Search

An analytical approach for halides determination in uranium-bearing phosphate rocks, based on halides extraction from natural calcium phosphate by a metathesis reaction, followed by ion chromatography with conductivity detection analysis, is presented in this work. Chloride extraction is performed by mixing samples with sulfuric acid, causing an interchange between phosphate and sulfate ions towards calcium ions in the solid phase (metathesis). Addition of small amounts of calcium hydroxide improves the chromatographic determination by eliminating artifacts located in proximity to chloride retention time, and reducing phosphate peaks area. Limit of quantitation (LOQ) for chloride and bromide were found to be 25 mg/Kg and 50 mg/Kg, respectively. The metathesis reaction is proven by ED-XRF analysis of the precipitate produced during this reaction, showing the interchange between sulfate and phosphate ions. Chloride determination based on this approach was performed on several uranium-bearing phosphate rock samples from different sources. Since geolocation is one of the primary techniques needed for attribution, in a nuclear forensic investigation, this methodology may contribute to find new signatures, e.g. halides, in natural phosphate rocks deposits, to support that. The Cl− content in 11 phosphate rock samples was determined after applying metathesis, and found to be in the range of 30–792 mg/Kg, supporting its relevance as nuclear forensic signature. The Br− content was below the detection limit in all the samples.

We use dip-pen nanolithography to accurately pattern Ni(OH)2 nanoclusters on a metachemical surface with an exceptionally large surface area. The distance between the nanoclusters can be manipulated to control the oxygen-evolution reaction current and overpotential, thereby improving the efficiency of the water-splitting process while using minute amounts of the catalyst.

Ethylene-di-amine-tri-acetate was covalently bound to a Silica-gel matrix (ED3A-SG). The resin thus obtained was examined as a possible Ion Exchange Resin for pre-concentration of actinides and lanthanides. ED3A-SG was prepared by reacting Sodium N-(tri-methoxy-silyl-propyl)-ethylene-di-amine-tri-acetate (ED3A-Silane coupler) with silica-gel. The porosity of the system was measured using BET analysis. The capacity of the resin was measured by two techniques: a. Determination of the carbon content of the Resin using Carbon Sulfur Analyzer (CS Analyzer). b. Saturating the Resin with nickel ions and determining their amount by inductively coupled plasma optical emission spectrometer (ICP-OES). The behavior of the ED3A-SG resin as function of pH was measured by determining the recovery value of cations solutions buffered at different pH values. The molecular structure of the resin was examined by 13C NMR and 29Si NMR.

We determined the oxidation mechanism of porous ST-198, which mainly comprises Zr2Fe. Oxidation kinetics depended on temperature, oxygen partial pressure, and oxidation extent. The passivation role of oxidation in hydrogen scavenging is probably due to the development of a surface oxide, independent of oxygen concentration. Zr2Fe would be a superior hydrogen getter in oxygen-contaminated environments at high temperatures, as most oxygen will be consumed at the outer shell by mass transfer limitations, protecting the bulk of the getter for hydrogen scavenging.

The effect of incorporation of pozzolanic additives on the immobilization of cesium and strontium ions in cementitious pastes was investigated. Pastes containing Portland cement together with ground granulated blast furnace slag (GGBFS) (50%, 75%), metakaolin (MK) (10%, 20%), or silica fume (SF) (20%), either in its densified or raw form, were prepared. The transport properties of the immobilized ions through the paste were evaluated using leaching tests. Single differential thermal analysis (SDTA) was used to estimate the extent of the pozzolanic reaction and the pozzolanic reactivity of the different formulations. For strontium ions, the best immobilization system was the 20% raw silica fume (RSF) paste, characterized by the highest relative pozzolanity (RP). However, for cesium ions the most effective additive was the densified silica fume (DSF), reducing the apparent diffusion coefficient by two orders of magnitude compared to the unblended paste.

Temperature programmed desorption mass spectrometry (TPD-MS) and thermal gravimetry (TG) were utilized for the study of the thermal dehydration and decomposition of copper selenate pentahydrate (CuSeO4·5H2O). From the two techniques we suggest that the dehydration is a 3-step process reaching completion at 300 °C. The decomposition process however, is far more complicated consisting of several successive steps occurring between 480 and 900 °C. Initiated with the emission of oxygen, the decomposition of the anhydrous salt continues with SeO2 emission via several unstable intermediates up to the conversion of the remaining copper monoxide into dicopper monoxide accompanied by oxygen emission.

We determined the oxidation mechanism of porous ST-198, which mainly comprises Zr2Fe. Oxidation kinetics depended on temperature, oxygen partial pressure, and oxidation extent. The passivation role of oxidation in hydrogen scavenging is probably due to the development of a surface oxide, independent of oxygen concentration. Zr2Fe would be a superior hydrogen getter in oxygen-contaminated environments at high temperatures, as most oxygen will be consumed at the outer shell by mass transfer limitations, protecting the bulk of the getter for hydrogen scavenging.