Browsing by Author "Kubilay, Senol"

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Adsorption of Textile Dyes on Willow Tree Pollen: Determination of Equilibrium, Kinetics, and Thermodynamic
(Jihad Daneshgahi, 2022) Alkan, Salih; Karakoc, Emel; Ilhan, Hasan; Caliskan, Meliha; Savran, Ali; Kubilay, Senol
In this study, the characterization and adsorption properties of Brilliant Cresyl Blue (BCB- ALD) and Acid Blue-25 (AB-25) dyes were investigated using willow tree pollen, a low-cost natural adsorbent. All adsorption tests were performed in consideration to contact time, adsorbent concentration, adsorbent dosage, and temperature functions. Equilibrium isotherms were explained in terms of the Langmuir, Freundlich, Temkin, and Dubinin Radushkevich (D-R) linear adsorption equations. It was found that adsorption complied with the Langmuir equation. Moreover, pseudo-first order, pseudo-second order, and intraparticle diffusion models were used to determine kinetic data. Experimental data showed a match with the pseudo-second-order kinetic model. Thermodynamic parameters such as enthalpy, Gibbs free energy, and entropy were examined for willow tree pollen samples. The data obtained led us to the conclusion that adsorption is a spontaneous process. On the other hand, positive enthalpy indicates that adsorption is endothermic. Positive entropy values are a result of changes on the adsorbent surface. Characteristic results and dimensionless separation factors (RL) indicate that pollen can be used as an alternative to commercial adsorbents to remove BCB- ALD and AB-25 from aqueous solution and wastewater.
Adsorption of the 2,2-Dichlorovinylphosphate on Raw and Modified Bentonites
(Asian Journal of Chemistry, 2013) Yonten, Vahap; Kubilay, Senol
This study aims to investigate the adsorption of the 2,2-dichlorovinylphosphate (DDVP) on raw and modified bentonite via high pressure liquid chromatography and infrared spectroscopy. The modified bentonites were prepared by adding HNO3 and Na2CO3. The Freundlich adsorption isotherm defines 2,2-dichlorovinylphosphate adsorption in aqueous and aqueous ethanol solutions through raw and modified bentonite. Variables such as temperature, time and pH were observed on 2,2-dichlorovinylphosphate adsorption. Then the capacity for maximum 2,2-dichlorovinylphosphate adsorption was measured on modified bentonite with HNO3 under the conditions of pH 3 and 40 degrees C. The modified bentonite with Na2CO3 clay used in experimental work played a major role on the adsorption of 2,2-dichlorovinylphosphate; thus modified bentonite with Na2CO3 is considered to possess better characteristics than modified bentonite with HNO3 and raw bentonite. The Freundlich isotherms of modified bentonite with Na2CO3 in aqueous-ethanol solution were found to be better than isotherms of aqueous solution for a much better 2,2-dichlorovinylphosphate adsorption.
Adsorption of the 2,4-Dichlorophenoxyacetic Acid Dimethylamine by Raw and Modified Bentonite
(Asian Journal of Chemistry, 2012) Yonten, Vahap; Kubilay, Senol; Battal, Peyami
The adsorption of the 2,4-dichlorophenoxyacetic acid dimethyl amine on raw bentonite (Tokat, Turkey), modified bentonite with base and modified bentonite with acid has been studied using high pressure liquid chromatography (HPLC) and FT- infrared spectrophotometer. Sorption of 2,4-dichlorophenoxyacetic acid dimethyl amine on raw bentonite, modified bentonite with base and modified bentonite with acid was compared solving in different solutions such as aqueous and aqueous-ethanol solutions based on adsorption isotherms. The effect of temperature, time and pH were observed on adsorption of 2,4-dichlorophenoxyacetic acid dimethyl amine. Sorption mechanisms in soils, the effect of surface functional groups as well as parameters influencing adsorption were discussed. Then maximum adsorption of 2,4-dichlorophenoxyacetic acid dimethyl amine capacity was measured on modified bentonite with base in pH 5 at 40 degrees C for 24 h. The modified bentonite with base used in experimental work played a major role than on the adsorption of 2,4-dichlorophenoxyacetic acid dimethyl amine so, the modified bentonite with base has better characteristics than raw bentonite and modified bentonite with acid adsorbents. The Freundlich isotherms of aqueous-ethanol solution was better than isotherms of aqueous solution for much better to adsorb of 2,4-dichlorophenoxyacetic acid dimethyl amine.
An Approach for Prediction of Optimum Reaction Conditions for Laccase-Catalyzed Bio-Transformation of 1-Naphthol by Response Surface Methodology (Rsm)
(Elsevier Sci Ltd, 2008) Ceylan, Hasan; Kubilay, Senol; Aktas, Nahit; Sahiner, Nurettin
Response surface methodology (RSM) was successfully applied to enzymatic bio-transformation of 1-naphthol. The experiments were conducted in a closed system containing acetone and sodium acetate buffer, with laccase enzyme. Laccase enzyme used as catalyst was derived from Trametes versicolor (ATCC 200801). The enzymatic bio-transformation rate of I-naphthol, based oil measurements of initial dissolved oxygen (DO) consumption rate in the closed system, was optimized by the application of RSM. The independent variables, which had been found as the most effective variables on the initial DO consumption rate by screening experiments, were determined as medium temperature, pH and acetone content. A quadratic model was developed through RSM in terms of related independent variables to describe the DO consumption rate as the response. Based on contour plots and variance analysis, optimum operational conditions for maximizing initial DO consumption rate, while keeping acetone content at its minimum value, were 301 K of temperature, pH 6 and acetone content of 7% to obtain 9.17 x 10(-3) mM DO/min for initial oxidation rate. (c) 2007 Published by Elsevier Ltd.
Dichromate and Arsenate Anion Removal by Pei Microgel, Cryogel, and Bulkgel
(Elsevier Sci Ltd, 2021) Kubilay, Senol; Demirci, Sahin; Can, Mehmet; Aktas, Nahit; Sahiner, Nurettin
Among the various metal ions, chromate (Cr(VI)) and arsenate (As(V)) are the two most hazardous toxic ion species and are found in nature in the form of dichromate and arsenate anions. In this investigation, polyethyleneimine (PEI)-based hydrogels were prepared with microgel, cryogel, and bulkgel morphologies employing glycerol diglycidyl ether as a crosslinker. The prepared PEI-based hydrogels were used to remove dichromate and arsenate anions from aqueous media. PEI microgel, cryogel, and bulkgels weighing 50 mg of each adsorbed 84.7 +/- 0.8, 76.5 +/- 5.2, and 108.9 +/- 2.4 mg.g(-1) of dichromate anions and 15.9 +/- 0.7, 45.4 +/- 1.9, and 79.2 +/- 11.6 mg.g(-1) of arsenate anions in 30, 120, and 240 min, respectively. The dichromate and arsenate anions adsorption of PEI-based hydrogels were found to fit to the pseudo-second-order kinetic, and nonlinear Langmuir isotherm models, respectively with higher R-2 values. The highest distribution coefficient (K-d) value of PEI-based hydrogels for dichromate adsorption was obtained on the cryogel forms of PEI as 1.89 +/- 0.05. Likewise, the highest K-d value for the arsenate adsorption was calculated on PEI-based bulkgels as 0.46 +/- 0.01. The thermodynamic parameters of PEI based hydrogels in the adsorption of dichromate and arsenate anions e.g., Delta G (all negative (except for the arsenate adsorption by PEI microgels), and Delta H that is around 2-10 kJ.mol(-1), and Delta S what is around 0.01-0.02 kJ.mol(-1). K-1 were calculated. The reusability studies showed that PEI-based hydrogels can be used for at least 5 consecutive adsorption-desorption cycles with almost 70 % anion removal efficiency after the fifth cycle.
Environmental Usage of Poly(2-Acrylamido Acid Sodium Salt -Co Ammonium Chloride)-Lentinus Tigrinus (Bull.) Fr. Composite Hydrogel
(Amer Chemical Soc, 2016) Alpaslan, Duygu; Ersen, Tuba; Kubilay, Senol; Uzun, Yusuf; Savran, Ali; Aktas, Nahit
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, Nurettin
In 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.
Optimization With Response Surface Methodology of Toluidine Blue Biosorption Conditions From Aqueous Solutions by Polyporus Squamosus (Huds.) Fr. and Lentinus Tigrinus (Bull.) Fr. Fungi as Biosorbent
(Amer Chemical Soc, 2016) Alpaslan, Duygu; Ersen, Tuba; Kubilay, Senol; Uzun, Yusuf; Kul, Ali Riza; Aktas, Nahit
Removal of As(V), Cr(Iii) and Cr(Vi) From Aqueous Environment by Modifiable Hydrogels
(Amer Chemical Soc, 2013) Alpaslan, Duygu; Ersen, Tugba; Kubilay, Senol; Aktas, Nahit; Sahiner, Nurettin
Removal of Cu(Ii) and Cd(Ii) Ions From Aqueous Solutions Using Local Raw Material as Adsorbent: a Study in Binary Systems
(desalination Publ, 2017) Caliskan, Necla; Sogut, Eda Gokirmak; Savran, Ali; Kul, Ali Riza; Kubilay, Senol
The purpose of this study is to examine the interaction of Cu(II) and Cd(II) ions in solution with the local raw clayey material of Tilkitepe located in the eastern shore of Lake Van in East Anatolia (Turkey). This material was used as an adsorbent without any chemical or physical treatment and was characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscope, Fourier transform infrared and differential thermal analysis-thermogravimetric analyses. Langmuir, Freundlich, Dubinin-Kaganer-Radushkevich, Temkin and Harkins-Jura non-linear adsorption isotherm models were applied to the experimentally obtained adsorption data and the isotherm constants were calculated. The highest R-2 values for adsorption of both ions in the binary system were obtained by applying the experimental data to the Freundlich isotherm model. In binary system, the experimental adsorption capacities for Cu(II) and Cd(II) ions obtained by kinetic data were 52.631 and 44..843 mg g(-1) at 600 mg L-1 initial metal ion concentrations, respectively In the competitive adsorption, the affinity of Cu(II) toward the adsorbent was much higher than that of the Cd(II). Adsorption kinetics was evaluated using the pseudo-first-order, pseudo-second-order, intraparticle diffusion, Avrami and mass transfer kinetic models. The experimental data proved a closer fit to the pseudo-second-order model. Thermodynamic parameters such as enthalpy (Delta H degrees), Gibbs free energy (Delta G degrees) and entropy (Delta S degrees) were calculated using adsorption isotherms obtained at different temperatures. The results show that the adsorption is spontaneous and controlled by a physical mechanism.
Synthesis and Characterization of Biocompatible Poly(Maleic Acid-Co Acid) Microparticles as a Smart Carrier for Thiamine
(Springer, 2021) Alpaslan, Duygu; Ersen Dudu, Tuba; Kubilay, Senol; Aktas, Nahit
Novel biocompatible homo and co-polymeric microparticles were synthesized from maleic acid (MA) and citric acid (CA) for uptake/release thiamine as a model drug. Surfactant-free self-emulsion polymerization technique was accomplished to synthesize the microparticles in a single step. The antimicrobial, antioxidant properties of those microparticles and their thiamine uptake/release capacities were investigated. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), particle-size/zeta-potential (Zeta/DLS) and scanning electron microscopy (SEM) instruments were utilized for the characterizations of microparticles. FTIR revealed the existence of bonding interaction between the carboxylic acid groups of CA and MA. TGA results represented that thermal decomposition of microparticles was gradually continuing up to 1000 degrees C. The hydrodynamic diameters of poly (CA), poly (MA), poly (CA-co-MA) microparticles were found to be in the range of 681 nm, 1273 nm, 1604 nm, respectively. The zeta potential of those microparticles was in the range of - 5.69 mV, - 16.90 mV and - 7.73 mV, respectively. The studies demonstrated that all microparticles have superior properties to absorb and release thiamine compared with similar candidates. Furthermore, controlled release behavior of thiamine was examined using zero sequence, first-order, Higuchi and Korsmeyer-Peppas models in PBS solutions at pH 7.4. Thiamine release from all microparticles exhibits a very high correlation with the Korsmeyer-Peppas semiempirical model and could be interpreted by the superposition of both Fickian diffusion and non-Fickian diffusion based on Peppas' semiempirical equation. Superior capacities of microparticles, synthesized in one step without formation of toxic by-products, to absorb and release thiamine, aside from their biocompatible, antioxidant and antimicrobial properties make them valuable materials in nanotechnology and biomedical applications.
Utilization of Environmentally Benign Hydrogels and Their Networks as Reactor Media in the Catalytic Reduction of Nitrophenols
(Taylor & Francis As, 2011) Ozay, Hava; Kubilay, Senol; Aktas, Nahit; Sahiner, Nurettin
Iron particles were synthesized inside poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) and used as a catalyst in the reduction of nitro benzene and 4-nitrophenol to aniline and 4-aminophenol, respectively, in acidic medium. It was demonstrated that hydrogel networks can be used effectively as catalysis media in the reduction of some organic toxic materials. The results verified that iron particles containing p(AMPS) hydrogel networks yield faster conversion rates. Additionally, iron nanoparticles containing p(AMPS) hydrogel networks could catalyze the reaction, giving 32% yield without any added cocatalyst, providing self cocatalyst mission.
Utilization of Magnetic Hydrogels in the Separation of Toxic Metal Ions From Aqueous Environments
(Elsevier, 2010) Ozay, Ozgur; Ekici, Sema; Baran, Yakup; Kubilay, Senol; Aktas, Nahit; Sahiner, Nurettin
We report the synthesis of poly(2-acrylamido-2-methyl-1-propansulfonic acid-co-vinylimidazole), p(AMPS-c-VI) hydrogels from various amounts of 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) and N-vinylimidazole (VI) monomers by photo-polymerization technique. Hydrogel composites with magnetic properties were synthesized in situ by incorporating Fe(II) and Fe(III) ions into p(AMPS-c-VI) hydrogels network and then reducing them with alkaline solution. Hydrogels swellings were performed for both bare and magnetic hydrogels. The selective removal capability of toxic metal ions, Cu(II), Cd(II), Fe(II), and Pb(II) by these hydrogels was studied in aqueous medium. Desorption studies were also performed in weakly acidic media to observe whether these hydrogel composites can be utilized as reusable tool for the toxic metal ion removal. The effects of the gel amount, contact time with metal ions, metal species and metal ion concentrations on absorption phenomena were evaluated. The equilibrium removal process of metal ions by the composite hydrogels complies well with the Langmuir adsorption isotherm model. (C) 2010 Elsevier B.V. All rights reserved.