VARIATIONS IN THE SOLVENT EXTRACTION BEHAVIOR OF BIFONCTIONAL PHOSPHORUS-BASED COMPOUNDS MODIFIED WITH TBP

ABSTRACT

The solvent extraction of americium from nitric acid by several modified bifunctional extractants in CCl₄has been investigated. For all the compounds examined, addition of a modifier such as tributylphosphate (TBP) enhances distribution ratios at high aqueous acidities. The effect of the modifier at lower acidities varies depending on the basicity of the bifunctional extractant. While the most basic extractants show significantly reduced distribution ratios from lower acid solutions upon TBP addition, for the less basic compounds only slight reductions or, in some cases, even moderate increases in extraction are observed. Studies of the effect of modifier basicity on extraction behavior have also been carried out. The changes in distribution ratios with modifiers fall within the range of variations observed for diluent effects with extractants of this type. Increases in high acid distribution ratios upon TBP addition to an extractant as simple as trioctylphosphine oxide indicate that this modification of extraction behavior may be of general use for a wide range of neutral extractants     

The Separation of Beryllium from Selected Elements Using the Dipex® Extraction Chromatographic Resin

Abstract

An extraction chromatographic resin containing the acidic chelating organophosphorus extractant, Dipex^®, sorbed onto an inert polymeric substrate has been evaluated for the separation of beryllium from a wide range of elements. The elements selected comprise those which can interfere with the determination of beryllium by inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES) and matrix elements which commonly occur in environmental and industrial samples. Based on batch uptake measurements, a method that separates beryllium from all potential ICP‐AES spectral interfering elements using a single extraction chromatographic column is outlined. The chromatographic parameters of the separation method have been optimized using simulated samples generated using the digestion process employed in beryllium analyses by the Y‐12 National Security Complex and simulated ground water samples.     

A MECHANISM FOR ENHANCING IONIC ACCESSIBILITY INTO SELECTIVE ION EXCHANGE RESINS

ABSTRACT

A bifunctional monophosphonic/sulfonic acid ion exchange resin with high capacity has been synthesized. Metal ion studies have been carried out with europium, americium, and ferric nitrate in solutions of varying acidity, with and without sodium nitrate added. The bifunctional resin complexes far higher levels of Eu(III) from 0.5 and 1 N nitric acid than the monofunctional phosphonic acid resin. It is postulated that the sulfonic acid ligand provides an access mechanism for the metal ions into the polymer matrix by hydrating the matrix and preventing its collapse in high ionic strength solutions thus allowing for rapid ionic complexation by the selective phosphonic acid ligands. The bifunctional monophosphonic/sulfonic acid resin has both ligands bound to a polystyrene support. It complexes higher levels of metal ions than a comparable resin differing only by having the monophosphonic acid ligand directly bound to the C-C backbone. Results are compared to a diphosphonic / sulfonic acid resin.     

The Characterisation of Pluripotent and Multipotent Stem Cells Using Fourier Transform Infrared Microspectroscopy

Fourier transform infrared (FTIR) microspectroscopy shows potential as a benign, objective and rapid tool to screen pluripotent and multipotent stem cells for clinical use. It offers a new experimental approach that provides a holistic measurement of macromolecular composition such that a signature representing the internal cellular phenotype is obtained. The use of this technique therefore contributes information that is complementary to that acquired by conventional genetic and immunohistochemical methods.     

Fast start-up of a diesel fuel processor for PEM fuel cells

Fuel cell systems based on liquid fuels are particularly suitable for auxiliary power generation due to the high energy density of the fuel and its easy storage. Together with industrial partners, Oel-Waerme-Institut is developing a 3 kW_el PEM fuel cell system based on diesel steam reforming to be applied as an APU for caravans and yachts. The start-up time of a fuel cell APU is of crucial importance since a buffer battery has to supply electric power until the system is ready to take over. Therefore, the start-up time directly affects the battery capacity and consequently the system size, weight, and cost.     

Retrofitting social housing: reflections by tenants on adopting and living with retrofit technology

Retrofit has been described as one of the major engineering challenges of the twenty-first century (Kelly 2009). However, the industry needs to look beyond regarding the problem as restricted to the physical upgrade of properties. Asset managers, engineers and installers work on and in people’s homes and, in many cases, are subsequently changing the way householders use their homes to meet their comfort and wider energy needs. Here we consider how the twin issues of adopting and living with retrofit technologies have affected groups of residents in social housing. We discuss issues of trust, social norms, engagement and concern that have shaped the adoption process, as well as investigating the everyday experience of living with new configurations of energy consumption. The findings have relevance not only for the social housing sector but also raise questions as to how to effectively deliver programmes such as the Green Deal and the Energy Company Obligation within the UK.     

Comparison of the Effect of Individual and Combined Zr and Mn Additions on the Fracture Behavior of Al-Cu-Li Alloy AA2198 Rolled Sheet

The effect of individual and combined addition of dispersoid-forming alloying elements Zr and Mn on the fracture behavior of the Al-Cu-Li alloy 2198 has been investigated by the Kahn tear test. Overall, the standard baseline 2198 alloy containing only Zr exhibited the best performance, while the alloy with the combined presence of Zr and Mn was slightly inferior. The lowest properties were seen for a Zr-free 2198-0.4Mn alloy variant. In the T351 temper fracture initiated at coarse constituent particles that formed large cavities and microvoid sheets linked the initial sites of void growth. In the Mn-containing alloys microvoids clearly nucleated at the coarser Al₂₀Cu₂Mn₃ dispersoids within the microstructure, while this was not identifiable for the finer coherent Al₃Zr dispersoids. However, this difference in the mechanism of cavity linkage had little effect on the overall toughness of the materials, which was more closely related to the effect of Mn and Zr on the level of recrystallization. Extended artificial aging promoted grain boundary decohesion due to the precipitation of high densities of T₁ particles on GBs and favored a cleavage fracture mode. Particle decohesive fracture was also promoted by T₁ precipitation on the Mn dispersoids.     

Isolation and identification of antimicrobial peptides derived by peptic cleavage of whey protein isolate

The antimicrobial potential of whey protein isolate hydrolyzed by gastrointestinal enzymes was determined by attempting to identify and characterize the antimicrobial peptides responsible. While tryptic and chymotryptic hydrolysates did not show antibacterial activity, whey proteins hydrolyzed for 45–90 min by pepsin exhibited significant activity. Fractionation of 60-min hydrolysate by reversed-phase high performance liquid chromatography yielded 5 fractions that were antibacterial, with minimum inhibitory concentrations comprised between 20 and 35 μg/mL. These fractions contained short peptides not previously identified as antimicrobial. Fragment 14–18 (KVAGT) of β-lactoglobulin is very close to a sequence previously identified as antibacterial and is found in antimicrobial sequences of diverse origin. Five other peptides derived from β-lactoglobulin, and one fragment from α-lactalbumin (f117–121, KVGIN), were also identified as antibacterial. The identified peptides do not match pepsin action exactly, indicating modified proteolysis of unknown origin. Protein by-products of the dairy industry offer potential for large-scale production of antimicrobial peptides.