Deborah S. Ehler

Beryllium in the Environment: A Review

Abstract Beryllium is an important industrial metal because of its unusual material properties: it is lighter than aluminum and six times stronger than steel. Often alloyed with other metals such as copper, beryllium is a key component of materials used in the aerospace and electronics industries. Beryllium has a small neutron cross-section, which makes it useful in the production of nuclear weapons and in sealed neutron sources. Unfortunately, beryllium is one of the most toxic elements in the periodic table. It is responsible for the often-fatal lung disease, Chronic Beryllium Disease (CBD) or berylliosis, and is listed as a Class A EPA carcinogen. Coal-fired power plants, industrial manufacturing and nuclear weapons production and disposal operations have released beryllium to the environment. This contamination has the potential to expose workers and the public to beryllium. Despite the increasing use of beryllium in industry, there is surprisingly little published information about beryllium fate and transport in the environment. This information is crucial for the development of strategies that limit worker and public exposure. This review summarizes the current understanding of beryllium health hazards, current regulatory mandates, environmental chemistry, geochemistry and environmental contamination.

Ultra-thin gates for the transport of phenol from supported liquid membranes to permanent surface modified membranes

Abstract We report on the development of membranes with an ultra-thin hydrophobic layer that can be used to support a liquid membrane or serve as a selective gate without further modification when the pore size is small enough. We use a thin layer of gold deposited on commercially available alumina supports to generate a layer on the surface that can be readily modified with thiols to control the hydrophobicity. Transport of 2,4,6-trichlorophenol (TCP) was attained with thiol-modified gold-coated alumina membranes sealed with dodecane. The flux rates through these membranes are five times faster than control experiments through unmodified membranes and show complete selectivity. This provides strong evidence that the flux rates are high enough to be limited by simple diffusion through the alumina support. We have also demonstrated that it is possible to make ultra-thin gates with the alkyl chain itself serving as the hydrophobic barrier. With a 17 carbon chain thiol attached to the membrane in the absence of dodecane, quantitative transport is observed with the same high flux rates observed for the dodecane-treated membranes. Fixing the hydrophobic barrier to the surface should allow for more stable membranes.

The Synthesis of Carbon-13 Enriched Monosaccharides Derived from Glucose and Mannose

Abstract A modified Kiliani-Fischer reaction is used to prepare multigram quantities of [1-13C]-enriched glucose and mannose which are converted chemically or enzymatically into other labeled monosaccharides. The simplest conversion is the synthesis of labeled fructose from labeled glucose using commercially available immobilized glucose isomerase. The equilibrium for this reaction provides a 1:l mixture of glucose and fructose which can be separated by chromatography. The equilibrium can be shifted toward fructose by treating the reaction with germanate ion. [1-13C]Mannose can be converted into more useful sugars using a modification of the Lobry de Bruyn-Alberda van Ekenstein transformation. In this reaction, D-[1-13C]mannose is treated with an aqueous solution of dilute alkali and phenylboronate to form a mixture of labeled fructose, mannose and glucose. Fructose can be converted to a mixture of methyl fructofuranosides by using trifluoroacetic acid in methanol. [2-13C]Dihydroxyacetone can be prepared ...

Synthesis of 2-deoxy-d-arabino-(6-13C)hexose

2-Deoxy-D-arabino-[6-13C]hexose (10), to be used to test the stability of 2-deoxy-D-arabino-hexose 6-phosphate in brain tissue, was prepared. 2-Deoxy-D-arabino-hexose was labeled at C-6 because of the large difference in chemical shift between C-6 in the free sugar and C-6 in the 6-phosphate. The synthetic scheme resembled that used for the synthesis of D-[6-13C]glucose that involved the removal of C-6 from D-glucose followed by its replacement with 13C. The protected derivative methyl 2-deoxy-alpha-D-arabino-hexofuranoside was prepared, using trifluoroacetic acid in methanol. This was treated with periodate, which cleaves only between C-5 and C-6, to afford an aldehyde which reacted directly with K13CN to give a mixture of the D-arabino and L-xylo nitriles. The enriched nitriles were reduced with hydrogen in the presence of 5% Pd-carbon catalyst to a mixture of 6-aldehydo sugars. These were reduced with NaBH4 to a mixture of the two labeled methyl furanosides. Acid hydrolysis followed by ion-exchange chromatography on AG-50(Ca2+) resin at 65 degrees gave 10 in an overall yield of 16% from K13CN.

Beryllium Binding by Functionalized Polyethylenimine Water-Soluble Polymers

A series of polyethylenimine (PEI)-based water-soluble polymers (WSPs) were prepared by attaching functional groups (beta-diketones, carboxylic acid, salicylic acids) to the polymer backbone, with the goal of characterizing the interaction between beryllium and the various polymers. The extraction of beryllium from aqueous solutions by the WSPs was examined as a function of pH and ionic strength to evaluate the potential for the WSPs to isolate beryllium from contaminated aqueous waste streams. The loading capacities of these polymers for beryllium at near-neutral pH were unusually high in the absence of ionic strength adjustment compared to that for other +2 cations, suggesting that polynuclear beryllium species were interacting with the polymers. Beryllium loading capacity values were similar for all polymers evaluated in the absence of ionic strength adjustment. However, when the ionic strength of the solutions was adjusted to 0.1 N (NaNO3) the loading capacities were significantly reduced, indicating that electrostatic attraction played a dominant role in the interaction between beryllium and the polymers. The extraction curves of beryllium for all polymers evaluated, even those not designed to be selective for beryllium extraction, were nearly identical irrespective of the nature of the functional groups. Collectively, these results suggest that oligomeric beryllium species were formed, which can bind to the polymers through a combination of electrostatic forces and, potentially, hydrogen bonding.

Robust membrane systems for actinide separations

Our objective in this project is to develop very stable thin membrane structures containing ionic recognition sites that facilitate the selective transport of target metal ions, especially the actinides.