# Preparation of Poly(Hydroxamic Acid) for Separation of Zr/Y, Sr

Authors: Khaled F. Hassan; Shaban A. Kandil; Hossam M. Abdel-Aziz; Tharwat Siyam
Journal: Chromatography Research International
 (2011)

---

## Abstract

Poly(hydroxamic acid) resin (PHA) was prepared by modification of polyacrylamide
(PAAm) prepared throughγ-irradiation technique and used for the first
time in separation of Zr(IV) from Y(III) and Sr(II) as a simulation mode for the
purification of 89Zr from its parents (Y or Sr). The adsorption
behaviors of zirconium, yttrium, and strontium on the prepared PHA resin in
different media, namely, hydrochloric acid, acetate buffer, and citrate buffer
were studied as a function of pH. In addition, in cation-exchange column
chromatography experiments using PHA, three different eluants, namely,
10
−
5 mol/L HCl, acetate buffer pH 3.5, and
2 mol/L HCl, were employed for elution of Zr(IV), Y(III) and Sr(II),
respectively, where Zr(IV), Y(III) and Sr(II) were eluted in amounts of
80%, 99.9%, and 100%, respectively. The purification process of
Y(III) from Zr(IV) was carried out using regenerated PHA.


---

## Body

## 1. Introduction

Hydroxamic acids have been known for their chelation ability with heavy metals. They
have been found to be effective chelating ligands with the ions such as
V5+, Fe3+, Mo6+, Ti4+,
Hg2+, Cu2+, and UO22+ [1]. Number of chelating polymers, containing
hydroxamic acid group, have been prepared from various starting materials using
different methods. Poly(hydroxamic acid) was synthesized from polyacrylamide at
different conditions [2–5]. They have been known for various analytical
applications. For example, extraction and purification of uranium [6], extraction and separation of gold and silver
[7], separations of iron from copper,
nickel, and cobalt [8], copper from lead
[9], uranium from neodymium [10], and cobalt from copper and nickel [11]. Also a preliminary study on application of
sago starch-based poly(hydroxamic acid) resin for extraction of lanthanide group
elements (La3+, Dy3+, Pr3+, Ce3+,
Nd3+, Gd3+, Eu3+, and Tb3+) from
aqueous media was done by using batch technique [12]. The chelating polymer materials are mainly used in analytical,
industrial and radiochemical laboratories [12].One of the main tasks of radiochemical laboratories is the purification of
radionuclides from their matrix. The medical interest radionuclides such asβ+ emitters have been developed [13]. One of them, 89Zr
(T
1
/
2
=
78 h), can be produced by either of two routes,
namely, alpha irradiation of strontium [14]
or proton irradiation of yttrium [15]. For
radiochemical purification of zirconium from yttrium and strontium, early studies
were based on the solvent extraction and the ion-exchange chromatography [16–18], but only a limited extent of purification is still there. Here, in
this study, the Poly(hydroxamic acid) resin (PHA) will be prepared by modification
of polyacrylamide (PAAm) (that was prepared through
γ-irradiation technique) and will be used for the first time
in separation of Zr from Y and Sr as a simulation mode for promising rise in
purification of 89Zr from its parents (Y and Sr).


## 2. Experimental

### 2.1. Chemicals and Reagents

Acrylamide used in this study was obtained from Merck (Darmstadt, Germany).
N,N-methylene-bis-acrylamide (NMBA) was used as a crosslinking agent, and it was
obtained from Sigma-Aldrich (St. Loius, MO, USA). Hydrochloric acid and sodium
hydroxide were used to adjust the pH of the medium were obtained from Merck,
hydroxylamine hydrochloride from Fluka (Buchs, Switzerland).
Y2O3 99.97% from Koch-Light Laboratories Ltd,
(Cambridge, England); zirconyl chloride octahydrate
ZrOCl2·8H2O 98% (Aldrich); strontium
carbonate 99.99% from Alfa Aesar Co., Karlsruhe, Germany). Other chemicals
used were of analytical reagent grade.


### 2.2. Instrumentation

The content of the separated material was determined via inductively coupled
plasma optical emission spectrometry (ICP-OES) using the system ULTIMA2 ICP,
Jobin Yvon S. A., France. The specifications of the device and operating
conditions are given in Tables1 and
2, respectively.Table 1
Specifications of the ULTIMA 2 ICP spectrometer.
Parameter
Specification
Optical mounting
Czerny-Turner
Far UV option
Yes
Focal length
1 m
Gratings: number of grooves
per mm
2400 g/mm
Resolution
5 pm
120–320 nm10 pm
320–800 nm
Thermoregulation
32
±
0.1 °C
Type of generator
40.68 MHz, Solid
state
Torch
VerticalTable 2
Operating conditions.
Parameter
Condition
Rf-power
1000 W
Plasma gas flow rate
12 L/min
Auxiliary gas flow
rate
0 L/min
Sheath gas flow rate
0.2 L/min
Nebulizer flow
0.8 L/min at
3 bars
Type of nebulizer
Glass concentric
Type of spray chamber
Glass cyclonic
Argon humidifier
Yes
Injector tube diameter
3 mm
Sample uptake
1 mL/min
Emission lines for
Zr
339.198
Sr
216.596
Y
319.561


#### 2.2.1. Gamma Cell

A cobalt-60 gamma cell of type MC-20 (Russia) was used as irradiation source,
with a dose rate of 2 KGy h−1; it has two chambers of 5
liters.


#### 2.2.2. FT-IR Analysis

Infrared spectra of polymer samples with KBr pellets were obtained from FT-IR
spectrometer (Bomen, Hartman & Borunz spectrometer, Model MB 157,
Canada).


### 2.3. Preparation of Poly(Hydoxamic Acid)

Crosslinked Polyacrylamide (PAAm) was prepared by radiation-induced
polymerization of acrylamide monomers in aqueous solution in the presence of
(NMBA) as a crosslinking agent [19].
About 10 g of acrylamide and 1 g of (NMBA) were dissolved in
100 mL distilled water. The mixture was transferred into glass ampoules
and nitrogen gas was purged into the ampoules to remove air from the solution.
The glass ampoules were sealed and then subjected to 60Co
γ-rays at a dose rate of
2 kGyh−1. After irradiation, the crosslinked
obtained polymers were cut into small pieces that were washed in acetone for
removal of unreacted monomers then dried and stored. The percent conversion was
determined gravimetrically and was about 90%.For preparation of PHA in hydrogen form [20], the solution of a calculated amount of hydroxylamine
hydrochloride and solution of sodium hydroxide were added to a suspension of dry
crosslinked PAAm. The resulting mixture was stirred for 5 min at the room
temperature. The reaction was continued for 6 h at 70°C. Ammonia was
liberated during the reaction. After completion of the reaction, the resin was
separated from the solution by filtration and washed several times with water.
Then, the resin was treated with 3 mol/L HCl solution for at least 5 min.
Finally, the resin was filtered and washed several times with water till it is
chlorine-free, and then dried at 50°C to a constant weight.


### 2.4. Batch Experiments

For separation of Zr(IV) from both Y(III) and Sr(II), it is necessary to
determine the distribution coefficient. A stock solution of 5000 mg/L of
each zirconium, yttrium, and strontium (strontium was only dissolved in a cold
HCl) was prepared by dissolving in a hot concentration HCl solution. The
solution was evaporated to incipient dryness, and the residue dissolved in
100 mL of double distilled water. To 100μL
of this solution, 4.9 mL different concentrations of HCl or other mediums
such as 0.1 mol/L of citrate buffer or 0.1 M of acetate buffer at
variable pH were added to a fixed weight of resin (50 mg). The contents
were shaken for 2 hours to attain equilibrium. From the separated two phases
(solid and liquid), the distribution coefficient (K
d) was obtained using the following equation
[21]:(1)K
d
=
C
ads
C
unads
×
V
m
, where C
ads is the concentration sorbed on the
resin,C
unads is the remaining concentration in solution,
V is the volume of the aqueous phase in mL, and m
is the mass of the resin in grams. For all batch experiments, determination of
zirconium, yttrium, and strontium concentrations will be measured by using
inductively coupled plasma optical emission spectrometry (ICP-OES).


### 2.5. Cation-Exchange Column Chromatography

An extensive study for separation of Zr(IV) from both Y(III) and Sr(II) via PHA
resin using different eluants, namely, 10−5 mol/L HCl,
acetate buffer, and 2 mol/L HCl was carried out in this work.A 100 mL stock solution containing 100 ppm of each Zr, Y, and Sr
dissolved in 10−5 mol/L HCl was loaded onto a glass
column, 22 cm long × 1.5 cm in diameter, packed with PHA with
depth of 2 cm. Quartz wool was put at the top exchanger to prevent
disturbance of the adsorbent particles during addition of solution and to
regulate flow of solutions through the column. A 1 mL stock sample was
retained as a control. Load samples were taken to test for breakthrough during
this step. Inductively coupled plasma (ICP) analysis of the load samples showed
no breakthrough of Y and Sr from the column while Zr passes through. The column
was washed with further 50 mL of the same loading solution (without
metals). About 150 mL of 0.1 mol/L acetate buffer with pH 3.5 and
flow rate (~1.5 mL/min) was used for the elution process of Sr. The
samples were collected (~16.5 mL); a total of 9 samples were
collected and analyzed by ICP. To remove the Y, about 150 mL of
2 mol/L HCl was used. The details of the separation process will be given
below.


## 2.1. Chemicals and Reagents

Acrylamide used in this study was obtained from Merck (Darmstadt, Germany).
N,N-methylene-bis-acrylamide (NMBA) was used as a crosslinking agent, and it was
obtained from Sigma-Aldrich (St. Loius, MO, USA). Hydrochloric acid and sodium
hydroxide were used to adjust the pH of the medium were obtained from Merck,
hydroxylamine hydrochloride from Fluka (Buchs, Switzerland).
Y2O3 99.97% from Koch-Light Laboratories Ltd,
(Cambridge, England); zirconyl chloride octahydrate
ZrOCl2·8H2O 98% (Aldrich); strontium
carbonate 99.99% from Alfa Aesar Co., Karlsruhe, Germany). Other chemicals
used were of analytical reagent grade.


## 2.2. Instrumentation

The content of the separated material was determined via inductively coupled
plasma optical emission spectrometry (ICP-OES) using the system ULTIMA2 ICP,
Jobin Yvon S. A., France. The specifications of the device and operating
conditions are given in Tables1 and
2, respectively.Table 1
Specifications of the ULTIMA 2 ICP spectrometer.
Parameter
Specification
Optical mounting
Czerny-Turner
Far UV option
Yes
Focal length
1 m
Gratings: number of grooves
per mm
2400 g/mm
Resolution
5 pm
120–320 nm10 pm
320–800 nm
Thermoregulation
32
±
0.1 °C
Type of generator
40.68 MHz, Solid
state
Torch
VerticalTable 2
Operating conditions.
Parameter
Condition
Rf-power
1000 W
Plasma gas flow rate
12 L/min
Auxiliary gas flow
rate
0 L/min
Sheath gas flow rate
0.2 L/min
Nebulizer flow
0.8 L/min at
3 bars
Type of nebulizer
Glass concentric
Type of spray chamber
Glass cyclonic
Argon humidifier
Yes
Injector tube diameter
3 mm
Sample uptake
1 mL/min
Emission lines for
Zr
339.198
Sr
216.596
Y
319.561


### 2.2.1. Gamma Cell

A cobalt-60 gamma cell of type MC-20 (Russia) was used as irradiation source,
with a dose rate of 2 KGy h−1; it has two chambers of 5
liters.


### 2.2.2. FT-IR Analysis

Infrared spectra of polymer samples with KBr pellets were obtained from FT-IR
spectrometer (Bomen, Hartman & Borunz spectrometer, Model MB 157,
Canada).


## 2.2.1. Gamma Cell

A cobalt-60 gamma cell of type MC-20 (Russia) was used as irradiation source,
with a dose rate of 2 KGy h−1; it has two chambers of 5
liters.


## 2.2.2. FT-IR Analysis

Infrared spectra of polymer samples with KBr pellets were obtained from FT-IR
spectrometer (Bomen, Hartman & Borunz spectrometer, Model MB 157,
Canada).


## 2.3. Preparation of Poly(Hydoxamic Acid)

Crosslinked Polyacrylamide (PAAm) was prepared by radiation-induced
polymerization of acrylamide monomers in aqueous solution in the presence of
(NMBA) as a crosslinking agent [19].
About 10 g of acrylamide and 1 g of (NMBA) were dissolved in
100 mL distilled water. The mixture was transferred into glass ampoules
and nitrogen gas was purged into the ampoules to remove air from the solution.
The glass ampoules were sealed and then subjected to 60Co
γ-rays at a dose rate of
2 kGyh−1. After irradiation, the crosslinked
obtained polymers were cut into small pieces that were washed in acetone for
removal of unreacted monomers then dried and stored. The percent conversion was
determined gravimetrically and was about 90%.For preparation of PHA in hydrogen form [20], the solution of a calculated amount of hydroxylamine
hydrochloride and solution of sodium hydroxide were added to a suspension of dry
crosslinked PAAm. The resulting mixture was stirred for 5 min at the room
temperature. The reaction was continued for 6 h at 70°C. Ammonia was
liberated during the reaction. After completion of the reaction, the resin was
separated from the solution by filtration and washed several times with water.
Then, the resin was treated with 3 mol/L HCl solution for at least 5 min.
Finally, the resin was filtered and washed several times with water till it is
chlorine-free, and then dried at 50°C to a constant weight.


## 2.4. Batch Experiments

For separation of Zr(IV) from both Y(III) and Sr(II), it is necessary to
determine the distribution coefficient. A stock solution of 5000 mg/L of
each zirconium, yttrium, and strontium (strontium was only dissolved in a cold
HCl) was prepared by dissolving in a hot concentration HCl solution. The
solution was evaporated to incipient dryness, and the residue dissolved in
100 mL of double distilled water. To 100μL
of this solution, 4.9 mL different concentrations of HCl or other mediums
such as 0.1 mol/L of citrate buffer or 0.1 M of acetate buffer at
variable pH were added to a fixed weight of resin (50 mg). The contents
were shaken for 2 hours to attain equilibrium. From the separated two phases
(solid and liquid), the distribution coefficient (K
d) was obtained using the following equation
[21]:(1)K
d
=
C
ads
C
unads
×
V
m
, where C
ads is the concentration sorbed on the
resin,C
unads is the remaining concentration in solution,
V is the volume of the aqueous phase in mL, and m
is the mass of the resin in grams. For all batch experiments, determination of
zirconium, yttrium, and strontium concentrations will be measured by using
inductively coupled plasma optical emission spectrometry (ICP-OES).


## 2.5. Cation-Exchange Column Chromatography

An extensive study for separation of Zr(IV) from both Y(III) and Sr(II) via PHA
resin using different eluants, namely, 10−5 mol/L HCl,
acetate buffer, and 2 mol/L HCl was carried out in this work.A 100 mL stock solution containing 100 ppm of each Zr, Y, and Sr
dissolved in 10−5 mol/L HCl was loaded onto a glass
column, 22 cm long × 1.5 cm in diameter, packed with PHA with
depth of 2 cm. Quartz wool was put at the top exchanger to prevent
disturbance of the adsorbent particles during addition of solution and to
regulate flow of solutions through the column. A 1 mL stock sample was
retained as a control. Load samples were taken to test for breakthrough during
this step. Inductively coupled plasma (ICP) analysis of the load samples showed
no breakthrough of Y and Sr from the column while Zr passes through. The column
was washed with further 50 mL of the same loading solution (without
metals). About 150 mL of 0.1 mol/L acetate buffer with pH 3.5 and
flow rate (~1.5 mL/min) was used for the elution process of Sr. The
samples were collected (~16.5 mL); a total of 9 samples were
collected and analyzed by ICP. To remove the Y, about 150 mL of
2 mol/L HCl was used. The details of the separation process will be given
below.


## 3. Results and Discussion

### 3.1. Preparation of the Resin

PHA resin was prepared from the reaction of the corresponding crosslinked PAAm
with hydroxylamine hydrochloride [20],
and sodium hydroxide. A schematic presentation of possible reaction between PAAm
and hydroxylamine hydrochloride with sodium hydroxide to form hydrogen and
sodium form of PHA is shown in Scheme 1.Scheme 1
Conversion of PAAm to PHA.


### 3.2. FT-IR Analysis

The IR spectra recorded for the (a) polyacrylamide (PAAm), (b) poly(hydroxamic
acid) (PHA), and (c) metal loaded PHA samples are given in Figure1. From Table 3, the infrared spectrum of crosslinked PAAm shows the
characteristic absorption bands of amide (N–H), CH2 stretching
and carbonyl groups at 3401, 2998, and 1649 cm−1,
respectively. The infrared spectrum of PHA resin showed the characteristic
absorption bands of hydroxamic (O–H), amide (N–H), carbonyl and
(N–O) groups at 3200, 3444, 1670 and 930 cm−1.
The absorption band at 2862 cm−1 is related to C=N
group in enol form of hydroxamic acid. Comparison of spectra of the PHA sample
and metal ion loaded PHA sample show a shift in the N–O band from 930 to
775 cm−1 in the metal ion loaded sample as a result
of interaction of corresponding groups with metal ions‏.
This indicates a strong interaction of metal ions with the N–O group of
the sorbent and as the M–O bond is stronger, the N–O bond exhibits
lower stretching frequency. Additional peaks at around
700 cm−1 can also be seen which are characteristic
of O–M–O stretching vibrations. The possible interactions between
metal ions and PHA polymers are shown in Scheme 2 [22].Table 3
FTIR spectra of PAAm, PHA, and metal loaded PHA.
Original groups
Absorption bands of
original groups (cm−1)
Experimental absorption
bands (cm−1)
PAAm
PHA
PHA-M
Amide:
Free > NH stretching
(amide II)
3500, 3400
3401
3444
3449
> C=O stretching
(amide I)
1650
1649
1670
1649
Aliphatic:
–CH2
stretching
2926–2853
2998, 2851
2919
–CH2
bending
1485–1445
1400
1418
–CH3
bending
1470–1430
Hydroxyl:
Free OH stretching
3650–3590
Bonded OH
3400–3200
3200
3449
Amine:
C–N stretching
1410
1400
1400
1416
NH stretching
3000–2700
Chelate compounds
3200–2440
2919
Metal–O bond
<1000
775Scheme 2
Possible interactions between metal ions and PHA resin.Figure 1
FTIR spectra of (a) PAAm, (b) PHA and (c) metal loaded PHA.


### 3.3. Adsorption Behaviors of Zr, Y, and Sr on Cation Exchangers

The adsorption behaviors of zirconium, yttrium, and strontium on synthetic PHA
resin in different media, namely, hydrochloric acid, acetate buffer, and citrate
buffer were studied. However, the effect of equilibrium time has been studied as
a function of uptake for each element in batch mode, where the equilibrium was
achieved after 2 h of shaking.


#### 3.3.1. Hydrochloric Acid

Figure2 shows the relationship
between the distribution coefficients (K
d-values) of these elements and the
concentration of hydrochloric acid on PHA, where Y and Sr both showed the
same adsorption behaviour over the acidity range of
10−5–1 mol/L where within the acidity range
of 10−5–10−3 mol/L their
K
d-values increase with increasing the
concentration of the acid and then decrease with acidity increase till
0.1 mol/L. On the other hand, for zirconium, the
K
d-values increase globally with HCl
concentration from 10−5 mol/L to 1 mol/L
where at 10−5 mol/L HCl zirconium showed no
specific adsorption (K
d
~
2) while over the concentration range
10−4–10−2 mol/L the
adsorbability was relatively low and almost constant
(~10); however, the adsorbability after
10−2 mol/L was rather high. The results given
also show that the adsorbability in the reverse order, Sr(II) > Y(III)
> Zr(IV), this may be due to the formation of hydrated complexes of Y
in diluted acid and zirconium is hydrolysed in aqueous HCl of varying
concentrations; a variety of intermediate hydrolysis products, such as the
oxochlorides MOCl2, are formed [23].Figure 2
Distribution coefficients of Zr(IV), Y(III) and Sr(II) as a function
of HCl concentration on PHA resin, shaking time 2 hours.


#### 3.3.2. 0.1 mol/L Acetate Buffer

Figure3 illustrates the adsorption
behavior of Zr, Y, and Sr in 0.1 mol/L acetate buffer over the pH
range 3 to 5.5. Where at pH 3.5 they have the drop in
K
d-values. After this drop over the pH range
3.5–5.5, the adsorbability of Y and Sr increase gradually with
raising the pH value. It is also observed that the adsorbability of Y is
higher than that of Sr. While for Zr, after this drop, the adsorbability
increases till pH 4.5 and then decreases with raising the pH to 5.5.Figure 3
Distribution coefficients of Zr(IV), Y(III), and Sr(II) as a function
of pH of 0.1 mol/L acetate buffers on PHA resin, shaking time
2 hours.


#### 3.3.3. 0.1 mol/L Citrate Buffer

The adsorption behaviours of these elements in 0.1 mol/L citrate buffer over
the pH range 3 to 5.5 on the PHA exchanger were studied (Figure4). As shown from the given results,
their adsorbabilities were low and almost constant over the range of pH
3–5.5 (for Y~25 and, for Zr and Sr~10) except at pH 5.5,
zirconium gives no significant absorption (K
d
~
2). However, the adsorption behaviours on
cation-exchanger (Dowex 50WX8) as discussed by Kandil et al. [16] for these elements differ
drastically from values for PHA where zirconium showed significant
adsorbability that is constant with varying the pH from 3.5 to 5.5, while
for strontium the K
d-value decreased gradually with changing the
pH from 3.5 to 5.5. The adsorbability of the trivalent element (Y) decreased
sharply by increasing the pH from 3.5 to 4.5, and by continuing the
increasing of pH to 5.5 the adsorbability of yttrium disappeared
(K
d
~
2).Figure 4
Distribution coefficients of Zr(IV), Y(III), and Sr(II) as a function
of pH of 0.1 mol/L citrate buffers on PHA resin, shaking time
2 hours.


### 3.4. PHA-Column Chromatography for the Separation of Zr from Y and Sr

From batch mode, the optimum conditions for separation of Zr from both Y and Sr
were obtained which have been used in the column mode where the column
chromatography is applicable for dealing with radioactive material. Practically,
from all given results on PHA in batch mode, these elements presented a
significant contrast that could facilitate separation of Zr from both Y and Sr.
Additionally, in the column mode, the effective parameter is the flow rate
related to the time. However, in the loading step, 100 ml has been loaded
with flow rate 1.5 mL/min. During the loading, all yttrium and strontium
were adsorbed on the resin while zirconium passed through the column. This means
that separation of Zr from both Y and Sr has occurred (the main task of the
work). In more details the elution profile for separation of Zr from both Y and
Sr was given in Figure5. As described
above, for PHA exchanger a 100 mL stock solution containing
100 ppm of each Zr, Y, and Sr dissolved in
10−5 mol/L HCl was loaded onto a glass column,
22 cm long × 1.5 cm in diameter, packed with PHA with depth
of 2 cm. At this molarity of HCl zirconium showed no specific adsorption
(K
d
~
2, Figure 2). So zirconium passed through the column with percentage 80%
of initial amount. Further washing by this molarity of HCl showed no zirconium
pass through the column while yttrium and strontium still remained on the column
(their K
d-values are rather high, Figure 2). For removal of strontium,
0.1 mol/L acetate buffer pH 3.5 is suitable for this purpose (Figure
3). Before elution of Sr, it is
necessary to adjust the pH of the column by continuous flowing of
0.1 mol/L acetate buffer pH 3.5. All amount of strontium passed through
the column while the residual of zirconium and all yttrium were still adsorbed
on the column. Complete elution of Y was done using 2 mol/L HCl where all
yttrium were collected in 100 mL. The elution of Y was accompanied by
elution of residual zirconium. Therefore, further purification is needed.Figure 5
Elution profile of Zr(IV), Y(III) and Sr(II) from a column packed with
PHA resin. Fraction volume = 16.5 mL.


### 3.5. Purification Step

The 100 mL of 2 mol/L HCl containing the whole yttrium and the
residual zirconium was evaporated to incipient dryness, and the residue
dissolved in 100 mL of double distilled water. The solution was loaded
onto a glass column of the same dimensions packed with a new portion of PHA at
flow rate 1.5 mL/min. The residual Zr passed through the column while
yttrium remained on the column. Again all yttrium was eluted by 2 mol/L
HCl.Regarding the recent work [16], separation
of radiozirconium (IV) from both Y(III) and Sr(II) has been carried out using
the Dowex 50W-X8 (cation exchanger) column chromatography and Dowex 21K (anion
exchanger) column chromatography. The separation efficiency for Zr from both
elements together by Dowex 50W-X8 and Dowex 21K was 75% and 22%,
respectively. It appears from our results that the zirconium was completely
separated (~100%) from Sr(II) in one step and from Y in two steps
using PHA column chromatography (Table 4). However, the process in this work was done by employing the
inactive elements. The investigated method could be applied for the separation
of radiozirconium from both parents (Y and Sr).Table 4
Comparison between PHA and ion-exchanger resins [16] on separation efficiency of Zr from both Y and
Sr.
Ion exchanger
Dowex 50W-X8
Dowex 21K
PHA
Separation efficiency
%
75
22
~100


## 3.1. Preparation of the Resin

PHA resin was prepared from the reaction of the corresponding crosslinked PAAm
with hydroxylamine hydrochloride [20],
and sodium hydroxide. A schematic presentation of possible reaction between PAAm
and hydroxylamine hydrochloride with sodium hydroxide to form hydrogen and
sodium form of PHA is shown in Scheme 1.Scheme 1
Conversion of PAAm to PHA.


## 3.2. FT-IR Analysis

The IR spectra recorded for the (a) polyacrylamide (PAAm), (b) poly(hydroxamic
acid) (PHA), and (c) metal loaded PHA samples are given in Figure1. From Table 3, the infrared spectrum of crosslinked PAAm shows the
characteristic absorption bands of amide (N–H), CH2 stretching
and carbonyl groups at 3401, 2998, and 1649 cm−1,
respectively. The infrared spectrum of PHA resin showed the characteristic
absorption bands of hydroxamic (O–H), amide (N–H), carbonyl and
(N–O) groups at 3200, 3444, 1670 and 930 cm−1.
The absorption band at 2862 cm−1 is related to C=N
group in enol form of hydroxamic acid. Comparison of spectra of the PHA sample
and metal ion loaded PHA sample show a shift in the N–O band from 930 to
775 cm−1 in the metal ion loaded sample as a result
of interaction of corresponding groups with metal ions‏.
This indicates a strong interaction of metal ions with the N–O group of
the sorbent and as the M–O bond is stronger, the N–O bond exhibits
lower stretching frequency. Additional peaks at around
700 cm−1 can also be seen which are characteristic
of O–M–O stretching vibrations. The possible interactions between
metal ions and PHA polymers are shown in Scheme 2 [22].Table 3
FTIR spectra of PAAm, PHA, and metal loaded PHA.
Original groups
Absorption bands of
original groups (cm−1)
Experimental absorption
bands (cm−1)
PAAm
PHA
PHA-M
Amide:
Free > NH stretching
(amide II)
3500, 3400
3401
3444
3449
> C=O stretching
(amide I)
1650
1649
1670
1649
Aliphatic:
–CH2
stretching
2926–2853
2998, 2851
2919
–CH2
bending
1485–1445
1400
1418
–CH3
bending
1470–1430
Hydroxyl:
Free OH stretching
3650–3590
Bonded OH
3400–3200
3200
3449
Amine:
C–N stretching
1410
1400
1400
1416
NH stretching
3000–2700
Chelate compounds
3200–2440
2919
Metal–O bond
<1000
775Scheme 2
Possible interactions between metal ions and PHA resin.Figure 1
FTIR spectra of (a) PAAm, (b) PHA and (c) metal loaded PHA.


## 3.3. Adsorption Behaviors of Zr, Y, and Sr on Cation Exchangers

The adsorption behaviors of zirconium, yttrium, and strontium on synthetic PHA
resin in different media, namely, hydrochloric acid, acetate buffer, and citrate
buffer were studied. However, the effect of equilibrium time has been studied as
a function of uptake for each element in batch mode, where the equilibrium was
achieved after 2 h of shaking.


### 3.3.1. Hydrochloric Acid

Figure2 shows the relationship
between the distribution coefficients (K
d-values) of these elements and the
concentration of hydrochloric acid on PHA, where Y and Sr both showed the
same adsorption behaviour over the acidity range of
10−5–1 mol/L where within the acidity range
of 10−5–10−3 mol/L their
K
d-values increase with increasing the
concentration of the acid and then decrease with acidity increase till
0.1 mol/L. On the other hand, for zirconium, the
K
d-values increase globally with HCl
concentration from 10−5 mol/L to 1 mol/L
where at 10−5 mol/L HCl zirconium showed no
specific adsorption (K
d
~
2) while over the concentration range
10−4–10−2 mol/L the
adsorbability was relatively low and almost constant
(~10); however, the adsorbability after
10−2 mol/L was rather high. The results given
also show that the adsorbability in the reverse order, Sr(II) > Y(III)
> Zr(IV), this may be due to the formation of hydrated complexes of Y
in diluted acid and zirconium is hydrolysed in aqueous HCl of varying
concentrations; a variety of intermediate hydrolysis products, such as the
oxochlorides MOCl2, are formed [23].Figure 2
Distribution coefficients of Zr(IV), Y(III) and Sr(II) as a function
of HCl concentration on PHA resin, shaking time 2 hours.


### 3.3.2. 0.1 mol/L Acetate Buffer

Figure3 illustrates the adsorption
behavior of Zr, Y, and Sr in 0.1 mol/L acetate buffer over the pH
range 3 to 5.5. Where at pH 3.5 they have the drop in
K
d-values. After this drop over the pH range
3.5–5.5, the adsorbability of Y and Sr increase gradually with
raising the pH value. It is also observed that the adsorbability of Y is
higher than that of Sr. While for Zr, after this drop, the adsorbability
increases till pH 4.5 and then decreases with raising the pH to 5.5.Figure 3
Distribution coefficients of Zr(IV), Y(III), and Sr(II) as a function
of pH of 0.1 mol/L acetate buffers on PHA resin, shaking time
2 hours.


### 3.3.3. 0.1 mol/L Citrate Buffer

The adsorption behaviours of these elements in 0.1 mol/L citrate buffer over
the pH range 3 to 5.5 on the PHA exchanger were studied (Figure4). As shown from the given results,
their adsorbabilities were low and almost constant over the range of pH
3–5.5 (for Y~25 and, for Zr and Sr~10) except at pH 5.5,
zirconium gives no significant absorption (K
d
~
2). However, the adsorption behaviours on
cation-exchanger (Dowex 50WX8) as discussed by Kandil et al. [16] for these elements differ
drastically from values for PHA where zirconium showed significant
adsorbability that is constant with varying the pH from 3.5 to 5.5, while
for strontium the K
d-value decreased gradually with changing the
pH from 3.5 to 5.5. The adsorbability of the trivalent element (Y) decreased
sharply by increasing the pH from 3.5 to 4.5, and by continuing the
increasing of pH to 5.5 the adsorbability of yttrium disappeared
(K
d
~
2).Figure 4
Distribution coefficients of Zr(IV), Y(III), and Sr(II) as a function
of pH of 0.1 mol/L citrate buffers on PHA resin, shaking time
2 hours.


## 3.3.1. Hydrochloric Acid

Figure2 shows the relationship
between the distribution coefficients (K
d-values) of these elements and the
concentration of hydrochloric acid on PHA, where Y and Sr both showed the
same adsorption behaviour over the acidity range of
10−5–1 mol/L where within the acidity range
of 10−5–10−3 mol/L their
K
d-values increase with increasing the
concentration of the acid and then decrease with acidity increase till
0.1 mol/L. On the other hand, for zirconium, the
K
d-values increase globally with HCl
concentration from 10−5 mol/L to 1 mol/L
where at 10−5 mol/L HCl zirconium showed no
specific adsorption (K
d
~
2) while over the concentration range
10−4–10−2 mol/L the
adsorbability was relatively low and almost constant
(~10); however, the adsorbability after
10−2 mol/L was rather high. The results given
also show that the adsorbability in the reverse order, Sr(II) > Y(III)
> Zr(IV), this may be due to the formation of hydrated complexes of Y
in diluted acid and zirconium is hydrolysed in aqueous HCl of varying
concentrations; a variety of intermediate hydrolysis products, such as the
oxochlorides MOCl2, are formed [23].Figure 2
Distribution coefficients of Zr(IV), Y(III) and Sr(II) as a function
of HCl concentration on PHA resin, shaking time 2 hours.


## 3.3.2. 0.1 mol/L Acetate Buffer

Figure3 illustrates the adsorption
behavior of Zr, Y, and Sr in 0.1 mol/L acetate buffer over the pH
range 3 to 5.5. Where at pH 3.5 they have the drop in
K
d-values. After this drop over the pH range
3.5–5.5, the adsorbability of Y and Sr increase gradually with
raising the pH value. It is also observed that the adsorbability of Y is
higher than that of Sr. While for Zr, after this drop, the adsorbability
increases till pH 4.5 and then decreases with raising the pH to 5.5.Figure 3
Distribution coefficients of Zr(IV), Y(III), and Sr(II) as a function
of pH of 0.1 mol/L acetate buffers on PHA resin, shaking time
2 hours.


## 3.3.3. 0.1 mol/L Citrate Buffer

The adsorption behaviours of these elements in 0.1 mol/L citrate buffer over
the pH range 3 to 5.5 on the PHA exchanger were studied (Figure4). As shown from the given results,
their adsorbabilities were low and almost constant over the range of pH
3–5.5 (for Y~25 and, for Zr and Sr~10) except at pH 5.5,
zirconium gives no significant absorption (K
d
~
2). However, the adsorption behaviours on
cation-exchanger (Dowex 50WX8) as discussed by Kandil et al. [16] for these elements differ
drastically from values for PHA where zirconium showed significant
adsorbability that is constant with varying the pH from 3.5 to 5.5, while
for strontium the K
d-value decreased gradually with changing the
pH from 3.5 to 5.5. The adsorbability of the trivalent element (Y) decreased
sharply by increasing the pH from 3.5 to 4.5, and by continuing the
increasing of pH to 5.5 the adsorbability of yttrium disappeared
(K
d
~
2).Figure 4
Distribution coefficients of Zr(IV), Y(III), and Sr(II) as a function
of pH of 0.1 mol/L citrate buffers on PHA resin, shaking time
2 hours.


## 3.4. PHA-Column Chromatography for the Separation of Zr from Y and Sr

From batch mode, the optimum conditions for separation of Zr from both Y and Sr
were obtained which have been used in the column mode where the column
chromatography is applicable for dealing with radioactive material. Practically,
from all given results on PHA in batch mode, these elements presented a
significant contrast that could facilitate separation of Zr from both Y and Sr.
Additionally, in the column mode, the effective parameter is the flow rate
related to the time. However, in the loading step, 100 ml has been loaded
with flow rate 1.5 mL/min. During the loading, all yttrium and strontium
were adsorbed on the resin while zirconium passed through the column. This means
that separation of Zr from both Y and Sr has occurred (the main task of the
work). In more details the elution profile for separation of Zr from both Y and
Sr was given in Figure5. As described
above, for PHA exchanger a 100 mL stock solution containing
100 ppm of each Zr, Y, and Sr dissolved in
10−5 mol/L HCl was loaded onto a glass column,
22 cm long × 1.5 cm in diameter, packed with PHA with depth
of 2 cm. At this molarity of HCl zirconium showed no specific adsorption
(K
d
~
2, Figure 2). So zirconium passed through the column with percentage 80%
of initial amount. Further washing by this molarity of HCl showed no zirconium
pass through the column while yttrium and strontium still remained on the column
(their K
d-values are rather high, Figure 2). For removal of strontium,
0.1 mol/L acetate buffer pH 3.5 is suitable for this purpose (Figure
3). Before elution of Sr, it is
necessary to adjust the pH of the column by continuous flowing of
0.1 mol/L acetate buffer pH 3.5. All amount of strontium passed through
the column while the residual of zirconium and all yttrium were still adsorbed
on the column. Complete elution of Y was done using 2 mol/L HCl where all
yttrium were collected in 100 mL. The elution of Y was accompanied by
elution of residual zirconium. Therefore, further purification is needed.Figure 5
Elution profile of Zr(IV), Y(III) and Sr(II) from a column packed with
PHA resin. Fraction volume = 16.5 mL.


## 3.5. Purification Step

The 100 mL of 2 mol/L HCl containing the whole yttrium and the
residual zirconium was evaporated to incipient dryness, and the residue
dissolved in 100 mL of double distilled water. The solution was loaded
onto a glass column of the same dimensions packed with a new portion of PHA at
flow rate 1.5 mL/min. The residual Zr passed through the column while
yttrium remained on the column. Again all yttrium was eluted by 2 mol/L
HCl.Regarding the recent work [16], separation
of radiozirconium (IV) from both Y(III) and Sr(II) has been carried out using
the Dowex 50W-X8 (cation exchanger) column chromatography and Dowex 21K (anion
exchanger) column chromatography. The separation efficiency for Zr from both
elements together by Dowex 50W-X8 and Dowex 21K was 75% and 22%,
respectively. It appears from our results that the zirconium was completely
separated (~100%) from Sr(II) in one step and from Y in two steps
using PHA column chromatography (Table 4). However, the process in this work was done by employing the
inactive elements. The investigated method could be applied for the separation
of radiozirconium from both parents (Y and Sr).Table 4
Comparison between PHA and ion-exchanger resins [16] on separation efficiency of Zr from both Y and
Sr.
Ion exchanger
Dowex 50W-X8
Dowex 21K
PHA
Separation efficiency
%
75
22
~100


## 4. Conclusion

Poly(hydroxamic acid) resin (PHA) was prepared by modification of polyacrylamide
(PAAm) and characterized by IR. From the presented study, the PHA-column
chromatography was employed in separation of Zr(IV) from Y(III) and Sr(II), where
the presented two-step route for purification of Zr from Y(III) was done while
purification of Zr from Sr(III) was achieved in one step. The investigated method
using PHA could be applied in purification of89Zr from its parents (Y or
Sr).



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*Source: 638090-2011-02-21.xml*