L-1 by monomers mixture grafted PET fibers. It was found that the reactive fibers were stable and regenerable by acid without loosing their activity.Öğe Graft copolymerization of N-vinyl-2-pyrrolidone onto sodium carboxymethylcellulose with azobisisobutyronitrile as the initiator(John Wiley & Sons Inc, 2007) Yigitoğlu, Mustafa; Işıklan, Nuran; Özmen, RukiyeGraft copolymers of sodium carboxymethylcellulose with N-vinyl-2-pyrrolidone were prepared in aqueous solutions with azobisisobutyronitrile as the initiator. The graft copolymers [sodium carboxymethylcellulose-g-poly(N-vinyl-2-pyrrolidone)] were characterized with Fourier transform infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The grafting parameters, including the graft yield of the graft copolymer and the grafting efficiency of the reaction, were evaluated comparatively. The effects of reaction variables such as the time, temperature, and monomer and initiator concentrations on these parameters were studied. The graft yield and grafting efficiency increased and then decreased with increasing concentrations of N-vinyl-2-pyrrolidone and azobisisobutyronitrile and increasing polymerization temperatures. The optimum temperature and polymerization time were 70 degrees C and 4.30 h, respectively. Further changes in the properties of grafted sodium carboxymethylcellulose, such as the intrinsic viscosity, were determined. The overall activation energy for the grafting was also calculated to be 10.5 kcal/mol. (c) 2007 Wiley Periodicals, Inc.Öğe Immobilization of Candida rugosa lipase on glutaraldehyde-activated polyester fiber and its application for hydrolysis of some vegetable oils(Elsevier Science Bv, 2010) Yigitoğlu, Mustafa; Temoçin, ZülfikarCandida rugosa lipase was effectively immobilized on the poly(ethylene terephthalate) grafted acrylamide (PET-g-AAm) fiber which was prepared through Hofmann reaction. The activities of the immobilized enzyme and the free enzyme were investigated in the hydrolysis reaction of olive oil in isooctane-water biphasic medium. The activities of the free and the immobilized lipases were measured at different pH values, and temperatures. The thermal stability and storage stability of them were also determined. The kinetic parameters of the free and the immobilized lipases, K-m and V-max were calculated, as well. Moreover, the application of immobilized lipase to the hydrolysis of different vegetable oils was realized. The effect of organic solvents on olive oil hydrolysis was examined and time course of the oil hydrolysis was studied. The optimum pH was shifted from 6 to 7 by immobilization of the enzyme. The maximum activity of the free and the immobilized enzymes occurred at 40 degrees C. It was found that the immobilized lipase stored at 4 degrees C retained 90% of its original activity after 60 days, whereas the free lipase stored at 4 degrees C retained 75% of its activity after the same period. In addition, the immobilized lipase exhibited as 0.06 U of the remaining activity even after 10 times reuses. Kinetics studies show that the corresponding values of K-m and V-max were 47.2 mg ml(-1) and 48.1 U mg(-1) protein for free lipase and 151.6 mg ml(-1) and 10.9 U mg(-1) protein for immobilized lipase. The immobilized and free enzymes showed similar behavior with respect to the different oil hydrolysis. The time course of the immobilized lipase on canola and olive oils hydrolysis used as substrate was much better than that of the free lipase. A high rate of oil hydrolysis was obtained when isooctane was used as solvent. (C) 2010 Elsevier B.V. All rights reserved.Öğe Immobilization of horseradish peroxidase on electrospun poly(vinyl alcohol)-polyacrylamide blend nanofiber membrane and its use in the conversion of phenol(Springer, 2018) Temoçin, Zülfikar; İnal, Murat; Gökgöz, Murat; Yigitoğlu, MustafaElectrospun nanofibers, with their porous structures, high surface-to-volume ratio, and good mechanical properties, are used as a support material for enzyme immobilization. In this study, the poly(vinyl alcohol) and polyacrylamide bicomponent (PVA-PAAm) nanofibers were fabricated via the electrospinning method. Synthesized PAAm was characterized with size exclusion chromatography (SEC). Nanofibers were characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). DSC and TGA analyses showed that the nanofibers were more durable than PVA and PAAm polymers. SEM images demonstrated that all nanofibers possessed uniform and smooth structures (average diameter about 300 nm). FTIR results have shown that PAAm successfully participates in nanofiber structure. The produced nanofibers were used as support material for covalent immobilization of horseradish peroxidase (HRP). The optimum temperature for free HRP was 45 A degrees C, whereas it was 50 A degrees C for the immobilized enzyme. The immobilized HRP showed better storage and thermal stability than free HRP. The kinetic parameters (K (m) and V (max)) were found to be 2.42 mM and 0.027 U for the immobilized HRP and 1.86 mM and 0.079 U for the free HRP, respectively. The immobilized enzyme could be used effectively for 25 cycles with 54% retention of the activity. The immobilized HRP was also used for the conversion of phenol. Phenol removal was found to be about 29.68% at 180 min in real wastewater. The novel PVA-PAAm nanofibrous material was successfully used as a support material for covalent immobilization of HRP. Immobilized enzymes such as oxido-reductases onto the PVA-PAAm bicomponent nanofiber could be recommended in the treatment of organic pollutants in industrial effluents.Öğe Removal of Benzidine-based Azo Dye from Aqueous Solution Using Amide and Amine-functionalized Poly(ethylene terephthalate) Fibers(Korean Fiber Soc, 2010) Yigitoğlu, Mustafa; Temoçin, ZülfikarIn this study, amide and amine groups bound to poly(ethylene terephthalate) fibers are used to remove the colored toxic Congo red dye from aqueous solution. The effects of process variables like pH, contact time, graft yield, and initial dye concentration on the adsorption were investigated. The maximum adsorption of Congo red to amide and amine groups was observed at pH 3 and 5 respectively. Equilibrium was attained at approximately 60 min for the amine group. The adsorption capacity of amine group on the poly(ethylene terephthalate) fiber was 46.5 mg g(-1) at 25 degrees C, which was higher than that of the amide group on the poly(ethylene terephthalate) fiber. Desorption was done using 0.1 M NH3, and recovery was measured at 58.2 %. The used adsorbent was regenerated and recycled six times. The results showed that the amine-functionalized fiber could be considered as potential adsorbents for removal of Congo red from aqueous solution.Öğe Selective removal of Cr(VI) ions from aqueous solutions including Cr(VI), Cu(II) and Cd(II) ions by 4-vinly pyridine/2-hydroxyethylmethacrylate monomer mixture grafted poly(ethylene terephthalate) fiber(Elsevier Science Bv, 2009) Yigitoğlu, Mustafa; Arslan, MetinIn this study, a new reactively fibrous adsorbent was prepared by grafting 4-vinly pyridine (4-VP) and 2-hydroxyethylmethacrylate (HEMA) monomer mixture onto poly(ethylene terephthalate) (PET) fibers for removal of Cr(VI), Cu(II) and Cd(II) metal ions from aqueous solution by using batch adsorption method. The influence of various parameters such as graft yield (GY), pH, adsorption time, initial ion concentration and adsorption temperature was investigated. The selectivity of the reactive fiber was also examined. The results show that the adsorbed amount of metal ions followed as given in the order Cr(VI) > Cd(II) > Cu(II). At pH 3, Cr(VI) was removed by 99% while the initial concentration of ions was at 5 mg L-1 and by 94% at 400 mg L-1. It was found that the grafted fiber is more selective for Cr(VI) ions in the mixed solution of Cr(VI)-Cu(II), Cr(VI)-Cd(II) and Cr(VI)-Cu(II)-Cd(II) at pH 3 and it was observed that the grafted fibers are stable and regenerable by acid and base without losing their activity. (C) 2008 Elsevier B.V. All rights reserved.
