1. Adsorption of thorium from aqueous solution
by HDTMA+
-pillared bentonite
You-Qun Wang • Zhi-bin Zhang • Qin Li •
Yun-Hai Liu
Received: 29 January 2012 / Published online: 26 April 2012
Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract The ability of hexadecyltrimethylammonium
cation pillared bentonite (HDTMA?
-bentonite) has been
explored for the removal and recovery of thorium from
aqueous solutions. The adsorbent was characterized using
small-angle X-ray diffraction, high resolution transmission
electron microscopy and Fourier transform infrared spec-
troscopy. The influences of different experimental param-
eters such as solution pH, initial thorium concentration,
contact time and temperature on adsorption were investi-
gated. The HDTMA?
-bentonite showed the highest tho-
rium sorption capacity at initial pH of 3.5 and contact time
of 60 min. Adsorption kinetics was better described by the
pseudo-second-order model and adsorption process could
be well defined by the Langmuir isotherm. The thermo-
dynamic parameters, DG° (298 K), DH° and DS° were
determined to be -31.78, -23.71 kJ/mol and 27.10 J/
mol K, respectively, which demonstrated the sorption
process of HDTMA?
-bentonite towards Th(VI) was fea-
sible, spontaneous and exothermic in nature. The adsorp-
tion on HDTMA?
-bentonite was more favor than
Na-bentonite, in addition the saturated monolayer sorption
capacity increased from 17.88 to 31.20 mg/g at 298 K after
HDTMA?
pillaring. The adsorbed HDTMA?
-bentonite
could be effectively regenerated by 0.1 mol/L HCl solution
for the removal and recovery of Th(VI). Complete removal
(99.9 %) of Th(VI) from 1.0 L industry wastewater con-
taining 16.8 mg Th(VI) ions was possible with 7.0 g
HDTMA?
-bentonite.
Keywords Hexadecyltrimethylammonium bromide Á
Bentonite Á Adsorption Á Thorium
Introduction
Thorium is found in tetravalent state and concentrates in
natural sediments, either in detrital reistate minerals such
as thorianite, monazite and rutile, or adsorbed onto natural
colloidal materials [1]. Thorium, a toxic and radioactive
heavy metal, has been extensively used in many areas like
nuclear fuel, alloy, and laboratory investigations [2]. These
activities generate a wide diversity of wastewaters con-
taining isotopes of thorium and its daughter products,
which can cause dangerous consequences for human beings
by affecting the ecosystems [3]. Therefore, the removal and
recovery of thorium from contaminated ground water has
attracted more and more attention.
Several methods are available for removing thorium
from the ground water such as solvent extraction [4, 5],
ion-exchange [6] and adsorption, among which adsorption
is an attractive method because of its high efficiency, ease
of handling, and the availability of different adsorbents.
Numerous adsorbents have been used for the removal of
thorium from the wastewaters, such as natural [7–9] and
modified clays [10–13], microorganism [14], carbon
Y.-Q. Wang Á Z. Zhang Á Q. Li Á Y.-H. Liu
Key Laboratory of Radioactive Geology and Exploration
Technology Fundamental Science for National Defense,
East China Institute of Technology, Fuzhou 344000,
People’s Republic of China
Y.-Q. Wang Á Z. Zhang (&) Á Q. Li Á Y.-H. Liu
Chemistry, Biological and Materials Sciences Department,
East China Institute of Technology, Fuzhou 344000,
People’s Republic of China
e-mail: zhangnjut@163.com
Z. Zhang Á Y.-H. Liu
State Key Laboratory Breeding Base of Nuclear Resources and
Environment (East China Institute of Technology), Ministry
of Education, Nanchang 330013, People’s Republic of China
123
J Radioanal Nucl Chem (2012) 293:519–528
DOI 10.1007/s10967-012-1793-z

2. materials [15], zeolite [16, 17] and cellulosic materials [18]
etc. Among these, natural clays and their composites are
particularly effective, low-cost and chemically stable.
Bentonite is a well-defined naturally occurring 2:1 alu-
mino silicate mineral consisting of one alumina octahedral
layer sandwiched between two silica tetrahedral layers. The
potential adsorption sites for metal ions on bentonite include
silanol (:SiOH) and aluminol (:AlOH), hydroxyl groups
on the mineral edges and the permanently charged (:X-
) on
the basal surfaces. The adsorption properties of bentonite can
be improved by surface modification. The pillaring of certain
metal oxides and polymeric species into bentonite results in
an increase in basal spacing, surface area and pore volume,
which produces a structure with 2D micro-pores. The appli-
cation of pillared clays for environmental pollution control in
terms of metal removal from aqueous media has received
much attention [19–23]. Among those, HDTMA?
-pillared
bentonite was used to remove heavy metal ions, such as Pb2?
,
Pd2?
, Cd2?
, Zn2?
, Cr6?
and UO2
2?
from aqueous solution
[24–28], but less attention was paid to the Th(VI) sorption.
The aim of the present investigation was to study the
efficiency of sodium bentonite modified by hexadecyl-
trimethylammonium bromide (HDTMAB) for removing
thorium from aqueous solutions. Various techniques were
used to characterize the structure and textural property of
HDTMA cation pillared bentonite (HDTMA?
-bentonite),
including small-angle X-ray diffraction (SAXRD), high res-
olution transmission electron microscopy (HRTEM) and
Fourier transform infrared spectroscopy (FTIR). The effect of
various experimental parameters including pH of the solu-
tion, contact time, initial thorium concentration, and tem-
perature, as well as adsorption kinetics, isotherm models,
thermodynamics and were studied. In addition, the regener-
ation method of HDTMA?
-bentonite and attempt for Th(VI)
removal from industry wastewater were also investigated.
Materials and methods
Materials
Sodium bentonite (Na-bentonite) was purchased from
Zhejiang Fenghong Clay Chemicals Co., Ltd., and the
cation exchange capacity (CEC) was 100 mmol/100 g
bentonite. For the preparation of a stock thorium(VI)
solution, 0.2457 g Th(NO3)4Á5H2O was dissolved in 20 mL
0.1 M HCl, and then the solution was transferred to a
100 mL volumetric flask and diluted to the mark with
distilled water to produce a thorium(VI) stock solution
(1 mg/mL). The thorium solutions were prepared by
diluting the stock solution to appropriate volumes
depending upon the experimental requirements. All other
reagents were of AR grade.
Preparation of HDTMA?
-bentonite
Five grams of Na-bentonite was swelled by 100 mL dis-
tilled water, then HDTMAB solution was slowly added to
bentonite suspension followed by stirring at 60 °C for 24 h
to obtain HDTMA?
-bentonite with HDTMAB to the CEC
of bentonite molar ratios of 1.0:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1
and 1.6:1 (labeled as 1.0CEC-bentonite, 1.2CEC-bentonite,
1.3CEC-bentonite, 1.4CEC-bentonite, 1.5CEC-bentonite
and 1.6CEC-bentonite), respectively. The suspension was
filtered and was washed with deionized water until a neg-
ative bromide test had been obtained with 0.1 M AgNO3,
and then dried at 60 °C for 12 h. All samples were
grounded and sieved to 200 mesh size.
Characterization
Small-angle X-ray diffraction (SAXRD) patterns were
recorded using Cu Ka radiation (c = 1.5418) on ARL
X’TRA diffractometer operating at 40 kV and 40 mA with
0.25° divergence slit and 0.5° anti-scatter slit between 1.0°
and 16° (2h) at a step size of 2° min-1
. High resolution
transmission electron microscopy (HRTEM) was carried
out using a Jeol 4010 operated at 400 kV. The FT-IR
spectra were recorded on Nicolet Nexus 870 Fourier
transform infrared spectrometer in the spectral range of
400–4,000 cm-1
using the KBr pellet technique (1:50)
with resolution 2 cm-1
.
Adsorption experiments
The adsorption of Th(VI) was studied as a function of pH,
contact time, initial concentration of thorium solution and
temperature. The batch sorption studies were performed in
a reciprocating water bath shaker with concussion speed of
200 rpm. In the experiments 0.05 g of sorbent was sus-
pended in 50 mL solution containing different amounts of
Th(VI) concentration and different initial pH (adjusted
with 0.1 mol/L HCl and 0.1 mol/L NaOH). The concen-
tration of thorium ions in the solution was determined by
the arsenazo III method with a 721 type spectrophotometer
at 650 nm [9]. The amount of thorium ions adsorbed per
unit mass of the bentonite and the removal of Th(VI) were
calculated by using expressions 1 and 2:
qe ¼
Ci À Ceð Þ V
W
ð1Þ
Removal=% ¼
C0 À Ce
C0
 100 % ð2Þ
where, qe is the adsorption capacity of the bentonite (mg/g);
C0 and Ce are the thorium concentration in the initial and
equilibrium solution (mg/L) respectively; Ci is the thorium
520 Y.-Q. Wang et al.
123

3. concentration of the initial solution subtracted the precip-
itated part at the fixed pH; V is the volume of aqueous
solution (L) and W is the mass of dry bentonite (g).
Results and discussion
Characterization
The SAXRD patterns of Na-bentonite and HDTMA?
-
bentonite was shown in Fig. 1, and the interlayer spacing
could be calculated by Eq. 3.
d ¼ nk=2 sin h ð3Þ
Where the d is the interlayer spacing (nm), h is the dif-
fraction angle (°) and the k is 0.154 nm.
The d001 value of Na-bentonite was 1.21 nm and
expanded gradually to 4.09 nm with pillared by HDTMA?
.
These results indicated that HDTMA?
cations had been
intercalated into the bentonite interlayer space. Base on the
molecular structure of HDTMA?
and the interlayer spac-
ing, different HDTMA?
arrangement models within the
bentonite interlayer space were proposed, i.e., lateral-
monolayer in 1.0CEC-bentonite and 1.2CEC-bentonite;
lateral-monolayer and lateral-bilayer in 1.3CEC-bentonite,
1.4CEC-bentonite and 1.5CEC-bentonite; lateral-mono-
layer (or pseudo-trilayer) and lateral-bilayer in 1.6CEC-
bentonite.
Figure 2 showed the FTIR spectra of the HDTMA?
-
bentonite in the range of 2,700 * 3,100 cm-1
. There were
two intense adsorption bands close at 2,920–2,850 cm-1
corresponding to the anti-symmetric and symmetric
vibrations C–H in CH2 group of the surfactant alkyl chains,
respectively. The peak intensity increased gradually with
the increase of HDTMA?
loading. The band attributed to
asymmetric stretching vibration shifted from 2,853 to
2,845 cm-1
, simultaneously, that related to the symmetric
stretching vibration changed its position from 2,924 to
2,918 cm-1
. This was probably the consequence of the
concentration increase of the surfactant cations appearing
in their ordered trans form of their hydrocarbon chain and
decrease of the concentration of gauche (disordered) con-
formers [29]. Therefore the HDTMA?
-bentonite with
HDTMA?
: CEC of 1.3 was used to investigated the sorp-
tion properties towards thorium in the following
experiments.
The HRTEM images of 1.3CEC-bentonite were shown
in Fig. 3, from which, it could be seen that the interlamellar
structure montmorillonite was till maintained after pillared
by HDTMA?
and the interlayer space was expanded.
However, the arrangement model of HDTMA was a mix
state and there were several arrangements coexist in the
interlayer.
The effect of solution pH
The pH of aqueous solution is an important variable for the
Th(IV) adsorption on bentonite, and influences the metal
speciation and surface metal binding sites [11]. The effect
of pH on the adsorption of Th(VI) onto Na-bentonite and
HDTMA?
-bentonite was carried out over the pH range
2.0–6.0 using 50 lg/mL initial thorium concentration at
298 K and the results were displayed in Fig. 4. The
adsorption capacity of Th(VI), as well as the removal ratio
were strongly affected by the solution pH. As for Na-
bentonite and HDTMA?
-bentonite, the sorption amount of
Fig. 1 SAXRD patterns of Na-bentonite and HDTMA?
-bentonite
(1.0CEC-bentonite to 1.6CEC-bentonite were HDTMA?
: CEC of
1.0:1, 1.2:1, 1.3, 1.4:1, 1.5:1 and 1.6:1 respectively)
Fig. 2 FTIR spectra of Na-bentonite and HDTMA?
-bentonite
(2,700–3,100 cm-1
)
Adsorption of thorium from aqueous solution 521
123

4. two adsorbents increased from pH 2.0 to 3.5, and reached
the maximum adsorption capacity of 15.00 and 30.67 mg/g
at pH 3.5, and then declined. Simultaneously, the removal
of Th(IV) due to adsorption and precipitation increased
sharply from pH 2.0 to 4.0, and then gradually reached the
maximum removal of around 90 % after 5.0. Therefore the
efficiency of Th(IV) onto adsorbents could be controlled by
the initial pH of the solid/liquid reaction. The reaction for
low adsorption capacity in high acidity was the competition
between the excess of H?
ions and positively charged
cations species present in the medium [11]. Th(VI) has a
very complex chemistry in terms of hydrolysis, such as
[Th(OH)]3?
, [Th(OH)2]2?
, [Th(OH)3]?
and Th(OH)4 [3],
then the increasing of pH led to a decrease of positive
surface charge, which results in lower electrostatic pull of
the charged Th(IV) hydrolysis products and the negative
charged group of bentonite. Therefore we speculated that
the obtained removal ratio after pH 3.5 was due to the
sorption of Th(IV) and the precipitation of Th(OH)4. The
solution pH at 3.5 was selected as the optimal value for
adsorption of Th(IV) on both Na-bentonite and HDTMA?
-
bentonite, and used for the following experiments.
The effect of contact time
Contact time is also an important factor reflecting the
adsorption kinetics. The variation of adsorption amount
with vibrating time was studied using 50 lg/mL initial
Th(IV) concentration at pH 3.5 and 298 K. As showed in
Fig. 5, the uptake of Th(IV) on to Na-bentonite and
HDTMA?
-bentonite increased sharply at the beginning,
and then gradually reached equilibrium after 60 min. The
faster adsorption rate at the beginning would be due to the
larger concentration gradient. Therefore, the contact time
of 80 min was deemed sufficient to establish sorption
equilibrium and used in all subsequent experiments.
Effect of initial Th(IV) concentration
The initial concentration provides an important driving
force to overcome all mass transfer resistance of thorium
between the aqueous and solid phases [30]. The effect of
initial Th(IV) concentration on sorption was studied at
298 K and revealed in Fig. 6. The adsorptive capacity
increased with the increase of the initial Th(VI) concen-
tration, and nearly got saturation at 50 mg/L. At low tho-
rium ion loading, the number of thorium ions in the
solution was smaller than the available sorption sites of the
two adsorbents, consequently, the adsorption was inde-
pendent of initial Th(VI) concentration. But when the
concentration of Th(VI) exceeded 50 mg/L, the active sites
were nearly captured by thorium ions, so the sorption
capacity revealed no further variation. Therefore, 50 mg/L
Th(VI) concentration was selected as an optimum con-
centration and used in the following experiments.
Adsorption isotherm
The equilibrium adsorption isotherms are one of the
essential data to understand the mechanism of the adsorp-
tion systems. Langmuir and Freundlich equations are the
most frequently used for describing sorption isotherms.
The Langmuir model is based on assumptions of adsorption
homogeneity such as equally available adsorption sites,
Fig. 3 TEM image of 1.3CEC-bentonite
522 Y.-Q. Wang et al.
123

5. monolayer surface coverage, and no interaction between
adsorbed species. The Langmuir equation can be described
by the linearized Eq. 4 [31].
Ce
qe
¼
1
qmKL
þ
Ce
qm
ð4Þ
where Ce is the equilibrium concentration (mg/L), qe is the
amount of solute sorbed per unit weight of sorbent (mg/g),
qm is the Langmuir constant, which represents the saturated
monolayer sorption capacity(mg/g). KL is a constant rela-
ted to the energy of adsorption.
The Freundlich model can be applied to nonideal sorp-
tion on heterogeneous surfaces as well as multilayer
sorption [32]. The empirical Freundlich equation can also
be transformed into linearized Eq. 5.
ln qe ¼ ln KF þ
1
n
ln Ce ð5Þ
Where Ce is the equilibrium concentration (mg/L), qe is the
amount of solute sorbed per unit weight of sorbent (mg/g),
KF is the Freundlich constant related to the adsorption
capacity, and n is relevant to the adsorption intensity.
Figures 7 and 8 present the effect of initial concentration
on the thorium adsorption on Na-bentonite and HDTMA?
-
bentonite at 298, 308 and 318 K.
The linearized form of Langmuir and Freundlich ad-
sorpiton isotherms obtained at 298, 308 and 318 K were
presented in Figs. 9, 10, 11, 12 respectively. And the
adsorption constants evaluated from the isotherms with the
correlation coefficients (R2
) were given in Table 1. The
value of R2
showed that Langmuir isotherm model fitted
better with the experimental data than Freundlich isotherm
model. Moreover, the saturated monolayer sorption
capacity (qm) increased from 17.60 to 32.64 mg/g at 298 K
after HDTMA?
pillaring. A larger value of KL also implied
strong bonding of thorium to HDTMA?
-bentonite.
Fig. 4 The effect of initial
solution pH on the Th(IV)
adsorption on Na-bentonite and
HDTMA?
-bentonite
Fig. 5 The effect of contact time on Th(IV) adsorption on Na-
bentonite and HDTMA?
-bentonite
Fig. 6 The effect of initial concentration on Th(IV) adsorption on
Na-bentonite and HDTMA?
-bentonite
Adsorption of thorium from aqueous solution 523
123

6. Furthermore, with the increase of the temperature, the
saturated monolayer sorption capacity decreased for the
same adsorbents, which indicated the sorption of U(VI)
was exothermic.
Adsorption kinetics
In order to explain the controlling mechanism of adsorption
processes such as mass transfer and chemical reaction,
pseudo-first-order and pseudo-second-order kinetic equa-
tions were applied to describe the kinetic characteristic of
Th(VI) onto the bentonite. The pseudo-first order kinetic
model is usually given as Eq. 6 [33].
ln qe À qtð Þ ¼ ln qe À k1t ð6Þ
Where k1 (min-1
) is the rate constant of first order
adsorption, qe and qt are the amounts of U(VI) adsorbed
Fig. 7 The adsorption isotherms of Th(IV) on Na-bentonite at 298,
308 and 318 K
Fig. 8 The adsorption isotherms of Th(IV) on HDTMA?
-bentonite at
298, 308 and 318 K
Fig. 9 The Langmuir adsorption isotherm models of Na-bentonite
Fig. 10 The Langmuir adsorption isotherm models of HDTMA?
-
bentonite
Fig. 11 The Freundlich adsorption isotherm models of Na-bentonite
524 Y.-Q. Wang et al.
123

7. (mg/g) at equilibrium and time ‘‘t’’, respectively. Using
Eq. 6, linear plot of ln(qe - qt) vs. t was plotted (Fig. 13).
The k1, qe,cal and correlation coefficient (R2
) were calcu-
lated from the plot and presented in Table 2.
The pseudo-second order kinetic model is always given
as Eq. 7 [34].
t
qt
¼
1
k2q2
e
þ
t
qe
ð7Þ
Where k2 (min-1
) is the rate constant of second order
adsorption. Using Eq. 7, linear plot of t/qt vs. t was
plotted (Fig. 14). The k2, qe,cal and correlation coefficient
(R2
) were calculated from the plot and presented in
Table 2.
As showed in Table 2, the square of correlation coeffi-
cients (R2
) of pseudo-second order equation was better than
the value of the pseudo-first order equation. Moreover, the
values of the amounts of Th(VI) adsorbed at equilibrium,
qe,cal (17.88, 31.20 mg/g) was very close to the experi-
mental values, qe,exp (15.36 and 29.25 mg/g). Therefore,
the adsorption process was more favor of the pseudo-sec-
ond order equation, which indicated that adsorption
involved chemical reaction in adsorption in addition to
physical adsorption [35].
Adsorption thermodynamics
Thermodynamic parameters such as enthalpy (DH°),
entropy (DS°) and Gibbs free energy (DG°) are useful in
defining whether the sorption reaction is endothermic or
exothermic, and spontaneity of the adsorption process [36].
The thermodynamic data are calculated using the following
Eq. 8 and 9.
ln kL ¼
DS
R
À
DH
RT
ð8Þ
DG
¼ DH
À TDS
ð9Þ
Where kL is the Langmuir constant, DS° is the change of
entropy (J/mol K), DH° is the change of enthalpy (kJ/mol),
T is the absolute temperature in Kelvin (K) and R is the gas
constant (8.314 J/mol K). DH° and DS° can be calculated
from the slope and intercept of the straight line (Fig. 15).
The change of Gibbs free energy values are calculated from
Eq. 9.
The values of thermodynamic parameters for the sorp-
tion of Th(VI) at different temperature were given in
Table 3. The negative value of DG° at different tempera-
tures confirmed the feasibility and spontaneous nature of
adsorption process. Further, the increase in the value DG°
with the increasing temperature indicated that lower tem-
perature favored the sorption process. In addition, the DG°
value of HDTMA?
-bentonite was smaller than the Na-
bentonite, which showed the adsorption on HDTMA?
-
bentonite was more favor than Na-bentonite. The positive
value of DS° reflected the affinity of the bentonite for
Th(VI) and confirmed the increased randomness at the
solid-solution interface during adsorption [37].
Fig. 12 The Freundlich adsorption isotherm models of HDTMA?
-
bentonite
Table 1 The isotherm constants and correlation coefficient for the
Th(VI) adsorption on bentonite
Adsorbents T (K) Langmuir isotherm Freundlich isotherm
KL qm
(mg/g)
R2
n KF R2
Na-
bentonite
298 0.21 17.60 0.9999 10.30 21.21 0.9674
308 0.15 14.62 0.9998 8.59 15.79 0.9558
318 0.13 13.71 0.9994 6.66 10.87 0.9393
HDTMA?
-bentonite
298 0.37 32.64 0.9999 7.25 9.33 0.9395
308 0.28 26.72 0.9999 5.65 6.42 0.9278
318 0.20 21.58 0.9999 5.12 5.53 0.9141
Fig. 13 The pseudo-first order adsorption kinetics of Th(VI) onto the
bentonite
Adsorption of thorium from aqueous solution 525
123

8. Desorption and regeneration studies
Desorption is an important process in adsorption studies
due to its enhancement of the economical value. Desorp-
tion studies will help to regenerate the spent adsorbent so
that it can be reused to adsorb metal ions. Desorption
efficiency of the spent HDTMA?
-bentonite was checked
by 0.001–0.1 mol/L HCl solution. The results demon-
strated that the adsorbed Th(VI) could be desorbed
completely from the spent adsorbent using 0.1 mol/L HCl,
and hence to investigate the regeneration properties, the
adsorption–desorption cycle was repeated four times with
same adsorbent using 0.1 mol/L HCl. It was clear from
Table 4 that the initial adsorption capacity, removal and
desorption ratio were 18.37 mg/g, 99.42 and 97.23%,
and after four cycles decreased to 17.21 mg/g, 91.03 and
90.71 %. Therefore 0.1 mol/L HCl solution could regen-
erate the adsorbent effectively.
Test with industry wastewater containing thorium
The Th(VI) industry wastewater, the affinate of rare-earth
leaching agent after extracting thorium and rare earth ions,
was treated by HDTMA?
-bentonite to demonstrate its
adsorption potential and utility in removing Th(VI) ion
from wastewater in the presence of other ions. The
wastewater contained Th(VI) (16.8 mg/L), SO4
2-
(14.4 g/
L), NO3
-
(0.4 g/L), total RE (3.4 mg/L), Mg2?
(0.3 g/L),
Ca2?
(0.6 g/L) and Fe3?
(0.05 g/L). The effect of adsorbent
dose on Th(VI) removal from wastewater was investigated,
and the results were revealed in Fig. 16. The percentage of
Th(VI) adsorption increases with increasing HDTMA?
-
bentonite dosage and almost complete removal (100 %)
of Th(VI) from the wastewater containing 16.8 mg/L was
achieved with 7.0 g HDTMA?
-bentonite in 1.0 L.
Conclusion
In this paper, HDTMA cation pillared bentonite (HDTMA?
-
bentonite) was prepared. The interlayer spacing expanded
gradually from 1.21 nm to 4.09 nm by HDTMA?
pillaring.
The HDTMA?
loading amount increased with the increase
of HDTMAB: CEC of bentonite during preparation. The
interlamellar structure of HDTMA?
-bentonite was till
maintained, however, the arrangement model of HDTMA?
was a mix state and there were several arrangements coexist
in the interlayer. The sorption performances were controlled
by solution pH, contact time, and initial thorium concen-
tration. The maximum capacity of HDTMA?
-bentonite was
observed at the pH value of 3.5 and contact time of 60 min.
The Th(VI) sorption on HDTMA?
-bentonite was well fitted
to the Langmuir adsorption isothermal and pseudo-second
kinetics models. The thermodynamic parameters, such as
Table 2 The adsorption kinetics of Th(VI) onto Na-bentonite and HDTMA?
-bentonite
Adsorbents Pseudo-first order kinetics Pseudo-second order kinetics
k1 (min-1
) qe,cal (mg/g) R2
k2 (g/mg min) qe,cal (mg/g) R2
Na-bentonite 0.0342 11.89 0.9568 0.0037 17.88 0.9986
HDTMA?
-bentonite 0.0281 11.19 0.9743 0.0049 31.20 0.9999
Fig. 14 The pseudo-second order adsorption kinetics of Th(VI) onto
the bentonite
Fig. 15 The adsorption thermodynamics of Th(VI) on Na-bentonite
and HDTMA?
-bentonite
526 Y.-Q. Wang et al.
123

9. DG°, DH° and DS°, clearly indicated that the adsorption
process was feasible, spontaneous and exothermic in nature,
in addition the adsorption on HDTMA?
-bentonite was more
favor than Na-bentonite. The adsorption–desorption study
showed that Th(VI) sorbed HDTMA?
-bentonite could be
effectively regenerated by 0.1 mol/L HCl solution for the
removal and recovery of Th(VI) from aqueous solution.
Attempts for the Th(VI) removal from industry wastewater
using HDTMA?
-bentonite revealed acceptability. Almost
complete removal (100 %) of Th(VI) from the waste-
water containing 16.8 mg/L was achieved with 7.0 g
HDTMA?
-bentonite in 1.0 L.
Acknowledgments This work is financially supported by the
National Natural Science Foundation of China (Grant No. 21101024),
Key Project of Chinese Ministry of Education (Grant No. 211086),
Natural Science Foundation of Jiangxi Province (No. 2010GQH0015),
Science and Technology Project of Jiangxi Provincial Department of
Education (No. GJJ11139) and Open Project Foundation of the Key
Laboratory of Radioactive Geology and Exploration Technology
Fundamental Science for National Defense, East China Institute of
Technology, China (2010RGET08).
References
1. Syed HS (1999) J Radional Nucl Chem 241(1):11–14
2. Khazaei Y, Faghihian H, Kamali M (2011) J Radioanal Nucl
Chem 289(2):529–536
3. Anirudhan TS, Rijith S, Tharun AR (2010) Colloids Surf A
368(1–3):13–22
4. Sato T (2008) Solvent Extr Res Dev Jpn 15:61–69
5. Bayyari MA, Nazal MK, Khalili FA (2010) J Saudi Chem Soc
14(3):311–315
6. ElSweify FH, Shehata MKK, ElShazly EAA (1995) J Radioanal
Nucl Chem 198(1):77–87
7. Talip Z, Eral M, Hicsonmez U (2009) J Environ Radioact
100(2):139–143
8. Zhang HX, Dong Z, Tao ZY (2006) Colloids Surf A
278(1–3):46–52
9. Zhao DL, Feng SJ, Chen CL, Chen SH, Xu D (2008) Appl Clay
Sci 41(1–2):17–23
10. Baybas D, Ulusoy U (2011) Appl Clay Sci 51(1–2):138–146
11. Guerra DL, Viana RR, Airoldi C (2009) J Hazard Mater
168(2–3):1504–1511
12. Guerra DL, Viana RR, Airoldi C (2009) J Braz Chem Soc
20(6):1164–1174
13. Guerra DL, Viana RR, da Costa LP, Airoldi C (2012) J Phys
Chem Solids 73(1):142
14. Tsuruta T (2004) Water Air Soil Pollut 159(1–4):35–47
15. Kutahyali C, Eral M (2010) J Nucl Mater 396(2–3):251–256
16. Kaygun AK, Akyil S (2007) J Hazard Mater 147(1–2):357–362
17. Salinas-Pedroza MG, Olguin MT (2004) J Radioanal Nucl Chem
260(1):115–118
18. Anirudhan TS, Rejeena SR (2011) Ind Eng Chem Res
50(23):13288–13298
19. Zhao HT, Jaynes WF, Vance GF (1996) Chemosphere 33:
2089–2100
20. Huh JK, Song DI, Jeon YW (2000) Sep Sci Technol 35:243–259
21. Upson R, Burns S (2006) J Colloid Interface Sci 297:70–76
22. Hsu YH, Wang MK, Pai CW, Wang YS (2000) Appl Clay Sci
16:147–159
23. Dentel SK, Jamrah AI, Sparks DL (1998) Water Res 32:
3689–3697
24. Lee JJ, Choi J, Park JW (2002) Chemosphere 49:1309–1315
25. Oyanedel-Craver VA, Fuller M, Smith JA (2007) J Colloid
Interface Sci 309:485–492
26. Akar ST, Yetimoglu Y, Gedikbey T (2009) Desalination 244:
97–108
27. Majdan M, Pikus S, Gajowiak A, Gładysz-Płaska A, Krzy_zano-
wska H, _Zuk J, Bujacka M (2010) Appl Surf Sci 256:5416–5421
28. Majdan M, Pikus S, Gajowiak A, Sternik D, Zieba E (2010) J
Hazard Mater 184:662–670
Table 3 Thermodynamic parameters for the U(VI) sorption on Na-bentonite and HDTMA?
-bentonite
Adsorbents DG° (kJ/mol) DH° (kJ/mol) DS° (J/mol K)
298 K 308 K 318 K
Na-bentonite -30.26 -30.67 -31.07 -18.13 40.72
HDTMA?
-bentonite -31.78 -32.05 -32.32 -23.71 27.10
Table 4 Four cycles of thorium adsorption–desorption with 0.1 mol/L
HCl as desorbing agent
Cycle Adsorption Desorption (%)
Capacity (mg/g) Removal (%)
1 18.37 99.42 97.23
2 17.96 96.77 95.37
3 17.82 95.53 93.29
4 17.21 91.03 90.71
Fig. 16 Th(VI) ion removal from industry wastewater by HDTMA?
-
bentonite
Adsorption of thorium from aqueous solution 527
123

10. 29. He HP, Frost LR, Zhu JX (2004) Spectrochim Acta Part A
60(12):2853–2859
30. Aytas S, Yurtlu M, Donat R (2009) J Hazard Mater 172:667–674
31. Hazer O, Kartal S¸ (2010) Talanta 82:1974–1979
32. Parab H, Joshi S, Shenoy N, Verma R, Lali A, Sudersanan M
(2005) Bioresour Technol 96:1241–1248
33. Ghaemi A, Torab-Mostaedi M, Ghannadi-Maragheh M (2011)
J Hazard Mater 190:916–921
34. Psareva T, Zakutevskyy O, Chubar N, Strelko V, Shaposhnikova
T, Carvalho J, Correia M (2005) Colloids Surf A 252:231–236
35. Anirudhan TS, Rijith S, Tharun AR (2010) Colloids Surf A
368:13–22
36. Anirudhan TS, Divya L, Suchithra PS (2009) J Environ Manage
90:549–560
37. Donat RJ (2009) Chem Thermodyn 41:829–835
528 Y.-Q. Wang et al.
123

11. Copyright of Journal of Radioanalytical Nuclear Chemistry is the property of Springer Science Business
Media B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the
copyright holder's express written permission. However, users may print, download, or email articles for
individual use.