Poly(hydroxamic acid) resin (PHA) was prepared by modification of polyacrylamide
(PAAm) prepared through
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+ [
One of the main tasks of radiochemical laboratories is the purification of
radionuclides from their matrix. The medical interest radionuclides such as
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
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 Tables
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 nm |
Thermoregulation | |
Type of generator | 40.68 MHz, Solid state |
Torch | Vertical |
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 |
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.
Infrared spectra of polymer samples with KBr pellets were obtained from FT-IR spectrometer (Bomen, Hartman & Borunz spectrometer, Model MB 157, Canada).
Crosslinked Polyacrylamide (PAAm) was prepared by radiation-induced
polymerization of acrylamide monomers in aqueous solution in the presence of
(NMBA) as a crosslinking agent [
For preparation of PHA in hydrogen form [
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 100
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.
PHA resin was prepared from the reaction of the corresponding crosslinked PAAm
with hydroxylamine hydrochloride [
Conversion of PAAm to PHA.
The IR spectra recorded for the (a) polyacrylamide (PAAm), (b) poly(hydroxamic
acid) (PHA), and (c) metal loaded PHA samples are given in Figure
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 | 775 |
Possible interactions between metal ions and PHA resin.
FTIR spectra of (a) PAAm, (b) PHA and (c) metal loaded PHA.
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.
Figure
Distribution coefficients of Zr(IV), Y(III) and Sr(II) as a function of HCl concentration on PHA resin, shaking time 2 hours.
Figure
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.
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 (Figure
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.
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 Figure
Elution profile of Zr(IV), Y(III) and Sr(II) from a column packed with PHA resin. Fraction volume = 16.5 mL.
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 [
Comparison between PHA and ion-exchanger resins [
Ion exchanger | Dowex 50W-X8 | Dowex 21K | PHA |
---|---|---|---|
Separation efficiency % | 75 | 22 | ~100 |
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 of 89Zr from its parents (Y or Sr).