Yazar "Kunkul, Asim" seçeneğine göre listele
Listeleniyor 1 - 15 / 15
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Application of arti ficial intelligence in modeling of the doxorubicin release behavior of pH and temperature responsive poly(NIPAAm-co-AAc)-PEG IPN hydrogel(Elsevier, 2020) Boztepe, Cihangir; Kunkul, Asim; Yuceer, MehmetModeling of the drug release behavior of stimuli-responsive hydrogels is a domain of steadily increasing academic and industrial importance. It is very difficult to accurately predict the drug release kinetic of this type drug carrier materials due to environmental variables in the body such as pH and temperature. In this study, a pH- and temperature-responsive poly(N-Isopropyl acrylamide-co-Acrylic acid)/Poly(ethylene glycol) (poly(NIPAAm-co-AAc)/PEG) interpenetrating polymer network (IPN) hydrogel was synthesized by free radical solution polymerization in the presence of poly(NIPAAm-co-AAc) microgels and PEG. The synthesized IPN hydrogels showed rapid pH- and temperature-responsive deswelling behavior. The textural properties and surface morphology of poly(NIPAAm-co-AAc) IPN hydrogel were characterized by scanning electron microscopy (SEM) analysis technique. The doxorubicin (DOX) was loaded to the hydrogels by swelling the hydrogels in the DOX solution. The cumulative release of DOX has been investigated as a function of time, pH and temperature. Experimental DOX release data obtained were successfully modeled using ANNs, LS-SVM and SVR methodologies. To evaluate the performance of these models, four statistical parameters: correlation coefficient (R), root mean squared error (RMSE), mean square error (MSE) and mean absolute percentage error (MAPE) were calculated. It was found that the developed ANN model show best performance in modeling the DOX release behavior of poly(NIPAAm-co-AAc)/PEG IPN hydrogels.Öğe Boric Acid Extraction from Calcined Colemanite with Ammonium Carbonate Solutions(Amer Chemical Soc, 2012) Kunkul, Asim; Aslan, Nezahat Ezgi; Ekmekyapar, Ahmet; Demirkiran, NizamettinColemanite, a calcium-borate hydrate, is found in significant amounts in Turkey. Colemanite is used as a raw material in the production of boric acid. In this study, the leaching kinetics of calcined colemanite in ammonium carbonate solutions was investigated in a batch reactor. The effects of calcination temperature, solution concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the dissolution rate were determined and evaluated. It was found that the dissolution rate of calcined samples was higher than that of the uncalcined sample. It was observed that the leaching rate of calcined colemanite enhanced with increasing calcination temperature up to 450 degrees C, and did not change above this temperature. Thus, it was found that the applied calcination temperature had a significant effect on the leaching of colemanite. It was determined that the leaching rate raised with an increasing ammonium carbonate concentration, increasing reaction temperature, and decreasing solid/liquid ratio. It was detected that calcium carbonate was not formed on the particle surface. The dissolution kinetics of calcined colemanite was examined using both heterogeneous and homogeneous reaction models, and it was determined that the reaction rate can be described by a first-order pseudohomogeneous reaction model. The activation energy for this process was calculated to be 59.03 kJ/mol.Öğe Dissolution kinetics of calcined ulexite in ammonium carbonate solutions(Korean Institute Chemical Engineers, 2007) Kunkul, Asim; Demirkiran, NizamettinThe leaching kinetics of calcined ulexite in ammonium carbonate was studied in this work. The effect of parameters of ammonium carbonate concentration, solid/liquid ratio, stirring speed, calcination temperature and reaction temperature was determined in the experiments. It was found that the conversion rate increased with increasing ammonium carbonate concentration, reaction temperature and decreasing solid/liquid ratio. However, the effect of stirring speed on the conversion rate was insignificant. The experimental data practised the heterogeneous and homogeneous models, and an acceptable model for the conversion rates of ulexite was determined to be a first-order pseudo-homogeneous reaction model. The activation energy of dissolution process was determined to be 35.3 kJ/mol.Öğe Heterogenization of homogeneous NHC-Pd-pyridine catalysts and investigation of their catalytic activities in Suzuki-Miyaura coupling reactions(Elsevier Science Sa, 2018) Boztepe, Cihangir; Kunkul, Asim; Yasar, Sedat; Gurbuz, NevinNew generation, novel, environmentally safe polymeric heterogeneous catalysts which included catalytically active NHC-Pd-pyridine complexes were prepared by radical polymerization of NHC-Pd-pyridine complexes with Acrylamide (AAm) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomers in the presence of N,N'-methylenebisacrylamide (MBA) crosslinker. Structural characterization of NHCPd-pyridine complexes was conducted by using NMR, FT-IR while the structural characterization of crosslinked polymeric catalyst systems was made by using FT-IR, SEM, SEM-EDX, TEM and TGA analysis techniques. The synthesized polymer-based NHC-Pd-pyridine catalysts showed good catalytic activity for Suzuki reaction of aryl bromides with phenylboronic acid in aqueous media. They exhibited good stability and they could be reused at least five times without remarkable loss of catalytic activity. (C) 2018 Elsevier B.V. All rights reserved.Öğe Hydrogel supported vinylimidazole based PEPPSI-Pd-NHC catalysts: The catalytic activities in Heck and Suzuki-Miyaura coupling reactions(Elsevier, 2020) Boztepe, Cihangir; Kunkul, Asim; Gurbuz, NevinIncreasing environmental awareness and limited raw material resources have increased the importance of catalysts by leading to green technology. For this purpose, there is a need for efficient, new, selective, reusable, environmentally friendly catalysts and catalytic systems. In this study, PEPPSI (pyridine enhanced precatalyst preparation, stabilization, and initiation) type and vinylimidazole (VI) based palladium complexes of N-heterocyclic carbenes (PEPPSI-Pd-NHCs) which have catalytic activity in homogeneous Suzuki and Heck reactions were prepared. To obtain environmentally safe polymeric heterogeneous catalysts, this novel PEPPSI-Pd-NHC complexes were polymerized with Acrylamide (AAm) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) by free radical polymerization. Characterization of PEPPSI-Pd-NHC complexes and polymer supported catalysts were made by using various elemental and structural analyses techniques. The synthesized polymeric supported heterogeneous catalysts have high activity, stability and reusability for Suzuki and Heck reaction of aryl bromides in aqueous media. (C) 2020 Elsevier B.V. All rights reserved.Öğe Investigation of Leaching Kinetics of Copper from Malachite Ore in Ammonium Nitrate Solutions(Springer, 2012) Ekmekyapar, Ahmet; Aktas, Evrim; Kunkul, Asim; Demirkiran, NizamettinThe production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303 K to 323 K [30 A degrees C to 50 A degrees C]) and diffusion through a porous product layer (323 K to 343 K [50 A degrees C to 70 A degrees C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50 kJ/mol, respectively.Öğe INVESTIGATION OF THE USE OF AMMONIUM ACETATE AS AN ALTERNATIVE LIXIVIANT IN THE LEACHING OF MALACHITE ORE(Assoc Chemical Eng, 2013) Kunkul, Asim; Gulezgin, Abdulvahap; Demirkiran, NizamettinSolutions containing ammonia allow for selective leaching of copper from a copper ore. In this study, the leaching and kinetics of malachite ore were examined using ammonium acetate solutions as an alternative lixiviant The effects of some experimental parameters on the leaching of malachite ore were investigated. A kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature and stirring speed, and decreasing particle size and solid-to-liquid ratio. It was found that the leaching reaction followed the mixed kinetic control model. The activation energy of this leaching process was determined to be 59.6 kJ moll. Consequently, it was determined that ammonium acetate solutions could be used as an effective leaching agent for copper extraction from malachite ore.Öğe Kinetic Investigation of Reaction Between Mineral Ulexite and Citric Acid(Taylor & Francis Inc, 2010) Ekmekyapar, Ahmet; Kunkul, Asim; Demirkiran, NizamettinIn this study, the dissolution kinetics of ulexite, a sodium-calcium-borate hydrate (Na2O center dot 2CaO center dot 5B2O3 center dot 16H2O) in citric acid solutions was investigated in a batch reactor. The rate of dissolution can be expressed according to surface chemical reaction controlling with changing fluid reactant concentration. The activation energy of the process was found to be 39.4kJ/mol.Öğe The kinetics and mechanism of polymer-based NHC-Pd-pyridine catalyzed heterogeneous Suzuki reaction in aqueous media(Wiley, 2019) Boztepe, Cihangir; Kunkul, Asim; Gurbuz, Nevin; Ozdemir, IsmailOne of the most important challenges of the Suzuki reaction is a green synthesis of reaction products. In terms of economy and ecology, the Suzuki reaction details must be characterized for the industrial-scale Suzuki reaction processes. In this paper, for the first time, a kinetic and mechanistic study on the Suzuki reaction catalyzed with hydrogel-supported PEPPSI (pyridine-enhanced precatalyst preparation stabilization (and) initiation) type NHC-Pd-pyridine composite has been investigated. To determine the rate-limiting step, the effects of reactants and experimental conditions on the heterogeneous Suzuki reaction have been experimentally defined. The experimental results demonstrated that it is possible to reach 100% yield under the optimum reaction conditions, which were found as 75 x 10(-3) mol/L of phenylboronic acid (FBA), 50 x 10(-3) mol/L of bromoacetophenone (Brac), 125 x 10(-3) mol/L of K2CO3, 1 g/L of catalyst, 80 degrees C of reaction temperature, 400 rpm of mixing rate, and 3 h of reaction time. The transmetalation step in the cycle was defined as the rate-limiting step. On the basis of kinetic results, a mathematical reaction rate expression was presented assuming the steady-state approach to steps of the catalytic cycle. The activation energy (E-a) of the reaction was estimated to be 34.88 kJ/mol.Öğe Modeling of drug release behavior of pH and temperature sensitive poly(NIPAAm-co-AAc) IPN hydrogels using response surface methodology and artificial neural networks(Elsevier, 2017) Brahima, Sanogo; Boztepe, Cihangir; Kunkul, Asim; Yuceer, MehmetAn interpenetrated polymer network (IPN) poly(NIPAAm-co-AAc) hydrogel was synthesized by two polymerization method: emulsion and solution polymerization. The pH- and temperature-sensitive hydrogel was loaded by swelling with riboflavin drug, a B2 vitamin.The release of riboflavin as a function of time has been achieved under different pH and temperature environments. The determination of experimental conditions and the analysis of drug delivery results were achieved using response surface methodology (RSM). In this work, artificial neural networks (ANNs) in MATLAB were also used to model the release data. The predictions from the ANN model, which associated input variables, produced results showing good agreement with experimental data compared to the RSM results. (C) 2017 Elsevier B.V. All rights reserved.Öğe Modeling of Swelling Behaviors of Acrylamide-Based Polymeric Hydrogels by Intelligent System(Taylor & Francis Inc, 2015) Boztepe, Cihangir; Solener, Musa; Yuceer, Mehmet; Kunkul, Asim; Kabasakal, Osman S.Hydrogels based on acrylamide (AAm) were synthesized by free radical polymerization in an aqueous solution using N, N'-methylenebisacrylamide (MBAAm) as crosslinker. To obtain anionic hydrogels, 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) and acrylic acid (AAc) were used as comonomers. The swelling behaviors of all hydrogel systems were modeled using an artificial neural network (ANN) and compared with a multivariable least squares regression (MLSR) model and phenomenal model. The predictions from the ANN model, which associated input parameters, including the amounts of crosslinker (MBA) and comonomer, and swelling values with time, produce results that show excellent correlation with experimental data. The parameters of swelling kinetics and water diffusion mechanisms of the hydrogels were calculated using the obtained experimental data. Model analysis indicated that the ANN models could accurately describe complex swelling behaviors of highly swellable hydrogels.Öğe Modeling of the Size Distribution Resulting from Dissolution of Spherical Solid Particles in Turbulent Flow(Taylor & Francis Inc, 2012) Ekmekyapar, Ahmet; Kunkul, Asim; Yuceer, Mehmet; Kelbaliyev, GudretThe process of dissolution of solid particles in turbulent flow regime is of importance in many industrial applications. A new size distribution takes place due to dissolving during the motion of a solid-liquid suspended system in a stirred vessel. An analytical relationship was derived to represent the concentration profile in diffusion boundary layer between solid and liquid. An expression was obtained between mass transfer flow from spherical particle area and particle size changing with time during dissolution of solids. A mathematical model was developed for calculating particle size distribution varying with time during dissolution of spherical solid particles. The Focker-Planck equation was used to construct the distribution function varying with particle size. Model parameters were estimated by the Genetic Algorithm, the validity of the model was confirmed with experimental data.Öğe Prediction of the deswelling behaviors of pH- and temperature-responsive poly(NIPAAm-co-AAc) IPN hydrogel by artificial intelligence techniques(Springer, 2020) Boztepe, Cihangir; Yuceer, Mehmet; Kunkul, Asim; Solener, Musa; Kabasakal, Osman S.One of the most important fields of interest in respect of stimuli-responsive hydrogels is modeling and simulation of their deswelling behavior. The problem mentioned above plays an important role regarding diffusion of fluid from hydrogel to media, what is very useful in biomedical applications, such as controlled drug delivery systems, biomaterials or biosensors. In this study, the pH- and temperature-responsive poly(N-isopropylacrylamide-co-acrylic acid) interpenetrating polymer network (poly(NIPAAm-co-AAc) IPN) hydrogel was synthesized by free radical solution polymerization method. In order to improve the deswelling rate of the conventional poly(NIPAAm-co-AAc) hydrogels, their IPN structure was synthesized by using poly(NIPAAm-co-AAc) microgels. The chemical structure and surface morphology of poly(NIPAAm-co-AAc) IPN hydrogels were characterized by FT-IR and SEM analysis techniques. The synthesized poly(NIPAAm-co-AAc) IPN hydrogel has high swelling capacity (112 g water/g dry polymer at 20 degrees C and pH 7) and exhibited fast and multivariable deswelling behaviors dependent on pH and temperature. The pH- and temperature-dependent mechanical property of IPN hydrogel was investigated. It was found that the compressive strength of the IPN hydrogels was changed inversely proportional to the swelling capacity. To develop the model for deswelling behaviors of IPN hydrogel, artificial neural network (ANN) model and least squares support vector machine model techniques were used. The predictions from the ANN model showed very good correlation with observed data. The results indicated that the ANN model could accurately predict complex deswelling behavior of pH- and temperature-responsive IPN hydrogels.Öğe Recovering of copper with metallic aluminum(Elsevier, 2011) Demirkiran, Nizamettin; Kunkul, AsimThe cementation of copper ions from aqueous copper sulfate solutions by using spherical aluminum metal particles was examined. The effects of the experimental parameters on copper cementation were investigated and evaluated. Reaction rate increases with increasing copper concentration, reaction temperature, stirring speed and decreasing pH. It was observed that the reaction follows the first-order kinetics, and progresses according to the diffusion controlling step.Öğe Reductive leaching of pyrolusite ore by using sawdust for production of manganese sulfate(Pleiades Publishing Inc, 2012) Ekmekyapar, Ahmet; Asin, Celal; Demirkiran, Nizamettin; Kunkul, Asim; Baysar, Ahmet; Ceylan, KadimManganese compounds, such as manganese sulfate, can be obtained from pyrolusite, a manganese ore. Low-grade manganese ores is usually treated by hydrometallurgical methods. In this study, the leaching and recovery of manganese from pyrolusite ore in sulfuric acid solutions containing sawdust as reducing agent was investigated. The effects of experimental parameters, such as sulfuric acid concentration, sawdust amount, solid-to-liquid ratio, stirring speed, particle size, reaction temperature, and leaching time, on the manganese extraction from ore were examined. The results showed that the leaching rate of pyrolusite ore increased with an increasing sulfuric acid concentration, sawdust amount, stirring speed, reaction temperature and leaching time, and decreasing in solid to liquid ratio and particle size. The kinetic analysis of leaching process was carried out, and it was determined that the reaction rate was controlled by diffusion through the product layer under the experimental conditions in this work. The activation energy was found to be 22.35 kJ mol(-1). Manganese can be recovered as manganese sulfate by the evaporative crystallization of the purified leach liquor.
