Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Cation Exchange (ag+, Zn2+, Cu2+) Behavior of Natural Zeolites(01. Izmir Institute of Technology, 2001) Top, Ayben; Ülkü, Semra; Top, Ayben; Ülkü, Semra; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn 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 Synergistic Effect of Natural Zeolites on Flame Retardant Additives(01. Izmir Institute of Technology, 2004) Demir, Hasan; Demir, Hasan; Ülkü, Semra; Ülkü, Semra; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIntumescent flame retardant systems were proposed to increase flame retardancy performance of polymers without environmental hazard. An intumescent system consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and natural zeolite (clinoptilolite, Gördes II) as a synergistic agent was used in this study for flame retardancy of polypropylene (PP). APP and PER combination were examined at different ratios (0.25, 0.33, 0.5, 1, 2, 3, and 4) for optimization of formulation of flame retardancy. The zeolite was incorporated into flame retardant formulation at four different concentrations (1,2, 5, and 10wt%) to investigate synergism with the flame retardant materials. Filler content was fixed at 30w% of total amounts of flame retardant PP composites. The zeolite and APP were treated with two different coupling agents namely, 3-(trimethoxysilyl)-1-Propanethiol and (3-aminopropyl)-triethoxysilane for consideration influence of surface treatments on mechanical properties and flame retardant performance of composites.To investigate thermal behaviour of flame retardant PP composites with and without zeolite, samples were heated on optic microscope hot stage. Both of the composites behaved similarly during heating from room temperature to 203oC. Molten pentaerythritol was observed as a second phase in molten polypropylene at 203 oC. Bubble formations were not observed. Flame retardants did not cause any foam formation during processing of mixture at 190oC in rheomixer and hot press. SEM pictures of non-burnt and burnt flame retardant (FR) PP composites with and without zeolites did not reveal significant difference considering foam size and shape compared to composites without zeolite. Zeolite crystals did not exhibit any deformation during burning of composite.Flammability of FR-PP composites were determined by UL-94 flame test in air. Burning rate of composite was measured for flammable composite in atmospheric condition. The limiting oxygen index (LOI) test method provided measuring the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that supports combustion of pure PP, zeolite reinforced PP and flame retardant PP composites. The best flame retardant performance was achieved with APP:PER(3:1)+PP+2% zeolite and APP:PER(2:1)+PP+5% zeolite formulations, exhibiting 37.4 and 38% LOI values respectively. LOI values reached maximum value 41% with mercapto silane treated APP:PER(2:1) at 5w% Zeolite PP composite Young's modulus of composites decreased with increasing amounts of APP in composite on the contrary to their elongation at break properties.