Cesium and strontium ion exchange on the framework titanium silicate M2Ti2O3SiO4.nH2O (M = H, Na)

The ion exchange properties of the titanium silicate, M2Ti2O3SiO4.nH2O (M = H, Na), toward stable and radioactive 137Cs+ and 89Sr2+, have been examined. By studying the cesium and strontium uptake in the presence of NaNO3, CaCl2, NaOH, and HNO3 (in the range of 0.01-6 M) the sodium titanium silicate was found to be an efficient Cs+ ion exchanger in acid, neutral, and alkaline media and an efficient Sr2+ ion exchanger in neutral and alkaline media, which makes it promising for treatment of contaminated environmental media and biological systems.     

Surface Preparation of Ti-6Al-4V for High-Temperature Adhesive Bonding

The role of surface preparation in high-temperature bond durability is investigated for Ti-6Al-4V adherends. Four surface preparations, including a newly-introduced treatment, plasma-sprayed Ti-6Al-4V coatings, are evaluated using a simple tensile test and a wedge/crack-propagation test. At temperatures approaching 300°C, the oxide-metal interface of oxide preparations becomes unstable. Such exposure results in a weakening of the oxide and, hence, bond failure at low tensile strength. The plasma-sprayed coating is a microscopically-rough metallic film with only a thin, native oxide. The plasma-sprayed adherend remains strong over prolonged, high-temperature exposures, and the micro-roughness is important for crack arrest in the wedge test.     

Rates of Exchange of Cs+ and Sr2+ for Poorly Crystalline Sodium Titanium Silicate (CST) in Nuclear Waste Systems

The compound sodium titanium silicate, popularly known as CST, is highly selective for Cs⁺. It was synthesized for the purpose of removing ¹³⁷Cs from basic nuclear waste systems. This compound has a tunnel structure in which the Cs⁺ ion just fits but diffusion through the tunnels is relatively slow. CST loses its ability to sequester Cs⁺ in the strongly basic nuclear waste solutions. However, replacement of titanium with 25 mol% of niobium increases the selectivity to a satisfactory level. It has been found that producing a less crystalline form of Nb-CST greatly improves the rate of Cs⁺ removal. Additionally, the non-niobium CST is selective for strontium both as Sr²⁺ and Sr(OH)⁺. It is suggested that both radioisotopes of cesium and strontium may be efficiently extracted by a combination of a mixture of poorly crystalline CST and Nb-CST.     

THE REMOVAL OF STRONTIUM AND CESIUM FROM SIMULATED HANFORD GROUNDWATER USING INORGANIC ION EXCHANGE MATERIALS

ABSTRACT

A number of inorganic ion exchange materials that are commercially available or under development were evaluated for the removal of strontium and cesium from a simulated groundwater found in the Hanford waste storage area using a groundwater simulant spiked with either 89Sr or 137 Cs. The most promising materials for strontium were found to be a sodium titanosilicate from Texas A&M University closely followed by two titanium silicate pharmacosiderites obtained from AlliedSignal. The most promising materials for the selective removal of cesium from the simulant was again the sodium titanosilicate followed by an alumina-pillared montmorillonite clay obtained from Laporte Industries Ltd. The ion exchange kinetics were shown to be very rapid for both the titanosilicate and the pharmacosiderite, whilst the alumina-pillared montmorillonite had slower kinetics more comparable to those of the zeolite AW500.     

THE ION EXCHANGE SELECTIVITY BEHAVIOR OF ZIRCONIUM SULPHOPHOSPHONATES TOWARDS ALKALI AND ALKALINE EARTH CATIONS

A new family of ion exchangers having a layered structure and a general composition of Zr(O₃PC₆H₄SO_{3 3}HPO_4x has been prepared. The ion exchange behavior of two members of the family (with x - 0.43 and 0.767) towards alkali and alkaline earth cations was determined. The sulfonic acid groups provide strong acid cation exchange sites while the phosphate protons exhibit moderate to weak acidity. Separation factors for the two layered exchangers were much higher than those for a conventional polystyrene sulfonic acid and even for zirconium phosphate.     

Effect of Nanoplatelets on the Rheological Behavior of Epoxy Monomers

The effect of nanoplatelets on the rheological behavior of epoxy monomers with variations in nanoplatelet exfoliation level and aspect ratio was investigated. The results show that the presence of exfoliated nanoplatelets in epoxy can significantly influence viscosity and lead to shear‐thinning phenomena, especially when the aspect ratio of the nanoplatelets is high. By employing the Krieger‐Dougherty model, the effectiveness of nanoplatelets in altering epoxy rheological behavior was quantitatively described and compared with experimental findings. Possible physical reasons for the observed rheological behaviors are discussed. The implication of the present study for polymer nanocomposites processing is also addressed.

     

On the proton conductor (H3O)Zr2(PO4)3

The compound HZr₂(PO₄)₃ was converted to (H₃O)Zr₂(PO₄)₃ by refluxing in water for 12 or more hours. The water is lost above 150°C to regenerate the original triphosphate. The hydronium ion phase is rhombohedral with hexagonal axes of a = 8.760(1) and $\text{c}\text{= 23.774(4)}\text{A}\text{?}$. Proton conduction in these compounds was investigated by an ac impedance method over the frequency range 5Hz – 10MHz. The activation energy for (H₃O)Zr₂(PO₄)₃ in the temperature range of 25 to 150°C was 0.56eV while the corresponding value for HZr₂(PO₄)₃ (125 – 300°C) was 0.44eV.     

Synthesis of Ultrafine Grain Ferrites

Methoxides of nickel(II) and iron(III) were synthesized, mixed in the ratio to form NiFe₂O₄, aerosolized, hydrated, and then fired in a streamline tubular reactor. Submicrometersized spherical particles were obtained from pyrolysis at temperatures up to 570°. At 425°, the sudden loss of volatiles shattered the particles to much smaller spheres (with 30% less than 0.1 μm) giving a remarkable increase in surface area. Pyrolysis up to 570° caused a gradual increase in the powder density toward that of NiFe₂O₄. Heating the aerosol product up to just 600° with a heating rate of 5°/min yielded pure crystalline nickel ferrite.     

Comment on “Sodium Hydroxide Anodization of Ti-6AI-4V Adherends”, J. Adhesion 20,283 (1987)

The recent article “Sodium Hydroxide Anodization of Ti-6A1-4V Adherends” by Filbey, Wightman and Progar' is commendable in that a wide variety of analytical techniques has been used to study the surface preparation first reported by Kennedy, Kohler and Poole. We too have conducted in-depth studies of surface preparations for Ti-6A1-4V adherends with recent emphasis on chromic acid and sodium hydroxide anodization (CAA and SHA, respectively). Our initial results were in agreement with those presented by Filbey et al. (hereafter “the authors”) regarding surface composition and oxide sputter-etching efficiency. However, the results of more detailed work have shown that these observations (and the subsequent conclusions) may be influenced by instrumentation effects. We wish to highlight these briefly.