الفهرس 
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Abstract
The management of radioactive wastes has become an issue of great concern. This type of wastes could be treated using solid adsorbents such
as ion exchanger. 137Cs is the main fission products in radioactive wastes from industrial and research applications.
The objectives of this thesis are the removal of cesium -134 from aqueous media, radioactive waste and milk by the preparation of PATiW
as anew composite ion exchanger.
The thesis is divided into three main chapters, introduction,
experimental and the results and discussion.
1. Introduction
This first chapter, introduction, includes brief account on history,
classification, chemical, thermal and radiation stabilities of ion exchangers, ion exchange theory, characterization of ion exchanger,concepts of ion exchange, applications of ion exchangers, and recent
developments. A literature survey related to different ion exchangers showing high selectivity for separation of cesium and different ions up to 2010 is reviewed.
2. Materials and Methods
This chapter, deals with the different materials employed and their chemical purity, as well as the methods utilized for the preparation of the
radioactive materials was given. Detailed descriptions of the instrumentations, the analytical techniques and procedures used in this
thesis were also detailed. A detailed description of the method of preparation of PATiW and TiW at different operative conditions and set
up used in this work were presented. Column chromatographic technique
and recovery of cesium from milk was also described.
3. Results and Discussion
This chapter deals with the results and discussion and is divided into six main sections:
3.1. Preparation and Characterization of TiW and PATiW Polyaniline gel was prepared by mixing equal volumes of of 10%
aniline (C6H5NH2) and 0.1M potassium persulphate. A precipitate of titanium tungstate was prepared at (65 ±2 °C) by adding 1 M titanium
chloride solution to an aqueous solution of 1M sodium tungstate (Na2WO2.2H2O). The gel of polyaniline was added to the white inorganic precipitate of titanium and mixed thoroughly with constant stirring.
Physicochemical properties of the prepared materials were identified by using different techniques, such as, elemental composition, stability,
pH-titration curve, IR-spectra, X-Ray diffraction patterns, SEM as well
as thermal analysis (DTA and TGA).
The spectrum of prepared polyaniline, PATiW and TiW were displayed in the IR technique. There are characteristic bands of PATiW indicating the binding of inorganic precipitate with organic polymer and
formation of PATiW. The characteristic peaks of PATiW are disappeared by increasing drying temperatures indicating the decomposition of the organic materials.
According to the X-ray powdered diffraction patterns, the crystallinity of PATiW slightly improved with the increase of heating temperature from 50 °C to 850 °C. The SEM pictures showed that the surface morphology of composite material is totally different from their
individual inorganic and organic components. from the DTA/TGA analysis of PATiW, the material shows high thermal stability up to
studied temperature.
The solubility experiments showed that the composite and inorganic ion exchangers have good chemical stability in acids and alkali solvents.
The solubility of composite material is slightly increased than the inorganic material. Elemental analysis determines the formula of PATiW
as:
[(TiO2)(WO3) (-C6H4NH-)]. 2.46 H2O.
The pH-titration curve of PATiW showed only one inflexion point indicating that behaves as monofunctional and may be acts a strong acid
cation-exchanger. The ion exchange capacity of Cs+ on PATiW as a function of pH is investigated. It was found that the capacity increase by
increasing the pH. The Cs+ ion-exchange capacity of the PATiW material is 1.82 meq g-1.
3.2. Distribution Studies
In order to find out the potentiality of the new composite PATiW
compared to the non-modified TiW in separation of metal ions,distribution coefficient studies were performed.
The distribution coefficient (Kd) of Cs+ on PATiW showed was found
to be the higher than that of TiW at different reaction temperatures.
The selectivity performance of PATiW as a new adsorbent was studied for separation of Cs+, Co2+, Zn2+, Cu2+, Cd2+ , Cr3+, Zr4+, V5+,
As5+ and Mo6+ were carried out on PATiW at different pH. It is found that the composite showed high selectivity towards Cs+ and the
selectivity trend in order of Cs+ > Zr4+ > Mo6+ > V5+> As5+ > Cr3+ > Co2+
> Cu2+> Zn2+ > Cd2+. The separation capability of the material has been
demonstrated by achieving some important binary separations such as Cs
– Co, Cs – Zn, Cs – Cd, Cs – Cu, Cs – Cr, Cs – AS, Cs – Zr, Cs – V, and Cs – Mo.
3.3. Kinetic Studies
The kinetic studies was performed at cesium concentrations (660,
1300 and 6600 mg/L), different particle size, different reaction
temperature and different drying temperatures for the sorption of Cs+ onto PATiW and TiW.
It is clear that the removal rate significantly affected by particle size.
The rate and extent of sorption is higher for small particles, which confirmed the particle diffusion control is the main mechanism.
The thermodynamics parameters for the studied systems were calculated, the negative values of Go confirm the feasibility of the
process and the spontaneous nature of the sorption processes. The positive value of Ho indicates the reaction is endothermic. The positive
values So reveal the increased randomness at the solid/solution interface
with some structural changes in the Cs+ sorbed on PATiW and TiW.
The data of the kinetics of Cs+ sorbed from aqueous solution onto
PATiW and TiW were found to be obeyed the pseudo second-order,
homogeneous particle diffusion model, shell progressive model and
intraparticle diffusion. This indicates that the rate determining step is
diffusion through the exchanger particles and this observation agreed
with the fundamental theory of particle diffusion mechanism.
The Di values of the studied system were found in the range of 10-12 m2 /s
which indicate to the chemisorptions process.
The energies of activation of Cs+ on both adsorbent, Ea, were below 42 kJ/mol which generally indicate diffusion-control processes.
3.4. Sorption Isotherms
Sorption equilibrium is usually described by an isotherm equation
whose parameters express the surface properties and affinity of the sorbent, at a fixed temperature and pH. Removing Cs+ on PATiW and
TiW was increase with increaseing Cs+ concentration in solution until it
reached the maximum capacity at different reaction temperatures.
The best fit values of the parameters together with the R2 values showed that the Freundlich model fit the adsorption data better than the Langmuir model. This indicates that Cs+ adsorb on PATiW and TiW as
monolayer deposition of Cs+ on localized sites followed by a multilayer sorption with interaction between adsorbed molecules that having
heterogeneous energy distribution, accompanied by interaction between
the adsorbed molecules. In addition, the sorption capacity (qo) increase with increasing temperature, this indicates that the process was
endothermic in nature.
Also, it was found that, the maximum adsorption capacity of Cs+ onto PATiW was significantly higher than that of TiW at different temperatures. This indicates that the sorption tendency of Cs+ towards onto PATiW was higher.
3.5. Column Operations
The breakthrough curves (C/C0 vs. volume) obtained for Cs+ sorption onto PATiW at different bed depths ( 3.0, and 4.0 cm) for a constant
linear flow rate of 2.5 ml min-1 and at 140 mg/L of neutral cesium concentration were studies. The bed capacity and the percent removal of
Cs+ was increase with increasing bed height, as more binding sites were available for sorption. The rate determining step can be inferred from a stop-flow test, in which the flow is halted and restarted during column
loading. There was a significant decrease in C/C0 when the operation was
restarted. This phenomenon is indicative of a particle diffusion controlled system.
The break-through curves for separation of cesium from acid solution (0.5 M HNO3+0.1 M NaNO3) and from alkaline simulant solution (0.5 M NaOH+0.1 M NaNO3) using PATiW columns at flow rate of 0.7 ml min-1, bed depth 1cm and 13 mg g-1 of cesium chloride. It is found that the PATiW can be applied to separate radiocesium from acidic solutionwhere for alkaline solution the break-through begins very early with capacity very small.
3.6. Recover Cesium from Milk The milk cesium-134 activity was measured over a 3-h period to determine the equilibrium time. As well as the removal efficiency of
cesium-134 and the decaying of cesium activity were studied. The reaction half-life was 30 min, and by 60 min the reaction was 80% complete. The reaction reached equilibrium at 2h.