Master Degree / Yüksek Lisans Tezleri

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Has files: YesSubject: search.filters.subject.Zeolites--Absorption and adsorption

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Now showing 1 - 6 of 6
  • Master Thesis
    Application of Zeolites in Biotechnology: Protein Adsorption
    (Izmir Institute of Technology, 1998) Özgü, Şebnem Karasu; Ülkü, Semra; Ülkü, Semra; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Recovery 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
    Gas adsorption in volumetric system
    (Izmir Institute of Technology, 2003) Becer, Metin; Özkan, Seher Fehime; Özkan, Seher Fehime; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, nitrogen adsorption on natural zeolitic tuff from Gördes, (Fındıcak) region and on its acid treated forms was studied. The natural zeolite, identified as clinoptilolite, has been treated with HCl, H2SO4, HNO3, and H3PO4 solutions at several concentrations to obtain the acid treated forms. Structural modifications arising from the acid treatments were determined by the techniques, namely XRD, FTIR, ICP, EDX, SEM, DTA, TGA, and microcalorimeter. Adsorption characteristics of zeolites, such as external and total surface areas, micropore volumes and pore size distributions were compared.Acid treatment of natural zeolite showed that as the acid concentrations were increased, more cations were removed from the structure, changing the Si/Al ratios from 4.04 (original zeolite) to 5.35 with H2SO4, to 6.39 with HNO3, to 10.8 with HCl and to 5.01 with H3PO4 treatments respectively. With acid treatment, the maximum nitrogen adsorption capacity at P/Po . 0.89 of natural zeolite (0.015 cm3/g) was increased to 0.089, 0.090, 0.086, and 0.050 cm3/g for HCl, HNO3, H2SO4 and H3PO4 treatments respectively. Nitrogen adsorption capacities of the zeolites increased with increasing Si/Al ratios, but further increase in concentrations caused to decrease the adsorption capacity for HCl and HNO3 treatments. HCl behaved in a different way that, dilute (1M) and highly concentrated (10 M) solutions has effect on the framework structure much more than the middle range concentrations (3 M and 5 M HCl) decreasing the nitrogen adsorption after Si/Al . 8.4 (5 M HCl).Dubinin-Raduskhevich model was used to determine the volume accessible to nitrogen (limiting micropore volume). It increased with increasing Si/Al ratios, but further increase in concentrations caused to decrease in microporous structure. The highest limiting micropore volumes (0.078 and 0.082 cm3/g), and Langmuir surface areas (213 and 226 m2/g) were obtained with the 5 M HCl and 2 M HNO3 treated samples respectively without any noticable loss in crystallinity.
  • Master Thesis
    Investigation of Fuel Oxygenate Adsorption on Clinoptilolite Rich Natural Zeolite
    (Izmir Institute of Technology, 2006) Yetgin, Senem; İnal, Fikret; İnal, Fikret; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The wide use of fuel oxygenates in gasoline as anti-knocking and emission reduction agent have recently led to serious environmental concerns due to their detection in groundwater and surface water. Among the various gasoline additives, methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE) are the most frequently used fuel oxygenates worldwide. Due to the physical and chemical properties of fuel oxygenates, the conventional treatment technologies are generally ineffective for their removal from contaminated water. Adsorption is a common process frequently used to remove fuel oxygenates from water. The use of natural zeolites as adsorbent have increased significantly because of their availability and low cost. Clinoptilolite is one of the most abundant zeolites in nature, and Turkey has very large clinoptilolite reserves. In this project the adsorption properties of clinoptilolite rich natural zeolites for use in the removal of MTBE and ETBE from water have been investigated using batch equilibrium and fixed-bed column experiments. The adsorption properties have been compared with those of two activated carbons (i.e., Powdered Activated Carbon (PAC) and Granulated Activated Carbon (GAC)). In addition, bisolute (i.e., benzene and oxygenate) adsorption experiments were also carried out to determine the effectiveness of these adsorbents in the presence of other gasoline hydrocarbons. All the experiments were performed at 25 °C with initial oxygenate and benzene concentrations of 2000 ppb and 400 ppb, respectively. In batch equilibrium experiments, it has been found that the powdered and granulated activated carbons had higher adsorption capacities for MTBE and ETBE than clinoptilolite. The highest capacity for the amount of MTBE adsorbed per unit mass of adsorbent was achieved using GAC while that of ETBE was obtained using PAC. The presence of benzene decreased the adsorption capacities of GAC and PAC. However, the effect of benzene was not clear and was dependent on the adsorbent loading for clinoptilolite. In fixed-bed column experiments, GAC and clinoptilolite were tested as adsorbents. The column breakthrough curves for clinoptilolite were steep indicating fast adsorption and narrow mass transfer region. For GAC, mass transfer regions were wider due to the relatively flat breakthrough curves. There was no significant effect of benzene on the breakthrough curves for GAC and clinoptilolite.
  • Master Thesis
    Co2, N2 and Ar Adsorption on Modified Zeolites
    (Izmir Institute of Technology, 2004) Ertan, Aslı; Özkan, Seher Fehime; Özkan, Seher Fehime; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this study, CO2 and N2 adsorption on synthetic zeolites namely, 5A and 13X, and acid treated natural zeolites was investigated by using volumetric adsorption device, ASAP 2010. The natural zeolites and its acid treated forms with HCl (1M, 3M and 5M), HNO3 (2 M), and H3PO4 (1.1 M) solutions at 60 oC for 6 or 3 hours were used as adsorbent. The effect of the acid treatment and temperature on the adsorption properties of the zeolites for the CO2 and N2 gases at 5 and 25 oC was studied. Langmuir, Sips, Vrial and Dubinin-Astakhov model equations were applied to the adsorption data in order to determine the affinity and the heterogeneity of the adsorbents.Calorimetric properties of the zeolites were also studied using CO2, N2 and Ar gases through a Tian-Calvet calorimeter, Setaram C80 at 25 oC. Isosteric heat of adsorption of the gases adsorbed on the adsorbents under investigation was determined at 5 oC and 25 oC using Clasius- Clapeyron equation. These results were compared with the heat of adsorptions obtained from the calorimetric studies directly.The zeolite treated with 1.1 M H3PO4, P1 has the highest adsorption capacity (2.24 mmol/g and 0.67 mmol/g) for CO2 and N2 while the natural zeolite has only 2.08 mmol/g and 0.51 mmol/g respectively at 5 oC. Synthetic zeolites 13X and 5A have higher CO2 (6.82 mmol/g and 5.46 mmol/g respectively) and N2 adsorption capacities (0.31mmol/g and 0.91 mmol/g respectively) than natural zeolites at 5 oC. Langmuir b parameter called the affinity constant decreased as adsorption temperature increased for CO2 and N2 adsorption. The Sips model t parameter characterizing the system heterogeneity is higher for CO2 adsorption than N2 adsorption and decreases with increasing temperature. This indicates that the CO2 molecules give more specific interactions than N2 molecules. The pure component selectivities of CO2 over N2 calculated from Langmuir equation, are the highest for NCW zeolite as 408 at 25 oC. This value follows by P1 zeolite which is 151 at the same temperature.The highest differential heat of adsorption value (80.29 kJ/mol) at zero coverage for CO2 also belongs to P1 sample. The heterogeneity parameters of the model equations applied also indicated that P1 sample is more heterogeneous when compared to other acid treated natural zeolites. Finally as expected, for both N2 and CO2 as temperature increased from 5 to 25 oC, the adsorbed amounts decreased when fresh samples were used at each run in the experiments. The temperature difference had a greater effect on N2 adsorption rather than CO2.
  • Master Thesis
    Removal of Hydrocarbons From Wastewaters
    (Izmir Institute of Technology, 2002) Koltuksuz, Gülsan; Ülkü, Semra; Ülkü, Semra; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Wastewater 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.
  • Master Thesis
    Physicochemical Characterization of the Sorption Behavior of Cs+ and Sr2+ Ions on Natural Kaolinite and Cliptilolite Minerals
    (Izmir Institute of Technology, 2005) Akar, Dilek; Shahwan, Talal; Shahwan, Talal; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study, aspects of the thermodynamics and kinetic profile of the sorption behavior of Cs+ and Sr2+ ions on natural minerals of kaolinite and clinoptilolite originating from Sındırgı and Manisa regions were investigated.Radioactive wastes that are caused by the increasing usage and production of radioactive substances give rise to big problems rising day by day. Natural substances such as clay minerals and zeolites decrease the dispersion of radioactive isotopes by sorption. Therefore they can be able to retard the radioactive pollution that is caused by radioisotopes, and the reach of these radioisotopes to the underground waters. 137Cs (t1/2 . 30.1 y) and 90Sr (t1/2 . 28.8) are radioisotopes that are important as radioactive wastes due to their long half-lives ,and that produce with high yields at the end of nuclear fission reactions. The experiments were performed using the batch technique at four different initial concentrations, two different temperatures, and time period ranging from 5 minutes up to 48 hours.The experimental findings revealed that the percentage sorption of Cs+ on clinoptilolite ranged 91-94, on kaolinite ranged 28-40 , and that the percentage sorptionof Sr2+ clinoptilolite ranged between 48-93 and 12-47 for the kaolinite case. In order to check the stability of sorption of Sr2+ and Cs+ ions fixed by kaolinite and clinoptilolite,desorption experiments were performed as well with tap water. The results indicated that in the case of Cs+ sorption on kaolinite the percentage desorption amounted to 40, but was smaller than 7 in the case of clinoptilolite. The desorption percentage of Sr2+ from clinoptilolite did not exceed 5, while it is amounted to 12 in kaolinite case, indicating a more stable fixation by clinoptilolite. The results showed that sorption of both Sr2+ and Cs+ on both minerals followed pseudo-second order kinetics, with the rate constants indicating faster sorption on kaolinite. The activation energies were 11.6 and 15.3 kj/mol for Cs+ sorption on kaolinite and clinoptilolite, respectively. Alternatively, the activation energy values for Sr2+ sorption on kaolinite and clinoptilolite were 8.5 and 17.3 kj/mol, respectively. Freundlich and D-R isotherm models were found to adequately describe the adsorption data of Sr2+ and Cs+ on both minerals.Cs+ sorption showed a spontaneous and exothermic behavior on both minerals with .H0 being .6.3 and .11.4 kj/mol for Cs+ uptake by kaolinite and clinoptilolite, respectively. On the other hand, Sr2+ sorption showed a spontaneous and endothermic behavior on both minerals with .H0 being 11.22 and 9.8 kj/mol for Sr2+ sorption on kaolinite and clinoptilolite, respectively. To check the effect of interlayer expansion on the uptake capacity of kaolinite, the clay was intercalated with DMSO, to overcome the tight H-bonding interconnecting the layers of the clay. Expanding the interlayer space of kaolinite from 0.71 nm to 1.12 nm using DMSO intercalation, lead to an increase in the sorption capacity of kaolinite, with the increase being more significant in Sr2+ case. Compared with the percentage sorption on natural kaolinite, the percentage sorption ofCs+ on DMSO-intercalated kaolinite for the initial concentrations of 100 and 500 mg/L of CsCl, increased, respectively, from 35 to 41, and from 27 to 33. On the other hand,the percentage sorption of Sr2+ on DMSO-intercalated kaolinite for the initial concentrations of 100 and 500 mg/L of Sr(NO3)2, increased from 17 to 58, and from 22 to 45,respectively. SEM/EDS characterization was carried out to investigate structural changes accompanying the sorption process. SEM analysis indicated that both minerals has a well-defined crystal structure. The EDS findings revealed some localization in the sorbed Sr2+ and Cs+ on the surfaces of both minerals and demonstrated the higher fixation ability of clinoptilolite.