الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
This thesis is consists of three chapters, namely introduction, experimental and results & discussion, which will be summarized more in the following sections.
Chapter (I): Introduction
This chapter includes the introduction, which covers a brief interpretation of the production, separation, and applications of radioactive isotopes. It also represents a brief concept concerning the use of radioisotopes in nuclear application, particularly in the use and production of sealed radioactive sources. This chapter provides a brief account of a literature survey on various manufactured sealed radioactive sources either in the research field for the calibration of γ-detectors or in the medical field for use in the production of brachytherapy seeds for the treatment of ocular and prostate cancer. It is a good explanation of the sealed radioactive sources being categorized according to their geometry, radioactivity level, capsule materials, and sealing techniques. This chapter also deals with the basis of nanotechnology, nanomaterials, and different techniques applied to nanoparticles synthesis.
Chapter (II): Experimental
This chapter contains a full description of chemicals, reagents and instrumentations used in this work. It offers a thorough description of the nano-sorbent materials preparation methods and the radioisotopes used. This chapter provides a summary of the different techniques used in characterizing of the nano-sorbents being prepared. It includes a detailed description of the experimental steps performed under various experimental conditions in the sorption process of the radionuclides studied onto the prepared nano-sorbents. This chapter also contains the experimental procedures used in the preparation of sealed radioactive sources 134Cs(I) and 60Co(II), and offers a brief description on the necessary quality control tests.
Chapter (III): Results and discussion
This chapter comprises three sections, the preparation and characterization of nano-sorbent materials, sorption studies of 134Cs(I) and 60Co(II) on prepared nano-sorbent materials and their use in the preparation of sealed radioactive sources, in addition to sorption studies of 131I on both prepared silver metal NPF and silver oxide NPs. It includes the experimental results, their interpretation and comparison to other published data.
The detailed and systematic studied include various techniques for the preparation of silver nano-structures. Sol-gel auto-combustion technique was used in silver metal NPF whereas wet chemical precipitation technique was used in silver oxide NPs preparation.
Physical and chemical properties of both prepared silver metal NPF and silver oxide NPs were investigated and characterized using FT-IR spectroscopy, thermal analysis, X-ray diffraction (XRD), High resolution transmission electron microscope (HRTEM), and Energy dispersive x-ray spectroscopy (EDX).
The prepared nano-sorbents were found to be chemically stable in water, salt solutions of Na+ and NH4+ chloride in the investigated concentration range . While silver metal NPF exhibits a slight dissolution at room temperature (25±1 °C) in 10 M of hydrochloric and nitric acids and 6 M of sodium hydroxide solutions. Whereas silver oxide NPs are slightly dissolved in 10 M hydrochloric and nitric acids and 9 M sodium hydroxide solutions at room temperature (25±1 °C). Noticeable dissolution was achieved in hot concentrated acid solutions. The FTIR spectrum confirmed the formation of sorbent materials made from silver metal and silver oxide. The X-ray diffraction pattern showed that both nano-sorbent materials prepared were crystalline in nature. The high resolution transmission electron microscope (HRTEM) images of both prepared nano-sorbent materials with different magnification powers confirmed the nano-scale size of both prepared silver nano-structures with an average particle size ≤ 20 nm for silver metal NPF and primary particle size of ≤ 2nm with some degree of agglomerated particles of average size 12 nm for silver oxide NPs. The EDX spectrum of silver metal NPF demonstrated the presence of carbon due to the combustion reaction involved in the preparation of silver metal NPF, thus confirming the purity of prepared silver oxide NPs.
Batch equilibrating technique was performed to determine the different criteria affecting the sorption behavior of 134Cs(I), 60Co(II), and 131I radionuclides from aqueous solutions to prepared silver metal NPF and silver oxide NPs such as pH, initial concentration of Cs(I), Co(II), and I, followed by contact time and reaction temperature for both 134Cs(I), 60Co(II) radionuclides. Depending on the uptake percentage of 134Cs(I), 60Co(II), and 131I on both prepared silver metal NPF and silver oxide NPs, it was found that silver metal NPF had a strong affinity for sorption of 134Cs(I), 60Co(II), and 131I radionuclides, while silver oxide NPs had a very strong affinity for 131I radionuclide and a weak affinity for sorption of 134Cs(I) and 60Co(II) radionuclides. As a result sorption studies for 134Cs(I), 60Co(II) were conducted only on the silver metal NPF, while sorption studies of 131I were performed on both silver metal NPF and silver oxide NPs
The uptake of 134Cs(I) and 60Co(II) on the prepared silver metal NPF depends on the pH medium. The results showed that the sorption on the prepared silver metal NPF sorbent of 134Cs(I) and 60Co(II) increased with the elongation of the contact time to reach its maximum value and reached equilibrium at 5.5 h and 16 h for 134Cs(I) and 60Co(II), respectively. The effect of the initial concentration of sorbate was studied and it was found that the percentage of uptake decreased with an increase in the initial concentration of metal, while the sorbed quantity of metal ions per unit mass of sorbent material increased (sorption capacity). The effect of the reaction temperature was studied at temperatures of 25, 40, 60 °C and it was observed that there was a decrease in the percentage of uptake of 134Cs(I) with an increase in temperature indicating an exothermic process, while the uptake of radionuclides increased with an increase in the reaction temperature indicating the endothermic process as shown in the sorption of 60Co(II).
Models of sorption kinetics, diffusion, isothermic, and thermodynamic were used. The data showed that the 134Cs(I) sorption kinetics were fitted to Elovich model indicating that the 134Cs adsorption forms multi-adsorption layers and the silver metal nanoparticles have a heterogeneous surface. Although the pseudo-second order model was the most appropriate model to describe the 60Co(II) sorption behavior that indicates 60Co(II) sorption of the silver metal NPF is based on the concentration of metal ion and the number of active sites on the adsorbent surface. For sorption diffusion models, it was found that the film diffusion mechanism was best suited to the sorption of 134CS(I), while intraparticle diffusion was the rate determining step for sorption of 60Co(II). Applying the isothermic sorption models, it was found that sorption of both 134Cs(I) and 60Co(II) obeyed Freundlich isotherm model.
Thermodynamic studies for sorption of 134Cs(I) clarified that the negative ΔH° values indicated that the sorption process being studied is exothermic, whereas the positive ΔH° values for sorption of 60Co(II) indicated that the sorption process being studied is endothermic. Furthermore, the negative values of ΔG° demonstrate the spontaneous behavior of both sorption processes. The advancing increase in ΔGo values with increasing temperature indicated that the sorption processes were less efficient at higher temperatures. The positive values of ΔS° demonstrated the increased randomness at the solid-solution interface during the sorption process.
The repeated equilibration of 134Cs(I) and 60Co(II) with silver metal NPF was performed to calculate its maximum sorption capacity. The results showed that the maximum sorption capacity of the silver metal NPF was 153.94 mg/g and 153.54 mg/g for 134Cs(I) and 60Co(II), respectively. A comparative study for maximum sorption capacity of 134Cs(I) and 60Co(II) radionuclides on different reported sorbent materials was conducted and confirmed that silver metal NPF prepared using a simple and cost-effective sol-gel auto-combustion technique, can be considered as a promising nano-sorbent material for removal and concentration of 134Cs(I) and 60Co(II).
134Cs(I) and 60Co(II) on silver metal NPF were used in the preparation of sealed radioactive sources for the calibration of γ-detectors such as the High Pure Germanium detector (HPGe) connected with a multi-channel analyzer. The radioactivity of 134Cs(I), and 60Co(II) is approximately 0.37 MBq (10 μCi) or 0.185MBq (5 μCi) on 1.6 mg or 2.7 mg of silver metal NPF. It was detected and then put in the cavity of the artelone capsule followed by the addition of a few drops of thermal silicone to stabilize the source material in the core and avoid any predicted radioactivity spread. The upper and lower parts of the artelone disc were gathered together and sealed using thermal silicone as an adhesive material. Quality control (Q.C) tests were performed on the prepared artelone sealed radioactive source of 134Cs(I) and 60Co(II) radionuclides. The results showed the validity of the use of 134CS(I)-silver metal NPF and 60Co(II)-silver metal NPF sealed radioactive sources for the gamma-detector calibration under the International Organization for Standardization.
Silver is commonly known for its high affinity for iodine. Both prepared silver metal NPF and silver oxide NPs were used for sorption of radioactive 131I. The uptake of 131I was found to be dependent on the pH value of the medium. The results showed that the sorption of 131I on both prepared silver metal NPF and silver oxide NPs increased with elongation of the contact time, reached its maximum value and achieved equilibrium in 6 h for sorption of 131I on silver metal NPF and 8 h on silver oxide NPs. The effect of the initial sorbate concentration was examined and it was found that the uptake percentage was reduced by increasing the initial metal concentration, while the sorbed amount of metal ions per unit mass of sorbent material (sorption capacity) increased in the case of silver metal NPF. Whereas for silver oxide NPs, a very slight decrease in uptake percentage as a function of an increase the initial concentration of iodine, implying the presence of plenty sorption active sites in silver oxide NPs.
Sorption kinetics, diffusion, isotherm and thermodynamic models were applied. The data showed that the sorption kinetics of 131I were fitted to pseudo-first-order model, while Elovich model was the most fitted model for describing the sorption behavior of 131I on silver oxide NPs. For sorption diffusion models it was found that film diffusion mechanism was best suited to sorption of 131I on the silver metal NPF, whereas intraparticle diffusion was the rate determining step for sorption of 131I on silver oxide NPs. Applying sorption isothermal models, it was found that the sorption of 131I on silver metal NPF and silver oxide NPs obeys Freundlich isothermal model.
Repeated equilibration of 131I on silver metal NPF and silver oxide NPs was performed to determine its maximum sorption capacity. The results showed that the maximum sorption capacity of iodine was 350 mg/g for NPF silver metal and 1111 mg/g for NP silver oxide. A comparison study of maximum sorption capacity of 131I on different reported sorbent materials was conducted and confirmed that both silver metal NPF and silver oxide NPs can be considered as promising nano-sorbent materials for 131I uptake. It also confirms the validity of these nano-materials for use in 131I brachytherapy seeds used for treatment of ocular and prostate cancer, but further studies need to be applied.