Browsing by Author "Eser A."
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Item Removal of nickel(II) ions by histidine modified chitosan beads(2012) Eser A.; Nüket Tirtom V.; Aydemir T.; Becerik S.; Dinçer A.In order to increase the nickel adsorption capacity of raw chitosan beads (CB), they were chemically modified with histidine (HIS-ECH-CB) by using crosslinking agent, epichlorohydrine (ECH). The nature and morphology of the sorbent were characterized using FTIR, TGA and SEM analysis. For optimization of adsorption conditions, sorption experiments were performed by varying contact time, pH, temperature and initial nickel concentration. Based on the adsorption experiment, the HIS-ECH-CB showed the significant adsorption capacity of 55.6mg/g under the optimal adsorption condition. Nickel adsorption isotherms data were fitted to Freundlich isotherm. Thermodynamic parameters namely ΔG°, ΔH° and ΔS° of the Ni(II) adsorption process were calculated. The negative values of Gibbs free energy of adsorption (ΔG°) indicated the spontaneity of the adsorption of Ni(II) ions on the histidine modified chitosan. Desorption of Ni(II) ions from HIS-ECH-CB could be done rapidly by using 0.1M HCl, HNO 3 and EDTA solutions and the beads could be used again to adsorb Ni(II) ions. © 2012 Elsevier B.V..Item Poly(methyl methacrylate-ethylene glycol dimethacrylate) copolymer for adsorptive removal of erythrosine dye from aqueous solution(Bellwether Publishing, Ltd., 2015) Altındağ İ.G.; Dinçer A.; Becerik S.; Eser A.; Aydemir T.The preparation and characterization of poly(methyl methacrylate-ethylene glycol dimethacrylate), (poly(MMA-EGDMA)) polymer for erythrosine adsorption has been investigated. Erythrosine is a synthetic red dye used to color food. Water-soluble acid dyes have caused serious water pollution. Poly(MMA-EGDMA) polymer showed better adsorption performance for erythrosine at acidic region and at 30°C. The adsorption process had also been verified by Langmuir and Freundlich adsorption isotherms at 30, 40, and 50°C. Free energy of adsorption (∆G°), enthalpy (∆H°), and entropy (∆S°) changes were calculated to predict the nature of adsorption. The estimated value for ∆G° was calculated as −125.6 kJ/mol at 303 K (30°C). The estimated value for ∆H° was found as −60.69 kJ/mol at 303 K. The negative value for ∆H° indicated that the adsorption of erythrosine on poly(MMA-EGDMA) polymer was an exothermic process. © 2014, © 2014 Balaban Desalination Publications. All rights reserved.Item Multicenter retrospective analysis regarding the clinical manifestations and treatment results in patients with hairy cell leukemia: Twenty-four year Turkish experience in cladribine therapy(John Wiley and Sons Ltd, 2015) Hacioglu S.; Bilen Y.; Eser A.; Sivgin S.; Gurkan E.; Yildirim R.; Aydogdu I.; Dogu M.H.; Yilmaz M.; Kayikci O.; Tombak A.; Kuku I.; Celebi H.; Akay M.O.; Esen R.; Korkmaz S.; Keskin A.In this multicenter retrospective analysis, we aimed to present clinical, laboratory and treatment results of 94 patients with Hairy cell leukemia diagnosed in 13 centers between 1990 and 2014. Sixty-six of the patients were males and 28 were females, with a median age of 55. Splenomegaly was present in 93.5% of cases at diagnosis. The laboratory findings that came into prominence were pancytopenia with grade 3 bone marrow fibrosis. Most of the patients with an indication for treatment were treated with cladribine as first-line treatment. Total and complete response of cladribine was 97.3% and 80.7%. The relapse rate after cladribine was 16.6%, and treatment related mortality was 2.5%. Most preferred therapy (95%) was again cladribine at second-line, and third line with CR rate of 68.4% and 66.6%, respectively. The 28-month median OS was 91.7% in all patients and 25-month median OS 96% for patients who were given cladribine as first-line therapy. In conclusion, the first multicenter retrospective Turkish study where patients with HCL were followed up for a long period has revealed demographic characteristics of patients with HCL, and confirmed that cladribine treatment might be safe and effective in a relatively large series of the Turkish study population. © 2015 John Wiley & Sons, Ltd.Item Removal of erythrosine dye from aqueous solutions using magnetic chitosan with erythrosine as imprinted molecules(Taylor and Francis Inc., 2016) Eser A.; Aydemir T.; Becerik S.; Dinçer A.A novel, chitosan coating on the surface of magnetite (Fe3O4) (erythrosine-imprinted magnetic chitosan (EIMC)) was successfully synthesized using erythrosine (ER) as a template for adsorption and the removal of ER from aqueous solutions. Characterization of the obtained EIMC was achieved by FTIR spectra, SEM micrographs, and TGA analysis. Batch adsorption experiments of EIMC and non-imprinted magnetic chitosan (NIMC) were performed to investigate the adsorption conditions. The results showed that the maximum adsorption capacity for EIMC and NIMC was observed at pH 6 and temperature 40°C. Equilibrium adsorption was achieved within 3 h. Adsorption process could be well described by Freundlich adsorption isotherms. Thermodynamic parameters namely ΔG°, ΔH°, and ΔS° of the ER adsorption process were calculated. The negative values of Gibbs free energy of adsorption (ΔG°) indicated the spontaneity of the adsorption of ER dye on the EIMC and NIMC. Desorption of ER from EIMC and NIMC could be done rapidly using 0.1 M NaOH solution and the beads could be used again to remove ER. Results show that imprinting technique increases the removal amount of ER dye from aqueous solutions. © 2015 Balaban Desalination Publications. All rights reserved.Item The effect of kinetin on wheat seedlings exposed to boron(Elsevier Masson SAS, 2016) Eser A.; Aydemir T.The objective of this study was to examine relationship between boron (B) induced oxidative stress and antioxidant system in boron sensitive and tolerant wheat cultivars Bezostaya and Kutluk, and also to investigate whether Kinetin (KN) enhances the level of antioxidant system, relative growth, concentration of hydrogen peroxide (H2O2), malondialdehyde (MDA) and proline and chlorophyll content in both cultivars exposed to B stress. B treatments diminished growth and chlorophyll content whereas, it enhanced accumulation of H2O2, MDA and proline, and various antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and lipoxygenase (LOX) in the shoot and root of both cultivars. However, the follow-up application of KN to the B stressed plants improved growth and chlorophyll content and further enhanced the mentioned antioxidant enzymes and level of H2O2, MDA and proline. This study thus suggests that KN improves B tolerance of the studied cultivars grown under B toxicity. © 2016Item Subtilisin Carlsberg immobilization and its application for eco-friendly leather processing(Elsevier Ltd, 2022) Eser A.; Aydemir T.Conventional dehairing based on application of huge amount of chemicals is the most polluting process of all leather manufacturing processes. In this study, Subtilisin Carlsberg (SC) was immobilized on magnetic chitosan (mCTS) using two different crosslinkers: 2% glutaraldehyde (GA) and 0.5% genipin (GE). The reaction medium for SC immobilization consisted of 500 mg carrier and 5 ml (1 mg/ml) enzyme solution. Also, the immobilization conditions were pH 8, 25 °C and 2 h incubation period. The hydrolysis activity of immobilized SC has been extensively investigated. The structure and surface morphology of the prepared carriers were characterized by Scanning Electron Microscop (SEM), Thermogravimetric Analyzis (TGA) and Energy Dispersive X-Ray Spectroscopy (EDX). Optimum temperature and pH values of SC activity were found to be 50 °C and pH 8.0, respectively for free and immobilized SC. Higher activity of SC at around pH 8 and 50 °C makes it suitable for industrial applications. Thermal stability of immobilized SC was found greater than free SC. At the end of 4 h of exposure to high temperature, while the immobilized enzyme can maintain its activity around 50%, the free enzyme can maintain around 20%. Enzymatic hair removal from leather skin with SC was carried out as an alternative eco-benign deharing process. In enzymatic hair removal, a softer and smoother skin surface was obtained compared to the chemical method. Leather skins was characterized by SEM images. © 2022 Elsevier LtdItem Immobilization of Subtilisin Carlsberg and its use for transesterification of N-acetyl-L-phenylalanine ethyl ester in organic medium(Springer Science and Business Media Deutschland GmbH, 2023) Eser A.; Aydemir T.In this study, inorganic-based carrier perlite (PER) and cyclodextrin-modified perlite (PER-CD) were used for Subtilisin Carlsberg (SC) immobilization. For enzyme immobilization, the supports aminated with 3-aminotriethoxysilane were first activated with glutaraldehyde (GA) and genipin (GE), and then, the immobilized enzymes (PER-SC and PER-CD-SC) were obtained. The reaction medium for SC immobilization consisted of 500 mg carrier and 5 ml (1 mg/ml) enzyme solution. The immobilization conditions were pH 8.0, 25 °C, and 2 h incubation time. Free and immobilized SC were used for transesterification of N-acetyl-L-phenylalanine ethyl ester (APEE) with 1-propanol in tetrahydrofuran (THF). The transesterification activity of the enzyme and the yield of the transesterification reaction were determined by gas chromatography (GC). 50 mg of immobilized or 2.5 mg of free SC was added to the reaction medium, which was prepared as 1 mmol APEE and 10 mmol alcohol in 10 mL of THF. The conditions for the transesterification reaction were 60 °C and 24 h of incubation. The structure and surface morphology of the prepared carriers were characterized using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Casein substrate was used in the optimization study. The optimum temperature and pH for SC activity were found to be 50 °C and pH 8.0, respectively, for free and immobilized SC. The thermal stability of immobilized SC was found to be greater than that of free SC. At the end of 4 h of exposure to high temperature, the immobilized enzyme maintained its activity at approximately 50%, while the free enzyme was maintained at approximately 20%. However, modification with cyclodextrin did not alter the thermal stability. The transesterification yield was found to be approximately 55% for the free enzyme, while it was found to be approximately 68% and 77% for PER-SC and PER-CD-SC, respectively. The effect of metal ions and salts on transesterification yield was examined. The results showed that the addition of metal ions decreased the percentage of transesterification by approximately 10% compared to the control group, whereas the addition of salt significantly decreased the percentage of transesterification by 60–80% compared to the control group. Graphical abstract: [Figure not available: see fulltext.]. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Item Application of crosslinked chitosan-nanoclay composite beads for efficient removal of Ponceau S azo dye from aqueous medium(Taylor and Francis Ltd., 2023) Çınar S.; Dinçer A.; Eser A.; Aydemir T.In this study, chitosan-nanoclay composite beads (CS/NC composite beads) were used to remove Ponceau S from aqueous solutions. CS/NC composites characterization was performed with FTIR, SEM-EDX, TGA, BET and XRD analyzes. The adsorption procedure was optimized by changing various parameters in batch experiments such as pH, dye concentration, contact time and temperature. Ponceau S adsorption took place at a higher rate in the acidic region, and the highest adsorption was observed at pH 2.0. The amount of adsorbed dye increased as the temperature increased at low dye concentrations and the time required to reach equilibrium was shorter than at higher dye concentrations. Linear and non-linear forms of Langmuir, Freundlich and Temkin adsorption models were applied. The adsorption behavior of Ponceau S is compatible with the linear Langmuir model, and the maximum adsorption capacity was found to be 140.85 mg g-1. Linear and nonlinear forms of adsorption kinetics and thermodynamic parameters were investigated for dye concentrations of 150-400 mg/L. The adsorption kinetics fit the linear pseudo-second-order kinetic model and the Ponceau S adsorption on CS/NC composites was spontaneous and endothermic. The results show that the CS/NC composites can be used as an effective adsorbent in industrial wastewater treatment. © 2023 Informa UK Limited, trading as Taylor & Francis Group.