الفهرس 
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Abstract
Radioactive waste is generated from the production of nuclear energy and the use of radioactive materials applications. Radioactive waste contains different radionuclides which are hazardous to human and environment. Therefore, the treatment of radioactive waste is a very important task. The main aim of this thesis is directed to evaluate the potential use of nano-cryptomelane as a sorbent material for aqueous radioactive waste treatment. The removal of Pb2+, Cs+ and Co2+ from single, binary and ternary solutions using nano-cryptomelane was assessed by investigating the sorptive behavior of these elements on the synthesized material. Modification of nan-cryptomelane was achieved by producing beads to be used in the column technique. Operational design criteria for the column and some aspects on studied elements also included. The work carried out in this thesis is presented in three chapters, namely, introduction, experimental, as well as results and discussion.
The first chapter, ”Introduction”, comprises background on radioactive wastes, their sources and classifications, different techniques of treatment of aqueous radioactive waste. This chapter includes also the definition of nanotechnology, importance and size dependent properties of nanomaterials. Classification of nanomaterial depending upon their composition or their dimensionality also reported. The different methods of preparation of nanoparticles including the advantages and disadvantages of each method also outlined. Toxicity of nanomaterials and the different types of nanomaterials used in wastewater treatment also illustrated.
Physical properties of bead presented also. A literature survey related to the present work is given at the end of this chapter.
The second chapter, ”Experimental”, contains detailed description of all chemicals, reagents and equipment used for the experimental investigations. Preparation of nano-cryptomelane using oxidation method and preparation of multi-system solutions are also outlined. Preparation of nano-cryptomelane-PVA beads and characterization of the prepared materials are involved. Batch investigation, determination of capacity, desorption investigation and column investigation are reported in this chapter.
The third chapter, ”Results and Discussion”, comprises the results obtained from the experimental study and sorption of metal ions from single, binary and ternary solutions onto the synthesized sorbents.
This chapter is divided into three main parts as follow:
1- Characterization of nano-cryptomelane
2- Factors affecting the sorption process
3- Column study
1- characterization of nano-cryptomelane
Characterization of the synthesized nano-cryptomelane was carried out using different techniques including HR-TEM, FE-SEM with mapping, XRD, Raman spectroscopy, thermal analysis (TGA-DTA) and FTIR. The solubility and apparent capacity of the synthesized nano-cryptomelane were experimentally measured.
- HR-TEM indicates that the crystal structure of nano-cryptomelane is fibrous-like structure, the diameter and length distribution calculations revealed that the mean diameter and length of nano-cryptomelane are 7.67 and 77.81 nm, respectively.
- FE-SEM with EDX-mapping show that nano-cryptomelane is mainly composed of O, K and Mn ions. Manganese is the more significant ion in nano-cryptomelane with a weight percentage of 72.11%, while oxygen and potassium ions are presented with the percentages of 23.41 and 4.48%, respectively.
- SEM with mapping of nano-cryptomelane bead indicates a homogeneous distribution of nano-cryptomelane inside the bead and presence of some pores on the surface of the bead.
- The XRD pattern reveals the existence of six diffraction peaks recorded at 2θ of 12.8°, 18.5°, 28.9°, 37.5°, 42° and 50° which are characteristic peaks for nano-cryptomelane.
- Seven Raman bands are observed at 183, 286, 330, 386, 512, 574, and 753 cm-1 which are characteristic bands of the Mn-O lattice vibrations within the (2x2) tunnel structure of MnO6 octahedral.
- Thermal analysis illustrate that the synthesized nano-cryptomelane is thermally stable at high temperatures.
- The feasibility of desorption of the studied metal ions was carried out using the best eluent (0.7 mol/L HNO3); results indicate that nano-cryptomelane can be regenerated and reused efficiently for six cycles.
- The loading capacity of nano-cryptomelane was found to be 179.6, 442.6 and 716.9 mg/g for Co2+, Cs+ and Pb2+, respectively.
2- Factors affecting the sorption process
Sorption experimental investigations of Co2+, Cs+ and Pb2+ ions by nano-cryptomelane by studying some factors such as pH, contact time, metal ion concentration and temperature, as follow:
• Effect of pH and speciation
- Sorption of Pb2+, Cs+, and Co2+ from single, binary and ternary systems was studied at different pH values ranging from 1 to 6.
- The results indicate the values of the distribution coefficient and the percentage of uptake for the three metal ions in all systems increased by increasing the pH values. The optimum pH value for the three metal ions in all systems was desired at pH 5.
- The speciation of Co2+, Pb2+ and Cs+ at different pH values in aqueous solution are presented as Co(OH)+, Pb(OH)+ and Cs+ , respectively. This confirms that the three metal ions are sorbed as monovalent species.
- The removal percent of the three metal ions in the single system is higher than that of the other systems.
• Effect of contact time and temperature
- The effect of contact time was studied at range of 1 to180 minutes at different temperatures of 25, 30, 40 and 50 Co for all systems.
- Results indicate that the sorption increases by increasing shaking time and the equilibrium time of sorption process was reached after 45 minutes for all ions of the all systems.
• Sorption kinetic modeling
Non-linear pseudo-first-order and non-linear pseudo-second-order kinetic models were studied at different temperature range (298-323 K) to determine the rate and the mechanism of the sorption process. The outlined data were more fitted to the non-linear pseudo-second-order than the non-linear pseudo-first-order model.
• Effect of metal ion concentration
Sorption of Pb2+, Cs+ and Co2+ ions onto nano-cryptomelane was performed at total initial concentrations of (0.5–6.0) ×10-3 mol/L at different temperatures. Sorption isotherms indicated that, increasing the metal ion concentration led to an increase in the amount sorbed of Pb2+, Cs+ and Co2+ ions to a certain point. Also, the amount sorbed was increased with an increase in temperature for all cations thereby reflecting the endothermic nature of the process.
• Isotherm models
Equilibrium isotherms have been determined and tested for different isotherm expressions and the sorption data were modeled using extended Langmuir and Freundlich isotherm models. The outlined results suggest that the extended Langmuir isotherm model fits the data reasonably well and it is more applicable than Freundlich isotherm.
• Thermodynamic studies
Thermodynamic parameters, ΔHo, ΔSo, ΔGo were determined;
- The obtained negative values of ΔGo confirm the feasibility of the process and the spontaneous nature of the sorption process.
- The values of enthalpy change (ΔHo) and entropy change (ΔSo) for all studied ions were calculated. The change in ΔHo was found to be positive confirming the endothermic nature of the sorption process.
- The positive values of entropy change (ΔSo) show the increased randomness at the solid/solution interface.
• Comparison of sorption capacity of nano-cryptomelane with different sorbents
- The comparison between the performances of nano-cryptomelane to that of other sorbent materials obtained in the literature. Results indicate that nano-cryptomelane has a high sorption capacity, therefore, can be considered as a promising sorbent material for removal of Pb2+, Cs+ and Co2+ metal ions from single, binary and ternary aqueous solutions.
3- Column Investigation
A chromatographic column of 10 cm length and 1.0 cm inner diameter was utilized. The column performance was investigated by studying some factors including flow rate, bed depth and metal ion concentration. The breakthrough curves for Pb2+, Co2+ and Cs+ ions were estimated for each factor.
• Effect of bed depth
Different bed depths, 2, 3 and 4 cm, were used to obtain the breakthrough curves for Pb2+, Cs+ and Co2+ ions sorption onto nano-cryptomelane for a constant flow rate of 1 mL/min and at 0.33 x10-3 mol/L initial concentration of each metal ion. It was indicated that the column performance and the capacity increased by increasing the bed depth for the three metal ions. The total bed capacity of Pb2+, Cs+ and Co2+ ions was 4.03, 4.50 and 4.84 mg/g at bed depths of 2, 3 and 4 cm, respectively.
• Effect of flow rate
At a constant bed depth of 3 cm and initial concentration of 0.3x10-3 mol/L of each metal ion, the effect of different flows (1-3 mL/min) has been studied. Results reveal that the column performance and the capacity decreased by increasing the flow rate for the three metal ions. The total bed capacity of Pb2+, Cs+ and Co2+ ions was 4.50, 2.87 and 2.12 mg/g at flow rates of 1, 2 and 3 mL/min, respectively.
• Effect of initial metal ion concentration
The effect of varying the initial metal ion concentrations (10-3, 5x10-3 and 5x10-4 mol/L) at a flow rate of 1.0 mL/min and bed depth of 3.0 cm for the sorption performance of nano-cryptomelane column has been studied. Results indicate that the capacity increased by increasing the metal concentration for the three metal ions. The total bed capacity of Pb2+, Cs+ and Co2+ ions was 7.63, 4.50, 2.58 mg/g at initial concentrations of 5, 1 and 0.5 mmol/L, respectively.