الفهرس 
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Abstract
The present thesis comprises three main chapters namely the introduction, experimental and results and discussion.
Chapter 1-Introduction
This chapter represents a general description of uranium and rare earth elements (represented by neodymium) chemistry including its occurrence, oxidation states, complexes formation and hydrolysis behavior. This chapter represents a scientific review concerned with the most popular separation and extraction technologies such as ion exchange, solvent extraction and the widely used solid-phase extraction technique (SPE). A special focus is on the literature of based sorbents and sorption properties in the field of separation and preconcentration of different metal ions.
Chapter 2-Experimental
This chapter represents the experimental work under study in the present thesis including chemicals, reagents, instruments, and analytical methods for uranium and neodymium determinations. Also, this section represents the preparation and characterization of a serious of α-aminophosphonates. It also gives the details about the variables affects adsorption behaviors of U(VI) and Nd(III) from aqueous sulfate solutions on the investigated resins and followed by elution experiments and sorbent regeneration.
Chapter III- Results and discussion
PART 1:
Two of α-aminophosphonates (B-AmPh (Bis-AP) and M-AmPh (Mono-AP)) have been successfully prepared through one-pot three component reaction of thiocarbazide, phthalaldehyde, and trimethylphosphite in the presence of copper triflate as a Lewis acid catalyst. The physicochemical properties are first characterized by elemental analyses, SEM-EDX, FTIR, XRD, BET, XPS, pHZPC. In a second step, the U(VI) and Nd(III) sorption properties of the two materials from synthetic sulfuric acid media have been investigated by batch equilibration and compared through the study of parameters and criteria such as pH, uptake kinetics, and sorption isotherms (including thermodynamic characterization). Also, the regeneration and recycling of the two sorbents have been investigated. For U(VI), At pH 4.5 (and T: 55 °C), the sorption capacity increases from 0.89 to 1.22 mmol U g-1 with the increase in the substitution degree of the derivatives (M-AmPh < B-AmPh). The pseudo-second order rate equation and the Crank equation (resistance to intraparticle diffusion) preferentially fit kinetic profiles. The Langmuir equation successfully describes sorption isotherms. The sorption process is systematically endothermic and spontaneous: enthalpy and entropy changes decrease with the substitution rate. Uranium is successfully desorbed using 0.2 M HCl solutions; after six cycles of re-use the loss in sorption properties ranges between 7 and 9% (while desorption efficiency decreases by 4-6%). Regarding to Nd(III) Maximum sorption capacities reached 1.4 and 1.3 mmol Nd g-1 for Bis-AP and Mono-AP, respectively at pH: 4.5 and 298 K. The kinetic profiles were fitted by the model of pseudo-second order rate equation for Bis-AP and pseudo-first order rate equation for Mono-AP, while the sorption isotherms were modeled using Langmuir and Freundlich isotherm models for Bis-AP and using Freundlich isotherm model for Mono-AP sorbent. Experimental results revealed that the neodymium sorption process is an exothermic and spontaneous reaction for the two sorbents. Metal desorption (0.2 M HCl) was highly efficient, and the sorbent can be reused for up to six cycles with just limited performance decrease.
Part 2:
Two aminophosphonate matrices (mono-aminophopshonate, MAP, and bi-aminophosphonate, BAP) are synthesized, varying the molar proportions of three precursors (thiocarbazide, p-phthalaldehyde, and triphenylphosphite). Nano-composites (CuO/MAP and CuO/BAP) are successfully elaborated by impregnation of the matrices with copper sulfate solution before processing to in situ precipitation of copper in alkaline solution (simultaneous partial Cu reduction). The materials were characterized using: XRD, TEM, SEM-EDX, BET, elemental analyses, titration (pHPZC), FTIR and XPS analyses. Uranium sorption properties are compared for the different sorbents through the study of pH effect (optimum close to 4.5), the uptake kinetics (equilibrium reached in 120 min), and sorption isotherms. Uptake kinetics are finely fitted by the pseudo-second order rate equation (and the resistance to intraparticle diffusion). The sorption isotherms are modeled by the Langmuir equation with maximum sorption capacity (mmol U g-1) decreasing according to CuO/BAP(1.15)>>CuO/MAP(0.80)> BAP(0.74) >>MAP(0.50). The enhanced textural properties and the increase in the density of sorption sites (probably completed by a better steric arrangement for improved reactivity) may explain this ranking. The sorption is endothermic: sorption capacity and affinity coefficient increase with temperature. Uranium is readily desorbed from loaded-sorbents (efficiency >98 %) using either 0.2 M HCl solution or 0.25 M acidified urea solution (pH 2.5) for aminophosphonate matrices and nano-composites, respectively. The type of sorbent does not affect the stability at recycling: at the sixth cycle, the loss in sorption and desorption performances varies by 6.2-7% and 4.2-4.9%, respectively.
Part 3:
(a): Application of the bench scale results to the extraction of uranium from El- Allouga ore material sample. In El- Allouga ore material, Uranium is present in the ore under its hexavalent and tetravalent form. In secondary minerals, uranium is present as soluble form U(VI), whereas in primary minerals is present as insoluble form U(IV). Moreover, the presence of MnO2 (with wt. 1.18%, i.e. high percent relative to uranium content) as a constituent of the ore itself which acts as an oxidizing agent that can oxidized U(IV) to U(VI). This is of critical importance for the design of leaching conditions; indeed, U(VI) can be extracted without introducing an oxidant (contrary to ores containing U(IV) form). In the present work 89% of uranium has been acid leached from Allouga ore material under the following optimum conditions: 50 g L-1 H2SO4, -100 mesh, solid /liquid ratio 1:4 at 25 oC. The treatment of leaching solution (PPLS) was operated in batch reactor under experimental conditions comparable to those used for synthetic solutions (i.e., pH0: 4.5; SD: 0.5 g L-1; time: 60 min; room temperature (i.e., 25 ±1 °C); and agitation speed: 200 rpm).
Despite the huge excess of competitor ions, the sorption capacities for U(VI) remains very high (i.e., 0.59 and 0.89 mmol U g-1 for B-AmPh and M-AmPh, respectively), and generally higher than the values reached for other metals. The decrease in maximum sorption (compared to synthetic solution) does not exceed 16% for bis-aminophosphonated sorbent and up to 23% for mon-grafted sorbent. The ranking in U sorption capacity according to CuO-BAP>>CuO-MAP≈BAP>>MAP; uranium sorption capacities are close to maximum sorption capacities reached with synthetic solutions. The loss in sorption capacity varies between 14% and 21%. Then elution of the loaded uranium was successfully achieved by 0.2M HCl for aminophosphonate sorbents and 0.25 M acidified urea for nano-composites. Finally, uranium was precipitated from the elute liquor using amm.hydroxide; as ammonium diuranate, filtered then dried at 110 °C for 2 hours.
(b): Application of the bench scale results to the extraction of Neodymium from Egyptian monazite ore material sample. Rare earth oxides represent about 60% of the mineral and are mostly formed of LREEs (light REEs). The analysis of Egyptian monazite (97%) showed the following composition: ThO2 (5.9%), U3O8 (0.44%), Ce2O3 (26.55%), while other rare earth oxides (REE2O3) account for 34.35%. In the present work, the hydrous/oxide concentrate (obtained from alkaline thermal processing of monazite) is leached with HCl acid solution at 80 ◦C, before thorium (and uranium) separation (followed by cerium separation). The rare earth pregnant liquor solution (PLS) was obtained from HCl digestion of the rare earth oxide concentrate (1 g) with 1 M HCl solution (10 mL), at 80 ◦C, for 1 h. The sorption tests were performed in batch reactor under experimental conditions comparable to those used for synthetic solutions (i.e., pH0: 3.8; SD: 0.5 g L-1; time: 60 min; room temperature (i.e., 25 ±1 °C); and agitation speed: 200 rpm), the pH0 was set to 3.8 to avoid REEs precipitation. After equilibrium, the solution was filtrated and analyzed for determination of the residual concentrations of REEs, using ICP-AES. The cumulative sorption capacities reach 1.48 and 1.26 mmol g-1 for Bis-AP and Mono-AP; the cumulative sorption capacities exceed (by 5.19%) the maximum sorption capacities obtained for Nd(III) in synthetic solutions for Bis-AP, where for Mono-AP, the trend is reversed; indeed, the cumulative sorption capacity decreases by 2.67% compared with Nd sorption (saturation level) from synthetic pure solutions. The two sorbents little enrich the LREEs after the sorption step; this is confirmed by the EDX analysis. Elution of the
loaded Neodymium was suc cessfully achieved by 0.2M HCl for aminophosphonate sorbents .Finally, REE concentrate was precipitated from the elute liquor using oxalic acid as REE oxalate.