Rare earths are the special minerals, which are considered by many
countries in the world and classified on material grade that can’t be
replaced because they have many special properties. Rare earth elements
play a very important role in development of high-tech fields, such as:
electricity, electronics, optics, lasers, superconductors materials and
luminescent materials.
Thus, the title of dissertation was proposed: “Study on the synthesis
and application of polymers containing suitable funtional groups for
seperation some light rare earth elements”, to study on synthesize,
characterization and application of polymers for sorption some light rare
earth elements
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MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ACADEMY OF
SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY
-----------------------------
HOANG THI PHUONG
STUDY ON THE SYNTHESIS AND APPLICATION OF
POLYMER CONTAINING SUITABLE FUNTIONAL GROUPS
FOR SEPERATION SOME LIGHT RARE EARTH ELEMENTS
NGƯỜI H Scientific Fied: Organic Chemistry
Classification Code: 9.44.01.14
S. Nguyễn
Văn Khôi
DISSERTATION SUMMARY
HA NOI - 2018
The dissertation was completed at:
Institute of Chemistry
Vietnam Academy of Science and Technology
Scientific Supervisors:
1. Prof. Dr. Nguyen Van Khoi
Institute of Chemistry – Vietnam Academy of Science and
Technology
2. Dr. Trinh Duc Cong
Institute of Chemistry – Vietnam Academy of Science and
Technology
1st Reviewer : .
2nd Reviewer: .
3rd Reviewer: .
The dissertation will be defended at Graduate University of Science
and Technology, Vietnam Academy of Science and Technology, 18
Hoang Quoc Viet, Cau Giay District, Ha Noi City.
At hour.date.month.2018
The dissertation can be found in National Library of Vietnam and the
library of Graduate University of Science and Technology, Vietnam
Academy of Science and Technology.
1
INTRODUCTION
1. Background
Rare earths are the special minerals, which are considered by many
countries in the world and classified on material grade that can’t be
replaced because they have many special properties. Rare earth elements
play a very important role in development of high-tech fields, such as:
electricity, electronics, optics, lasers, superconductors materials and
luminescent materials.
Thus, the title of dissertation was proposed: “Study on the synthesis
and application of polymers containing suitable funtional groups for
seperation some light rare earth elements”, to study on synthesize,
characterization and application of polymers for sorption some light rare
earth elements.
2. Objectives of the dissertation
Successfully synthesis polymers containing suitable funtional groups
to seperate the light rare earth element (La, Nd, Pr, and Ce); evaluted the
efficiency of polymers on seperating light rare earth element; evaluated the
ability of polymers on separating each of the rare earth metal ions on the
ion exchange column.
3. Main contents of dissertation
- Synthesis polymers containing suitable funtional group for the
separation of the rare earth elements:
+ Synthesis poly(hydroxamic acid) from acrylamide (PHA-PAM).
+ Synthesis poly(hydroxamic acid) from acrylamide and vinyl
sulfonate (PHA-VSA).
- Studied on adsorption, desorption process; and evaluted the ability
of two polymers on adsorpting some light rare earth metal ions (La3+, Ce4+,
Pr3+ and Nd4+).
- Studied and evaluted the capable of PHA resin on seperating some
light rare earth elements (La3+, Ce4+, Pr3+ and Nd4+).
4. Structure of the thesis
The dissertation has 138 pages, including the literature review,
experiment, results and discussions, conclusions, pubblication, with 45
2
images, 45 tables and 114 references.
B. CONTENTS OF DISSERTATION
CHAPTER I. LITERATURE REVIEW
An overview of domestic and foreign publications on rare earths,
methods for seperate light rare earth metal ions; overview researchs on
synthesis and application of polymers containing suitable funtional groups
to separate rare earth metal ions. From there, the research orientation of the
dissertation were proposed.
CHAPTER II. EXPERIMENTAL
2.1. Materials and equipments
2.1.1. Materials
Acrylamide (AM), Sodium vinyl sulfonate (VSA), Ammonium
persulfate; N, N’ - methylene bisacrylamide hydroxylamine hydrochloride
(HA); Span 80, Paraffin oil, diesel oil, Dowex HCR-s resin, Amberlite IR
120 resin, standard solution: La(NO3)3, Ce(NO3)3, Pr(NO3)3, Nd(NO3)3;
solution which contain light rare earth metal ions with content: La3+ 36.76
wt%, Ce4+ 47.79 wt%, Pr3+ 4.41 wt%, Nd3+ 11.03 wt% was seperated and
provided by Institute for Technology of Radioactive and Rare Elements,
Vietnam.
Chemicals for analysis: distilled water, NaOH, NaHCO3,HCl, H2SO4,
CH3OH,C2H5OH, C20H14O4, HNO3, C6H14, CHCl3, H2C2O4, CH3COOH,
CH3COONa were used without purification.
2.1.2. Equipments
Equipments for suspension polymerization with three-liter of
volume, ion exchange column, vacum dry cabinet, thermostatic tank,
analytical balance, magnetic stirrer instrument, thermometer, flasks, the
condenser system, triangular flasks, pipette,...IR spectrometer, Perkin
Elmmer emission spectrometer, thermogravimetric analyze instrument,
FESEM scanning electron microscope, pH measuring equipment.
2.2. Methods
2.2.1. Synthesis poly(hydroxamic acid) based on acrylamide
Processes of synthesize cross-linking polyacrylamide (PAM gel) and
3
synthesize poly(hydroxamic acid) (PHA) based on cross-linking
polyacrylamide were presented in figure 2.4-2.6.
Figure 2.4. Synthesis of PAM-gel
Figure 2.6. Sythesis of poly(hydroxamic axit) based on modification of
Filtered
- Acrylamide: C%
- MBA
- APS
Dispersed Phase
V2 (ml)
Continuous Phase
V1 (ml)
- Diesel
- Span 80
Feed speed:
10ml/min
Reaction flask
with 3 liters of
volume
Cross-linking PAM
Washed by n-
hexane
Cross-linking PAM
(granulate form with
same size)
Dried at 60oC
long in 5 hours
Invesstigated the
factors:
- AM Concentration
- Temperature and time
- Content of MBA
- Content of ABS
- Content of Span 80
- The stirrier speed
- Monomer phase/oil
phase ratio
PAM-gel
(10 g PAM + 50 g H2O)
Add NH2OH.HCl solution with
concentration: 1-3.5 M, pH:10-14
Stirred: 100 rpm
Time: 30 minutes
Reation mixture: temperature
T (oC), time t (min)
Filtered Washed by water to
pH=7
Dried: 60oC, in 5 hours
Polyhydroxamic acid
(granulate form had similar
size and light yellow of colour)
Reaction flask
with 3 liters of volume
Invesigated the
factors
- Temperature and time
of reation
- pH of medium
-Concentration of
NH2OH.HCl
4
PAM-gel
2.2.2. Synthesis poly(hydroxamic acid) from acrylamide and sodium
vinyl sulfonate
2.2.2.1. Co-polymerization process of acrylamide and sodium vinyl sulfonate
To investigated the coefficient of copolymerization process,
controlled the conversion of reactions ≤ 10% (by reacting at very low
concentration condition, experimented several times to conversion reached
≤ 10%). Synthesis 5 samples of copolymer with difference of VSA/AM
molar ratio: 10/90, 30/70, 50/50, 60/40, 70/30 and 90/10; other conditions
of reaction didn’t change.
2.2.2.2. Synthesis cross-linking P(AM-co-VSA) by suspension
polymerization
Process of synthesize cross-linking P(AM-co-VSA) was similar the
suspension polymerization of AM; monomer were AM and VSA with
VSA/AM weight ratio was 60/40.
2.2.2.3. Modification of P(AM-co-VSA) to poly(hydroxamic acid)
modified processes of copolymer of AM and VSA (P[AM-co-VSA]-
gel) were carried out similarly the modification of PAM-gel to PHA-PAM.
2.2.3. Adsorption and de-adsorption the rare earth matal ions by PHA-PAM
and PHA-VSA
Adsorption: take 0.15 g PHA-PAM (or PHA-VSA) to reation flask
containing 50 ml each of ion solution: La3+, Ce4+, Pr3+ and Nd3+ with
research concentration, strirred at room temperature. After reation time,
measured the remaining concentration of each metal ion in solution using
ICP-OES method.
* Investigated the factors that effect on adsorption process: pH, time,
initiator concentration of metal ions.
* Adsorption isotherms: From the results obtained when investigated
of factors on the adsorption process, Langmuir isotherm models was
constructed.
2.2.4. Studied on desorption and repeated use of poly(hydroxamic acid) resin
Conducted six adsorption - desorption cycles using 0.15g of
adsorbent material. After each cycle, measured the percentage of metal
adsorbed, the percentage of metal desorbed and the loss weight of
5
absorbent.
2.2.5. Absorbed the light rare earth ions on column by PHA-PAM
Process of seperation light rare earth metal ions was showed in figure
2.8
Figure 2.8. Process of seperation light rare earth metal ions from rare earth
metal solution by PHA resin
CHAPTER III. RESULTS AND DISCUSSION
3.1. Study on synthesis of poly(hydroxamic acid) based on acrylamide
3.1.1. Study on synthesis of cross-linked polyacrylamide (PAM-gel)
Eluted by
HCl: 0,6M
Eluted by
HCl: 0,1M
Eluted by
HCl: 0,2M
Eluted by
HCl: 0,4M
Light rare earth metal ions composition:
La3+, Nd3+, Pd3+ và Ce4+
- Concentration: 500mg/l
-pH=6; acetate buffer: 0.5 M
Ion exchange column
- Dcolumn : 20mm
- Lcolumn : 800mm
- Lresin : 500mm
Quantitative pump
- : 130 ml/minute
Adsorbed in 180 minutes Washed with HCl 0.5M
- Flow: 3-7 ml/minute
- Vr/Vn: 3/1 – 18/1
Nd3+
rich fraction
Pd3+
rich fraction
Ce4+
rich fraction
Adsorbed and desorped each fraction on ion exchange column
6
In this study, the continuous phase used was diesel oil. Factors
influencing product properties were investigated such as temperature (70-
95oC) and time (60-240 min), monomer concentration (15-35%), APS
concentration (0, 5-1.75), crosslinker concentration (7-11%), monomer /
oil phase ratio (1 / 5-1 / 3), surfactant span 80 concentration (0.1-0, 35)
and stirring speed (200-400 rpm). The results are presented in tables 3.1-
3.6)
Table 3.1. Effect of temperature and reaction time on characterization of
PAM-gel
Temp. (oC)
Time
(min)
Gel1
(%)
D2TB
(m)
Product characteristics
70
180 91,4 - Granular, block
240 95 - Granular, block
80
60 94,8 ~ 180 Granular, block
90 98,6 187 Discrete round granular
90 60 99,5 230 Discrete round granular
95 60 - - block
Reaction efficiency reached the maximum value at 90oC, 60 minutes.
Thus, the condition of 90oC and 60 minutes was chosen as the reaction
condition for the next study.
Figure 3.1. Effect of monomer concentration and reaction time on gel
content of PAM-gel
When the monomer concentration increases from 15% to 30%, the
gel content increases and the reaction time decreases. However, when
monomer concentration is high (35% sample), the polymerization process
is very fast, difficult to control the reaction process. Therefore, 30%
monomer was chose for optimal reaction temperature and time.
1Gel content of products
2 Average granular diameter of the product
0 20 40 60 80 100
G
el
c
o
n
te
n
ts
(
%
)
Time (min)
35%
30%
25%
20%
15%
7
Table 3.2. Effect of initiator concentration on gel content and swelling
capacity of PAM-gel
KPS concentration, % 0,5 0,75 1,0 1,25 1,5 1,75
Gel content, % 93,2 96,8 99,5 98,4 98,0 97,3
Swelling capacity, g/g 3,2 3,9 4,7 4,2 3,8 3,6
Results showed that the optimum KPS concentration for PAM-gel
synthesis was 1.0%.
Table 3.3. Effect of crosslinker concentration on swelling capacity and
gel content of PAM-gel
MBA concentration (%) 7 8 9 10 11
Swelling capacity (g/g) 6,2 5,8 5,5 4,7 4,1
Gel content (%) 98 98 98,4 99,5 99,5
Increasing of crosslinker concentration from 7 to 11%, reduce the
swelling capacity from 6,2 to 4,1 g/g. Chosen MBA content is 10% for
next study.
Table 3.4. Effect of ratio of monomer/oil phase on particle
characteristics
Ratio of
monomer/oil
phase
Average diameter of
granular` DTB(m)
Characteristics and
separability of granular
1/5 225 Round granules, evenly
1/4 230 Round granules, evenly
1/3 - partially blocked
At a monomer/oil phase ratio of 1/4, the granulation process is better,
distributing the particle size more uniformly than the rest.
Table 3.5. Effect of suspension stabilizer on particle characteristics
Span 80
content (%)
Gel content
, %
Average
diameter of
granular
DTB(m)
Characteristics and
separability of particles
0,10 99,2 - Unround granules, block
0,20 99,6 - Unround granules, block
0,30 99,5 230 Round granules, evenly
0,35 98,5 - Granular and partially
emulsified
8
Results in table 3.5 showed that, with 0,3% span 80, product are
round granules, evenly.
Table 3.6. Effect of stirring speed on particle size distribution
Stirring speed
(rpm)
Particle size distribution (%)
500(m)
200 7 55 38
300 4 92 4
400 38 57 5
With 300 rpm, the product is more uniform, with a particle size of
100-500m is 92% (Average diameter of granular is about 230 m).
Thus, the optimal conditions for PAM-gel synthesis are: Reaction
temperature 90oC for 60 minutes, 30% of monomer, 10% of crosslinker (in
monomer), 1% of initiator, 0,3% of Span 80 at 300 rpm and ¼ of the phase
ratio monomer/oil.
+ Characteristic of PHA-gel: Particle size distribution with D ~230
µm, swelling capacity: 4.7 g/g and gel content of 99.5%.
3.1.2. Sythesis of poly(hydroxamic axit) based on modification of PAM-gel
To study the modification of PAM-gel into poly(hydroxamic acid)
(PHA-PAM) by hydroxylamine, PAM-gel are 100-500 µm in size,
humidity <58%. Study on factors affacting the modification of acrylamide
group to hydroxamic acid group such as temperature (25-40oC), time (0-24
hours), pH (pH=10-14) and concentration of NH2OH.HCl (1.0-3.5M). The
results are shown in figure 3.6 and tables 3.9-3.10.
Figure 3.6. Effect of reaction temperature and time on funtional group
content
When the temperature increases form 250C to 300C, -CONHOH
content increases from 9,8 to 11,4 mmol/g after 24h.
Table 3.9. Effect of pH on funtional group content
pH -CONH2 (mmol/g) - COOH (mmol/g) - CONHOH (mmol/g)
0
2
4
6
8
10
12
0 6 12 18 24
-C
O
N
H
O
H
(
m
m
o
l/
g
)
Time (hrs)
25 0C
30 0C
40 0C
9
10 12,93 1,25 1,14
11 12,57 1,50 1,25
12 8,54 1,75 5,03
13 3,94 1,70 9,68
14 2,30 1,68 11,34
Table 3.9 shows that the pH in the 10-11 range, the modification is
very slow (low -CONHOH content). In the pH range of 12-14, the content
of -CONHOH group increased gradually and reached the maximum value
at pH=14.
Table 3.10. Effect of NH2OH.HCl concentration on funtional group
content
NH2OH.HCl
Concentration
(M)
-CONH2
(mmol/g)
-COOH
(mmol/g)
-CONHOH
(mmol/g)
1,0 5,38 1,45 8,49
2,0 4,39 1,57 9,36
3,0 3,09 1,61 10,62
3,3 2,30 1,68 11,34
3,5 2,26 1,72 11,34
Table 3.10 shows that at the concentration of NH2OH.HCl 3.3M, the
content of -CONHON group is the highest.
➢ Physical and chemical characteristics of PHA-PAM
Characteristic properties of PHA-PAM are evaluated by FTIR
spectroscopy, thermo gravimetric analysis (TGA), scanning electron
microscopy (SEM). The results are shown in Tables 3.11-3.12 and Figures
3.9-3.10.
Table 3.1. FTIR characteristic of groups in PHA-PAM
Wavenumber (cm-1) Bending Funtional group
3436-3190 N-H, -OH Amine (-NH2), -COOH
2928 C-H Alkyl (-CH2)
2857 C=N -CONHOH (enol form)
1668 C=O Cacbonyl (-C=O)
1009 N-O -CONHOH
10
Hình 3.9. TGA curves of PHA-PAM Hình 3.10. SEM image of
PHA-PAM
Table 3.12. The PHA-PAM thermal analysis data
Stage Range of temp. oC TMax, oC Loss weight, %
1 Tp-220 186 9,33
2 220-340 307 17,81
3 340-450 385 35,15
The optimal conditions for the modification of PAM-gel into PHA-
PAM are 3.3 M hydroxylamine hydrochloride, at 30oC for 24 hours at pH
14. PHA-PAM contains -CONH2 group content of 2.3 mmol/g, -COOH
group 1.68 mmol/g and -CONHOH group 11.34 mmol/g.
3.2. Synthesis of poly(hydroxamic axit) based on acrylamide and
sodium vinyl sulfonate
3.2.1. Copolymerization of acrylamide và sodium vinyl sulfonate
3.2.1.1. Effect of reaction temperature, time and initiator concentration
The temperatures were studied 65, 70, 75oC, time range of 60-24
minutes, initiator concentration: 0,5; 0,75; 1; 1,2%. The results are shown
in figure 3.11-3.12.
11
Figure 3.10. Effect of reaction
temperature and time on
conversion
Figure 3.11. Effect of initiator
cocentration on conversion
The react condition was chosen: temp. 70oC, time 180 minutes and
1% initiator.
3.2.1.2. Determine the reactivity ratios of monomers
Determination of intermediate coefficients and in the Kelen-
Tudos equation. The results are shown in Table 3.14.
Table 3.14. Determination of coefficients và
Mẫu
M1 0,111 0,175 0,07 -0,52
0,88
0,07 -0,55
M2 0,429 0,630 0,29 -0,25 0,25 -0,21
M3 1,000 1,070 0,93 0,07 0,51 0,04
M4 1,500 1,580 1,42 0,55 0,97 0,40
M5 2,333 2,380 2,29 1,35 0,72 0,43
M6 9,000 7,310 11,08 7,77 0,93 0,65
From equation = 1,3883 – 0,6197 with α = 0,88 extrapolation to
= 0 so rVSA = 0,547, = 1 so rAM = 0,768.
3.2.2. Copolymerization of acrylamide and sodium vinyl sulfonate by
suspension polymerization
In this study, continuous phase is diezen oil. Factors influencing
product properties were investigated such as temperature (70-90oC) and
time (60-240 min), monomer concentration (4,63-40%), APS
concentration (0, 5-1.75), crosslinker concentration (7-11%), monomer /
oil phase ratio (1 /5-1/3), surfactant span 80 concentration (0.1-0, 35) and
stirring speed (200-400 rpm). The results are presented in tables 3.15-3.20)
0
20
40
60
80
100
0 60 120 180 240
C
o
n
v
er
si
o
n
(
%
)
Time (min)
65 oC
70 oC
75 oC
0
20
40
60
80
100
0 60 120 180 240
0,50%
0,75%
1,00%
1,20%C
o
n
v
er
si
o
n
(
%
)
Time (min)
x
M
M
=
][
][
2
1
y
Md
Md
=
2
1
y
x
F
2
=
y
yx
G
)1( −
=
maxminFF=
F
F
+
=
F
G
+
=
12
Table 3.15. Effect of reaction time and temperature
Temp.
(oC)
Time
(phút)
Gel3
(%)
D4TB
(m)
Characteristics of product
700C
180 93 - Granular, block
240 100 175 Granular, unblock
800C
60 - - Granular, adhesive
90 100 230
Even round granules,
separately
900C 60 100 232
Even round granules,
separately
Table 3.16. Effect of crossliker concentration on gel content and
swelling capacity of copolymer P[AM-co-VSA]
MBA concentration (%) 7 8 9 10 11
Gel content, (%) 99 99 99 99 99
Swelling capacity (g/g) 12,6 9,5 7,2 5,4 4,3
Table 3.17. Effect of monomer concentration on product characteristics
Monomer
concentration
(%)
Gel5
(%)
Time
D6TB
(m)
Product characteristics
4,63 100 180 85 Small granules
10 100 150 115 Small granules
20 100 90 175 granularly
30 100 60 232
Even round granules,
separately
40 100 50 325 Uneven granules, separately
Table 3.18. Effect of monomer/oil ratio
Ratio of
monomer/oil
Average granular
diameter DTB(m)
Product characteristics
1/5 215 Round granules, good
dispersion
1/4 232 Round granules, good
dispersion
1/3 - Partially blocked
3Gel content of products
4 Average granular diameter of the products
5 Gel content of products
6 Average granular diameter of the products
13
Table 3.19. Effects of surfactant span 80 concentration
Span 80 (%) Average granular
diameter DTB(m)
Product characteristics
0,10 - Unround granules
0,20 - Unround granules
0,30 232 Evenly, round granules
0,35 - Granular and partially suspenion
Table 3.20. Effect of stirring speed
Mix speed
(rpm)
Gel content (%) Average granular diameter DTB(m)
500
200 >99 8 50 42
300 >99 5 90 5
400 >99 45 50 5
The result was a optimum synthetic condition: reaction temperature
90oC for 60 minutes, 30% of monomer, 8% of crosslinker (in monomer),
0,3% of Span 80 at 300 rpm.
3.2.3. Sythesis of poly(hydroxamic axit) based on modification of P[AM-
co-VSA]
In this study, Study on factors affacting the modification of P(AM-
co-VSA) to poly(hydroxamic acid) (PHA-VSA) were investered such as
temperature (25-50oC), time (0-24 hours), pH (pH=10-14) and
concen