Arab Journal of Nuclear Science and Applications, 46(3), (40-51) 2013

40

Recovery of Uranium (VI) From Treated Technological Sample, El Sela

Area, South Eastern Desert, Egypt

L.A.Yousef, M.S.Abdel Ghany and S.Y.Afifi

Nuclear Materials Authority, P.O.Box 530 El Maadi, Cairo, Egypt.

Received: 22/12/2012 Accepted: 1/2/2013

ABSTRACT

The extraction of uranium from aqueous nitrate solution was studied using

the organic extractant tributyl phosphate or 1,4 Dioxane dissolved in different

diluents. The parameters affecting the extraction and stripping of U (VI) include

types of diluents, extractants concentrations, aqueous to organic phase ratio (A/O),

shaking time and stripping agents. The factors studied were followed by application

of the suitable extraction system to extract U content from two fractions of the solid

waste (slime and coarse size) from El Sela area, Egypt.

The data obtained showed that, best results were obtained using each of the

following systems; 20 % TBP dissolved in toluene, A/O 1:1, 4 min. of shaking time

and 5M HNO3 acid stripping solution, or; 5 % 1,4 Dioxane dissolved in CCl4, A/O

1:1, 5 min. of shaking time and 0.5M HNO3 acid for the stripping process.

It was recommended to wash the slime sample by acidified water to decrease

the range of pH to 1 to overcome the problem of hydrolysis and precipitation of

uranium.

The data obtained from statistical calculations showed that, Error (%) in

studied samples is less than 2 %. While, the accuracy (Δ) is less than ±3 declaring

high accuracy and precision for the obtained results.

Key words: Uranium extraction / TBP /1,4 Dioxane / Nitric Acid / Arsenazo III / XRD.

INTRODUCTION

Gabal El Sela lies between longitude 36º 14' 36'' E and latitude 22º 15' 36'' N, covering an area

about 70 Km2 of basement rocks (Fig.1). El Sela granite was actually considered as highly weathered

uraniferous granite in southern Egypt and was displayed high uranium content in the form of

uraninite (1). The geological, mineralogical and the geochemical criteria of the El Sela area as well as

the prevailing of arid to semi-arid weather conditions had been favorable for forming a pedogenic

surficial uranium deposit in the northern part of the area.

These deposits were enriched with primary and secondary uranium mineralization as indicated

by microprobe analyses (2). In El Sela, primary uranium minerals U (IV) as pitchblende and coffinite

and secondary uranium minerals U (VI) as autunite and uranophane were found side by side in the

iron and calcareous nodules of sedimentary origin (3).

Uranium is used extensively in nuclear energy programs; hence several methods were required

for its separation and determination.

Solvent extraction is one of the most common and important methods for separation and

purification of many elements and always proved itself very helpful as a recovery method for many

components. Uranium (VI) was extracted using different organic extractants such as

41

trioctylphosphine oxide (TOPO) dissolved in cyclohexane (C6H12) from nitric acid medium, but

suffers from interferences of aluminium, fluoride and chloride (4).

Di (2-ethylhexyl) phosphoric acid (DEHPA) diluted in carbon tetrachloride (CCl4) was used for

extraction of U (VI) from 7 M HCl and determind by infrared spectroscopy (5). Whereas tri (2-

ethylhexyl) phosphate (TEHP) was used for extraction of U (VI) from salicylate media (6). Uranium

was extracted using tributylphosphine oxide (TBPO) diluted in toluene (C6H5CH3), from 4 M HCl

and determined by fluoride fusion method (7). Many solvents containing amine group were applied to

extract uranium as 8-hydroxylqunoline (8). Meanwhile, uranium was recovered using (R3PO) cyanex-

923 (9). Selective extraction and separation of uranium and thorium was carried out using N-

phenylbenzo-18-crown-6-hydroxamic acid (PBCHA) (10, 11). Extraction of uranium (VI) by di-2,4,4-

trimethyl-bentyl phosphoric acid (cyanex – 272) dissolved in toluene (12) was reported. Tributyl

phosphate (TBP) was used for extraction of U (VI) from nitric acid medium in presence of sodium

nitrate as salting agent (13).

Many types of reagents were applied for spectrophotometric determination of uranium (VI).

Arsenazo III (1, 8 dihydroxy naphthalene – 3,6 disulphonic acid – 2,7 bis (azo-2) -2- phenylarsonic

acid) is the most sensitive reagent and find wide use in the practice than 4-(2-pyridyl azo)

resorcinol (14). The use of Arsenazo III in strong acid medium overcomes difficulties associated with

the hydrolysis of some multivalent metals (e.g. Zr, Th and U) and it has been used as a sensitive and

selective reagent for a large number of metal ions (15-17).

In the present study, several attempts have been made to extract and determine uranium using

tributyl phosphate (TBP) [C4H9O)3PO] or 1, 4 Dioxane [C4H8O2] as extractants from nitric acid

medium. The success of TBP as extractant compared to other processes for purification of uranium is

due to its highly selectivity for uranium and provide excellent decontamination from most impurities.

42

While, 1,4 Dioxane is relatively stable against degradation under conditions normally used to purify

and extract the uranium due to the presence of two oxygen atoms, each with free electrons which

made it hydrophilic and highly soluble (18, 19).

The main purpose of the research is how to extract uranium from the fine solid waste (clay

minerals) as a second stage to the initial separation processes of granite in the first stage of project, El

Sela area, South Eastern Desert, Egypt.

EXPERIMENTAL

INSTRUMENTATIONS:

Double distilled water was used for preparing all standard solutions and reagents using

Aquatron 4L/h (England).

Generally, the samples and reagents used in this work were weighed using an electronic

analytical balance of Shimadzu AY 220 (Germany) giving a maximium sensitivity of 10-4g and an

accuracy of ±0.01%. The hydrogen ion concentration for the solution was measured using Inolab

digital pH-meter, level 1 (England) with an error of ±0.01 at ambient laboratory temperature. The

major oxides and uranium were determined by spectrophotometer Metertech Inc model Sp-8001,

(Germany) with the range 200-1100 nm with a wavelength accuracy of ±1nm. One match of 5 cm3

quartz cell with a pass length of 1cm was used for both samples and blank reagent. Sodium and

potassium were determined by a Sherwood flame photometer model 410 (England), using a series of

chemical standard solutions. X-ray diffraction unit Philips PW-3710 with generator PW-1830, Cu

target tube and Ni filter at 40 kV and 30 mA was used to detect the minerals present in the studied

samples.

Chemicals Used :

All chemicals and reagents used were of analytical grade (AR). Uranium stock solution was

prepared by dissolving 2.109 g of UO2 (NO3)2.6H2O with purity > 99.99 % in a definite volume 1000

ml double distilled water containing 2 ml of 6M HNO3 acid to get a fixed concentration of 1000 ppm.

The different concentrations of uranium were prepared by dilution. For preparing Arsenazo III, 0.25g

of Arsenazo III were added to 0.5 g of sodium acetate and diluted to 100 ml by distilled water (20, 21).

Different concentrations from 5 to 100 % of tributyl phosphate or 1,4 Dioxane were prepared in

appropriate diluents such as toluene (C6H5CH3), kerosene (C12H26) , benzene (C6H6 ), chloroform

(CHCl3 ), carbon tetrachloride (CC4 ) or cyclohexane (C6H12) .

Extraction process :

In the present work, the extraction behavior of uranium (VI) was carried out by applying the

batch technique. The organic solvents were prepared by dissolving different concentrations of tributyl

phosphate or 1, 4 Dioxane in different diluents to prepare the organic phase. This organic phase was

added to the uranium solution in a separating funnel and shaken well according to certain time

contact. After equilibration, a complete separation of the two phases was carried out and uranium was

measured spectrophotometrically in the aqueous phase by the Arsenazo III method (22).

43

Chemical preparation of El Sela uraniferous material :

The technological sample (highly weathered granite), collected from El Sela area, South

Eastern Desert was crushed to the grain size of about "–60 mesh" through two stages using jaw

crusher and roll mill. The leaching process was carried out using sulphuric acid under moderate

conditions of 75 g/l, solid/liquid ratio 1/1.5 and agitation for 6 hours. The heat of dilution generated

due to addition of concentrated sulphuric acid to the slurry where itself heating the mixture to about

45 ºC. During the solid/liquid separation (23) and washing steps, classification of the solids to slime (or

fine solids) and coarse size were done.

The fine solids contained in the slime fraction was well washed through several decantation

and re-slurry steps to reach the uranium concentration in the clear solution of < 5 ppm. The

remained fine solids after washing were filtered out then dried which represent the source of the fine

solids (slime waste).

RESULTS AND DISCUSSION

Factors affecting the extraction of uranium :

The extraction behavior of U (VI) was investigated using the two different extractants, TBP

and 1,4 Dioxane. Each of these extractants was diluted with different diluents. The different

parameters affecting the extraction process were studied.

1-Effect of diluents:

To choose which diluent is the best for uranium extraction, the extractant organo-phase TBP or

1,4 Dioxane was dissolved in different diluents namely; toluene, benzene, kerosene, chloroform,

carbon tetrachloride or cyclohexane. Each of these organic phase was shaked with an equal volume of

the aqueous phase containing the uranyl ions in 6M HNO3 medium at the ambient room temperature

(22±1ºC). From the experiments applied for checking the suitable diluent, it was found that TBP in

toluene as a diluent gives the highest extraction efficiency, more than (99 %) to extract uranium from

6M nitric acid medium if compared with kerosene (82.9 %), benzene (70.94 %), chloroform

(52.13%), CCl4 (22.22%) and cyclohexane (5.12%) for one contact. It mean that, the priority at which

the extraction increases is toluene > kerosene > benzene > chloroform > carbon tetrachloride >

cyclohexane (Fig.2).

0102030405060708090

100

Toluene Kerosene Benzene Chloroform CCl4 Cyclohexane

Diluent types

% E

TBP 1,4 Dioxane

Extraction conditions :

Uranium concentration: 10 ppm in 6M HNO3 , A/O:1/1, shaking time:5min.

30 % TBP or 30 % 1,4Dioxane used as extractants dissolved in different diluents.

Fig.2: Effect of different diluents on uranium extraction (%E).

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While the solvent 1, 4 Dioxane in CCl4 as a diluent gives high extraction efficiency more than

(99 %) to extract uranium in one contact if compared with chloroform (53.43%), kerosene and

toluene (19.08%), cyclohexane and benzene (17.55%). It mean that, the extraction increases at carbon

tetrachloride > chloroform > kerosene and toluene > benzene and cyclohexane (Fig.2).

2-Effect of extractant concentrations: Different extractant concentrations of TBP in toluene or 1,4 Dioxane in carbon tetrachloride

had been applied during the experiments run to study the extraction percent (%E) of uranium (Fig. 3).

By changing the concentrations of extractants TBP or 1,4 Dioxane from 5 to 100 %, it was found that

the %E values increase then decrease with increasing TBP concentrations and reach the maximum

extraction percent at 20 % of TBP in toluene. While, %E values decreased with increasing the

concentration of 1, 4 Dioxane and reached the maximum extraction percent at 5 % of 1, 4 Dioxane in

CCl4 (Fig.3).

0102030405060708090

100

0 10 20 30 40 50 60 70 80 90 100

Extractant conc., %

% E

TBP 1,4 Dioxane

Extraction conditions :

Uranium concentration: 10 ppm in 6M HNO3 , A/O:1/1, shaking time:5min..

TBP dissolved in toluene, 1,4 Dioxane dissolved in CCl4 .

Fig.3: Effect of extractant concentrations on uranium extraction (%E).

3-Effect of A/O phase ratio:

The effect of aqueous phase (A) to organic phase (O) ratio on extraction of uranium was

studied covering the range 1:1, 1:2, 1:4 and 2:1, the obtained results are shown in (Fig. 4). It is clear

from this figure that, the ratio 1:1 showed the best extraction percentage (99%) for TBP and ~ 98 %

for 1, 4 Dioxane. Accordingly, the ratio A/O of 1:1 is chosen in further experiments.

0102030405060708090

100

1:1 1:2 1:4 2:1

A/O phase ratio

% E

TBP 1,4 Dioxane

Extraction conditions:

Uranium concentration: 10 ppm in 6M HNO3 , shaking time:5min.

TBP dissolved in toluene, Extractant conc. 20 % TBP.

1,4 Dioxane dissolved in CCl4, Extractant conc.5%1,4 Dioxane.

Fig.4: Effect of A/O phase ratio on uranium extraction (%E).

45

4-Effect of shaking time.

The effect of shaking time was studied by fixing the other parameters affecting the extraction. The

time applied during the extraction was 1, 2, 3, 4, 5 till 10 minutes. It was found that the shaking time

of U (VI) extraction for TBP extractant changes from 68.05 % with 0.5 min. till 99.2 % through 4

minutes. Hence, the required shaking time to extract most U from its acid mineral solutions was taken

as 4 minutes. While, shaking time of uranium extraction for 1, 4 Dioxane changed from 68.03 % after

0.5 min. to 98.63 % through 5 minutes of shaking. Accordingly, 4 minutes was used for the best

shaking time of uranium from the organic solvent extractant of TBP. While, 5 min. was taken as the

suitable shaking time of uranium from 1,4 Dioxane as organic extractant (Fig.5).

0102030405060708090

100

0 1 2 3 4 5 6 7 8 9 10

Time (min.)

% E

TBP 1,4 Dioxane

Extraction conditions:

Uranium concentration : 10 ppm in 6M HNO3.

TBP dissolved in toluene, Extractant conc. 20 % TBP, A/O :1/1 .

1,4 Dioxane dissolved in CCl4, Extractant conc.5%1,4 Dioxane, A/O :1/1.

Fig.5: Effect of shaking time on uranium extraction (%E).

5-Effect of different stripping agents:

Different stripping agents were tried for back extraction of uranium from the organic phase of

TBP. Different stripping agents were used: acids (HNO3, H2SO4, HCl) and bases (NaOH, NH4OH). In

all cases, the volumetric phase ratio was 1:1 and 5 min. shaking time. The nitric acid molarity ranged

from 0.5 to 6M was used as strippant. It was found that 99.21 % U can be stripped by 5M of HNO3

acid. While, when 0.5M H2SO4 was used as stripper, only 65.6 % U was stripped. HCl acid do not

strip uranium from the TBP organic phase. On the other hand, only 43.12 % of uranium was stripped

by 6M NH4OH and 31.84 % uranium was stripped by 6M NaOH. Accordingly, 5M HNO3 was taken

as the suitable solution to strip 99.21 % of U from TBP as organic extractant (Fig.6). Therefore, 5M

HNO3 acid was used as the best stripping solution for uranium from the organic phase of TBP (Fig.6).

46

0102030405060708090

100

0 1 2 3 4 5 6

Stripping agent conc., (M)

% S

trip

pin

g

HNO3 H2SO4 NH4OH NaOH HCl

Extraction conditions

Uranium concentration: 10 ppm in 6M HNO3 .

TBP dissolved in toluene, Extractant conc. 20 % TBP, A/O :1/1,shaking time 4min.

Fig. 6: Effect of different stripping agents on the stripping process of U from TBP.

In case of 1, 4 Dioxane, different stripping agents were tried. It was found that 97.4 % U can

be stripped by 0.5M of HNO3 acid. While, 0.5M H2SO4 stripped only 70.06 % U. In case of HCl

acid, the uranium was not stripped from the organic phase of 1,4 Dioxane. Whereas, 63.69 % U was

stripped by 6M NH4OH and 6M NaOH stripped only 57.32 % U. Therefore, 0.5M HNO3 acid was

used as a best stripper for uranium process from the organic phase of 1, 4 Dioxane (Fig. 7).

0102030405060708090

100

0 1 2 3 4 5 6

Stripping agent conc., (M)

% S

trip

pin

g

HNO3 H2SO4 NH4OH NaOH HCl

Extraction conditions

Uranium concentration: 10 ppm in 6M HNO3 .

1,4 Dioxane dissolved in CCl4, Extractant conc.5%1,4 Dioxane, A/O :1/1, shaking time 5min.

Fig. 7: Effect of different stripping agents on the stripping process of U from 1,4 Dioxane.

Application for the extraction methods of solid waste, El Sela area:

The studied samples collected from El Sela area, South Eastern Desert (original, slime waste

and coarse waste) was leached as two parts; the first one was leached using 1M H2SO4. The second

part was leached using 6M HNO3 (24, 25), where the leaching of the studied samples using 6M HNO3

acid eliminate most of the interference elements that may affect on the determination of uranium.

Uranium extracted by TBP or 1, 4 Dioxane dissolved in different diluents and determined by

Arsenazo III method. The determination of uranium in the two cases 1M H2SO4 and 6M HNO3 (Table

1), showed high concentration of uranium in the nitrate medium than that of sulphate medium.

47

Table (1): Uranium extraction (ppm) using TBP or 1,4 Dioxane by leaching 1M H2SO4 and

6M HNO3 .

Sample

Uranium concentration, ppm

TBP/Toluene

Uranium concentration, ppm

1,4 Dioxane/ CCl4

1M

(H2SO4)

6M

(HNO3)

1M

(H2SO4)

6M

(HNO3)

Original* 408 563 405 561

Slime* 97 103 93 103

Coarse* 10 28 9 28

*Average means of 10 samples

Extraction conditions for TBP: Extraction conditions for 1,4 Dioxane:

TBP in Toluene, Extractant conc. 20 % TBP, 1,4 Dioxane inCCl4, Extractant conc. 5% 1,4 Dioxane,

Shaking time: 4min., A/O :1/1, Shaking time :5min., A/O :1/1,

5M HNO3 for stripping process. 0.5M HNO3 for stripping process.

The original, slime and coarse samples were completely attacked using mixture of acids (26)

(HF, HNO3, HClO4 and HCl) to determine the concentration of major oxides (Table 2).

Table (2): Chemical analysis of major oxides (wt %).

Sample

Oxides

Original* Coarse* Slime*

SiO2 61.31 54.21 50.41

Al2O3 13.56 11.83 12.18

TiO2 3.3 1.5 3.5

Fe2O3 T 6.79 9.58 6.39

CaO 2.8 1.4 4.2

MgO 1.0 1.0 2.0

Na2O 1.26 2.4 0.62

K2O 0.969 1.72 0.804

P2O5 1.98 1.98 1.43

L.O

.I 110º C 0.56 3.53 1.42

550º C 3.86 7.56 9.64

1000º C 2.61 3.13 7.3

Total % 99.99 99.84 99.89

*Average means of 10 samples

X- ray diffraction data of studied samples indicated the presence of montmorillonite, quartz,

kaolinite, albite, gypsum and muscovite (Table 3).

The character of certain clay such as montmorillonite and illite show a weak exchange affinity for

uranium (27). It is of great benefit to extract these values by using ion exchange resins which had a

stronger power and would lead to increasing the uranium recovery efficiency (28).

48

Table (3): X-ray diffraction data of the studied samples, El Sela area, South Eastern Desert,

Egypt.

Sample

Identified minerals

Original Montmorillonite, Quartz and Kaolinite Montmorillonite

(Na. K. Mg. Ca. Al2Si4O10(OH)2.nH2O, a group of

expending lattice clay minerals. They are generally derived from alteration of ferromagnesian minerals, calcic feldspars and volcanic glasses. They are the

chief constituents of bentonite and are common in soils sedimentary rocks and some mineral deposits.

Kaolinite

(Al2Si2O5(OH)4, main clay mineral in the kaolin

rocks. It is derived from the decomposition of

aluminous minerals such as feldspars.

Quartz

SiO2, important rock-forming mineral, next to

feldspar in bearing most common. The main

constituent of sands and of wide distribution in

igneous rocks as granites .

Slime Montmorillonite, Quartz and Kaolinite

Coarse Montmorillonite, Quartz and Kaolinite

The pH played a very important role in the separation of components. So, it was very necessary

to maintain the pH of the compound during the uranium determination because pH changes the

medium from high acidic to low acidic medium and leads to precipitation or dissolution of uranium.

Accordingly, the pH of slime sample (fine grain size) is equal "3" and uranium concentration was 104

ppm, when pH adjusted to "1" by a concentrated HNO3 acid, it was found that 64 ppm of uranium

was dissolved and 40 ppm of uranium was captured by clay montmorillonite (X.R.D. confirmed).

Therefore, the sample must be washed by acidified water to decrease the pH to 1 to overcome the

hydrolysis and precipitation of uranium. When the slime was leached by 1M HNO3, 99 ppm of

uranium concentration was dissolved from the slime sample. When increase the molarity of nitric acid

to 6M, all uranium concentration in the slime sample was completely dissolved in solution.

Proposed flow diagram:

Based on the previous data, we proposed a flow sheet diagram discuss the steps of leaching

uranium from slime sample collected from El Sela area, South Eastern Desert, Egypt (Fig.8).

Statistical calculations of the results.

Statistical analysis had been carried out for the studied technological sample to calculate the

standard deviation (S), standard error (S.E), error percentage (Error %) (29) and accuracy (30) (Δ)

(Tables 4 and 5).

49

Fig.(8): Flow sheet summarizes the steps of El Sela uraniferous material treatment (23).

Table (4): Statistical calculations for uranium extraction (ppm) using TBP / toluene by leaching

1M H2SO4 and 6M HNO3 acid.

Sample

No.

Leaching

Uranium

after

extraction

(ppm)

(X-)

Repeated

observations

(ppm)

d

d2

Δ

(accuracy)

Standard

deviation

Standard

error

Error

(%)

Original*

1M

H2S

O4

408 407.9 0.1 0.01 ±0.1 0.1 0.058 0.014

408.0 0.1 0.01

408.10 0.2 0.04

Slimes* 97 96.5 0.5 0.25 ±0.5 0.5 0.29 0.29

97 0.5 0.25

97.5 1 1

Coarse* 10 10.1 0.1 0.01 ±0.1 0.1 0.058 0.58

10 0.1 0.01

9.9 0.2 0.04

Original*

6M

HN

O3

563 562.5 0.5 0.25 ±0.5 0.5 0.29 0.051

563 0.5 0.25

563.5 1 1

Slimes* 103 102.9 0.1 0.01 ±0.1 0.1 0.058 0.056

103 0.1 0.01

103.1 0.2 0.04

Coarse* 28 28.5 0.5 0.25 ±0.5 0.5 0.29 1

28 0.5 0.25

27.5 1 1

*Average means of 10 samples

Sulphuric acid

El Sela uraniferous material (630 ppm U)

Solid crushing & Grinding (- 60 mesh)

Leaching, 75 g/l acid, 6.0 hrs agitation, 33% solid

Slurry classification during Washing

Slime to further wash (280 ppm U)

Clear solution for uranium

recovery (115 ppm U)

Decanted slime waste pH=3, (104 ppm U) Coarse size waste (29 ppm U)

Uranium capable to wash (64 ppm U) Capture by clay montmorillonite (40 ppm U)

Filtration then drying

Washing with acidified water, pH 1.0

50

Table (5): Statistical calculations for uranium extraction (ppm) using 1,4 Dioxane/CCl4 by

leaching 1M H2SO4 and 6M HNO3 acid.

Sample

No.

Leaching

Uranium

after

extraction

(ppm)

(X-)

Repeated

observations

(ppm)

d

d2

Δ

(accuracy)

Standard

deviation

Standard

error

Error

(%)

Original*

1M

H2S

O4

405 405.2 0.2 0.04 ±0.2 0.2 0.12 0.029

405 0.2 0.04

404.8 0.4 0.16

Slimes* 93 92.7 0.3 0.09 ±0.3 0.3 0.17 0.19

93 0.3 0.09

93.3 0.6 0.36

Coarse* 9 9.1 0.1 0.01 ±0.1 0.1 0.058 0.64

9 0.1 0.01

8.9 0.2 0.04

Original*

6M

HN

O3

561 561.2 0.2 0.04 ±0.2 0.2 0.12 0.02

561 0.2 0.04

560.8 0.4 0.16

Slimes* 103 103.1 0.1 0.01 ±0.1 0.1 0.058 0.56

103 0.1 0.01

102.9 0.2 0.04

Coarse* 28 28.4 0.4 0.16 ±0.4 0.4 0.23 0.83

28 0.4 0.16

27.6 0.8 0.64

*Average means of 10 samples

The Error (%) of the studied samples using TBP / toluene ranges from 0.014 to 1.0 % while

when using Dioxane / CCl4, it ranges from 0.020 to 0.83 %. It is clear that Error (%) less than 2, this

leads to high accuracy and precision for the obtained results.

Accuracy (Δ) for the studied samples ranges from ±0.1 to ±0.5 showed values of less than ±3

declaring high accuracy and precision for the obtained results.

CONCLUSION AND RECOMMENDATIONS

The present study showed that uranium (VI) is quantitavely extracted using TBP or 1,4

Dioxane under suitable extraction conditions. It was found that the best extraction / stripping

conditions for TBP are; 20 % TBP dissolved in toluene, A/O 1:1 and 4 min. shaking time and 5M

HNO3 acid as stripping. Under these conditions more than 99 % of uranium is recovered from the

matrix used. On the other hand, for the 1,4 Dioxane system the best conditions are; 5 % 1,4 Dioxane

dissolved in CCl4, A/O is 1:1, 5 min. shaking time and 0.5M HNO3 acid as stripping agent. For this

system, more than 97 % of uranium is recovered from the original uranium matrix.

The aforementioned extraction / stripping condition were successfully applied for extraction of

uranium from samples collected from El Sela area, South Eastern Desert, Egypt.

It is to be mentioned that slime sample should be washed first by acidified water (nitric acid)

till pH 1.0 to overcome any problems related to uranium hydrolysis and precipitation.

The results obtained indicates the feasibility of the use of TBP or 1,4 Dioxane system for

extraction followed by Arsenazo III with an error of determination less than 2% and accuracy less

than ±3.

51

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