Master Degree / Yüksek Lisans Tezleri
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Master Thesis Ion exchange in natural zeolite packed column(Izmir Institute of Technology, 2004) Can, Özge; Ülkü, SemraTurkish natural clinoptilolites were examined to evaluate their ion exchange performance for the removal of copper, nickel and cobalt ions by performing both batch and packed column experiments.Initial metal solutions were prepared using metal nitrate solutions at various concentrations.All of the experiments were carried out at 29oC.Before performing the ion exchange experiments zeolites were characterized and their clinoptilolite contents were determined quantitatively as 80 and 64 % for zeolites named as CP1 and CP2, respectively.The copper exchange capacities of CP1 and CP2 were determined from equilibrium studies as 10.01 mg (0.32 meq) Cu2+ / g CP1 and 8.33 mg (0.262 meq) Cu2+ / g CP2. Ion exchange capacity of CP2 zeolite was determined as 6.64 mg (0.226 meq) Ni2+ / g and 4.55 mg (0.154 meq) Co2+ / g.The equilibrium behaviour of the system was best described by Langmuir model.Experiments were designed to investigate the optimum parameters and significance of the interactions between these parameters.In column studies, the parameters such as packing height, inlet metal concentration and flow rate were investigated.The concentration of the metals in the sample solutions which were taken from the exit of the ion exchange column at specific time intervals were analyzed by using Optical Emission Spectrometry (ICP-OES).Afterwards, by making use of the data obtained from ICP-OES, breakthrough curves were constructed.By the help of these curves, breakthrough capacity and ion exchange capacity of natural zeolites were calculated.The ion exchange capacity of CP2 zeolite was calculated as 8.04 mg Cu2+/g CP2, which was consistent with the capacity calculated from batch experiments, 8.33 mg Cu2+/g CP2.Also, breakthrough points were determined. Furthermore, solid phase was also analysed for determining its crystal structure and chemical composition using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX) devices (Philips XL 30S FEG).In addition to these, natural zeolite particles which have been ion exchanged throughout this process were regenerated using 0.2M and 1.7M of NaCl solutions.According to regeneration studies, it was determined that 94 and 95% of copper were recovered within the first 100 minutes for both experiments.After the experiments were performed, model equations were applied to the system in order to be able to investigate the dynamic behavior of the system.As a result of this simulation, breakthrough was well predicted.Master Thesis Cation Exchange in Zeolites Structure Modification by Using a Microwave(Izmir Institute of Technology, 1999) Akdeniz, Yelda; Ülkü, SemraIn this research, characterization and modification of clinoptilolite minerals from different deposits have been studied to determine its utility for different Clinoptilolite minerals obtained from the source located in Western (FTIR) to determine the structural properties. The FTIR spectra of the samples showed the characteristic vibrations of the clinoptilolite framework. Thermal properties were determined using Differential Thermal Analyzer (DTA), Thermal Gravimetric Analyzer (TGA), and Differential Scanning Calorimetry (DSC). The analysis showed that the structure of the samples were stable up to 650 DC and due to the Fe203 present in the tuff, phase inversion was observed. Accelerated Surface Area and Porosimeter (ASAP 2010) used to determine the adsorptionrelated properties using N2 and Ar adsorption isotherms. The samples showed different adsorption behaviour toward each gas. The pore size distribution of clinoptilolite samples showed that they have mesaporous structure.The clinoptilolite was modified by ion exchange using 1N NaCI salt solution in waterbath, and in microwave maintained at 80 DC for 10 min, 60 min and 120 min. The efficiency of each method on ion exchange was compared. The Na+ amount in the zeolite was found to be 2.25 and 3.24 % by weight after 2 hours of exchange in waterbath and microwave, respectively. The results showed that microwave method used for modification was more efficient.Master Thesis Application of Zeolites in Biotechnology: Protein Adsorption(Izmir Institute of Technology, 1998) Özgü, Şebnem Karasu; Ülkü, SemraRecovery of proteins from vanous culture broths is a complex engmeenng problem, involving multi-step schemes that lead to significant loss of the desired bioproduct by conventional methods. The bioproduct is not only present in very low concentrations, but also it is subject to chemical/enzymatic degradation. An alternative cost-effective method for recovery of proteins in a highly purified form may be through adsorption, which is a separation technique based on specific and reversible binding, with the use of zeolites that have favorable adsorption characteristics over the other adsorbents. Protein adsorption characteristics of a natural zeolite (clinoptilolite from Turkey) and a synthetic (3A) zeolite were determined through various experiments, altering parameters as pH (range 3.5-6), the amount of zeolites used for adsorption (0.01-0.05 g/ml) and the initial protein concentration (0.01-0.1%). Within the concentration and pH ranges studied, the adsorption capacity of the zeolites was around 50 mg protein/g zeolite. For natural zeolite, approximately 98% was adsorbed within the first 2 minutes, while for the synthetic zeolite, 70% was adsorbed within the first 15 minutes. Uptake diagrams were obtained, adsorption isotherms were determined and Langmuir method was used to describe the isotherms. Desorption was also investigated after treating the zeolites with salt and acid, but further work is necessary for obtaining better recovery. It can be concluded that clinoptilolite is capable of adsorbing proteins in a short time. This study may be the preliminary step, followed by further laboratory work and necessary scale-up experiments, towards the use of zeolites in the recovery of proteins in industry as an alternative to conventional methods.Master Thesis Zeolite Based Composites in Energy Storage(Izmir Institute of Technology, 1999) Negiş, Fikri; Ülkü, SemraIn this thesis, second phases were used for the zeolite-based composites with high thermal conductivity for energy storage applications. Natural zeolite, clinoptilolite received from large deposits in Turkey was used as matrix while aluminum, aluminum hydroxide and graphite were used as second phases for composite preparation.Composites of different compositions (from 10 to 40 wt% additive loading) were prepared by mixing different amount of second phases to the clinoptilolite.Powder mixtures were pelletized using poly vinyl alcohol as a binder. The use of the binder was necessary to obtain mechanically strong pellets. The thermal treatment temperature and press pressure were determined as 150°C and 60 bar for the pellet preparation. Powders were further characterized by thermo gravimetric analysis, differential thermal analysis and differential scanrung calorimetry. These characterizations have shown that three types of water is present in clinoptilolite: external water, loosely bound water and tightly bound water.Thermal conductivities of these composite pellets prepared were determined using hot plate method.Thermal conductivity of pure matrix cIinoptilolite pellets were measured as 0.26 W/mK. Thermal conductivity increased significantly by using aluminum as the second phase while it did not change much for graphite and aluminum hydroxide composites.For composites containing 40% aluminum or aluminum hydroxide or graphite, thermal conductivities of 1.18, 0.50, 0.43 W/mK were measured, respectively. Aluminum containing composites could be used as adsorbent bed materials and by this way, it may increase the performance of adsorption heat pumps.Master Thesis A Chromatographicstudy of Carbon Monoxide Adsorption in Clinoptilolite(Izmir Institute of Technology, 2001) Narin, Güler; Ülkü, SemraAdsorption equilibrium and kinetic parameters for CO/clinoptilolite adsorbate/adsorbent pair were determined by perturbation gas chromatography. Chromatographic experiments were performed at temperatures in the 60-120°C range and at carrier gas flow rates in the range of 10.31-24.36 em/sec. The chromatographic response peaks were obtained by concentration pulse method. A packed column of 10 em length and 0.46 em inlet diameter which was packed with clinoptilolite particles with narrow size distribution (500-850 §) around mean diameter of301.9 § was used. The clinopti10lite particles were excavated from Gordes, Western Anatolia. The moments of the response peaks were calculated by integration of experimental chromatographic data and matched to the .model parameters in order to determine the equilibrium constants and diffusion coefficients. The dynamic model (Haynes and Sarma, 1973) was applied to describe the adsorption and diffusion processes in the packed column. This model includes axial dispersion, external mass transfer resistance, micropore and mesopore diffusion resistances. The equilibrium constants (Henry's law constants, K) were calculated in the range of 40 - 952 and were found to be in good agreement with the results in the literature. These constants were found to decrease with increasing temperature. The heats of adsorption were obtained in the range of 54.15 - 57.14 kl/mol from the slope of van't Hoff plots and compared with those in the literature. The heats of adsorption were found to be lower than those reported in the literature obtained for the same adsorbate/adsorbent pair. The higher heats of adsorption were explained by the smaller pore size, higher cation content of the clinoptilolite and more accessibility of the cations in the clinoptilolite framework by CO molecules. Heats of adsorption remained almost constant over the carrier gas velocity range studied. The contributions of axial dispersion and other mass transfer resistances Indiffusion of CO in clinoptilolite were also determined. The total dispersion exhibited slight change (average 0.035 see) with temperature implying that the micropore diffusional resistance was not dominant for diffusion of CO in clinoptilolite under the experimental conditions studied. The axial dispersion coefficient was determined in the range of 1.149.88 cm2/sec and the total mass transfer resistances were found between 0,02-0.06 sec. The results showed that the mesopore diffusion resistance was the controlling mechanism in CO diffusion in clinoptilolite. Mesopore diffusion coefficient was estimated as 2.98xlO-3 cm2/sec. This value was in good agreement with the theoretically determined value.Master Thesis Removal of Heavy Metals From Wastewaters by Use of Natural Zeolites(Izmir Institute of Technology, 2001) Türkmen, Müşerref; Ülkü, SemraIn the present study, clinoptilolite rich local natural zeolite was proposed as an ion-exchanger for the removal of heavy metals (Pb2+, Cu2+, Zn2+) from wastewaters.Natural zeolite samples were exposed to a simple pretreatment process which included washing and drying to remove impurities and dust.Thermal and adsorption related properties of washed and original zeolite samples were determined by TGA and N2 adsorption analyses. In TGA analyses, average water content for washed and original samples were found as 9.44 and 10.13 % respectively. In N2 adsorption studies, both washed and original samples showed the characteristic Type IIb isotherm. BET surface areas of the samples were calculated as 39.73 and 47.72 m2/g for washed and original samples respectively.Pretreatment process was found to improve the adsorption capacity of clinoptilolite due to the removal of impurities and dust.In ion-exchange studies, efficiency of natural zeolite in removal of heavy metals from the solutions was investigated based on some physical and chemical variables. For this purpose, particle size and the amount of zeolite in the solution, contact time of the metal containing solution with zeolite were selected as physical variables and pH, metal concentration of the solution, and the presence of other ions were selected as chemical variables. The chemical analyses of all exchange solutions were performed by using ICP-AES. Removal % of the metal ions from the solutions were obtained. Based on the experimental results, zeolite exhibited a significant affinity to Pb2+, followed by Cu2+ and Zn2+ even in the presence of competing cations.To test the applicability of natural zeolite for the treatment of Acid Mine Drainage (AMD), zeolite samples were allowed to contact with simulated AMD solutions.Consequently, natural zeolite was found to be an efficient ion exchanger for removing lead, copper and zinc ions from aqueous solutions.Master Thesis Production of Proanthocyanidins From Grape Seed(Izmir Institute of Technology, 2003) Altıok, Evren; Ülkü, Semra; Ülkü, SemraProanthocyanidin is a potent antioxidant that is why it directly affects many important diseases such as coronary heart disease, cholesterol etc. Thus, proanthocyanidin is one of the important dietary supplements, which is mainly found in grape seeds. In this study the extraction of this valuable antioxidant from grape seeds was studied. For the extraction of proanthocyanidins, different solvents such as ethanol, methanol, acetone and their aqueous forms were used. The maximum extraction yield was achieved after 24 h at room temperature. It was observed that 70% aqueous acetone was the best solvent with the highest yield of 17.5%. Yield of proanthocyanidin extracted with 70% aqueous acetone was 3 times greater than proanthocyanidins extracted with other solvents. The extract was freeze dried to obtain the product as powdered form. To compare the product with commercial ones HPLC chromatograms and FTIR spectra were taken and similar spectra were obtained. With HPLC, monomers of proanthocyanidins; (+)-catechin and (-)- epicatechin were determined. (+)-catechin was observed at 17.2 min as 3.06%w/w. Also, (-)-epicatechin was observed at 42.8 min as 1.99%w/w. Most of the drying methods are performed at high temperatures which may result negative effects on proanthocyanidin`s antioxidant capacity. Even the applications at low temperatures in case of freeze-drying have some disadvantages e.g. the process takes a long time, it is expensive and has some difficulties. Therefore as an alternative to other concentration and drying techniques, adsorption process was thought to be a promising technique. Although adsorption of proanthocyanidins on zeolites were not obtained, removal of excess water from the extracts can be achieved by using zeolites. This would possess as a promising technique for the concentration of the end productThe antioxidant capacities of proanthocyanidins from the grape seed extracts were also determined. Proanthocyanidin has an antioxidant capacity with 57 TEAC value, which is more than synthetic antioxidants; BHT, BHA, TBHQ and PG, 6.66, 0.593, 1.168 and 12.62 TEAC respectively. .Master Thesis Cation Exchange (ag+, Zn2+, Cu2+) Behavior of Natural Zeolites(01. Izmir Institute of Technology, 2001) Top, Ayben; Ülkü, SemraIn this study, clinoptilolite, most abundant zeolite present in nature, was proposed as a low cost antibacterial material. As a preliminary work, antibacterial activities of the original, Ag, and Zn forms of the clinoptilolite were investigated against several strains and compared to the commercial antibiotics. No antibacterial action was observed for the original clinoptilolite. Ag loaded clinoptilolite was found to be superior to the Zn-form against Proteus spp. and Pseudomonas aeruginosa.The original, Na, Ag, Zn, and Cu forms of the clinoptilolite samples were characterized by FTIR spectroscopy, thermal analyses (TGA, DTA, and DSC), and N2 physisorption studies. Specific attention was given in to the chemical analysis of the clinoptilolite by ICP-AES. Using the standard addition method, the respective idealized formulas of the original and Na-clinoptilolite based on 72 oxygen atoms in the unit cell were calculated as:(Na0.816 K2.070) (Ca1.060 Mg0.264) (Al5.653 Fe0.390) (Si30.084) O72. 20.023 H2O, and (Na4.763 K1.057) (Ca0.076 Mg0.094) (Al5.843 Fe0.221) (Si29.911) O72.17.049 H2O.In the FTIR spectra of the original and exchanged forms of the clinoptilolite, considerable shifts (from 3460 to 3494.8 cm-1) were observed in the band, which is formed due to the interactions of water molecules with the framework via hydrogen bonds. The positions of the other bands were not affected by cation exchange significantly. From the TGA curves, the water contents ranged between 14.31 and 11.00 % for the original and the cation-exchanged forms of the clinoptilolite. Mainly, two endotherms and one exotherm were obtained in the DTA curves. The first endotherm occurred up to about 150 oC, the second endotherm lied between 200 and 700 oC, and the exotherm was obtained at about 850 oC. Significant differences observed between the shapes of the DSC curves indicated that the cations control the dehydration behavior of the samples. N2 physisorption isotherms of five samples were all, Type IV with BET surface areas ranging between 34.97 and 46.76 m2/g.Ag, Zn and Cu ion exchange equilibria were investigated at 25 oC for both the original clinoptilolite and Na-clinoptilolite. In the former case, from the plateau of the isotherms cation exchange capacities were determined as 1.184, 0.439, 0.539 meq/g clinoptilolite for Ag+, Zn2+, and Cu2+ respectively. The major portion of the exchanges was contributed by Na+ and Ca2+. Distribution coefficient values indicated that at Ag, Zn and Cu ion exchange equilibria were investigated at 25 oC for both the original clinoptilolite and Na-clinoptilolite. In the former case, from the plateau of the isotherms cation exchange capacities were determined as 1.184, 0.439, 0.539 meq/g clinoptilolite for Ag+, Zn2+, and Cu2+ respectively. The major portion of the exchanges was contributed by Na+ and Ca2+. Distribution coefficient values indicated that at relatively low initial concentrations, the preference of the clinoptilolite for Zn2+ and Cu2+ was significant. At higher concentrations, higher distribution coefficients were obtained for Ag+ compared to Zn2+ and Cu2+. Langmuir and Freundlich models were applied for each equilibrium data. For Zn2+ and Cu2+ exchanges, Langmuir model gave better correlation and Freundlich model fitted experimental data slightly better in the case of Ag+ exchange.Equilibrium isotherms for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs were investigated. Silver exchange isotherm lied above the diagonal over the whole composition range. For zinc and copper exchanges, the isotherms were above the diagonal up to equivalent fractions of exchanging ion in solution phase (As) at about 0.2. While full exchange was attained for silver, partial exchanges were obtained in the case of zinc and copper. The standard free energy of exchange values were found as .6.0, 2.03 and 3.09 kj/equiv for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs respectively. From these values selectivity sequence was obtained as Ag+ > Na+ > Zn2+ > Cu2+.Consequently, by considering the preliminary antibacterial activity results, specific cation exchange capacities, and selectivity sequence of the clinoptilolite, Ag-clinoptilolite seemed to be promising antibacterial material. The results of the current study compared to the literature data pointed out that cation exchange behavior of the clinoptilolite is dependent on its original cationic composition. Therefore, it is necessary to carry out specific studies on representative samples from the deposit before any practical application.Master Thesis Determination of Characteristics of Adsorbent for Adsorption Heat Pumps(Izmir Institute of Technology, 2013) Sayılgan, Şefika Çağla; Ülkü, SemraAdsorption heat pumps, which are environmentally friendly and operating with thermal sources, have gained attention in recent years. Although they have higher primary energy efficiency than traditional heat pumps, adsorption heat pumps require improvements due to the low COP and SCP/SHP values. The selection of appropriate working pair, the determination of adsorption equilibrium and kinetics of the pair is quite important in the design of adsorption heat pumps. In this study, the working pairs used in adsorption heat pumps were discussed, and the models used in adsorption equilibria and kinetics were explained. In the experimental part, the effect of the adsorption and desorption temperatures on adsorption capacity and mass diffusivity were investigated. Type RD silica gel-water and zeolite 13X-water were selected as working pairs in the adsorption experiments. Accordingly, two volumetric systems were constructed; adsorption experiments were conducted and pressure changes were recorded against time. The experimental studies showed that the adsorption capacity was decreased with increasing adsorption temperature and with decreasing desorption temperature, and zeolite 13X-water pair had higher adsorption capacity than type silica gel-water pair under the same conditions. Type II and Type I isotherms were observed for type RD silica gel-water pair and zeolite 13X-water pair, respectively. The effective diffusivity of zeolite 13X-water pair was found in the range of 2x10-8-9x10-9 m2/s for the short time period and in the range of 7x10-10-10-8 m2/s for the long time period. In addition, it was seen that the effective diffusivity was effected from the initial adsorptive concentration and the effective diffusivity was decreased with increasing adsorbate concentration. This may be related to the effects of the heat transfer resistance, surface resistance or hydration and migration of the cations in the structure of the zeolite 13X.Master Thesis Removal of Hydrocarbons From Wastewaters(Izmir Institute of Technology, 2002) Koltuksuz, Gülsan; Ülkü, SemraWastewater of chemical industries and petrochemical spills are the main sources of hydrocarbon pollution. Benzene, toluene and o- xylene are generally found in petrochemical spills which effect the all livings in the environment because of its toxicity.This thesis was an investigation of benzene, toluene and o- xylene (nonpolar aromatics) adsorption on clinoptilolite rich natural zeolite and surfactant modified zeolite. The aim of surfactant modification was to make highly polar zeolite surface hydrophobic and thereby remove the hydrophobic benzene, toluene and o- xylene molecules from the aqueous phase with the help of hydrophobic attraction forces.Cationic surfactants Dodecyl Amine (DA), Tetramethylammonium (TMA+) and an anionic surfactant Sodium Dodecyl Sulfate (SDS) were used for surface modification.The degree of surface hydrophobicity was examined by calculating the change in Gibbs free energy of the zeolite-water system by using the contact angle and surface tension measurement results in the presence and absence of surface modification. For natural zeolite the mean contact angle value was found 7.76o. Modification by DA and TMA+ increased .m from 7.76o to 51.13o and 29.37o respectively at a concentration of M. In case of SDS, at the pH value of 4, there was only a slight increase from 7.76 o to 18.03 o at a concentration of M. Effect of these surfactants on interfacial tension at air water interface was also different from eachother. DA decreased the surface tension from 72.8 to 37 dynes/cm while TMA+ did not bring any change. This part of the study showed that the presence of surfactant makes zeolite surface more hydrophobic.In adsorption studies, natural zeolite removed 20% of hydrocarbons from water. Except toluene, there was an optimum time that the removal was high. Presence of surfactant was able to increase this percent up to 40% under some conditions depending on the surfactant and hydrocarbon type and concentration. The highest benzene adsorption was obtained with TMA+ modified zeolite. The sequence was benzene > toluene > o-xylene. In case of DA modified zeolite, on the other hand, oxylene was adsorbed more than the other hydrocarbons. The removal follows the order o- xylene > toluene > benzene in this case.