Selenium uptake onto natural pyrite

79Se is a major dose-determining redox-sensitive nuclide in safety analysis of radioactive waste disposal sites. In aqueous solutions, selenium forms soluble anionic species (SeIVO3 2− and SeVIO4 2−) that hardly sorb on negatively charged surfaces of common host-rock minerals. However, Se is known to have a strong affinity with sulphides and interacts with pyrite, a common minor mineral of argillaceous rocks being considered as host formations for radioactive waste repositories. In this study, we present micro- and bulk X-ray spectroscopy data (μ-XRF, μ-XANES, and EXAFS) showing that, under nearly anoxic conditions, dissolved SeO3 2− and SeO4 2− sorb directly onto the pyrite surface and are subsequently reduced to Se0 with increasing ageing time (up to 8months). These results suggest that the mobility of 79SeIV released from radioactive waste could greatly decrease through uptake on the pyrite surface followed by transformation into a sparingly soluble reduced for

Iodide interaction with natural pyrite

129I is one of the major dose-determining nuclides in the safety analysis of deep storage of radioactive waste. Iodine forms anionic species that hardly sorb on the surfaces of common host-rock minerals. Recently, interest has arisen on the role of pyrite, an accessory mineral capable of binding anionic selenium. Whereas the interaction of selenium with pyrite is well documented, corresponding results on iodine sorption are still scarce and controversial. Pyrite is present in argicilleous rocks which are being considered in many countries as potential host rocks for a radioactive waste repository. The uptake of iodide (I−) on natural pyrite was investigated under nearly anoxic conditions (O2<5ppm) over a wide concentration range (10−11-10−3 M total I−) using 125I as the radioactive tracer. Weak but measurable sorption was observed; distribution coefficients (Rd) were less than 0.002m3kg−1 and decreased with increasing total iodide concentration. Iodide sorption was connected to the presence of oxidized clusters on the pyrite surface, which were presumably formed by reaction with limited amounts of dissolved oxygen. The results obtained indicated that pyrite cannot be considered as an effective scavenger of 129I under the geochemical conditions prevailing in underground radioactive waste geologic storag

Goma arábiga, un ingrediente funcional para la formulación de productos saludables

El consumo de fibra en nuestro país, se encuentra muy por debajo de la recomendación. Esto lleva a buscar alternativas, como el desarrollo de productos adicionados con ingredientes funcionales, como la goma arábiga. Esta fibra prebiótica, posee propiedades tecnológicas, tales como una elevada solubilidad, por lo que puede ser ampliamente utilizada en la industria de bebidas, permitiendo elevar el contenido en fibra sin aumentar la viscosidad. Además, se destaca por sus propiedades biológicas, como estimular el crecimiento de bacterias ácido lácticas, aumentar la masa fecal, retardar la absorción de glucosa y secuestrar ácidos biliares. Asimismo, su consumo regular se ha asociado a la disminución del índice de masa corporal (IMC) y porcentaje de masa grasa, que junto a su bajo aporte calórico, hacen que sea considerada adecuada para el tratamiento o prevención de la obesidad. Otras propiedades que se pueden mencionar son su efecto antioxidante, anticancerígeno, no cariogénico y protector cardiovascular y gastrointestinal. Por todo lo mencionado, la utilización de esta fibra en la formulación de productos alimenticios destinados a la personas con Enfermedades Crónicas No Transmisibles, resulta una buena alternativa para aumentar su ingesta.The consumption of fiber in our country is far below the recommendation. This leads to look for alternatives, such as the development of products added with functional ingredients, such as gum arabic. This prebiotic fiber has technological properties, such as a high solubility, so it can be widely used in the beverage industry, allowing to increase the fiber content without increasing the viscosity. In addition, it stands out for its biological properties, such as stimulating the growth of lactic acid bacteria, increasing fecal mass, slowing the absorption of glucose and sequestering bile acids. Likewise, its regular consumption has been associated with a decrease in body mass index (BMI) and percentage of fat mass, which together with its low caloric intake, make it considered adequate for the treatment or prevention of obesity. Other properties that can be mentioned are its antioxidant, anticarcinogenic, non-cariogenic and cardiovascular and gastrointestinal protective effects. For all the above, the use of this fiber in the formulation of food products for people with Chronic Noncommunicable Diseases, is a good alternative to increase your intake.Fil: Alcocer, Jimena Cecilia. No especifica;Fil: Paz, Noelia Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Cruz, Violeta Evangelina. No especifica;Fil: Garay, Pablo Agustín. No especifica;Fil: Goncalvez de Oliveira, Enzo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Villalva, Fernando Josué. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Curti, Carolina Antonela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; ArgentinaFil: Rivas, Marisa Ayelen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. No especifica;Fil: Ramón, Adriana Noemí. No especifica

Inulin and its relation to the prevention of obesity and associated pathologies

A nivel mundial, son cada vez más las personas adultas que presentan sobrepeso y obesidad, y Argentina no es la excepción. Esto lleva a buscar alternativas, como el desarrollo de productos adicionados con ingredientes funcionales, como la inulina. Esta fibra prebiótica posee efectos benéficos para la salud, que incluyen el aumento en la sensación de saciedad, control de peso, mejora de la regulación intestinal, tratamiento de la diabetes, absorción de calcio y magnesio, disminución de los lípidos séricos, entre otros. Además, posee atributos tecnológicos y funcionales, tales como: aportar un sabor suave; aumentar la viscosidad actuando como espesante, estabilizante y gelificante; mejorar la textura de los productos en combinación con ciertos hidrocoloides; y estabilizar emulsiones y espumas. Por todo lo mencionado, la utilización de esta fibra en la formulación de productos alimenticios destinados a personas con obesidad y patologías asociadas, resulta muy favorable.Worldwide, more and more adults are overweight and obese, and Argentina is no exception. This leads to look for alternatives, such as the development of products added with functional ingredients, such as inulin. This prebiotic fiber has beneficial effects for health, which include increased satiety, weight control, improved intestinal regulation, diabetes treatment, absorption of calcium and magnesium, decreased serum lipids, among others. In addition, it has technological and functional attributes, such as: providing a smooth flavor; increase the viscosity by acting as a thickener, stabilizer and gelling agent; improve the texture of the products in combination with certain hydrocolloids; and stabilize emulsions and foams. For all the above, the use of this fiber in the formulation of food products for people with obesity and associated pathologies, is very beneficial.Fil: Cruz, Violeta Evangelina. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Paz, Noelia Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Alcocer, Jimena Cecilia. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Goncalvez de Oliveira, Enzo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Villalva, Fernando Josué. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Garay, Pablo Agustín. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Curti, Carolina Antonela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Rivas, Marisa Ayelen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones para la Industria Química. Universidad Nacional de Salta. Facultad de Ingeniería. Instituto de Investigaciones para la Industria Química; Argentina. Universidad Nacional de Salta. Facultad de Ciencias de la Salud; ArgentinaFil: Ramón, Adriana Noemí. No especifica

Durability of Silicate Glasses: An Historical Approach

We present a short review of current theories of glass weathering, including glass dissolution, and hydrolysis of nuclear waste glasses, and leaching of historical glasses from an XAFS perspective. The results of various laboratory leaching experiments at different timescales (30 days to 12 years) are compared with results for historical glasses that were weathered by atmospheric gases and soil waters over 500 to 3000 years. Good agreement is found between laboratory experiments and slowly leached historical glasses, with a strong enrichment of metals at the water/gel interface. Depending on the nature of the transition elements originally dissolved in the melt, increasing elemental distributions are expected to increase with time for a given glass durability context

On the Coordination of Actinides and Fission Products in Silicate Glasses

The local structure around Th, U, Ce and Nd in leached silicate glasses was examined using XAFS spectroscopy at their L3 edges and also at the K edge of Fe, Co, Ni, Zr and Mo. Pellets of inactive borosilicate glasses with a simplified or a complex composition were leached statically at 90 C, at pH buffered to 0 or 6 for 28 days (surface/volume, S/V, ratios of 0.1 cm{sup -1}). These glasses are compared to another SON68 sample (denoted ''SP1'' in this paper) that was statically leached for 12 years under similar conditions, except for a higher S/V of 12 cm{sup -1} and a higher unconstrained pH of 9.6. The speciation of Fe, Co, Ni, Zr and Mo in the simple and the complex unleached are similar. In the statically leached glasses, the speciation of these transition metals is mostly identical to in the unleached glasses, except in the gels formed at the surface of the glasses leached at low pH, where large speciation differences are observed. Surface precipitates, especially for Fe (as ferrihydrite), Mo (possibly sidwillite) and Th (as ThO{sub 2}) were detected. Finally, the drying of the gels considerably affects the metal speciation by enhancing metal polymerization

Iodide interaction with natural pyrite

29I is one of the major dose-determining nuclides in the safety analysis of deep storage of radioactive waste. Iodine forms anionic species that hardly sorb on the surfaces of common host-rock minerals. Recently, interest has arisen on the role of pyrite, an accessory mineral capable of binding anionic selenium. Whereas the interaction of selenium with pyrite is well documented, corresponding results on iodine sorption are still scarce and controversial. Pyrite is present in argicilleous rocks which are being considered in many countries as potential host rocks for a radioactive waste repository. The uptake of iodide (I−) on natural pyrite was investigated under nearly anoxic conditions (O2 < 5 ppm) over a wide concentration range (10−11–10−3 M total I−) using 125I as the radioactive tracer. Weak but measurable sorption was observed; distribution coefficients (R d) were less than 0.002 m3 kg−1 and decreased with increasing total iodide concentration. Iodide sorption was connected to the presence of oxidized clusters on the pyrite surface, which were presumably formed by reaction with limited amounts of dissolved oxygen. The results obtained indicated that pyrite cannot be considered as an effective scavenger of 129I under the geochemical conditions prevailing in underground radioactive waste geologic storage

The influence of carbonate complexes on the solubility of zirconia: new experimental data

New experiments conducted at pH 9 and 298 K clearly indicate that addition of bicarbonate ions in aqueous solutions increases the solubility of both cubic and monoclinic zirconia by several orders of magnitude. In pure water the solubility of zirconia proved to be very low (about 10−10 to 10−8 M), while in the presence of 0.05 M NaHCO3 it increased to 10−6– 10−5 M, indicating the formation of strong carbonate complexes. Due to the limited number of available data and the restricted experimental conditions (fixed pH) it was not possible to identify the stoichiometry of the complex(es). However, up to a total carbonate concentration of 0.05 M, our data are consistent with the formation of a mononuclear tetracarbonate or pentacarbonate complex. At higher carbonate concentrations basic Zr carbonates are possibly formed. The formation constant fitted for the pentacarbonate complex is at the upper limit of a range previously estimated with the help of data on analogous actinide-carbonate complexes. Although our results are not sufficient to determine reliable thermodynamic data for the complexation of Zr with carbonate, they can be used to set limits to the solubility of inert matrix spent fuel in radioactive waste storage environments. Our measurements indicate a Zr solubility in the order of 10−6 to 10−5 M for typical repository conditions, which is still 2–3 orders of magnitude below silica concentrations measured from the dissolution of nuclear waste glasses