A poly[dibenzo-18-crown-6] exhibits good chemical stability, reusability, and faster rate equilibrium for the separation of Gd(III). Both uptake and stripping of metal ions were rapid, indicating a better accessibility of the complexing sites. The proposed method has been applied for chromatographic separation of Gd(III) by using picric acid as medium and poly[dibenzo-18-crown-6] as stationary phase. The influences of picric acid concentration, different eluting agents, and so forth, were discussed and the optimum conditions were established. The breakthrough capacity of poly[dibenzo-18-crown-6] for Gd(III) was
In recent years the separation chemistry of rare earth elements (REEs) continues to receive a growing interest. The major reasons for this stems from the importance of rare earths not only in industrial application but also in energy generation activities and environmental mitigation. Gadolinium is useful in nuclear techniques, in fuel element fabrication and in ceramic industries and as control rod and as refractory material [
The main focus of the extensive research on chelating resins is the preparation of functionalized polymer that can provide more flexible working conditions together with good stability, selectivity, high concentrating ability, high capacity of metal ions, and simpler operation [
Crown ethers are effective extractants due to their ability to form stable complexes with metal ions. In recent years extraction chromatography has emerged as a versatile and effective method for analytical and preparative scale metal ion separation [
By using poly[dibenzo-18-crown-6] we have reported the sorption behavior and separation study of alkali and alkaline earth metal in various mediums like ascorbic acid, sodium nitrate, hydrochloric acid, and L-arginine [
To our knowledge no successful attempts were reported in the literature for the separation of Gd(III) using poly[dibenzo-18-crown-6] in picric acid media and column chromatography. The present paper describes a simple and sensitive method for the determination of Gd(III) using poly[dibenzo-18-crown-6] as stationary phase in picric acid media. In our study we use picric acid as medium because picrate is bulkier anion with higher hydrophobicity. The proposed method has been successfully applied for the separation and determination of Gd(III) from real materials.
All absorbance measurements were carried out using a digital visible spectrophotometer (215 D, Thermo Electron LLS, India), a digital pH meter (Model LI-120. Elico, India) equipped with glass and a calomel electrode for pH determination, and a digital flame photometer (PI, Model no. 041, India).
A stock solution of Gd(III) was prepared by dissolving 1.091 g of gadolinium nitrate (AnalR grade, BDH, Poole, UK) in 100 mL of distilled deionised water and standardized gravimetrically [
Poly[dibenzo-18-crown-6] from Merck Darmstadt, Germany was used after screening to 100–200 mesh. A total of 0.5 g of polymer was slurred with distilled deionised water and poured into a Pyrex glass chromatographic column (20 × 0.8 cm i.d.). The column was used after preconditioning with picric acid solution. All chemicals used are of analytical grade.
100
Sorption studies of Gd(III) were carried out from picric acid medium using 100
Sorption of gadolinium(III) as a function of picric acid concentration (Gd(III): 100
Picric acid concentration | Sorption of gadolinium(III) |
---|---|
1 | 100 |
1× 10−3 | 100 |
1 × 10−4 | 100 |
1 | 97.4 |
1 | 95.4 |
1 × 10−7 | 90.2 |
Gd(III) was eluted out from the column with different strengths of acids such as HCl, H2SO4, HClO4, CH3COOH, and HBr. The concentrations of the eluting agents were varied from 0.1 to 8.0 M. Gadolinium(III) was eluted quantitatively with 2.0–8.0 M HCl, 0.1–0.5 M H2SO4, 1.0–8.0 M HClO4, 7.0-8.0 M CH3COOH, and 0.1–5.0 M HBr. Further, the elution study of Gd(III) in this work was carried out with 0.1 M HBr. The elution profile of Gd(III) with different eluting agents is shown in Figure
Elution study of Gd(III) with various eluents. Eluents used such as HCl, H2SO4, HClO4, HBr, CH3COOH out of this 2.0–8.0 M HCl, 0.1–0.5 M H2SO4, 1.0–8.0 M HClO4, 0.1–5.0 M HBr and 7.0-8.0 M CH3COOH were efficient eluting agent for Gd(III).
The breakthrough capacity of Gd(III) was carried out on 1.0 g of poly[dibenzo-18-crown-6] with 1 × 10−3 moleL−1 picric acid. The volume of Gd(III) sample solution employed was 10.0 mL. The concentration of Gd(III) was varied from 100 to 1100
Effect of varying concentrations of Gd(III). The concentration of Gd(III) was varied from 100 to 1100
To assess the usefulness of this method, the effects of foreign ions, which are likely to interfere with the proposed method for determination of Gd(III) were studied. An aliquot of solution containing 100
Diverse ion effect (Gd(III): 100
Ion | Added as | Tol. limit (mg) | Ion | Added as | Tol. limit (mg) |
---|---|---|---|---|---|
Li+ | LiCl | 4 | Al3+ | Al2(SO4)3·16H2O | 0.5 |
Na+ | NaCl | 4 | Zr4+ | Zr(NO3)4·4H2O | 1 |
K+ | KCl | 2 | La3+ | La(NO3)3 | 0.8 |
Rb+ | RbCl | 5 | Ce3+ | CeCl2·6H2O | 0.2 |
Cs+ | CsCl | 4 | V4+ | VOSO4·4H2O | 0.4 |
NH4Cl | 4 | Th4+ | Th(NO3)4 | 0.2 | |
Be2+ | BeSO4·4H2O | 0.1 | Mo6+ | (NH4)6Mo7O244H2O | 0.9 |
Ca2+ | CaCl2 | 0.4 | W6+ | Na2WO4·4H2O | 0.8 |
Sr2+ | Sr(NO3)2 | 0.5 | U6+ | UO2(NO3)2·6H2O | 0.5 |
Ba2+ | Ba(NO3)2 | 0.3 | Cl− | HCl | 3 |
Co2+ | CoCl2·6H2O | 8 | Br− | HBr | 4 |
Ni2+ | NiCl2·6H2O | 0.8 | SCN− | NaSCN | 1 |
Mn2+ | MnCl2·4H2O | 2 | HClO4 | 5 | |
Zn2+ | ZnCl2 | 0.5 | CH3COO− | CH3COOH | 5 |
Cd2+ | (CH3COO)2Cd·H2O | 3 | H2SO4 | 0.8 | |
Pb2+ | Pb(NO3)2 | 1 | Tartrate | Tartaric acid | 4 |
Cr3+ | Cr(NO3)3·9H2O | 0.5 | EDTA | EDTA | 4 |
Fe3+ | FeCl3·6H2O | 0.1 | Ascorbate | Ascorbic acid | 4 |
Cu2+ | CuCl2 | 0.8 | Citrate | Citric acid | 4 |
A mixture of Li(I)/Fe(III)/Mo(VI)/Sr(II)/Ca(II), U(VI), Gd(III), and Ba(II) was resolved by following the proposed procedure of Gd(III). The mixture was passed through the poly[dibenzo-18-crown-6] column under optimum condition of Gd(III), where Li(I)/Fe(III)/Mo(VI)/Ca(II)/Sr(II) was not sorbed and passed through column which was then determined by standard procedure [
Separation of gadolinium(III) from associated elements (multicomponent mixture).
Sr. no. | Mixture | Taken ( | Recovery* (%) | S.D. | Eluent |
---|---|---|---|---|---|
1 | Fe(II) | 100 | 98.16 | NSPC** | |
U(VI) | 100 | 98.78 | 0.2 M LiOH | ||
Gd(III) | 100 | 98.83 | 2.0 M HClO4 | ||
Ba(II) | 100 | 97.94 | 4.0 M HCl | ||
2 | Ca(II) | 100 | 100 | NSPC** | |
U(VI) | 100 | 97.76 | 0.2 M LiOH | ||
Gd(III) | 100 | 100 | 2.0 M HClO4 | ||
Ba(II) | 100 | 98 | 4.0 M HCl | ||
3 | Li (I) | 100 | 99 | NSPC** | |
U(VI) | 100 | 99 | 0.2 M LiOH | ||
Gd(III) | 100 | 98.6 | 2.0 M HClO4 | ||
Ba (II) | 100 | 98.10 | 4.0 M HCl | ||
4 | Mg(II) | 100 | 98.4 | NSPC** | |
U(VI) | 100 | 98 | 0.2 M LiOH | ||
Gd(III) | 100 | 100 | 2.0 M HClO4 | ||
Ba(II) | 100 | 97.5 | 4.0 M HCl | ||
5 | Mo(II) | 100 | 99.1 | NSPC** | |
U(VI) | 100 | 98.6 | 0.2 M LiOH | ||
Gd(III) | 100 | 99.2 | 2.0 M HClO4 | ||
Ba(II) | 100 | 97.3 | 4.0 M HCl | ||
6 | Sr(II) | 100 | 98.9 | NSPC** | |
U(VI) | 100 | 98 | 0.2 M LiOH | ||
Gd(III) | 100 | 99 | 2.0 M HClO4 | ||
Ba(II) | 100 | 97.92 | 4.0 M HCl |
*Average of triplicate analysis.
**No sorption passing through the column.
Chromatogram of Multicomponent Mixtures. Separation different metal ions such as U(VI), Ba(II), Mo(VI), Ca(II), Sr(II), Mg(II) from Gd(III).
Separation of Fe(III), U(VI), Gd(III), Ba(II)
Separation of Ca(II), U(VI), Gd(III), Ba(II)
Separation Li(I), U(VI), Gd(III), Ba(II)
Separation of Mg(II), U(VI), Gd(III), Ba(II)
Separation of Mo(VI), U(VI), Gd(III), Ba(II)
Separation of Mo(VI), U(VI), Gd(III), Ba(II)
Reproducibility of the method was checked by thirty replicate analyses of a standard Gd(III) solution. The results indicate the method to be fairly reproducible. The poly[dibenzo-18-crown-6] could be recycled many times without affecting its sorption capacity. The reusability of poly[dibenzo-18-crown-6] with standard deviations is shown in Table
Reproducibility of the method.
Sr. no. | Gd(III) 100 | Recovery % | S.D |
---|---|---|---|
1 | 100 | 99.9 | 0.010 |
2 | 100 | 99.9 | 0.069 |
3 | 100 | 98.9 | 0.005 |
4 | 100 | 99.2 | 0.032 |
5 | 100 | 99 | 0.014 |
6 | 100 | 99.3 | 0.010 |
7 | 100 | 98.9 | 0.032 |
8 | 100 | 99.6 | 0.062 |
9 | 100 | 99 | 0.015 |
10 | 100 | 99.8 | 0.033 |
11 | 100 | 99.8 | 0.047 |
12 | 100 | 99.8 | 0.023 |
13 | 100 | 99.6 | 0.010 |
14 | 100 | 99 | 0.015 |
15 | 100 | 99.8 | 0.037 |
16 | 100 | 99.85 | 0.031 |
17 | 100 | 99.92 | 0.060 |
18 | 100 | 99.8 | 0.034 |
19 | 100 | 98.75 | 0.010 |
20 | 100 | 98.99 | 0.016 |
21 | 100 | 99.96 | 0.011 |
22 | 100 | 99.93 | 0.040 |
23 | 100 | 98.8 | 0.015 |
24 | 100 | 98.88 | 0.010 |
25 | 100 | 99.9 | 0.010 |
26 | 100 | 98.75 | 0.053 |
27 | 100 | 98.89 | 0.016 |
28 | 100 | 99 | 0.005 |
29 | 100 | 99.36 | 0.008 |
30 | 100 | 99.63 | 0.011 |
The composite material sample (GdSrO2) after acid treatment is subjected to the proposed method for the determination of Gd(III). The percentage of Gd(III) found after triplicate analysis is 9.89 (±0.11) as against the reported value of 10.0%.
The proposed method affords an attractive feature as compared to the solvent extraction technique, that is, it is free from any organic diluents, leading to potential green chemistry applications. It permits the separation of Gd(III) from nuclear fission products such as Ba(II), U(VI) and Sr(II) is the significant achievement of our work. The poly[dibenzo-18-crown-6] could be recycled many times without affecting its sorption capacity, that is, it has higher stability as a stationary phase. Low reagent and acid concentrations are required for quantitative recovery of Gd(III). Precision in terms of the standard deviation of the present method is very retainable for the determination of Gd(III). It is applicable for the analysis of Gd(III) in real sample.