Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
Characteristics of the Solid Residue from Leaching
Gattar (V) Uraniferous Material
Sayyah, E.M.a, El-Hussaini, O.M.*, Abd El-Ghany, M.S.,
Abuzaid , A.H.M., and Abd-El Gawad, H.H.M.
a
Chemistry Department, Faculty of Science, Beni- Seuf University , Egypt
Nuclear Materials Authority, P.O. Box 530, El-Maadi, Cairo, Egypt
* e-mail:omneya @link.net
ABSTRACT
Gattar (V) mineralization is located at 35 km west of Hurgharda City, Egypt. The
mineralization is mainly considered as uranium ore material and is also associated with
other economic minerals. The ground uraniferous material of Gattar (V) was subjected to
sulphuric acid leaching for uranium, solid liquid separation by filtration then washing.
Physical upgrading was performed upon the dry residue; this involved desliming, removal
of silicates and the other light minerals constituents using shaking table and finally the
separation of magnetite. The valuable and economic minerals zircon, rutile, ilmenite,
euxenite and samarskite were detected. The remained amount of high percent iron can be
leached by hydrochloric acid. More than 90% of iron was leached out under the
conditions of ground heavy fraction residue to -200 mesh size , 6.0 M hydrochloric acid
concentration at solid/acid ratio of 1/3 for 2.0 hours at 75o C.
1-INTRODUCTION
Gabal Qattar area is located in the north Eastern Desert of Egypt between Latitudes 26° 52´ and
27° 08´ N, and Longitudes 33° 13´ and 33° 25´ E(1). The geological importance of Gabal Gattar area
began with the discovery of molybdenite deposit in 1924. Later, the economic importance of Gabal
Gattar increased with the discovery of uranium mineralization in 1987. Gattar (V) mineralization
material is situated in the Hammamat sediment directly at contact with altered younger granite. The
mineralogical composition of the host rock was composed of 30% feldspar, 40% quartz, 10% clay
minerals, 7% iron oxides, 5% carbonate minerals and 8% other minerals (2).
Recovery of metal values from the ores includes three main processes namely the physical
upgrading, leaching and finally the metals recovery then purification with a great deal of chemical
treatments through extraction of the metals from the obtained solutions. This would be properly
applied upon some minerals such as zircon, ilmenite, rutile, euxenite and samarskite. The physical
treatments involve minerals beneficiation to liberate and separate heavy minerals from ores or
residues either by gravitational differences and the slight difference in magnetism ability (3). Leaching
involves the use of an aqueous solution containing a lixiviant which is brought into contact with a
material containing a valuable metal. Generally, hydrochloric acid can be used as selective reagent to
achieve a high dissolution efficiency of Fe 2 O3 (4). Leach liquor normally undergoes concentration of
its metals' contents in order to be easily recovered. Additionally, some undesirable metals may also be
taken into solution during the leach process and should therefore be properly separated.
In the present work, a ton sample of Gattar (V) uraniferous material assaying 0.112% U and
7.18% Fe was first subjected to uranium leaching at Inchass pilot unit using the suitable conditions
that verify high uranium leaching with minimum dissolution of gangues (represented as iron). These
conditions included ground ore to -60 mesh (- 0.25 mm) size with 100 g/l sulfuric acid at acid/ore
ratio of 1.0 for 6.0 hours at ambient temperature. The residue was then deslimed and the remaining
solids were subjected to tabling to obtain heavy minerals concentrates. To further concentrate the
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
heavy fraction, it was found necessary to leach most of its iron content using hydrochloric acid under
various conditions , thus increasing Ta, Nb, REE, Zr, U and Ti contents in the remaining solid.
2-EXPRIMENTAL
The experimental work was performed upon a solid residue remaining after sulphuric acid
leaching of the ground uraniferous material from Gattar (V) mineralization. The mineralization is
considered mainly as a uranium ore material which is also associated with other economic minerals.
Several experiments were carried out upon the residue to specify some of these economic minerals as
well as physical upgrading and chemical treatment procedures, thus the experimental work involved
the following topics after desliming:
a. Characterization of the deslimed residue grain size and chemical analysis for the major constituents
of metal oxides.
b. Characterization of the heavy fraction produced after residue beneficiation using the shaking table
step, involving microscopic separation and identification of some valuable minerals as well as
chemical analysis for the major constituents of metal oxides.
c. Further iron minimization through chemical treatment after magnetic separation.
2.1 Instruments :
- XRD Philips model PW 223/20 operated at 40 KV and 20 mA with Cu target, for identification of
the heavy fraction content.
- The pH measurements were carried out using Digital pH meter model DM-21, together with a
combined glass electrode obtained from HANA.
- Scanning Electron Microscope Philips (SEM–EDAX 32) was used for conducting semi-quantitative
analysis of the chemical composition of the residue samples and the prepared products that have
resulted from the practical work. Its analytical conditions were 15-52 kV accelerating voltages and
60-120 seconds counting time.
- Stereomic roscope model Meigi EMZ-TR attached with Olympus digital camera was used for
mineralogical identification.
- Flame atomic absorption spectrometry (FAAS) model Unicam 969 was used to estimate trace metal
ions in solution.
- Double beam UV-VIS recording spectrophotometer Shimadzu UV160A was used to determine
some elements concentrations in the leach liquors.
2.2 Residue preparation and upgrading:
The solid uranium-leached residue under study, after the filtration step and good washing, was left
to dry in open air before the physical upgrading steps.
- The dry solid residue was re-ground using a roll mill and was then subjected to slimes removal
through solids slurry with water in agitated tank, decantation for few minutes and then withdrawn
the suspended slimes through side valve in the tank. Solids re-pulping and decantation was done
several times until almost free from the slimes. The weight of the remain ing residue after dryness
was about 450 kg.
- A sample weighing about 10 kg was screened into different particle size fractions using a
mechanical shaker with a set of sieves 1, 0.75, 0.5, 0.25, 0.16 and 0.063 mm. These fractions were
weighed and analyzed for their chemical composition.
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
- The dry solids of 440 kg, free from slimes, were then subjected to separate its constituents of silicate
and other light minerals fraction using shaking table. The produced heavier minerals fraction is
considered the starting material for the experimental work of this study.
- Sample from this heavier minerals fraction (which weighed about 14 kg) was characterized for its
chemical composition and microscopically studied for its mineralogical composition as well as
separation and identification of some valuable minerals.
- About 100 g of the latter heavy concentrate was subjected to hand magnet for magnetite separation.
The produced magnetite represents 2.9% of the heavy concentrate.
- Samples from the heavy concentrate after magnetite separation were subjected to iron leaching
experiments.
2.3 Analytical Methods:
-Preparation of the residue under study for chemical analysis was carried out as follows:
Each 0.5 gram finely ground sample portion from the residue was heated with 12 ml of a mixture
HNO3 :HCl in the ratio of 1:3 in 100 ml teflon beaker till complete evaporation, then 25 ml HF was
added and left to dry. Finally 50 ml of 1:1 HCl treated the attacked residue and the solution was
filtered(5). The remaining solid was fused with 1.0 gram of NaOH and dissolved in 1:1 HCl solution.
Both the filtrate and the dissolved residue were combined and made up in a standard flask to 250
ml(6). The major and trace elements were analyzed.
-Spectrophotometric analysis:
Determination of yttrium was done by arsenazo III where the absorbance of its complex was
measured at the wavelength 650 nm(7). Titanium was determined by hydrogen peroxide and the
corresponding absorbance was measured at 410 nm, using water as reference (7). Xylenol orange was
used to determine zirconium at respective absorbance of 535 nm, while determination of both niobium
and tantalum was done by the pyrogallol(8) at 372 nm and 392 nm respectively.
-Other Analytical Methods:
Total iron was determined by titration against EDTA using sulfosalicylic acid (9).
Calcium and magnesium were also determined by titration against EDTA using Murexide and
Eriochrome-Black indicators.
Silica content was determined using molybdate reagent in the presence of tartaric acid (9)
Uranium was analyzed by titration against ammonium meta vanadate (10).
Trace elements analysis such as Al, Cu and Pb were performed by means of atomic absorption at the
wavelengths 279, 324.7 and 217 nm respectively.
2.4 Chemical Treatment for the Heav y Concentrate:
The heavy concentrate, after magnetite separation, was still found to contain relatively high
proportion of iron which may hinder the extraction steps for separating the required valuable
elements. Therefore, chemical treatment using hydrochloric acid was studied to reduce the iron
content to as a low degree as possible. Accordingly, a series of iron leaching experiments was carried
out upon 10 grams sample portion of the heavy concentrate ground to - 200 mesh size. The studied
factors involve: HCl concentration, solids to acid "S/A" ratio, leaching temperature and time (Table
1). The acid and sample mixture was agitated in 100 ml conical flask using a hot plate fitted with a
magnetic stirrer.
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
Table (1): The studied factors affecting iron leaching
Factor
Variable
Values
HCl concentration, M
2, 4, 6 and 9
o
Temperature, C
45,60, 75 and 90
Agitation time, h
1/2, 1, 2, and 3
Solid/Acid"S/A" ratio
1/1, 1/2, 1/3 and 1/4
Fixed Conditions
HCl Conc.,
Temp.,
Time,
o
M
C
h
varied
90
2
varied
9
varied
90
2
S/A
Ratio
1/3
Varied
After each experiment the leach slurry was filtered out using filter paper (Whatman 41), washed
thoroughly with hot distilled water and both filtrate and washings were made up to 250 ml. Iron
leaching efficiency was calculated according to the following equation:
Leached quantity
Iron leaching efficiency, % =
X 100
Original Fe Conc.
3-RESULTS &DISCUSSION
The uraniferous ore of Gabal Gattar (V) is located at 35 Km west of Hurghada city Eastern
Desert, Egypt. Gross sample of the uraniferous Gattar (V) containing 0.112% U and 7.18% Fe was
subjected to leaching maximum of the uranium under moderate conditions of acid concentration of
100 g H2 SO4 /Kg ore without oxidant addition, acid/ore ratio 1/1, -60 mesh size, and 6 h agitation time
at ambient temperature. The leaching efficiencies of uranium and iron were 96.8% and 4.1%,
respectively (2). The uranium-leached solid residue was found to contain some valuable minerals that
are representing the aim of this study. 3.1 Characterization of Gattar (V) Residue:
Results of Gattar (V) uranium-leached residue characterization after each upgrading step (first
through desliming and second through separation of the silicates and other light minerals using
shaking table ) would be discussed. Characterization of the final remain ing heavier minerals fraction
would be also specified.
3.2 Characterization of the Solid Residue after the Deslimiming Step:
The solid residue after desliming was fractionated into six portions of different particle sizes. The
particle size distribution as weight percent is illustrated in table (2). From this table it is clear that
more than 90% of the deslimed solids having a particle size of - 0.75 + 0.036 mm. However, more
than 50% was in the size range - 0.5 + 0.25 mm while the two sizes
- 0.75 + 0.5 mm and - 0.16 +
0.036 mm were of about 19% and 18% respectively.
The chemical composition of each fraction is given in Table (3). It is clear that the
concentration of the interested metal oxides; namely ZrO2 , TiO2 and RE2 O3 are distributed in all
fractions. Accordingly, the deslimed solid residues were subjected to a further upgrading step though
a shaking table without rejecting any size fraction.
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
Table (2): Particles size distribution of Gattar (V) residue after desliming
Sizes
Weight, (kg)
Weight, (%)
-1.0 mm + 0.75 mm
0.379
3.73
- 0.75 mm + 0.5 mm
1.923
18.91
- 0.5 mm + 0.25 mm
5.219
51.33
- 0.25 mm + 0.16 mm
0.393
3.87
- 0.16 mm + 0.036 mm
1.792
17.62
- 0.063 mm
0.462
4.54
? 10.168
? 100
Table (3): Chemical composition of different size fractions of Gattar (V) residue
Particle Size Fraction, (mm)
Composition, (%)
SiO2
Al2 O3
CaO
MgO
Fe 2 O3
K2O
Na2 O
TiO2
ClZrO2
RE2O3
L.O.I
Total
-1
0.75
0.5
- 0.25
- 0.16
- 0.036
??.0
25.4
1.42
0.42
4.0
4.0
2.12
0.2
1.0
0.3
0.4
0.42
99.68
56.0
29.0
1.42
0.42
3.3
4.6
1.90
0.2
1.30
0.23
0.43
0.32
99.1
62.3
19.3
1.40
0.40
4.5
7.0
2.40
0.26
1.30
0.31
0.48
0.3
99.4
60.0
23.0
1.40
0.41
3.6
6.4
2.42
0.15
1.22
0.30
0.46
0.25
99.6
60.0
23.1
1.35
0.40
3.2
7.5
2.30
0.15
1.20
0.18
0.40
0.22
100.0
??.0
21.3
0.84
0.23
3.7
5.8
2.64
0.22
1.20
0.12
0.36
0.27
99.6
3.3 Characterization of the Heavy Fraction Produced from the Shaking Table Step:
The heavy fraction produced from the shaking table was studied for its mineralogical and
chemical compositions as given below.
3.3.1 Mineralogical Characterization:
The mineralogical composition of Gattar (V) heavy fraction of the shaking table (Table 4) reveals the
presence of a high percent of the light minerals such as Feldspar and Quartz besides Fluorite. This is
most probably due to the presence of mixed grains of the present large particle sizes and so it would
be preferred to reduce the particle size to - 0.16 mm for better liberation before subjection to the
upgrading step by the shaking table.
The main valuable and economic minerals present in this heavy fraction include Zircon
(ZrSiO 4 ),
Rutile (TiO 2 ), Ilmenite (FeTiO 3 ), Euxenite ((Y, Er, Ce, La, U)(Nb,Ti,Ta)2 (O, OH)) and Samarskite
((Fe,Y,U)2 (Nb,Ti,Ta)2 O7 ). The photomicrographs of these picked heavy minerals under microscope
are shown in Figure (1).
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
Table (4): Approximate mineralogical composition of Gattar (V) heavy
fraction from the shaking table (microscopic counting)
Mineral
Content, (%)
Feldspar
??.0
Quartz
??.?
Hematite
30.6
Fluorite
15.4
Zircon
7.4
Ilmenite
0.3
Rutile
1.0
Samrsakite
4.5
Euxe nite
0.3
Total
100
Ilmenite
Euxenite & Samrsakite
Zircon
Rutile
Fig (1): Photomicrographs pictures of the valuable and economic minerals separated from
Gattar (V) heavy fraction of the shaking table
3.3.2 Chemical Characterization:
The chemical composition of Gattar (V) heavy fraction residue is given in Table (5). The
chemical analysis reflects the mineralogical composition. In this regard, the high percentage of SiO 2
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
and Al2 O3 (50.6 % and 18.0% respectively) assures the presence of high percentage of light minerals
such as Quartz and Feldspar also containing more than 13% Fe 2 O3 . On the other hand, the valuable
constituents of interest composed of 6.0% ZrO2 , 2.1% TiO2 , 1.1% Nb2 O? , 0.9% Ta 2 O? and 0.45%
Y2 O3 .
From the above results, it would be recommended to reduce the particle size of Gattar (V) residue to 0.16 mm before subjecting to the upgrading step using shaking table in a manner to obtain adequate
minerals liberation which also would be necessary in order to produce higher percentage of heavy
fraction containing the valuable and economic minerals.
Table (5): Chemical composition of Gattar (V) heavy fraction of the shaking table
Element Oxide
Content, (%)
SiO2
Al2 O3
Fe 2 O3
Na2 O
K2O
CaO
MgO
P2 O5
PbO 2
CuO
ZrO2
TiO2
Nb2 O3
Ta2 O5
Y2 O3
U3 O8
L.O.I
50.6
18.0
13.35
2.50
1.44
0.64
0.40
0.37
0.50
0.20
6.0
2.10
1.10
0.9
0.45
0.05
1.40
100.0
3.3.2.1 Treatment of the Heavy Concentrate:
Gattar (V) heavy concentrate residue produced from the shaking table was found to contain a high
percent of iron oxides (more than 13%). Therefore it would be required to reduce the iron content to
be as low as possible in order not to interfere or hinder the extraction steps for the recovery of
required valuable elements. This could be conducted through physical separation for the magnetite
then chemical treatment through iron dissolution using hydrochloric acid.
3.3.2.1.1 Magnetite Separation:
The heavy concentrate was subjected to magnetite separation using a hand magnet. The separated
magnetite represented about 3.0 wt% of the heavy fraction. However, magnetite can be considered as
one of the valuable and economic minerals.
3.3.2.1.2 Chemical Treatment:
The heavy fraction after magnetite separation still containing a high percent of Fe 2 O3 (more than
9.0%), thus it was subjected to chemical treatment using hydrochloric acid. Results of the studied
factors involving HCl concentration, solids to acid "S/A" ratio, leaching temperature and time would
be herein discussed.
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3.3.2.1.2.a Effect of Hydrochloric Acid Concentration:
The effect of hydrochloric acid concentration on iron leaching was studied in the range of 2 - 9 M
HCl under the conditions of - 200 mesh size, 90o C, 2.0 hours and S/A ratio of 1/3. The obtained
results are tabulated in Table (6) and represented by Figure (2).
The results revealed that more than 72 % of iron was leached at the acid concentration 2.0 M and
was reached to more than 90% and 97% when the acid concentration increased to 4.0 and 6.0 M
respectively. Iron leaching efficiency was slightly increased to be 98.9% when the acid concentration
increased to 9.0 M, however, under these conditions both titanium and yttrium (represented the rare
earths) were substantially dissolved by 9.8% and 29.7% respectively. On the other hand, the mass loss
of Gattar (V) heavy fraction residue after leaching was 15%.
Table (6): Effect of hydrochloric acid concentration on iron leaching from Gattar (V) heavy
fraction (- 200 mesh, 90 o C, 2.0 h and S/A ratio of 1/3)
HCl Concentration, (M)
Iron Leaching Efficiency, (%)
2
72.2
4
90.4
6
97.7
Iron Leaching Efficiency, (%)
100
95
90
85
80
75
70
1
2
3
4
5
6
7
8
9
10
Concentration of HCl, (M)
9
98.9
Fig (2): Effect of hydrochloric acid concentration on iron
leaching efficiency from Gattar (V) heavy fraction
3.3.2.1.2.b Effect of Temperature:
The effect of temperature upon iron leaching was studied in the range of 45o C to 90o C,
while the other leaching conditions were fixed at -200 mesh size, 9.0 M acid concentration in
solid/acid ratio 1/3 for 2.0 hours. The obtained results are shown in
Table (7) and Figure (3). The
results indicated that half of the iron amount was leached at 45o C while at 75o C it was 95%.
Table (7): Effect of temperature on iron leaching efficiency of Gattar(V)heavy fraction (- 200
mesh, 9.0 M HCl, 2.0 hours and S/A ratio of 1/3)
Temperature , (o C)
Iron Leaching Efficiency, (%)
45
50.2
60
78.?
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
75
95.0
90
98.9
100
Leaching Efficiency, (%)
90
80
70
60
50
40
40
50
60
70
80
90
o
Temperature , ( C )
100
Fig. (3): Effect of temperature on iron leaching
efficiency of Gattar (V) heavy fraction
3.3.2.1.2.c Effect of Time:
The effect of varying time in periods ranging from ½ to 3.0 hours on iron leaching was
studied at fixed conditions of -200 mesh size, 9.0 M acid concentration, solid/acid ratio 1/3 and at 90o
C. The obtained results are shown in Table (8) and Figure (4). These results indicated that 77% of iron
was leached after ½ hour and most of its content was dissolved from the residue within 2.0 hours.
Table (8): Effect of time on iron leaching efficiency from Gattar(V)heavy fraction (- 200 mesh,
9.0 M HCl, 90o C and S/A ratio of 1/3)
Time, (hour)
½
1.0
2.0
3.0
Iron Leaching Efficiency, (%)
` ` .0
´ 2.0
98.8
98.9
Iron Leaching Efficiency, (%)
100
95
90
85
80
75
0.0
0.5
1.0
1.5
2.0
Time, (hour)
2.5
3.0
3.5
Fig. (4): Effect of time on iron leaching efficiency
of Gattar (V)heavy fraction
3.3.2.1.2.d Effect of Solid/Acid Ratio:
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
The effect of solid to acid solution (S/A) ratio ranging from 1/1 to 1/5 upon iron leaching was
studied under the conditions of -200 mesh size, 9.0 M acid concentration at temperature 90o C for 2.0
hours. The results shown in Table (9) and Figure (5) indicated that 76.4% was leached at the ratio of
1/1 and above this ratio the leaching efficiency was found to exceed ^0%.
Table (9): Effect of S/A ratio on iron leaching efficiency from Gattar (V)heavy fraction (- 200
mesh, 9.0 M HCl, 90o C and 2.0 hours ).
S/L Ratio
Iron Leaching Efficiency, (%)
1/1
76.4
½
^?.3
1/3
98.8
¼
99.1
Iron Leaching Efficiency, (%)
100
95
90
85
80
75
1/1
1/2
1/3
1/4
S/L Ratio
Fig. (5): Effect of S/A ratio on iron leaching efficiency
from Gattar (V) heavy fraction
According to the results of the studied iron leaching factors, it is recommended to conduct
this step upon Gattar (V) heavy fraction of the shaking table ground to -200 mesh under the conditions
of 6.0 M hydrochloric acid concentration in solid/acid ratio of 1/3 for 2.0 hours at 75o C. At these
conditions, more than 90% of iron was leached out.
4-CONCLUSIONS
The uraniferous material of Gattar (V) is mainly considered as a uranium ore material that is
also associated with other economic minerals. Gattar (V) mineralization is located at 35 km west of
Hurgharda City, Egypt. Sulphuric acid leaching of the ground uraniferous material separated the non
leachable economic elements in the residue. This study concerned with the solid residue that resulted
after separating the leach liquor by filtration, and which was properly subjected to washing and drying
in the open air.
The ground residue was subjected to physic al upgrading steps. Desliming was first done by
slurring the solids. The particle size distribution indicated that more than 50% was in the size range 0.5 + 0.25 mm while the two sizes - 0.75 + 0.5 mm and - 0.16 + 0.036 mm amounted to about 19%
each. The metal oxides ZrO2 , TiO2 and RE2 O3 were found distributed in all the size fractions.
Upgrading through shaking table was done to separate the silicate and the other constituents of light
minerals.
The chemical composition of the produced final heavy minerals fraction revealed the
presence of 6.0% ZrO2 , 2.1% TiO2 , 1.1% Nb2 O? , 0.9% Ta 2 O? and 0.45% Y2 O3 . These metal oxides
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Arab Journal of Nuclear Sciences and Applications, 45(2)130-141(2012)
correspond to the minerals: zircon, rutile, ilmenite, euxenite and samarskite and which are mixed with
the light minerals feldspar and quartz besides fluorite.
The heavy fraction containing about 13% Fe 2 O3 , however, about 3.0 wt% was magnetically
separated as magnetite before iron leaching studies. Iron was reduced to be as low as possible through
leaching by hydrochloric acid. Under the conditions of ground the heavy fraction residue to -200
mesh, 6.0 M hydrochloric acid at solid/acid ratio of 1/3 for 2.0 hours at 75o C, the leach solution
containing about 123.5 g/L Fe 2 O3 , 2.0 g/L TiO2 and 1.3 g/L Y2 O3 .
. The upgrading process of Gattar (V) uranium-leached solid residue under study is
summarized in Figure (6).
Gattar (V Dry Solids’ Residue
(-0.16 mm)
Desliming
Slimes
Shaking Tables
Heavy Minerals
Silicates and
Light Minerals
Magnetic Separation
HCl
Magnetite
Iron Leaching
Economic Heavy Minerals
(for further treatment)
Fig (6): Flow sheet of the stages involved in upgrading
Gattar (V) uranium leached solid residue.
5-ACKNOWLEDGMENTS
The authors express their thanks to all the colleagues in the Production and Research Divisions,
Nuclear Materials Authority, for their assistance to accomplish this work and the friendly atmosphere.
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