Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Characterization of the Adsorption Behaviour of Aqueous Cd (ii) and Ni (ii) Ions on Nanoparticles of Zero-Valent Iron(Izmir Institute of Technology, 2008) Efecan, Nazlı; Shahwan, Talal; Shahwan, TalalIron nanotechnology is recently concieved as a promising tool in environmental remediation. By virtue of their high surface/volume ratio, iron nanoparticles were shown to demonstrate outstanding sequestration capacity for various organic and inorganic pollutants.In this work iron nanoparticles were synthesized using the borohydride-reduction method. The obtained material showed chain like morphology, with the diameter of the nanoparticles being with in 20-80 nm range. HR-TEM images showed that the nanoparticles have a core-shell structure, with the core containing iron in its zero-valent state, while the shell is composed of iron oxides (Fe2O3, Fe3O4, FeOOH)and is generally < 3 nm in thickness.Nano-sized zero valent iron (nZVI) was then tested as a sorbent material for aqueous Cd2+ and Ni2+ ions. The uptake of these ions was investigated under various experimental conditions like time, concentration, pH, repititive application, and liquid/solid ratios. In addition, the uptake of these ions was compared with that of Cu2+, Zn2+, and Sr2+ in order to assess the effect of the reduction potential on the extent of removal.The results showed that nZVI is a very effective sorbent in terms of both kinetics and capacity of removal of the ions. Under the investigated conditions, the uptake reached equilibrium in less than one hour of contact time. Up to the initial concentration of 500 mg/L, the ions were removed almost completely utilizing an nZVI amount of 0.025 g and a solution volume of 10 ml. According to XRD and XPS results, both of Cd2+ and Ni2+ ions were fixed by nZVI through a non-reductive mechanism, that seems to be dominated by interaction of these ions with the exposed iron oxyhydroxide groups at the interface with the solution.Master Thesis Synthesis and Characterization of Clay-Supported Naoparticles of Zero-Valent Iron and Its Application for the Removal of Aqueous Co2+ and Cu2+ Ions(Izmir Institute of Technology, 2008) Üzüm, Çağrı; Shahwan, TalalIn recent years Permeable Reactive Barriers (PRBs) are being developed and used in the removal of organic and inorganic pollutants from surface water and groundwater. Zero-valent iron is viewed as an ideal reactive material for PRBs by means of its high sorption/reduction capacity towards various toxic ions. Zero-valent iron synthesized in nanoscale has a greater affinity to reduce/adsorb various toxic aqueous ions by virtue of its large surface area.In this work, nanoscaled (10-100nm) zero-valent iron (nZVI) was synthesized in ethanol by borohydride reduction method in atmospheric conditions. It was observed that iron nanoparticles are mainly in zero-valent oxidation state and that they remain without significant oxidation for weeks. To enhance its effect and usability, nZVI was supported by kaolinite and montmorillonite during synthesis. Characterization of those clay-supported nZVI was performed using XRD, SEM, TEM, EELS, XPS, Zeta Meter, BET-N2. Iron nanoparticles consist of a zero-valent core and a surrounding oxide shell with approximate thickness of 3-5 nm. The application of clays as support materials have led to a partial decrease in the aggregation of iron nanoparticles known to normally form chain-like structure. The diameter of unsupported iron nanoparticles was predominently within the range 20-80 nm, while clay-supported iron nanoparticles existing as dispersed nano spheres had particle diameters within 10-50 nm.The synthesized materials were applied as adsorbents for Co2+ and Cu2+ ions. According to the results , unsupported and clay-supported nZVI has a great capacity to immobilize Co2+ and Cu2+ ions with very fast kinetics. While Co2+ seems to be fixed via the oxohydroxyl groups on the surface of iron nanoparticles, Cu2+ was fixed by a redox mechanism that lead to formation of Cu2O and Cu0. The performed studies indicate that kaolinite- and montmorillonite-supported zero-valent iron nanoparticles are promising reactive materials for environmental applications.Master Thesis Kinetic Morphological, and Compositional Characterization of the Uptake of Aqueous Ba2+, Mn2+, and Cd2+ Ions by Calcite and Aragonite Over a Wide Range of Concentration(Izmir Institute of Technology, 2007) Tunusoğlu, Özge; Shahwan, TalalThe large availability and widespread distribution of calcium carbonate, CaCO3, in Earth.s crust makes it among the most important minerals to investigate in terms of environmentally and geochemically important aqueous-metal partitioning interactions. In this study, the interactions of Ba2+, Mn2+, and Cd2+ with calcite and aragonite were investigated over a wide range of experimental conditions. The experiments were conducted to examine the effects of time, concentration, pH, temperature on the uptake process assess at low concentrations and the composition and morphology of the precipitated carbonates. The kinetic data corresponding to adsorption were adequately described by the pseudo-second order rate equation. At equilibrium, the extent of adsorption on both minerals followed the order Cd2+ > Mn2+ > Ba2+. Precipitation of metal carbonates proceeded at a slower rate and led to large removal of the ions under consideration. The mass fractions of the precipitated metal carbonates were determined using quantitative XRD. For this purpose, empirical equations were developed for binary carbonate mixtures. FTIR was used to follow the possible modifications in vibrational modes of calcite and aragonite, and the newly emerging vibrations of various carbonate phases. According to SEM results, BaCO3 crystals appeared to be 1-2 micrometers in size with an olivary-like shape and MnCO3 crystals assumed a cubic shape with 200-400 nm size. The particles of precipitated CdCO3 did not demonstrate a well defined shape and its texture appeared to be composed of aggregated sub-micron crystals that form micron sized particles with irregular appearance.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, TalalIn 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.Master Thesis Aas, Xrpd, Sem/Eds, and Ftir Studies of the Effect of Calcite and Magnesite on the Uptake of Pb2+ and Zn2+ Ions by Natural Kaolinite and Clinoptilolite(Izmir Institute of Technology, 2005) Zünbül, Banu; Shahwan, Talal; Shahwan, TalalIn this study, the effect of magnesite and calcite on the uptake of lead and zinc ions by mixtures of these carbonates with kaolinite and clinoptilolite was investigated at various loadings and mixture compositions. The concentration of both ions in the liquid phase was in measured using AAS, while XRPD, SEM/EDS, and FTIR techniques were used in characterizing the solid samples. Thestudy included the determination of kinetics and sorption isotherms of lead and zinc on pure kaolinite and clinoptilolite. Moreover, the sorption behavior of lead and zincat different concentrations and pH conditions was investigated on mixtures of calcite and magnesite with kaolinite and clinoptilolite at carbonate mass percentage compositions of 5, 10, 25, 60 in addition to pure calcite and magnesite. The morphologies of theformed precipitates, the plausible structural change in the lattice of calcite, magnesite, kaolinite, and clinoptilolite originating from sorption of lead and zinc ions was examined. According to obtained results, the sorption affinity of kaolinite and clinoptilolite towards lead is larger than their affinity towards zinc. Within the operating experimental conditions, the sorption capacity increased with increasing the amountsof calcite, and magnesite. The overall order of retention of lead and zinc was observed as magnesite . calcite> clinoptilolite> kaolinite under neutral and alkaline pH conditions and high loadings. When the initialconcentration of zinc and lead ions is raised to saturation conditions, rapid overgrowth of cerussite and hydrozincite was observed. Increasing the initial pH to 10,0 causedenhancement in the dissolution of calcite and magnesite, leading to the enhancingthe precipitation of hydrozincite, and an increased formation of hydrocerussite instead ofcerussite. The uptake of Zn2+ and Pb2+ions by calcite and magnesite have lead to modifying the geometry of the carbonate groups, the thing reflected as variation in their vibrational bands.Master Thesis Effect of Reaction Conditions and Organic Additives on the Morphologies of Synthetic Calcium Carbonates(Izmir Institute of Technology, 2006) Altay, Esra; Shahwan, TalalIn this study, the effects of experimental conditions on the facile morphosynthesis of CaCO3 were investigated. The analyzed conditions included the pH, concentration, mixing and aging temperature, and aging time. After establishing the optimal conditions for calcite and aragonite formation, the effects of organic additives, i.e., PVP, PDDA, PEG, CTAB and EDTA, on the stability and morphology of both polymorphs were examined. Finally, the applicability of calcite as a filling material in polyester was tested. The results indicated that calcite was optimally synthesized at pH 9.0, 0.05 M initial reactant concentration, and 30oC mixing and aging temperatures while the aging time was 24h. The morphologies of produced calcites were dominated by rhombohedra and cubic with particle size range of 5-6 m. On the other hand, the precipitation of CaCO3 dominated with aragonite requires mixing and aging temperatures of 70-90 in addition to shorter aging times. Within such experimental condition, aragonites displayed needle-like and branch-like morphologies with ca. 95% aragonite fraction and aspect ratio of around 8. The applied additives demonstrated various effects on the morphology of precipitated CaCO3. These effects ranged from changing the particle morphology of calcite and aragonite up to suppression of aragonite formation. Finally the application of calcite as a filler in polyester polymer is discussed in light of a comparative determination of mechanical and thermal properties.