A high-performance impregnated resin for recovering thorium from radioactive rare earth waste residue

Article abstract of DOI:10.1016/j.molliq.2017.04.100

A novel impregnated resin with n-octyl diphenyl phosphate (ODP-IR) was developed for the separation of thorium from leaching solution of rare earth (RE) waste residue. Nitrogen adsorption, FT-IR spectra, scanning electron microscopy and energy dispersive spectrometer were conducted for the characterization of ODP-IR. Uptake of ODP-IR for Th^4?+ was significantly affected by changing HNO₃ concentration. The adsorption data were fitted well with pseudo-second-order rate model. Thermodynamic parameters for the adsorption of Th^4?+ were calculated and discussed. The adsorption was fitted well with the Langmuir isotherm model than Freundlich isotherm model. ODP-IR was repeatedly used five times without obvious loss for Th^4?+ adsorption, indicating that the adsorbent was stabilized. The ODP-IR was successfully used to separate Th from RE and Fe using the feed solution from ion-adsorption type RE waste residue, which revealed potentials in the fields of RE resource utilization, radioactive contamination treatment and nuclear fuel preparation.

Full text of DOI:10.1016/j.molliq.2017.04.100

Accepted Manuscript
A high-performance impregnated resin for recovering thorium
from radioactive rare earth waste residue
Sen Qiu, Shun Li, Yamin Dong, Xiang Su, Yanliang Wang,
Yinglin Shen, Xiaoqi Sun
PII:
DOI:
Reference:
S0167-7322(17)30696-7
doi: 10.1016/j.molliq.2017.04.100
MOLLIQ 7256
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15 February 2017
19 April 2017
20 April 2017
Please cite this article as: Sen Qiu, Shun Li, Yamin Dong, Xiang Su, Yanliang Wang,
Yinglin Shen, Xiaoqi Sun , A high-performance impregnated resin for recovering thorium
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ACCEPTED MANUSCRIPT
A high-performance impregnated resin for recovering
thorium from radioactive rare earth waste residue
Sen Qiu1, Shun Li2, Yamin Dong1, Xiang Su1, Yanliang Wang1, Yinglin Shen2*,
Xiaoqi Sun1*
a Fujian Research Center for Rare Earth Engineering Technology, Xiamen Institute of
Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen 361021,
China
b Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000, China
*Corresponding author at Fujian Research Center for Rare Earth Engineering Technology,
Xiamen Institute of Rare Earth Materials, Haixi Institute, Chinese Academy of Sciences, Xiamen
361021, China.
Email addresses: xqsun@fjirsm.ac.cn (X. Q. Sun)
*Corresponding author at Radiochemistry Laboratory, Lanzhou University, Lanzhou 730000,
China.
Email addresses: shenyl@lzu.edu.cn (Y. L. Shen)
ABSTRACT
A novel impregnated resin with n-octyl diphenyl phosphate (ODP-IR) was developed
for the separation of thorium from leaching solution of rare earth (RE) waste residue.
Nitrogen adsorption, FT-IR spectra, scanning electron microscopy and energy
dispersive spectrometer were conducted for the characterization of ODP-IR. Uptake
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of ODP-IR for Th4+ was significantly affected by changing HNO3 concentration. The
adsorption data was fitted well with pseudo-second-order rate model. Thermodynamic
parameters for the adsorption of Th4+ were calulated and discussed. The adsorption
was fitted well with the Langmuir isotherm model than Freundlich isotherm model.
ODP-IR was repeatedly used five times without obvious loss for Th4+ adsorption,
indicating that the adsorbent was stabilized. The ODP-IR was successfully used to
separate Th from RE and Fe using the feed solution from ion-adsorption type RE
waste residue, which revealed potentials in the fields of RE resource utilization,
radioactive contamination treatment and nuclear fuel preparation.
Keywords: Rare earth, Thorium, Adsorption, Impregnated resin
1. Introduction
The natural thorium, 232Th, is a potential nuclear fuel because it can be
transformed into fissile 233U by absorbing slow neutrons[1]. As for the rare earth (RE)
separation industry, many RE waste residues containing Th were accumulated. The
accompanied Th was not recovered as a by-product and caused environmental
pollution. The waste residues containing Th should be recovered in order to prevent
radioactive pollution. Hence, the separation of Th from RE in the waste residues is
significant due to the elimination of radioactive pollution[2]. Solvent extraction[3] is a
major technique for the industrial separation of Th and RE elements[4]. Various
extractants, such as amine[5], neutral organophosphorus compound[6] and acidic
organophosphorus compound[7], were investigated for the extraction and separation of
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Th and RE. Unfortunately, some disadvantages on the separation of Th and RE using
those extractants could be still observed, i.e., lower extraction capacities[8] and higher
stripping acidities[7]. As for the TBP system, it required high concentration of
hydrochloric acid to control the form of third phase[9]. Also, the optimized condition
of Th4+ stripping from HEHEHP system was 3.50 mol/L of H2SO4 solution[10]. In
addition, large inventories of hazardous diluents and modifiers were used in the
extraction systems[11], thereby leading to environmental problems[12]. Hence, it is
significant to develop a high performance material for the separation of Th.
The recovery of metal ions from aqueous solutions using adsorption[13] was
proposed as a technological alternative to solvent extraction[14]. In recent years, the
adsorption of metal ions with various adsorbents has been extensively studied. Tan et
al.[15] investigated the adsorption of Th4+ with nano particles of anatase. Qiu et al.[16]
studied the adsorption of RE by magnetic silica hybrid material. Ihsanullah et al.[17]
reported the adsorptive removal of Cd2+ ions from liquid phase using acid modified
carbon-based adsorbents. Amberlite XAD resin is a kind of commercial resin with
high surface area, uniform pore size distribution and chemical stability[18]. The resin is
a middle polarity adsorbent with acrylic ester group (RCOO-), which attract both
hydrophobic and hydrophilic ends of molecules[19]. It was used to impregnate some
extractants, i.e., titan yellow was impregnated on XAD-7 resin to concentrate and
2+
determinate ultra-trace amount of UO2 and Th4+[20]. Separation and recovery
processes of Dy3+, Y3+, Tm3+, and Yb3+ from leached solutions of heavy RE residues
were studied using a column method with solvent impregnated XAD-7 resin[21]
.
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Medium and heavy RE are critical elements to produce advanced magnets, lasers
and optics. Ion-adsorption RE minerals were discovered in Jiangxi Province and other
southern areas of China. The minerals are rich in medium and heavy RE elements
(accounting for more than 80% of the world’s total medium and heavy RE).
Unfortunately, surface mining and heap leaching of the significant RE resource
caused severe environmental damages. Moreover, waste residues with low-level
radioactive Th were generated during the ion-adsorption type RE minerals separation
processing. To our knowledge, less research has been reported for the separation of Th
and RE in the waste residues. In this article, a novel impregnated resin with ODP was
developed for the separation of Th and RE elements from radioactive waste residues
of ion-absorbed type RE minerals.
2. Experimental
2.1. Materials
The XAD-7 resin was purchased from Sigma-Aldrich Company and purified
before use. Chlorinated diphenoxy phosphate, n-bromooctane and magnesium were
obtained from Xiya Reagent. All other chemicals were reagent grade and used
without further purification. The structure of XAD-7 and n-OPD are shown in Figure
1[22]
.
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Fig. 1. Chemical structures of XAD-7 resin and n-OPD.
The extractant of n-octyl diphenyl phosphate (n-ODP) used in this study was
synthesized by two steps: (i) Preparation of Grignard reagents by mixed magnesium
and n-bromooctane in ether solution. (ii) The ether solution of diphenyl
chlorophosphate was added dropwise to the ether solution of Grignard reagent with
the ice bath. The mixed solution was kept mechanically stirred for 12 h at room
temperature, then the mixture was added to the ice water. After the aqueous layer was
removed, the ether layer was dried with anhydrous sodium sulfate. Finally, the
purified product was obtained by drying under reduced pressure and separating by
silica gel column chromatography as yellow solid. The synthetic scheme was shown
in Fig. 2 and the following NMR data were recorded for the synthesized compound.
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Fig. 2. Scheme for the synthesis of extractant. R1 = R3 = H, R2 = n-heptyl.
1H NMR (500 MHz, CDCl3): δ 7.2-7.35 (m, CH, 10H), 2.05 (t, P-CH2, 2H), 1.27-1.38
(m, CH2, 12H), 0.91 (m, CH3, 3H).
13C NMR (500 MHz, CDCl3): δ 150.44 (2C), 129.84-120.25 (10CH), 31.77 (2CH2),
29.04 (3CH2), 22.61 (2CH2), 13.91 (CH3).
2.2. Instrumentations
Nitrogen adsorption was tested with ASAP2020 M+C produced by
Micromeritics. FT-IR spectra were obtained with wave number from 4000-500 cm-1
using Nicolet IS 50 spectrometer. The surface of impregnated resin was examined
using HITACHI-SU1510 scanning electron microscopy (SEM) and energy dispersive
1
12
spectrometer (EDS). H and C NMR spectra were obtained in CDCl3 with an AV
III-500 Bruker spectrometer. The concentration of metal ions was determined by
Thermo scientific ICP 6500 series inductively coupled plasma-atomic emission
spectroscopy (ICP-OES).
2.3. Preparation of impregnated resin
For further purification, the XAD-7 resin was washed with ethanol and deionized
water for three times before the impregnation process. After filtering, the resin was
dried overnight at 383 K under vacuum to remove residue. Then the XAD-7 resin was
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immersed into acetone solution containing n-ODP, and the mixture was mildly stirred
at room temperature for 24 h. The redundant acetone solution on resin was distilled at
343 K. Subsequently, the impregnated resin with n-ODP（ODP-IR）was dried at 383 K
for 12 h after washing with deionized water for three times.
2.4. Adsorption studies
Adsorption experiments were carried out by shaking 5 mL aqueous phase
containing Th(NO3)4 and 70 mg ODP-IR for 60 min in an equilibrium tube with the
help of mechanical shaker. The concentration of Th(NO3)4 was 1×10-4 mol/L with 0.1
mol/L HNO3 unless otherwise stated. All the experiments were conducted at 301 K.
After adsorption, the aqueous phase was separated from ODP-IR by centrifugation at
4000 rpm for 10 min. The residual metal ions in aqueous phase were determined by
ICP-OES. The amounts of adsorbed metal ions were calculated by mass balance
between initial and raffinate concentration. The uptake percentage (%) and amount
adsorbed per unit mass of adsorbent at equilibrium (qe) are defined in Eq. (1)-(2)[23]
:
(1)
(2)
where Cini and Ce (10-4mol/L) represent the initial and equilibrium concentration
in aqueous phase, respectively. V (L) is the volume of solution and m (g) is the mass
of dry ODP-IR.
2.5. Adsorption equations
2.5.1. Kinetics parameters of adsorption
The pseudo-first-order[24], pseudo-second-order[25] and intraparticle diffusion[26]
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models were applied to investigate kinetics behavior of ODP-IR, and corresponding
equations are shown as Eq. (3)-(5). In this section, 5 mL Th(NO3)4 solution with 0.1
mol/L HNO3 was mixed with 70 mg ODP-IR in every tube. The extraction time was
varied from 5 to 120 minutes.
(3)
(4)
(5)
where qe and qt are the amounts of Th4+ adsorbed on the ODP-IR at equilibrium
and time t, respectively, k1, k2 and kp are the pseudo-first-order rate constant,
pseudo-second-order rate constant and intraparticle diffusion rate constant,
respectively. L represents the boundary layer diffusion effects.
2.5.2. Thermodynamic parameters of adsorption
Thermodynamic parameters such as Gibbs free energy change (ΔGθ), enthalpy
change (ΔHθ) and entropy change (ΔSθ) were determined for the sake of investigating
the effect of temperature on adsorption process. Those thermodynamic parameters
were acquired at different temperature (301 K, 311 K, 321 K, 331 K) and estimated
with Eq. (6)-(8)[27]
:
(6)
(7)
(8)
Below, Kd is the equilibrium constant, Cad is the concentration of Th4+ adsorbed
on ODP-IR at equilibrium, Ce is the equilibrium concentration of Th4+ in the solution,
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R (8.314 J/(mol K)) is the gas constant and T(K) is temperature. ΔHθ and ΔSθ are
obtained from the slop and intercept of Vatn’t Hoff plot of lnKd versus 1/T.
2.5.3. Adsorption isotherms
The Langmuir and Freundlich models were applied to analyze the relationship
between Th4+ concentration and adsorption capacity of ODP-IR. The adsorption
isotherm experiments were investigated by 5mL various initial concentration of Th4+
mixed with 70 mg ODP-IR at 301 K. The Langmuir model[28] assumed that the
surface of adsorbent was uniform and the interaction between adsorbed molecules
were negligible. Hence, equilibrium was attained while the monolayer was saturated.
The linear form of Langmuir model can be expressed by Eq. (9):
(9)
where qe is the amount of metal ion adsorbed at equilibrium (mg/g), qmax and b
are the Langmuir constants related to adsorption capacity and adsorption energy,
respectively. Ce is the equilibrium concentration (mmol/L) of metal ion at solution.
The Freundlich model[29] was an empirical equation which assumed a
heterogeneous surface with a nonuniform distribution of the heat of adsorption over
the surface. The linear form of the Freundlich model can be expressed by Eq. (10):
(10)
where Kf and 1/n are Freundlich constants, represent adsorption capacity and
adsorption intensity of the system, respectively.
3. Results and Discussion
3.1. Characterization of ODP-IR
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With successfully coated by n-ODP in the XAD-7 resin, obvious changes were
happened on the surface morphology of XAD-7 resin. Fig. 3 shows the SEM images
of blank XAD-7 resin (a,b) and ODP-IR (c,d). Unlike the surface of blank XAD-7
resin, the surface of impregnated XAD-7 resin was obviously coated with a
homogeneous film of n-ODP. A reasonable explanation is that both n-ODP and
XAD-7 resin were polar, accordingly, the n-ODP could be effectively impregnated in
the XAD-7 resin by electrostatic interaction[30]
.
Fig. 3. SEM images of blank XAD-7 resin (a,b) and prepared ODP-IR (c,d).
For investigating the effect of impregnated n-ODP in the XAD-7 resin, the
surface areas, pore volumes and pore sizes of blank XAD-7 resin and ODP-IR were
compared. As shown in Table 1, all the parameters of blank XAD-7 resin were
decreased after the impregnation of n-ODP on the XAD-7 resin. The decrease can be
attributed to the filling of mesopore on blank XAD-7 resin by n-ODP, which is
consistent with the SEM images.
Table 1.
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Nitrogen adsorption of blank XAD-7 resin and ODP-IR.
Parameters
Blank XAD-7 resin
ODP-IR
222.55
0.502
Surface area (m2/g)
448.65
0.805
9.96
Pore volume (cm3/g)
Average pore diameter (nm)
8.05
Also, IR spectrum was used to analysis the adsorbent, the characteristic stretching
vibrations of XAD-7 and n-ODP are listed in Table 2.
Table 2.
Characteristic stretching vibrations of XAD-7 and n-ODP.
No.
v (cm-1)
1141
Assignments
XAD-7
C-O stretching vibration of ester
C=O stretching vibration of ester
P=O stretching vibration
1718
n-ODP
1172
1582, 3065
2852, 2923, 2953
Characteristic peaks of benzene
C-H stretching vibration of -CH3
Fig. 4 shows the IR spectra of n-ODP, blank XAD-7 resin and ODP-IR. As shown
in the Fig. 4 (a), the stretching vibrations of 1582 cm-1 and 1172 cm-1 are the
characteristic peaks of benzene and P=O, respectively. Those bands are absent on the
spectra of blank XAD-7 resin but can be observed on the ODP-IR shown by spectrum
(b), (c) and (d). Those spectral features confirm the presence of n-ODP in the
impregnation resin. The stretching vibration of 1718 cm-1 is the characteristic peak of
XAD-7. For spectrum (c) and (d), the bands due to P=O stretching shift from 1182
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cm-1 to 1167 cm-1, suggesting the P=O functional group involved in the coordination
of Th4+ with n-ODP in the ODP-IR.
1167
(d)
(c)
1182
(b)
(a)
1141
3065
2852
2923
1718
2953
1582
1172
4000
3500
3000
2500
2000
1500
1000
500
-1
Wave number (cm )
Fig. 4. IR spectra of (a) n-ODP, (b) XAD-7 resin, (c) ODP-IR and (d) ODP-IR loaded
with Th4+.
3.2. EDS result
EDS is an efficient technique applied in the elemental analysis or chemical
characterization of a sample. Fig. 5 shows the EDS result of ODP-IR before and after
Th4+ adsorption. The red rectangle area in Fig. 5 is the test range. From the obtained
results, it can be easily observed that P element is present in the ODP-IR before and
after Th4+ adsorption. As shown in Fig. 5 (b), the weight percentage of Th4+ is 2.424%.
The EDS results confirm the presence of n-ODP and Th4+ in the ODP-IR after
adsorption. Also, the presence of Pd and Au can be attributed to the pre-processing of
sample.
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Fig. 5. EDS result of ODP-IR before and after Th4+ adsorption.
3.3. Effect of acidity on Th4+ adsorption
In order to reach higher adsorption efficiency, the Th adsorption was studied with
the HNO3 concentration ranging from 0.001 mol/L to 3 mol/L. As shown in Fig. 6, the
blank XAD-7 resin reveals almost no adsorption capacity of Th4+ in the studied range
of HNO3 concentration, while the ODP-IR has a high qe for Th4+. The difference
suggests that the adsorption capacity of Th4+ is due to the ODP rather than bank
XAD-7. Th4+ uptake is significantly affected by changing HNO3 concentration, and
the maximum Th4+ uptake by ODP-IR can be observed at the HNO3 concentration of
0.1 mol/L to 0.5 mol/L. Increasing or decreasing the HNO3 concentration on either
side of the uptake peak result in the decline of Th4+ uptake. The increase of adsorption
capacity can be attributed to the salting-out effect of HNO3[31]. While the
concentration of HNO3 is more than 0.1 mol/L, the decreasing adsorption capacity of
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ODP-IR at higher acidity can be attributed to the competitive adsorption between
proton from HNO3 and Th4+[32]
.
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
n-ODP-IR
Blank XAD-7 resin
0.0
0.5
1.0
1.5
2.0
2.5
3.0
HNO3 (mol/L)
Fig. 6. Effect of HNO3 concentration on the adsorption of ODP-IR and blank XAD-7
resin for Th4+. Cini = 10-4 mol/L, m = 70 mg, contact time = 60 min, T = 301 K.
3.4. Adsorption kinetics
The effect of time on the Th4+ adsorption was studied and the results are shown in
Fig. 7. It is obvious that the adsorption equilibrium can be achieved within 40 min.
Accordingly, 60 min of contacting time was indicated to be enough for the adsorption
experiments.
The pseudo-first-order, pseudo-second-order and intraparticle diffusion models
were used to analyze the adsorption kinetics of Th4+ and their linear plots are shown
in Fig. 8a-c, respectively. Among the applied reaction based kinetic models, the
pseudo-second-order kinetic model provided the best fit. The experimentally obtained
qe revealed high correlation coefficient. Also, the experimentally obtained qe (qe=1.48)
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and the calculated one (qe=1.58) matched well. If the regression of qt versus t0.5 is
linear and passes through the origin in the intraparticle diffusion model, the
adsorption process would be controlled by intraparticle diffusion. As shown in Fig. 8c,
the low correlation coefficients (R2=0.748) and the positive values of L indicate that
the intraparticle diffusion was not the only rate-controlling step.
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
20
40
60
80
100
120
t (min)
Fig. 7. The effect of time on the Th4+ adsorption. Cini = 10-4 mol/L, m = 70 mg, CHNO3
= 0.1 mol/L, T = 301 K.
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Fig. 8. Adsorption kinetic data fitted by pseudo-first-order (a), pseudo-second-order
(b) and intraparticle diffusion (c) model.
3.5. Thermodynamic studies
The thermodynamic parameters were calculated according to Eq. (6)-(8) and the
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results are shown in Table 3. The negative values ofΔG at all the experiment
temperatures indicate that adsorption of Th4+ was a feasibility and spontaneous
process. The weakly decrease ofΔG values with temperature implies that the
adsorption reaction was mildly affected by temperature. It matches well with the
smallerΔH andΔS. The positive value ofΔS reflects a high affinity of the cations for
the adsorbents and an increasing randomness solid-liquide interface during the
adsorption process. The positive value ofΔH implies that the adsorption of Th4+ was
endothermic which fits well with the experiments. One possible explanation of
endothermicity of adsorption heat is that Th4+ ions are solvated, and the Th4+ ions
have to lose part of their hydration sheath for adsorption. This dehydration process of
ions requires energy which offsets the exothemrmicity of the ions getting attach to the
surface[33]
.
Table 3.
Estimation of thermodynamic parameters for the adsorption of Th4+. Cini = 10-4 mol/L.
T (K)
301
311
Kad
ΔG (kJ/mol)
-3.083
ΔH (kJ/mol)
ΔS (J/mol K)
3.429
3.634
3.752
4.071
4.517
25.22
-3.336
321
331
-3.529
-4.071
3.6. Adsorption isotherms
The adsorption equilibrium of metal ions between aqueous solution and the
adsorbent can be described by adsorption isotherm. The results (Fig. 9) indicate that
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the adsorption capacity (qe) increases as the increasing of equilibrium concentration of
Th4+ and reaches a plateau at high concentration representing maximum adsorption
capacity (qmax). In order to explain the adsorption behavior, Langmuir and Freundlich
models were investigated for the adsorption. Langmuir isotherm model is a
representative of monolayer adsorption occurring on an energetically uniform surface
on which the adsorbed molecules are not interactive. Unlike Langmuir, Freundlich
model describes the adsorption on an energetically heterogeneous surface on which
the adsorbed molecules are interactive. As for the Langmuir equation and Freundlich
equation, qmax, b and 1/n, Kf are calculated to be 1.7 mg/g, 15.05 and 0.246, 1.86,
respectively. As indicated by the correlation coefficient (R2), the adsorption is fitted
well with the Langmuir isotherm model than Freundlich isotherm model.
Consequently, the applicability of monolayer coverage chemisorption on the surface
of ODP-IR is more likely for the adsorption of Th4+.
Fig. 9. Adsorption isotherms of ODP-IR. m = 70 mg, CHNO3 = 0.1 mol/L, T = 301 K.
3.7. Desorption and recycling
The reusability is essential for an adsorbent. Several consecutive
adsorption-desorption cycles were performed in this study. 70 mg impregnated
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ODP-IR was equilibrated with 5 mL aqueous phase containing 0.05 mmol/L Th4+. 2
mol/L HCl was chosen as reagent to desorb the Th4+ from the adsorbent. After each
adsorption-desorption step, ODP-IR was washed with deionized water for several
times to remove the residue. As shown in Fig. 10, the adsorbent can be repeatedly
used five times without obvious loss in the initial binding affinity. That is to say, the
ODP could be immobilized on resin without obvious lose for adsorption. Accordingly,
the adsorbent was stabilized within several adsorption-desorption cycles.
Uptake (%)
Elution (%)
100
80
60
40
20
0
1
2
3
4
5
Number of cycle
Fig. 10. The adsorption-desorption cycles of ODP-IR.
3.8. Adsorption of Th, Fe and RE by ODP-IR
Radioactive residue containing Th from RE industry results in serious pollution.
The recovery of valuable RE elements from the residue is important, moreover,
separation of Th from the radioactive residue contributes to providing primary nuclear
fuel for nuclear power industry. In this article, the prepared ODP-IR was used to
separate Th and RE using feed solution from ion-adsorption type RE waste residues.
The feed solution was prepared by digesting roasted RE waste residue at 373 K for 2
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h, evaporating excessive HCl, then diluting by deionized water. As shown in Fig. 11,
ODP-IR reveals almost no adsorption of Fe and RE elements, while the uptake
percentage of Th4+ reaches 64%. That is, the ODP-IR possesses excellent selectivities
for Th over RE and Fe. The decrease of uptake of Th4+ with the increase of HNO3
concentration is consistent with the results mentioned in Fig. 6.
Fig. 11. Adsorption of Th, RE and Fe using feed solution of ion-adsorption type RE
waste residues. CTh4+ = 0.0066 mmol/L, CFe3+ = 4.9 mmol/L, CRE = 0.189 mmol/L. m
= 150 mg, T = 301 K.
4. CONCLUSIONS
In this article, an adsorption material ODP-IR was synthesized and used for the
adsorption of Th4+ from feed solution of ion-adsorption type RE waste residue. The
high selectivity of ODP-IR for Th4+ reveals its potentials in the field of radioactive RE
waste residue treatment, moreover, the novel adsorption material shows the potentials
of Th purification for nuclear power. Adsorption capacity of ODP-IR for Th4+ was
affected by HNO3 concentration strongly and the optimal HNO3 concentration was
0.5mol/L with the maximal adsorption capacity of 1.4mg/g. The adsorption followed
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the second-order model, it was fitted better with the Langmuir isotherm model than
Freundlich isotherm model. SEM, nitrogen adsorption, IR, EDS were used to
investigate the adsorption process of ODP-IR for Th4+. There was no obvious
decrease in adsorption/desorption capacity after five times of adsorption-desorption
cycles. The study reveals importance in the perspectives of RE resource, radioactive
pollution and nuclear power.
Acknowledgements
This work was supported by ‘Hundreds Talents Program’ from Chinese Academy
of Sciences, National Natural Science Foundation of China (21571179), Science and
Technology Major Project of the Fujian Province, China (2015HZ0101).
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Highlights
1. A novel impregnated resin ODP-IR was developed for the separation of Th.
2. ODP-IR was repeatedly used five times without obvious loss for Th4+ adsorption.
3. Thermodynamic parameters for Th4+ adsorption using ODP-IR were discussed.
4. ODP-IR was used to separate Th from ion-adsorption type RE waste residue.
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