Sherrod L. Maxwell

Bio: Sherrod L. Maxwell is an academic researcher from Westinghouse Electric. The author has contributed to research in topics: Ion exchange & Mass spectrometry. The author has an hindex of 4, co-authored 4 publications receiving 469 citations.

Method for digesting spent ion exchange resins and recovering actinides therefrom using microwave radiation

Abstract: The present invention relates to methods for digesting diphosphonic acid substituted cation exchange resins that have become loaded with actinides, rare earth metals, or heavy metals, in a way that allows for downstream chromatographic analysis of the adsorbed species without damage to or inadequate elution from the downstream chromatographic resins. The methods of the present invention involve contacting the loaded diphosphonic acid resin with concentrated oxidizing acid in a closed vessel, and irradiating this mixture with microwave radiation. This efficiently increases the temperature of the mixture to a level suitable for digestion of the resin without the use of dehydrating acids that can damage downstream analytical resins. In order to ensure more complete digestion, the irradiated mixture can be mixed with hydrogen peroxide or other oxidant, and reirradiated with microwave radiation.

Novel Extraction of Chromatographic Resins Based on Tetraalkyldiglycolamides: Characterization and Potential Applications

Abstract: Two new extraction chromatographic resins containing the diglycolamide class of molecules have been prepared and characterized, and potential applications identified. The new resins consist of 40 weight percent N,N,N′N′ tetraoctyldiglycolamide (TODGA) and N,N,N′N′ tetrakis‐2‐ethylhexyldiglycolamide (TEHDGA) sorbed onto 50–100 µm particle size Amberchrom® CG‐71. The new resins have capacities for Eu of approximately 0.086 mmol/mL of bed and are quite stable to extractant leaching. The resins were characterized by measuring the batch uptake of actinides, lanthanides, and yttrium, alkaline earths and 13 selected transition and post‐transition elements from HNO3 and HCl. Based on the uptake data, a number of very efficient separations were achieved using 0.5–2 mL bed volume columns and room temperature operation.

Identical extraction behavior and coordination of trivalent or hexavalent f-element cations using ionic liquid and molecular solvents

Abstract: The extraction of both UO22+ and trivalent lanthanide and actinide ions (Am3+, Nd3+, Eu3+) by dialkylphosphoric or dialkylphosphinic acids from aqueous solutions into the ionic liquid, 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide has been studied and compared to extractions into dodecane. Radiotracer partitioning measurements show comparable patterns of distribution ratios for both the ionic liquid/aqueous and dodecane/aqueous systems, and the limiting slopes at low acidity indicate the partitioning of neutral complexes in both solvent systems. The metal ion coordination environment, elucidated from EXAFS and UV-visible spectroscopy measurements, is equivalent in the ionic liquid and dodecane solutions with coordination of the uranyl cation by two hydrogen-bonded extractant dimers, and of the trivalent cations by three extractant dimers. This is the first definitive report of a system where both the biphasic extraction equilibria and metal coordination environment are the same in an ionic liquid and a molecular organic solvent.

DIPEX: A new extraction chromatographic material for the separation and preconcentration of actinides from aqueous solution

Abstract: A novel extraction chromatographic resin consisting of a liquid diphosphonic acid supported on an inert polymeric substrate for the sorption of actinides from strongly acidic chloride media is described. The resin is shown to exhibit stronger affinity for actinides in the tri-, tetra- and hexavalent oxidation states and superior selectivity for americium(III) over aluminum(III) or iron(III) than an analogous chelating ion-exchange resin containing chemically bonded geminally substituted diphosphonic acid functionalities. These properties, along with the comparative ease of recovery of sorbed actinides, make the resin readily applicable to the separation and preconcentration of actinides, as a group, from complex matrices such as soils and bioassay samples.