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Successive uranium and thorium adsorption from Egyptian
monazite by solvent impregnated foam
A. E. M. Hussein
Received: 22 December 2010 / Published online: 1 May 2011
ÓAkade
´miai Kiado
´, Budapest, Hungary 2011
Abstract The present work deals with uranium and tho-
rium recovery from the Egyptian monazite sulfate leach
liquor using the extraction chromatography technique
(solvent impregnated material), where tributylamine (TBA)
and di-n-octylamine (DOA) solvents were impregnated
onto foam uranium and thorium separate recovery. The
calculated theoretical capacities of the latter solvents were
about 1.4 gU/g foam and 1.6 gTh/g foam, respectively.
The attained uranium and thorium adsorption efficiencies
(using ion-exchange columnar technique) were about 75
and 70% of its theoretical capacities, respectively. Using
1 M NaCl–0.1 M H
2
SO
4
and 2 M H
2
SO
4
as eluent solu-
tions for uranium and thorium from the loaded solvents
impregnated foam gave 95.8 and 98.7% elution efficien-
cies, respectively.
Keywords Uranium Thorium Adsorption Elution
Monazite Polyurethane foam
Introduction
Monazite is the most important commercial source of tho-
rium and lanthanides occurs in nature as a common acces-
sory mineral in pegmatites, granites and gneisses. Uranium
is extracted from monazite as a valuable by-product. Mon-
azite occurs as a detrital mineral in placer deposits, princi-
pally in river and beach sands. Large commercial detrital
deposits are found in Australia, USA, India, Brazil and
Egypt. In Egypt monazite occurs as large reserves in black
sand (1.06%) that are found along the beaches of northern
parts of the Nile Delta from Rosetta to Damietta [1,2].
Several methods are used for industrial processing of
monazite in order to extract its content of thorium, uranium
and lanthanides contents. These involved acid (sulfuric
acid) leaching, alkaline leaching (with sodium hydroxide
solutions), sintering with sodium carbonate and with
sodium carbonate flux, sintering with sodium hydroxide,
chlorination with a mixture of coal, and lime ?CaF
2
flux
in an electric arc furnace [2–11].
Commercially, both the alkaline (sodium hydroxide)
and the acid (sulfuric acid) leaching are the commonly used
methods. The hydroxide cake obtained from alkaline pro-
cessing of monazite is leached with HCl (at 80 °C), and
then diluted with water. In order to separate thorium and
uranium from lanthanides, selective neutralization of
solutions with ammonia (at pH =5.8–6) is carried which
leads to complete precipitation of thorium and uranium as a
concentrate (containing about 3% lanthanides). On the
other hand uranium, thorium and rare earth elements could
be recovered from the sulfate leach liquor obtained from
the sulfuric acid dissolution of monazite by the following
methods, namely; direct precipitation, ion exchange and
solvent extraction [3,11–14].
The present work deals with recovery of uranium and
thorium from the Egyptian monazite sulfate leach liquor
using the extraction chromatography technique. The latter
was found to be more advantageous than either the liquid–
liquid extraction or the solid–liquid separation techniques.
The extraction chromatography (solvent impregnated
material) characterized by its high binding capacity,
selectivity and enhanced mobility of the extractant on the
solid surface.
It well known that the tertiary amines (in general) are
excellent extractants for uranium but could not extract
A. E. M. Hussein (&)
Nuclear Materials Authority, Box 530, Maadi-Kattameya,
Cairo, Egypt
e-mail: ah_mady@yahoo.com
123
J Radioanal Nucl Chem (2011) 289:321–329
DOI 10.1007/s10967-011-1107-x
thorium. On the other hand many primary and secondary
amines are stronger extractants for thorium than for ura-
nium [15]. Accordingly, we decided to impregnate tribu-
tylamine (TBA) (tertiary amine) onto the polyurethane
foam [15–29] to recover uranium and impregnate di-n-
octylamine (DOA) (secondary amine) onto other foam
sample to recover thorium from the uranium-free liquor.
Primarily, the relevant factors affecting solvents
impregnation onto foam were studied. These including
solvent concentration, temperature, impregnation time,
mass/volume ratio and diluents type. Secondly, the relevant
factors affecting uranium and thorium sorption onto the
foam were thoroughly studied. These including initial
uranium and thorium concentrations, contact time, pH and
temperature. From the obtained results, the theoretical
capacity of the prepared solvent impregnated foam sample
was calculated.
Experimental
Materials and analytical procedures
The representative sample of monazite sand used in this
study was obtained from NMA Monazite Processing Unit
(Inshass, Cairo, Egypt). In this unit, several ore-dressing
techniques are used to obtain a high grade concentrate of
about 96% monazite purity [30].
Stock solution of Egyptian monazite sulfate leach liquor
having the chemical composition of 32.20 g/L REE,
2.358 g/L Th, 0.371 g/L U, 200.12 g/L SO
42-
, 8.94 g/L
PO
43-
, 1.26 g/L SiO
2
, 0.28 g/L CaO, 0.23 g/L Fe
2
O
3
and
0.12 g/L TiO
2
; was properly prepared by applying the
following optimum breakdown conditions, i.e., 80% sul-
furic acid concentration, 1:3 solid/liquid ratio for 2.5 h
reaction time at 180 °C[11].
A uranium stock standard solution assaying 1000 mg/L
was prepared by dissolving 1.782 g of uranyl acetate
[UO
2
(CH
3
COO)
2
2H
2
O] of BDH Chemicals Ltd. Poole,
England.
A thorium stock standard solution assaying 1000 mg/L
was prepared by diluting thorium chloride solution (56%
ThCl
4
) of Adwic Co. Cairo, Egypt.
Different concentrations of TBA ([CH
3
(CH
2
)
3
]
3
N) of
Riedel–deHaen of and assaying 95% were used for ura-
nium separation.
Different concentrations of DOA (C
16
H
35
N) of Riedel–
deHaen and assaying 96% were used for thorium
separation.
Uranium and thorium were all the time analyzed in the
different working aqueous phases by the ArsenazoIII and
Thoron methods, respectively [31]. Absorbance of the
formed uranium-ArsenazoIII and thorium-Thoron
complexes were measured at 650 and 540 nm, respectively
against proper standard solutions. For this purpose, a
Lambada3 UV/VIS spectrophotometer (Perkin–Elmer,
USA) was used.
The working polyurethane foam sample was obtained
from Foam Industries Co. Cairo, Egypt. (Polyurethane
foam plugs, 4.5 cm in diameter and 2.2 cm long (average
weight =0.500 ±0.002 g), were cut from a foams sheet.
Each foam plug was squeezed in 2 M HCl for 1 h, washed
with distilled water until free from HCl, and squeezed
again, and air-dried overnight before using.
Experimental
Preparation of the impregnated foam
In order to study the factors affecting the impregnation
process, several series of impregnation experiments have
been performed by shaking 0.25 g of the dry clean foam
samples with the properly prepared impregnation solutions
by magnetic stirrers. The amount of solvent impregnated
on the foam samples were calculated by the difference
between the foam weight before and after the process. The
studied factors included solvent concentration, impregna-
tion temperature, impregnation time, mass/volume ratio
and diluents type.
After the end of the impregnation experiments, the foam
is dried in the oven for 1 h at a temperature of 60 °Cto
evaporate the diluent (leaving the diffused solvent into the
foam pores).
Equilibrium studies
Several series of adsorption experiments were performed
using the stock of uranium and thorium synthetic solutions
for studying the following relevant adsorption factors:
contact time, the initial uranium and thorium concentra-
tions, the pH and the adsorption temperature. These batch
sorption experiments were performed by shaking 0.05 g of
impregnated foam with 20 mL of the uranium and thorium
synthetic solution (200 ppm each) using magnetic stirrer.
The adsorbed amounts of uranium and thorium were cal-
culated by the difference between the equilibrium and
initial concentrations. Langmuir and Freundlich isotherms
were obtained depending upon the attained data of the
above mentioned adsorption experiments.
Columnar procedure
The uranium and thorium adsorption and elution studies
were performed using two separate glass columns each of
1 cm diameter, packed with 1 g of the impregnated foam.
322 A. E. M. Hussein
123
In each column, two glass wool plugs were inserted at the
bottom and top of the foam bed.
The foam bed in the first column was then loaded with
uranium by passing the monazite sulfate liquor through it
using 2 mL/min initial rate. Periodical sample portions
were taken each 20 mL throughput volume (until satura-
tion of the foam bed was reached).
The uranium-free monazite sulfate liquor then passed
through the foam bed of the second column for the
adsorption of its thorium content using the initial flow rate
of 2 mL/min. Periodical sample portions were taken each
20 mL throughput volume (until saturation of the foam bed
was reached).
In order to elute the loaded uranium and thorium from
the foam beds in the two columns. The latters were firstly
washed with a sulfuric acid solution having the same
molarity of the working liquor. For eluting uranium from
the first column, a solution of 1 M NaCl acidified with
0.1 M (or 0.5 M) H
2
SO
4
was passed onto the top of its
loaded foam bed. For thorium elution a solution of 2 M
HNO
3
was passed onto the top of the loaded foam bed of
the second column. The applied flow rate was fixed at
1 mL/min periodical sample portions were collected each
10 mL throughput volumes for uranium and thorium
analysis.
Results and discussion
Results of the relevant factors of foam impregnation
Effect of the concentration of impregnated solvent
In order to study the effect of solvent (TBA and DOA)
concentration upon the impregnated amount on the work-
ing foam sample, two series of impregnation experiments
were performed using different concentrations ranging
from 0.05 up to 1 M. The experiments were carried out
under fixed conditions of 25 °C impregnation temperature
for 1 h shaking time, 60/1 volume/mass ratio and using
benzene as a diluent solvent. The obtained data are plotted
in Fig. 1. From this figure, it is clearly obvious that the
amount of solvent loaded solvents increased proportionally
with increasing its concentration.
Effect of impregnation time
In order to study the effect of impregnation time upon the
impregnated amounts of TBA and DOA onto the working
foam sample, two series of impregnation experiments
were performed using impregnation time ranged from 1 up
to 15 h. The experiments were performed under fixed
conditions of 25 °C impregnation temperature, 0.5 M
solvent concentrations, 60/1 volume/mass ratio and using
benzene as a diluent. The obtained results are plotted in
Fig. 2from which it is clearly evident that the amounts of
loaded solvents increased with increasing the impregna-
tion time till the 5 h impregnation time. Beyond the latter,
no significant increase in the loaded solvent amounts were
observed.
Effect of volume/mass ratio
In order to study the effect of volume/mass ratio upon the
amounts of TBA and DOA impregnated onto the working
foam sample, two series of impregnation experiments were
performed using a range of solution volume/foam mass
ratios started from 20/1 up to 90/1. These experiments were
performed under fixed conditions of 25 °C impregnation
temperature, 5 h impregnation time, 0.5 M solvent con-
centrations and using benzene as a. The obtained results are
plotted in Fig. 3. From this figure, it is clearly obvious that
the amount of loaded solvent onto the foam increased with
increasing the impregnation solution volume in case of
TBA, while in case of DOA no significant increase in the
amount of loaded solvent onto the foam was observed
beyond the 60/1 volume/mass ratio.
0.00
0.02
0.04
0.06
0.08
0.10
Solvent concentration, M
Loaded TBA amine, m
mol/g foam
0
2
4
6
8
10
Loaded DOA amine, m
mol/g foam
TBA
DOA
00.51
Fig. 1 Effect of solvents (TBA and DOA) concentration upon loaded
solvent onto polyurethane foam
0.00
0.01
0.01
0.02
0.02
0.03
0.03
0.04
Time, h
Loaded TBA amine, m
mol/g foam
0
2
4
6
8
10
12
Loaded DOA amine, m
mol/g foam
TBA
DOA
03691215
Fig. 2 Effect of impregnation time upon loaded solvent (TBA and
DOA) onto polyurethane foam
Successive uranium and thorium adsorption from Egyptian monazite 323
123
Effect of impregnation temperature
In order to study the effect of impregnation temperature
upon the amounts of impregnated solvents (TBA and
DOA) onto the working foam, two series of impregnation
experiments were performed under temperature ranged
from 25 up to 70 °C. The experiments were performed
under fixed conditions of 0.5 M solvent concentrations, 5 h
impregnation time, 75/1 and 60/1 volume/mass ratios for
TBA and DOA, respectively and using benzene as a dilu-
ent. The obtained data are plotted in Fig. 4. It is clearly
obvious from the latter mentioned figure that, in case of
TBA the amounts of the loaded solvent onto the foam
increased fastly with increasing temperature till 40 °C,
after which a sharp decrease in the loaded solvent amounts
was observed. While in case of DOA, no significant
increase of the loaded solvent amounts in association with
increasing temperature was observed.
Effect of diluent type
The used impregnation solvents were diluted before its
impregnation onto the foam for reducing its viscosity. Such
a process leads to solvent extension on the surface of the
dry foam for filling its interior pores. The following dilu-
ents were tested for dilution of the studied solvents (TBA
and DOA), namely; benzene, toluene, acetone, methanol,
and cyclo-hexane. The impregnation experiments were
carried out under fixed conditions of 0.5 M solvent con-
centrations, 75/1 and 60/1, 5 h impregnation time and the
impregnation temperatures were fixed at 40 °C and 25 °C
for TBA and DOA, respectively. Table 1summarizes the
obtained results where from which it is clearly obvious that
benzene is the most suitable diluent for both solvents.
Choice of optimum conditions of foam impregnation
As it was mentioned later, the impregnation process of
TBA and DOA on polyurethane foam is mainly due to a
combination of pore filling as well as surface adsorption
i.e. the extractant fill almost all porous system of poly-
urethane foam as shown in Fig. 5. Owing to the obtained
results of the study of the relevant factors affecting foam
impregnation, we could safely choice the following opti-
mum conditions; 0.5 M solvent concentration, 5 h
impregnation time, 75/1 and 60/1 volume/mass ratio for
TBA and DOA, respectively and 40 and 25 °Cas
impregnation temperature for TBA and DOA, respectively
and using benzene as a diluent material.
Results of equilibrium studies
In order to study the different factors affecting uranium and
thorium adsorption onto the prepared foam impregnated
with solvents, suitable amount (1.5 g) of foam was treated
with the two solvents under the above mentioned optimum
impregnation conditions. The studied relevant factors are,
effect of contact time, effect of initial uranium and thorium
concentrations, effect of pH and effect of adsorption
temperature.
Effect of contact time
In order to study the effect of contact time upon uranium
and thorium adsorption efficiencies upon the prepared
solvent impregnated foam, two series of adsorption
experiments were performed by contacting a fixed weight
0.00
0.05
0.10
0.15
0.20
0.25
0 20406080100
v/m ratio
Loaded TBA amine, m
mol/g foam
0
2
4
6
8
10
12
Loaded DOA amine, m
mol/g foam
TBA
DOA
Fig. 3 Effect of impregnation solution (TBA and DOA) volume/
foam mass ratio upon loaded solvent onto polyurethane foam
0.00
0.05
0.10
0.15
0.20
0.25
0.30
20 30 40 50 60 70
Temp., °C
Loaded TBA amine, m
mol/g foam
0
2
4
6
8
10
Loaded DOA amine, m
mol/g foam
TBA
DOA
Fig. 4 Effect of impregnation temperature upon loaded solvent (TBA
and DOA) onto polyurethane foam
Table 1 Effect of diluent type upon the loaded amine amounts onto
the dry foam
Diluent type Loaded TBA,
mmol/g foam
Loaded DOA,
mmol/g foam
Benzene 0.28 9.12
Toluene 0.02 5.80
Acetone 0.01 6.16
Methanol 0.07 7.08
Cyclo-hexane 0.05 7.80
324 A. E. M. Hussein
123
(0.05 g) of the impregnated foam with fixed volumes of
uranium and thorium solutions having a fixed initial con-
centration (200 mg/L). The studied contact time ranged
from 0.5 up to 5 h. The experiments were carried out at
room temperature (&25 °C) and pH 0. From the obtained
results, the uranium and thorium adsorption efficiencies
about 61% and 45%, respectively were observed at the first
experiment (0.5 h) by increasing the contact time up to 1 h,
the adsorption efficiencies increases up to 71% and 60%
for uranium and thorium, respectively. On the other hand,
extending contact time above one hr led to gives a non
pronounced increasing of adsorption efficiencies of either
uranium or thorium.
Effect of initial uranium and thorium concentrations
For studying the effect uranium and thorium initial con-
centrations upon its adsorption efficiencies onto the pre-
pared solvent impregnated foam, two series of adsorption
experiments were performed by contacting a fixed weight
(0.05 g) of the impregnated foam with fixed volumes of
uranium and thorium solutions of different concentrations
(ranging from 200 up to 10000 mg/L for each). The
experiments were performed under fixed conditions of 1 h
contact time at room temperature (&25 °C) and pH 0. The
obtained data are plotted in Fig. 6, from which it is clearly
obvious that uranium and thorium adsorption efficiencies
decrease with increasing there initial concentrations.
Adsorption isotherms
Several common adsorption isotherm models such as
Langmuir and Freundlich and others were considered to fit
the obtained isotherm data under the equilibrium adsorp-
tion of the activated carbon (sorbent).
Langmuir isotherm According to the Langmuir model,
adsorption occurs uniformly on the active sites of the
sorbent, and once a sorbate occupies a site, no further
sorption can take place at this site. Thus, the Langmuir
model is given by the following Eq. 1[32,33].
Ce=qe¼1=bQ0þCe=Q0ð1Þ
where Q
0
and b, the Langmuir constants, are the saturated
monolayer sorption capacity and the sorption equilibrium
constant, respectively. A plot of C
e
/q
e
versus C
e
would
result in a straight line with a slope of (1/bQ
0
) and intercept
of 1/Q
0
as seen in Figs. 7and 8for TOA and DOA
impregnated polyurethane foam, respectively. The
Langmuir parameters given in Tables 2and 3for TOA
and DOA impregnated polyurethane foam, respectively can
be used to predict the affinity between the sorbate and
sorbent using the dimensionless separation factor R
L
equation number (2)[34,35].
RL¼1=1þbC0
ðÞ ð2Þ
R
L
value indicate the type of isotherm to be irreversible
(R
L
=0), favourable (0 \R
L
\1), linear (R
L
=1) and
unfavourable (R
L
[1) [36,37]. The values of R
L
for
adsorption of uranium and thorium are shown in Fig. 9.
They indicate that adsorption of uranium and thorium are
more favorable at higher initial concentrations than at
Fig. 5 SEM photographs of the polyurethane foam surface before impregnation (a), after impregnation with TBA (b) and after impregnation
with DOA (c)
0
20
40
60
80
100
0 2000 4000 6000 8000 10000 12000
Initial Uranium and Thorium concentrations, mg/l
Adsorption efficiency, %
U
Th
Fig. 6 Effect of uranium and thorium concentrations on adsorption
efficiency
Successive uranium and thorium adsorption from Egyptian monazite 325
123
lower concentrations. From the obtained data the adsorp-
tion on the prepared TBA and DOA impregnated poly-
urethane foam were fitted well with Langmuir isotherm and
not fitted with Freundlich isotherm.
Freundlich isotherm The Freundlich model stipulates that
the ratio of solute adsorbed to the solute concentration is a
function of the solution. The empirical model was shown to
be consistent with exponential distribution of active cen-
ters, characteristic of heterogeneous surfaces. The amount
of solute adsorbed at equilibrium, q
e
, is related to the
concentration of solute in the solution, C
e
, following Eq. 3
[32,33].
qe¼KFC1=n
eð3Þ
This expression can be linearized to give the Eq. 4
log qe¼log KFþ1=nlog Ceð4Þ
where K
F
and nare the Freundlich constants, which rep-
resent sorption capacity and sorption intensity, respec-
tively. A plot of log q
e
versus log C
e
would result in a
straight line with a slope of (1/n) and intercept of log K
F
as
seen in Figs. 10 and 11 for TOA and DOA impregnated
polyurethane foam, respectively. Freundlich constants are
given in Tables 2and 3for TOA and DOA impregnated
polyurethane foam, respectively.
Effect of pH
In order to study the effect of pH value of sulfuric acid
upon uranium and thorium adsorption efficiencies onto the
solvent impregnated foam, two series of experiments were
performed using different pH values ranged from 0 up to
8.5. The experiments were performed under fixed
y = 0.0007x + 3.4769
R2 = 0.9816
0
1
2
3
4
5
6
7
8
9
0 2000 4000 6000 8000
Ce, mg/l
Ce/qe
Fig. 7 Langmuir adsorption isotherm of sorption uranium onto TBA
impregnated foam
y = 0.0006x + 3.143
R2 = 0.928
0
1
2
3
4
5
6
7
8
0 2000 4000 6000 8000
Ce, mg/l
Ce/qe
Fig. 8 Langmuir adsorption isotherm of sorption thorium onto DOA
impregnated foam
Table 2 Langmuir and Freundlich parameters for uranium adsorption onto TBA impregnated foam
Metal Adsorbent Langmuir model parameters Freundlich model parameters
Q°(mg/g) b(L/mg) R
2
1/nK
f
(mg/g) R
2
Uranium TBA impregnated foam 1428.5 0.2 910
-3
0.981 0.6038 7.5 0.965
Table 3 Langmuir and Freundlich parameters for thorium adsorption onto DOA impregnated foam
Metal Adsorbent Langmuir model parameters Freundlich model parameters
Q°(mg/g) b(L/mg) R
2
1/nK
f
(mg/g) R
2
Thorium DOA impregnated foam 1666.6 0.19 910
-3
0.928 0.554 13.2 0.845
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0 2000 4000 6000 8000 10000 12000
Co, mg/L
RL
RL U
RL Th
Fig. 9 Separation factor R
L
of U and Th on the TBA and DOA
impregnated Polyurethane foam, respectively
326 A. E. M. Hussein
123
conditions of 200 mg/L uranium and thorium concentra-
tions and 1 h contact time at room temperature (&25 °C).
Thus, different aliquots of acidic (sulfuric) uranium and
thorium synthetic solutions treated with 10% NaOH solu-
tion for adjusting to the required pH values were contacted
with the impregnated foam under the above mentioned
conditions. The obtained data are plotted in Fig. 12. From
this figure, it is clearly obvious that the decrease of acidity
(from 0 to 1) is associated with an increase of adsorption
efficiency of uranium and thorium (from 62 and 51% up to
68 and 64%, respectively). It is important to mention herein
that turbidity and even precipitation were observed in the
experiments in which the solution acidities were decreased
(higher pH values). Increasing the pH values from 1 to 4
gave no any significant increase in uranium and thorium
adsorption efficiencies. Increasing the pH values
(decreasing the acidity) beyond 4 was associated with
sharp decrease of uranium and thorium adsorption effi-
ciencies (33.5 and 33.8%, respectively in the last experi-
ments in the two series of experiments). Accordingly, the
pH value of 1 (±0.2) could be considered as the optimum
acidity for obtaing the highest uranium and thorium
adsorption efficiencies (68 and 64% for uranium and tho-
rium, respectively.
Effect of adsorption temperature
For studying the effect of temperature upon the uranium
and thorium adsorption efficiencies onto the solvent
impregnated foam, two sires of adsorption experiments
were performed using different temperatures started from
25 up to 60 °C. The experiments were performed under
fixed conditions of 200 mg/L uranium and thorium con-
centrations, pH 1 for 1 h contact time. From the obtained
results, the uranium and thorium adsorption efficiencies
about 66% and 69%, respectively were observed at the first
experiment (&25 °C) by increasing the temperature up to
60 °C, the adsorption efficiencies decreases down to 54%
and 60% for uranium and thorium, respectively. On the
other hand, extending temperature above 25 °C led to gives
a pronounced decreasing of adsorption efficiencies of
either uranium or thorium.
Results of columnar application
Uranium and thorium recovery
In the present work, uranium and thorium recovery from
the monazite sulfate leach liquor was carried out separately
in two glass column as previously mentioned (in the pro-
cedure section). The first which was packed with 1 g of the
prepared impregnated foam (with TBA) was used for
uranium recovery. The second one packed with 1 g of the
prepared impregnated foam (with DOA) was used for
thorium recovery from the uranium-free liquor. It is
important to mention herein that, the calculated theoretical
capacities of the foam impregnated with TBA and DOA
solvents are about 1.4 g U/g foam and 1.6 g Th/g foam,
respectively.
Uranium adsorption The impregnated foam bed was
loaded with uranium by passing the monazite sulfate leach
liquor (feed solution) through the column and periodical
samples have been taken each 60 mL throughput volume
until saturation (influent concentration =effluent concen-
tration). Figure 13 is a plot of the results of uranium
y = 0.6038x + 0.8313
R2 = 0.9656
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
1 1.5 2 2.5 3 3.5 4
log Ce
log qe
Fig. 10 Freundlich adsorption isotherm of sorption uranium onto
TBA impregnated foam
y = 0.5546x + 1.1127
R2 = 0.8453
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
log Ce
log qe
1 1.5 2 2.5 3 3.5 4
Fig. 11 Freundlich adsorption isotherm of sorption thorium onto
DOA impregnated foam
0
20
40
60
80
100
pH
Uranium and thorium
adsorption efficiency, %
U
Th
03412 56789
Fig. 12 Effect of solution pH upon uranium and thorium adsorption
efficiency onto impregnated foam
Successive uranium and thorium adsorption from Egyptian monazite 327
123
analysis in the collected effluent samples versus throughput
volumes (adsorption or loading curve). Uranium break-
through has indeed been observed at the 36th throughput
sample where uranium concentration in the effluent attains
about 1.3% of that in the feed (about 0.22 mg/L). On the
other hand, an almost adsorbent saturation capacity has
been obtained at the 67th throughput sample. Calculation
of the adsorbed uranium content of the adsorbent after its
complete saturation gives 1.08 gU. Comparing the latter
amount with the calculated theoretical capacity of the study
foam impregnated adsorbent (TBA) of 1.428 gU/g adsor-
bent indicates that under working conditions of about 75%
of its theoretical capacity has been realized.
Thorium adsorption The uranium-free effluent is sub-
jected to the second step (thorium adsorption) using the
second column (packed with 1 g of the impregnated DOA
foam). The uranium-free liquor was passed through the
column for thorium adsorption (feed solution). Periodical
samples have been taken each 40 mL throughput volume
until saturation (influent concentration =effluent concen-
tration). Figure 13 is a plot of the results of thorium anal-
ysis in the collected effluent samples versus throughput
volumes (adsorption or loading curve). Thorium break-
through has indeed been observed at the 9th throughput
sample where thorium concentration in the effluent attains
about 1.6% of that in the feed (about 1.3 mg/L). On the
other hand, an almost adsorbent saturation capacity has
been obtained at the 22nd throughput sample. Calculation
of the adsorbed thorium content of the adsorbent of its
complete saturation gives 1.16 g Th. Comparing the latter
amount with the calculated theoretical capacity of the study
foam impregnated adsorbent (di-n-octylamine) of 1.666 g
Th/g adsorbent indicates that under the working conditions,
about 70% of its theoretical capacity has been realized.
Uranium elution Using the 1 M NaCl (acidified to 0.1 M
H
2
SO
4
) eluent was found effective in uranium elution from
the loaded impregnated adsorbent foam bed. The plotted
elution curve (Fig. 14) exhibits the famous bell-shaped
curve with a major peak at the 14th throughput sample.
Systematic calculation of the eluted uranium amounts
(after uranium analysis in the collected eluate samples
(each sample 80 mL)) revealed that the 1 M NaCl–0.1 M
H
2
SO
4
elution system gave 95.8% uranium elution
efficiency.
Thorium elution For thorium elution from the loaded
impregnated adsorbent foam bed, 2 M H
2
SO
4
solutions
was used as an effective eluent. The thorium elution curve
(Fig. 14) shows also the bell shaped curve with a major
peak at the 15th throughput sample. Systematic calculation
of the eluted thorium amounts (after thorium analysis in the
collected eluate samples (each sample 20 mL)) revealed
that the 2 M H
2
SO
4
elution system gave 98.7% thorium
elution efficiency.
Conclusions
The obtained results of uranium and thorium adsorption on
the solvent impregnated foam encouraged the application
of this method (extraction chromatography technique) for
uranium and thorium recovery from the monazite sulfate
leach liquor (using ion-exchange columnar technique). The
calculated theoretical capacities of TBA (the uranium
adsorbent) and DOA (the thorium adsorbent) were
1.428 g U/g foam and 1.666 g Th/g foam, respectively.
However, the attained uranium and thorium adsorption
efficiencies were about 75 and 70% of its theoretical
capacities, respectively. Using 1 M NaCl–0.1 M H
2
SO
4
and 2 M H
2
SO
4
as eluent solutions for uranium and tho-
rium from their columns containing the loaded solvents-
impregnated foam, gives 95.8 and 98.7% elution efficien-
cies, respectively.
0
20
40
60
80
100
0204060
Sample No.
Uranium and Thorium
adsorption efficiency, %
U
Th
Fig. 13 Uranium and thorium adsorption curve of monazite leach
liquor on the TBA and DOA impregnated foam, respectively
0
20
40
60
80
100
120
140
160
180
0 5 10 15 20 25 30
Sample No.
Uranium and Thorium conc.,
mg/L
U
Th
Fig. 14 Uranium and Thorium elution curve from the loaded solvent
impregnated foam using 1 M NaCl–0.1 M H
2
SO
4
and 2 M H
2
SO
4
328 A. E. M. Hussein
123
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Successive uranium and thorium adsorption from Egyptian monazite 329
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