Nancy N. Sauer

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.

Selective Anion Binding from Water Using Soluble Polymers

We investigated water-soluble dendrimers and polymers as ligands for selective anion binding. PAMAM Starburst dendrimers and polyethylenimine have been chemically modified to incorporate new ligands or hydrogen bonding groups at the primary amines. These molecules, along with the unmodified parent compounds, bind arsenate, chromate, and phosphate, even in the presence of competing anions such as chloride. Such systems could potentially be employed for remediation of contaminated water and soils using well-established ultrafiltration technology. Selectivity is achieved through bringing together moieties with a combination of electrostatic and hydrogen bonding capabilities. Total binding capacity for several metallooxyanions has been determined, as well as relative ion selectivity.

Potential binding modes of beryllium with the class II major histocompatibility complex HLA-DP: a combined theoretical and structural database study.

In an effort to understand the molecular basis of chronic beryllium disease (CBD), a study of the chemical relationship between beryllium, antigen, and the major histocompatibility complex II, HLA-DP, was undertaken. A homology model of the HLA-DP protein was developed. An analysis of the sequences of HLA-DPB1 and HLA-DPA1 alleles most common among CBD patients revealed several carboxylate rich regions in the peptide-binding cleft. These regions contain many hard Lewis base sites that may provide bonding opportunities for beryllium, a hard Lewis acid. Quantum chemistry calculations and structural database results support the presence of beryllium clusters, bridged by carboxylate, hydroxo, and/or oxo ligands, in the HLA-DP binding cleft. These results strongly suggest that beryllium clusters are an integral part of the antigen, and may even act solely as antigen. This work provides an initial model for thinking about beryllium interactions with proteins relevant to CBD and other metal-induced diseases.

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.

Tetrahydrofuran adducts of uranium tetrachloride

Abstract Pale green crystals of UCl 4 (THF) 3 ( 1 ) were isolated from saturated THF solutions after standing undisturbed for 12 h. The molecular structure of the compound was determined by single crystal X-ray diffraction. The molecule adopts a unique structure based on a distorted pentagonal bipyramid with two chlorides occupying the axial positions and the other two chlorides occupying adjacent positions in the pentagonal plane. Crystal data for 1 (UCl 4 O 4 C 12 H24 ) at 203 K: monoclinic space group P 2 1 a =7.835(1), b =14.428(1), c =8.456(1) A, β=100.97(1)°, Z =2, D calc =2.110 g cm −3.

PREPARATION OF WATER-SOLUBLE POLYMERS MODIFIED WITH SULFUR DONORS FOR RECOVERY OF HEAVY METALS

Polyethylenimine (PEI) was modified with ligands containing sulfur donors to give soluble polymers for binding toxic metal ions. Reaction of purified PEI with mercaptosuccinic anhydride, ethylene sulfide, or methylthiocyanate gave PEI-MSA (25% functionalization), PEI-ET (100% functionalization), and PEI-TU (25% functionalization), respectively. Purification of the polymers was accomplished by diafiltration. The capacities for toxic metal ions (Hg, Cd, and Pb) and transition metal ions (Cu and Ni) were measured for each of the polymers. PEI-ET and PEI-TU showed high affinity for the softer metal ions, Hg and Cd, with loading capacities substantially higher than those for the base polymer PEI. Both polymers had high capacities for Cu. Release of the metal ions from the polymers was accomplished by lowering pH; however, small amounts of metal remained bound to the polymers at pH 1. Competition studies showed that PEI-TU and PEI-ET bound Hg and Cu more strongly than Cd and Pb.

Beryllium colorimetric detection for high speed monitoring of laboratory environments

The health consequences of beryllium (Be2+) exposure can be severe. Beryllium is responsible for a debilitating and potentially fatal lung disease, chronic beryllium disease (CBD) resulting from inhalation of beryllium particles. The US Code of Federal Register (CFR), 10 CFR 850, has established a limit of 0.2 microg beryllium/100 cm(2) as the maximum amount of beryllium allowable on surfaces to be released from beryllium work areas in Department of Energy (DOE) facilities. The analytical technique described herein reduces the time and cost of detecting beryllium on laboratory working surfaces substantially. The technique provides a positive colorimetric response to the presence of beryllium on a 30.5 cm x 30.5 cm (1 ft(2)) surface at a minimum detection of 0.2 microg/100 cm(2). The method has been validated to provide positive results for beryllium in the presence of excess iron, calcium, magnesium, copper, nickel, chromium and lead at concentrations 100 times that of beryllium and aluminum and uranium (UO2(2+)) at lesser concentrations. The colorimetric detection technique has also been validated to effectively detect solid forms of beryllium including Be(OH)2, BeCl2, BeSO4, beryllium metal and BeO.

Fluorination of the high- Tc superconductors YBa2Cu3O7−δ and GdBa2Cu3O7−δ

Powdered samples of the high-temperature superconductors A Ba 2 Cu 3 O 7−δ (A = Gd,Y) were treated with fluorine gas (100 Torr) at room temperature and 400 °C for varying times (12–64 h). Magnetic shielding measurements on fluorinated products showed that the superconducting volume fraction in treated samples was greatly reduced or even completely eradicated. All samples were structurally characterized by x-ray powder diffraction. Two yttrium samples, one fluorinated at 25 °C and one at 400 °, were also examined by neutron powder diffraction. For samples treated at room temperature, no change in the structure or composition of the products was apparent by either technique. However, samples fluorinated at 400 °C are tetragonal, with a = 3.8641 (3), c = 11.704(1) A, and bulk composition corresponding to the formula YBa 2 Cu 3 F 3.5 O 4.5 . Nuclear activation analysis, nuclear reaction analysis, and Auger spectroscopy were used to determine fluorine concentration and distribution in the fluorinated materials. For samples treated at room temperature, fluorine was found primarily within approximately 1 μm of the surface of the product particles. No evidence for a fluorinecontaining superconducting phase was found in any sample; fluorine was found to be detrimental to superconductivity in all cases. These results suggest that the 123 oxides are sensitive to surface effects.

Tetrahydroborate complexes of uranium: preparation and crystal structure of mixed-valent [Na(THF)6][C5Me5)U(BH4)3]2

Abstract Reaction of U(BH4)3·nTHF with Cp*2Th(PPh2)2 in a THF/toluene solution containing NaCl resulted in isolation of the novel tetrahydroborate complex [Na(THF)6][Cp*U(BH4)3]2, Cp*=C5Me5. The complex crystallizes in the space group P 1 with cell parameters of a=11.110(3), b=15.140(3), c= 17.856(3) A, α=88.27(1), β=74.49(2) and γ= 85.42(2)o, Z=2 and Dcalc=1.49 g/cm3. The unit cell contains two crystallographically independent uranium atoms in general positions, each coordinated by three tridentate, hydrogen-bridged BH4− groups and one η5-pentamethylcyclopentadienyl ligand. Two Na(THF)6+ cations, which occupy centers of crystallographic symmetry, complete the structure. Metrical parameters are not significantly different between the two independent uranium centers (av. UB distances 2.61 A) or the two independent sodium containing cations. Crystallographically independent Cp*U(BH4)3 moieties pack to form two separate chains parallel to the crystallographic a axis. The stoichiometry and accompanying black color for the crystal suggest a mixed-valent charge transfer compound for which the average uranium oxidation state is 3.5. An unexpected Cp* transfer from thorium to uranium is also noted in the reaction chemistry.

Soluble and Volatile Precursors for the Preparation of Superconducting Films

Attempts to identify intermediates in an alkoxide-based solution route to films of the high temperature superconductor YBa 2 Cu 3 O 7 reported by Fahrenholtz et al.[1] have led to the isolation of the first molecular barium-copper cluster, Ba 2 Cu 2 (OR) 4 (acac) 4 ·2 HOR, R = CH 2 CH 2 OCH 3 . The extension of this route to the preparation of the bismuth superconductors has necessitated the investigation of bismuth alkoxide chemistry. Two separate routes to bismuth alkoxides have been examined: the metathesis of the metal halides with NaOR, (R = t-butyl, and diisopropylphenoxide) and the alcoholysis of bismuth amides, Bi(NR 2 ) 3 , [R = N(SiMe 3 ) 2 ] The alcoholysis preparation gives high yields of several alkoxides suitable as precursors to the high T c materials. A monomeric bismuth phenoxide, which is targeted as a volatile precursor, and a bismuth t-butoxide cluster have been isolated and stucturally characterized. Solubility and volatility studies have also been undertaken.