Master Degree / Yüksek Lisans Tezleri

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Author: search.filters.author.Shahwan, TalalSubject: search.filters.subject.Clinoptilolite

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  • 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
    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.
  • 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, Talal
    In 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.