Showing papers by "Mark L. Dietz published in 1997"

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.

Pre-concentration of actinide elements from soils and large volume water samples using extraction chromatography

Abstract: The analysis of environmental samples for low levels of U, Pu, Am and other actinide elements is often hampered by sample-dependent problems involving the composition and/or mineralogy of specific samples. While relatively small samples (1–2 g of soil or 1–2 of water) are required to reach the extremely low detection limits occasionally mandated for environmental monitoring. One approach to avoid the troublesome and often inexplicable problems collectively referred to as “matrix effects” is to pre-concentrate actinides into a common form that would then behave uniformly and predictably during a subsequent separation scheme. Recently, a new extraction chromatographic resin based on diphosphonate chemistry was developed at Argonne National Laboratory. This resin commercialized as Eichrom's Actinide Resin, exhibits extremely high affinity for actinide elements even in the presence of high concentrations of salts. We have measured the uptake of actinides by the Dipex® extractant from natural waters and natural matrix soil standards. Water samples have been analyzed for gross α-activities and gave results that compared favorably to the traditional approach. In addition, we have obtained good recoveries and excellent separations for soil samples as judged by resolution on the α-spectra and the complete absence of interfering energies.

Effect of crown ethers on the ion-exchange behavior of alkaline Earth metals. Toward improved ion-exchange methods for the separation and preconcentration of radium.

Abstract: The effect of selected crown ethers on the uptake of alkaline earth cations by sulfonic acid and diphosphonic acid-based cation-exchange resins from hydrochloric acid media is examined. The effect observed is shown to vary with the hydrophobicity of the crown ether. Water-soluble crown ethers enhance the sorption of certain cations, thereby improving the selectivity of the resin for other alkaline earths over calcium ion, an apparent result of a synergistic interaction between crown ether present in the resin phase and the ionic functional groups of the resin. In the presence of more hydrophobic crown ethers, a decrease in cation sorption is often observed, a result of the exclusion of the crown ether from the resin phase and the formation of cation-crown complexes in the solution phase. The result can be a reversal of the selectivity sequence ordinarily exhibited by the resin.