Deliverable for FαST project: Ln Resin based PLE
- Los Alamos National Laboratory
This memo describes the fabrication of a polymer ligand extractant based on Eichrom's LN-1 resin. This work has been in support of the Fast Alpha Spectrometry Tool (F{alpha}ST) project. The first part of LANL's role in this project is to evaluate new extractants for use in polymer ligand extractants (PLEs). The first new extractant evaluated is Di(2-ethyl hexyl) phosphoric acid (HDEHP), which is an effective metal extractant. It has very efficient chelating properties for a wide variety of metal ions. HDEHP is an amphiphillic molecule with two long hydrocarbon chains and a polar end with a phosphoryl oxygen (P=O) and an acidic -OH group as shown in Figure 1. HDEHP has shown effectiveness in extracting lanthanides, selective actinides, and other trivalent elements. Several authors have reported that lanthanides and elements with +3 oxidation state have similar extraction behavior in nitric acid. The distribution ratio for lanthanides rapidly decreases at lower nitric concentration then start to increase at higher concentration as shown in. The trivalent americium, curium, and yttrium exhibit similar trend as trivalent lanthanides. This extraction trend can be also observed from hydrogen chloride solution. This work describes the use of this ligand in a PLE to extract plutonium from solution. Polymer ligand films were prepared by dissolving HDEHP ligands and polystyrene beads in THF. The solution was directly deposited onto a 40 mm diameter stainless steel substrate using an automated pipette. HDEHP based PLEs with direct stippling method are shown in Figure 2. The solution was air dried at room temperature overnight to ensure complete evaporation of THF. The plutonium tracer solution was prepared in 0.01, 0.1, 1, and 8M nitric solutions to study the effect of nitric concentration in plutonium extraction. 0.1667 Bq {sup 239}Pu tracer solution was directly stippled on each PLE and was allowed to equilibrate for 3 hours before removing the solution. The plutonium activity of each sample was measured by direct alpha counting to quantify the plutonium recovery by HDEHP PLE. The alpha spectra from alpha spectroscopy are shown in Figure 3. 1:5, 1:10, and 1:20 PLEs had sharp peak with low tailing. 1:2 had an extremely long tail, which is a possible indication that a large amount of ligands caused the film to not form a smooth surface. Also, it can be noted that 1:2 ratio PLE surface was not as rigid as the other ratio PLEs and it was prone to scratching during sample handing. The resolution of alpha spectra was quantified by measuring Full Width at Half of the Maximum (FWHM) using Bortels equation. The tailing component of the peak was also measured along with FWHM. The peak resolutions and tailing measurements for 0.1M nitric solution samples are given in Table 1. The best resolution was achieved with 1:5 PLE and worst was given by 1:2 PLE. The plutonium recovery by HDEHP PLE was dependent on both nitric concentration and ligand to polymer ratio. 1:2 PLE consistently had the highest recovery followed by 1:5 as shown in Figure 4. It should be noted that 1:2 ratio PLEs consistently had long tailing and the ROI of the spectrum had to be increased to encompass total counts from the tracer. 1:10 and 1:20 PLEs had close to zero percent recovery in all nitric concentration except for 0.01M. The highest plutonium recovery was observed for 0.1M nitric acid. 1:5 PLE gave the best combination of alpha spectroscopy resolution and plutonium recovery. Radiography image of samples were generated to study the plutonium distribution on the PLE surface. Samples were placed on an imaging plate (Fujifilm BAS-TR 2025) for 24 hours and the plate was scanned using GE Typhoon FLA 7000 system. The radiography image in Figure 5 shows uneven distribution with hot spots along the edge and in the center of the samples. These hot spots may be the result of highly localized concentration of ligands or surface defects that were observed in SEM. This unevenness in distribution may cause inaccurate activity measurement by alpha spectroscopy due to a bias in the energy calibration. PLEs based on HDEHP have been evaluated. The concentration of ligand in polystyrene is critical in the performance of the PLE; both for extraction efficiency as well as for alpha spectrometry results. The optimal PLE using this ligand has a concentration of 1:5 ligand to polystyrene. Under laboratory conditions, this configuration can produce similar results to those obtained for DIPEX based PLEs from previous studies. The concentration is very important to the results obtained for this ligand. This PLE is a good candidate for use in later field studies. Our next report will detail the evaluation of PLEs utilizing crown ether ligands.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOD
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1040014
- Report Number(s):
- LA-UR-12-21086; TRN: US201211%%91
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
ACTINIDES
ALPHA SPECTRA
ALPHA SPECTROSCOPY
CALIBRATION
CONFIGURATION
CROWN ETHERS
EVAPORATION
FABRICATION
HOT SPOTS
HYDROCARBONS
HYDROCHLORIC ACID
NITRIC ACID
PHOSPHORIC ACID
PLUTONIUM
POLYMERS
POLYSTYRENE
RARE EARTHS
RESINS
RESOLUTION
STAINLESS STEELS
SUBSTRATES
TAILINGS
VALENCE