الفهرس 
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Abstract
The new developed extraction technique namely solvent-impregnated resin ”SIR” was applied in this study to modify the purity of uranium concentrate prepared from low grade ore deposits. This modification can be regarded as the classically applied process known as ”ELUEX” which has been used in concentration and further direct purification to ensure advanced uranium product.
The initial step of this study was uranium elution from the Amberlite IRA - 400 anion exchange resin, loaded with 80 gUll w.s.r, by nitric acid instead of the traditionally used acidified solutions of NaCI. This was found necessary since in the subsequent extraction step by the prepared ”SIR”, where tri-butyl phosphate (TBP) would be used and nitric acid is best working media. However, 2 N nitric acid, without aluminum nitrate addition, at flow rate of 1.5 I/l.w.s.r Ihr is the most efficient elution condition, where 97% overall elution efficiency was achieved and produces more concentrated eluate solution.
The wet impregnation method for the polymeric resin Amberlite XAD-4 either by fresh (unloaded) or loaded tri-butyl phosphate (TBP) organic solvent achieve successful impregnation rather than the dry method. The polymeric resin was impregnated by 1.148 gram TBP/gram when using 70% TBP at a solvent I resin ratio of 3 for three days at ambient temperature. However, a gross sample weighing about 860 gram of the impregnated resin was then prepared using these conditions for the further studies of the factors affecting uranium extraction from nitric acid medium.
The presence of aluminium nitrate Al (N03)3, as a salting out agent in the aqueous nitrate medium, greatly enhances uranium extraction by tributyl phosphate solvent. It is obvious that uranium distribution coefficient in nitrate media, using SIR, increased with increasing the added amount of aluminum nitrate to reach its maximum value of 437.5 when using an aluminum nitrate concentration of 1.5 M with I N nitric acid, where almost complete extraction was occurred. On the other hand, the flow rate of 0.75 ml/min was the effective in case of uranium adsorption from 5.5 N nitric acid while Iml/min was the effective in case of using a feed solution containing 1.5 M AI (N03)3 + I N HN03. However, at an initial uranium concentration of 140 g Uti (SIR = 5), the SIR has been loaded with its maximum practical value which is equivalent to about 217 g Ulkg SIR.
Elution of loaded TBP - impregnated Amberlite XAD-4 resin using distilled water, as an eluant, at a flow rate of 0.25 ml/min (equivalent to 0.75 I Il.w.s.r Ihr) is more effective. This is due to the higher eluant residence time, which lead to minimum eluant volume and more concentrated solution.
A fine grained lemon yellow concentrate product was obtained by precipitation of uranium from eluate solutions with hydrogen peroxide, where it was found match well with uranium peroxide hydrate identified using XRD. Moreover, it has accepted specifications from the chemical point of view and according to the intemationallimits.
The equilibrium isotherm of uranium distribution between the TBP-impregnated resin and the aqueous phase was linearized by the Langmuir equation. From the resultant straight line, the constants ”Q” & ”K” were determined (”223.312” & ”0.3919” respectively) where these values were used further in the Mathematical Models. On the other hand, the extraction adsorption kinetics data resulting from the fractional approach to
equilibrium ”Y” were used in calculations for evaluating the diffusion control during uranium adsorption and elution and in turn determining the corresponding mass transfer coefficients in Modeling.
The validity of Mathematical Model for diffusion through liquid film reveals that another rate process controlling the mass transfer, while the diffusion through the combined liquid film and solid indicates the equation validity for controlling the mass transfer rate process. On the other hand, diffusion through solid controls the mass transfer rate during the elution step, however, the diffusivity inside the impregnated resin beads ”Dp” was 165.2 x 10-12 (m2j s).