Polymer based sorbent materials for thermal ionization mass spectrometric determination of uranium(vi) and plutonium(iv) ions

Abstract

Thermal ionization mass spectrometry (TIMS) is a widely used method for obtaining information about the isotopic composition of individual isotopes with high resolution and accurate quantification with considerably low detection limits. However, analyses by TIMS require an elaborate sample preparation step to eliminate the matrix and subsequent manual loading of small volumes of purified aqueous samples on a filament surface for thermal ionization. This is cumbersome, particularly for the handling of radioactive solutions. Therefore, in the present work, polymeric material based sorbents were explored for the single step matrix elimination and source preparation for the loading of U(VI) and Pu(IV) ions preconcentrated from a variety of environmental and nuclear fuel reprocessing samples. The solid phase loading offers a number of advantages for handling radioactive materials, and is amenable to matrix elimination and preconcentration of analytes that would further improve the detection limit of TIMS. The polymer based sorbents were prepared by anchoring neutral and acidic phosphate functional groups selective to actinide ions in porous poly(propylene) and poly(ethersulfone) matrices. One of the procedures used for the preparation of polymeric sorbents involved grafting of the monomers phosphoric acid 2-hydroxyethyl methacrylate ester and 2-ethylhexylmethacrylate (EHM) in 1 : 1 molar proportion by UV-initiator induced polymerization in the pores of the host matrix. In another route, the liquid extractants tris(2-ethylhexyl) phosphate (TEHP) along with bis(2-ethylhexyl) phosphoric acid (HDEHP), in different molar proportions, were physically immobilized by capillary force in the pores of poly(propylene) and poly(ethersulfone) membranes and beads. It was observed that the poly(propylene) pyrolyzed easily at a filament temperature close to that used for solution based sample loading, and thus was best suited for the analyses of U(VI) and Pu(IV) by TIMS. The composition of the polymer membrane supported liquid extractant based sorbents was optimized for the preconcentration of U(VI) from ground water and seawater, and also for the preconcentration of Pu(IV) from 3 mol L À1 HNO 3 , which is normally encountered in nuclear fuel reprocessing facilities. The parameters affecting the analytical performance of polymer sorbent based TIMS were evaluated, and tested for the quantification of U and Pu in the ppb concentration range in seawater and urine samples using the isotope dilution method. Sample Pu(IV) conc. (ppm) PolymSorb-TIMS Solution-TIMS Avg. RSD (%) Avg. RSD (%) Dissolver solution 12.90 AE 0.07 0.51 13.05 AE 0.04 0.30This journal is

Rapid and Precise Uranium Isotopic Screening in Natural Water Using Bis(2-ethylhexyl)phosphoric Acid-Modified Membranes

“…In the present study, a pore filled membrane was prepared by equilibrating a microporous poly­(propylene) (PP) membrane with a solution of 2 M DEHPA in dodecane. During equilibration, DEHPA infiltrated through the micropores of PP and immobilized inside the pores due to the hydrophobic interaction of the nonpolar solvent dodecane with the PP membrane––such systems where a liquid extractant immobilized in the microporous membrane are popularly termed as “supported liquid membranes” in the field of separation science. , The weight of the DEHPA-Dod@PP membrane was found to be 3–4 times more compared to the weight of the pristine PP membrane. The SEM image of the DEHPA-Dod@PP membrane in Supporting Information Figure S4a shows considerable porosity, which is very crucial for the quantitative sorption of actinide ions with improved kinetics.…”

“…Anion-exchange or bifunctional beads have been developed for preconcentration and TIMS analysis of Pu­(IV) and U­(VI) ions, , but it is difficult to mount a circular bead on a flat filament, and specially designed “V”- or “U”-shaped filaments are required to hold the bead at a fixed position. We have previously developed and reported various functionalized polymeric membranes that are capable of fast and efficient preconcentration of actinides from aqueous matrices and, at the same time, amenable to easy and hassle-free loading on a flat filament for TIMS analysis. − …”

Rapid and precise determination of the 238Pu/239Pu isotope ratio using thermal ionization mass spectrometry

“…Novel polymeric substrates have been reported from our laboratory for rapid and selective separation of actinides from complex matrices as well as partitioning of plutonium and uranium in an acidic medium. 19–24 The method is based on a supported liquid membrane (DOHA-PP) containing a hydrophobic, liquid extractant N , N ′-dioctyl-α-hydroxyacetamide (DOHA) in dodecane, that was found to be highly selective towards Pu( iv ) in a 3–4 M nitric acid medium, compared to other actinides such as Am( iii ), Np( v ) and U( vi ). Using a DOHA-PP membrane, it was possible to measure the 238 Pu/ 239 Pu atom ratio by TIMS i.e.…”

Lithium-Irradiated Poly(vinylidene fluoride) Nanohybrid Membrane for Radionuclide Waste Management and Tracing

“…Therefore, they find applications in various fields. − One of the most important applications is the management of radioactive waste which is generated during the operation of the nuclear facilities worldwide for nuclear energy production using various radioisotopes. Radioactive waste from nuclear fuel cycle in the reactor is a major concern globally as it cannot be disposed off directly into the environment. , Therefore, radioactive waste management is of prime importance − along with the detection of the radioactive element using a scintillation detector . Radionuclides can be identified/quantified by measuring the various types of primary radiations emanating from the sources, for example, α-, β-, and γ-rays and neutrons, or subsequent effects arising from their interaction with matter .…”