Collection of lanthanides and actinides from natural waters with conventional and nanoporous sorbents.

Effective collection of trace-level lanthanides and actinides is advantageous for recovery and recycling of valuable resources, environmental remediation, chemical separations, and in situ monitoring. Using isotopic tracers, we have evaluated a number of conventional and nanoporous sorbent materials for their ability to capture and remove selected lanthanides (Ce and Eu) and actinides (Th, Pa, U, and Np) from fresh and salt water systems. In general, the nanostructured materials demonstrated a higher level of performance and consistency. Nanoporous silica surface modified with 3,4-hydroxypyridinone provided excellent collection and consistency in both river water and seawater. The MnO(2) materials, in particular the high surface area small particle material, also demonstrated good performance. Other conventional sorbents typically performed at levels below the nanostructured sorbents and demonstrate a larger variability and matrix dependency.

Rapid separation of beryllium and lanthanide derivatives by capillary gas chromatography.

Previous studies describe derivatization of metal ions followed by analysis using gas chromatography, usually on packed columns. In many of these studies, stable and volatile derivatives were formed using fluorinated ß-diketonate reagents. This paper extends previous work by investigating separations of the derivatives on small-diameter capillary gas chromatography columns and exploring on-fiber, solid-phase microextraction derivatization techniques for beryllium. The ß-diketonate used for these studies was 1,1,1,2,2,6,6,7,7,7-decafluoro-3,5-heptanedione. Derivatization of lanthanides also required addition of a neutral donor, dibutyl sulfoxide, in addition to 1,1,1,2,2,6,6,7,7,7-decafluoro-3,5-heptanedione. Unoptimized separations on a 100-µm i.d. capillary column proved capable of rapid separations (within 15 min) of lanthanide derivatives that are adjacent to one another in the periodic table. Full-scan mass spectra were obtained from derivatives containing 5 ng of each lanthanide. Studies also developed a simple on-fiber solid-phase microextraction derivatization of beryllium. Beryllium could be analyzed in the presence of other alkali earth elements (Ba(II) and Sr(II)) without interference. Extension of the general approach was demonstrated for several additional elements (i.e. Cu(II), Cr(III), and Ga(III)).

Rapid separation of beryllium and lanthanide derivatives by capillary gas chromatography.

DOI: 10.1002/jssc.201200537 Europium(III) derivative formed by reaction of the europium ion with a fluorinated ß-diketonate reagent and a neutral donor. The resulting non-polar, thermally stable, and luminescent derivative partitions into cyclohexane upon formation and can be subjected to high-resolution capillary gas chromatography. This approach is used to separate derivatives of lanthanides that are adjacent to one another in the periodic table. In addition, an on-fiber SPME derivatization/concentration GC/MS method that uses a fiber preloaded with the same ß-diketonate reagent is described for the analysis of beryllium(II) ion.

Collection of fission and activation product elements from fresh and ocean waters: a comparison of traditional and novel sorbents.

Monitoring natural waters for the inadvertent release of radioactive fission products produced as a result of nuclear power generation downstream from these facilities is essential for maintaining water quality. To this end, we evaluated sorbents for simultaneous in-situ large volume extraction of radionuclides with both soft (e.g., Ag) and hard metal (e.g., Co, Zr, Nb, Ba, and Cs) or anionic (e.g., Ru, Te, Sb) character. In this study, we evaluated a number of conventional and novel nanoporous sorbents in both fresh and salt waters. In most cases, the nanoporous sorbents demonstrated enhanced retention of analytes. Salinity had significant effects upon sorbent performance and was most significant for hard cations, specifically Cs and Ba. The presence of natural organic matter had little effect on the ability of chemisorbents to extract target elements.

Optimization and evaluation of mixed-bed chemisorbents for extracting fission and activation products from marine and fresh waters.

Chemically selective chemisorbents are needed to monitor natural and engineered waters for anthropogenic releases of stable and radioactive contaminants. Here, a number of individual and mixtures of chemisorbents were investigated for their ability to extract select fission and activation product elements from marine and coastal waters, including Co, Zr, Ru, Ag, Te, Sb, Ba, Cs, Ce, Eu, Pa, Np, and Th. Conventional manganese oxide and cyanoferrate sorbents, including commercially available Anfezh and potassium hexacyanocobalt(II) ferrate(II) (KCFC), were tested along with novel nano-structured surfaces (known as Self Assembled Monolayers on Mesoporous Supports or SAMMS) functionalized with a variety of moieties including thiol, diphosphonic acid (DiPhos-), methyl-3,4 hydroxypyridinone (HOPO-), and cyanoferrate. Extraction efficiencies were measured as a function of salinity, organic content, temperature, flow rate and sample size for both synthetic and natural fresh and saline waters under a range of environmentally relevant conditions. The effect of flow rate on extraction efficiency, from 1 to 70 mL min(-1), provided some insight on rate limitations of mechanisms affecting sorption processes. Optimized mixtures of sorbent-ligand chemistries afforded excellent retention of all target elements, except, Ba and Sb. Mixtures of tested chemisorbents, including MnO(2)/Anfezh and MnO(2)/KCFC/Thiol (1-3 mm)-SAMMS, extracted 8 of the 11 target elements studied to better than 80% efficiency, while a mixture of MnO(2)/Anfezh/Thiol (75-150 µm)-SAMMS mixture was able to extract 7 of the 11 target elements to better than 90%. Results generated here indicate that flow rate should be less of a consideration for experimental design if sampling from fresh water containing variable amounts of DOM, rather than collecting samples from salt water environments. Relative to the capability of any single type of chemisorbent tested, optimized mixtures of several sorbents are able to increase the number of elements that can be efficiently and simultaneously extracted from natural waters.

Verifying the presence of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy.

This paper examines the problems associated with analysis of low levels of neptunium in a uranium matrix with electron energy-loss spectroscopy (EELS) on the transmission electron microscope (TEM). The detection of neptunium in a matrix of uranium can be impeded by the occurrence of a plural scattering event from uranium (U-M(5)+U-O(4,5)) that results in severe overlap on the Np-M(5) edge at 3665 eV. Low levels of Np (1600-6300 ppm) can be detected in a uranium solid, uranophane [Ca(UO(2))(2)(SiO(3)OH)(2)(H(2)O)(5)], by confirming that the energy gap between the Np-M(5) and Np-M(4) edges is at 184 eV and showing that the M(4)/M(5) ratio for the neptunium is smaller than that for uranium. The Richardson-Lucy deconvolution method was applied to energy-loss spectral images and was shown to increase the signal to noise ratio.