Thermal Decomposition of Europium Hydroxide

The thermal decomposition of europium hydroxide in an air atmosphere was investigated by means of weight-loss measurements, infrared spectroscopy, X-ray diffraction analysis, and electron microscopy. These studies showed that EU(OH)° decomposed at temperatures between 225° and 300°C into EuOOH, which was stable up to about 425°C. Between 435° and 465°C this compound decomposed into cubic Eu₂O₃, which was stable until its inversion to the high-temperature monoclinic form. X-ray diffraction data were collected for Eu(OH)₃ and EuOOH and showed that the trihydroxide has a hexagonal crystal structure and the oxyhydroxide is possibly orthorhombic. The Eu(OH)₂, EuOOH, and cubic EunOa powders contained particles up to several microns in size consisting of agglomerates of crystallites in the size range 200 to 400 A. The single monoclinic Eu₂O₃ sample studied contained crystallites whose average size was greater than 2000 A.     

Changes in serum lipids in rats treated with oral cooper

Disturbances in lipid metabolism during copper deficiency in rats are well recognized. Copper deficiency is associated with the spontaneous retention of hepatic iron. Previous studies have reported that hypercholesterolemia and hypertriglyceridemia are associated with elevated hepatic iron concentrations in copper deficient rats. There was a direct relationship between the magnitude of blood lipids and the concentration of hepatic iron. Based on these data, it has been hypothesized that iron was responsible for the development of lipemia of copper deficiency. In this study was determined the effect of increasing doses of Cu(10, 20 and 50 ppm) in the diet, on the serum total lipids, total cholesterol, triglycerides (triacylglicerols), phospholipids, non-esterified fatty acids (NEFA) and liver iron and zinc concentrations in normal rats. The results were compared with normal rats that received a balanced diet containing 0.6 and 6 ppm of Cu, respectively. The results show that Cu-supplement diminished the cholesterol and triglyceride serum levels, increased the level of phospholipids, NEFA and concomitantly decreased the hepatic concentrations of Fe and Zn. There was a statistically significant (p < 0.05) simple correlation between triglycerides and liver Fe (r = 0.917; R2 = 64.03%), cholesterol and liver Zn (r = 0.872; R2 = 76.07%), cholesterol and liver Fe (r = 0.995; R2 = 99.10%), liver Fe and liver Cu (r = -0.612), liver Fe and liver Zn (r = 0.837), liver Cu and liver Zn (r = -0.612), and serum triglycerides and liver Zn (r = 0.967). The mechanism(s) by which Fe and Zn determine these changes is not known; none of the enzymes that act in cholesterol and triglyceride metabolism and biosynthesis require Fe and/or Zn. The increase of NEFA is due to changes in the process of lipolysis and re-esterification of the fatty acids in blood. However, additional studies are needed for the precise mechanisms of this interrelationships to be clarified.     

Functional properties of a protein product from Caryodendron orinocense (Barinas nut)

The functional properties of Caryodendron orinocense protein product were investigated and compared with those of soybean (Glycina maxima). The product protein content was 24.47 g/100 g (Nx6.25). Solubility increased at both sides of the isoelectric point (pH 4.0) and with increased NaCl concentration up to 0.5M. Compared with soybean flour (50% protein), the protein product exhibited higher water and oil absorption, but lower emulsifying activity, emulsion stability, foaming capacity, and foam stability, the last one increase at higher pH. Emulsifying activity, foaming capacity, and foam stability were ionic strength dependent. C. orinocense protein product increased its emulsifying activity steadily from 0.05M to 0.75M NaCl, while it remained almost constant for soybean flour. Foaming capacity increased drastically at pH 10. The minimum time and concentration to form a gel was 20% in 4 min and 10% in 8 min for the Caryodendron protein product and soybean flour, respectively. The bulk density was 0.5056+/-0.0041 g/mL.     

Theoretical Aspects Of The Kinetics Of Competitive First Reactions Of Ozone In The O3/H2O2 And O3/UV Oxidation Processes

Kinetics of competition between the ozone direct reaction with compounds in water, ozone-hydroperoxide ion reaction leading to free radicals in the O₃/H₂O₂ process, and the photolysis of ozone in the O₃/UV process are discussed in terms of diffusion and reaction times to establish conditions for these reactions to be competitive. Film theory and chemical kinetic concepts then are applied to estimate initial rates of ozone absorption and consumption, removal rates of compounds present in water, and the importance of the radical oxidation path versus direct ozone and/or photolysis reactions.     

Preparation of a Novel Composite Material Based on a Nafion® Membrane and Polypyrrole for Potential Application in a PEM Fuel Cell

The process of embedding polypyrrole (PPy) on the surface of a Nafion^® membrane was studied. Three methods of PPy synthesis directly on the membrane surface were compared. The diffusion method based on the separation of monomer and oxidant (peroxidisulphate) solutions by the membrane to be modified is proposed as the most promising one. The monomer diffuses through the membrane to the oxidant side, where it is polymerized. In this case sulphate is incorporated into the film as a counter-ion. PPy film prepared in this way adheres well to the Nafion^® surface and shows promising electrochemical activity. The permeability of the composite for monomer in comparison to self-standing Nafion^® film is reduced significantly. This may be important for the potential application of this composite, especially in a direct methanol fuel cell, as an alternative membrane-electrode assembly (MEA), particularly with regard to the currently used MEA’s permeability for fuel.     

A comparative study between chloride and calcined carbonate hydrotalcites as adsorbents for Cr(VI)

Hydrotalcite-type solids with different metal ions within the layers (M^II = Mg or Zn and M^III = Al and/or Fe) and carbonate or chloride between them have been synthesized. Chloride-LDHs and the solids obtained upon carbonate-LDHs calcination have been evaluated in the adsorptive removal of Cr(VI) from aqueous solutions. All the adsorption tests were carried out at 30 °C following two different stirring conditions: a) using a thermostatic bath with mechanical stirring at a speed of 52 rpm or b) in a sonicator bath under ultrasound waves. It was observed that no significant difference in the amount of adsorbed chromate is produced in both cases but the time spent to reach the equilibrium is much lower when the adsorbent/adsorbate mixture is submitted to ultrasounds. In all experiments L-type adsorption isotherms were obtained. The results show that chloride hydrotalcites are better adsorbents than calcined CO₃-hydrotalcites and in these last ones their adsorption capacity increases with increasing the surface area: MgAlFe > MgAl > MgFe > ZnAl.     

Coking kinetics of a Cr2O3/Al2O3 catalyst during 1-butene dehydrogenation: Effect of H2 partial pressure

The influence has been studied of the partial pressure of hydrogen (0–30 kPa) upon the coking rate of a Cr₂O₃/Al₂O₃ commercial catalyst during 1-butene dehydrogenation. Coke deposition has been analysed using a monolayer-multilayer reversible coke growth model (MMRC model). This model provides good fits to the experimental data, within the range of partial pressure of H₂ studied, and allows us to estimate the main kinetic parameters involved in the coking-deactivation process. The results obtained reveal a dual effect of hydrogen: competition against 1-butene for the active sites and the removal of coke precursors from the catalyst surface. Bom effects diminish the coking rate as the H₂ partial pressure is increased.     

Effect of refining on the phenolic composition of crude olive oils

By definition, virgin olive oil is consumed unrefined, although a great proportion of the olive oil produced has to be refined to render it edible. Phenolic compounds are among the substances eliminated during the refining process; in the present work these were characterized by HPLC, and their evolution during the different refining steps was studied. The complete refining process removed most polyphenols from oils, but the behavior of individual compounds at each step also was observed. o-Diphenols (hydroxytyrosol, catechol, and hydroxytyrosol acetate) and flavonoids (luteolin and apigenin) were eliminated first during the alkaline treatment. Tyrosol and 4-ethylphenol remained in the oil until the deodorization step. A large amount of phenolic compounds was discovered in the refining by-products such as soapstocks and deodorization distillates. In the latter streams, the concentrations of tyrosol and 4-ethylphenol reached up to 149 and 3720 mg/kg by-product, respectively. This high level of 4-ethylphenol and its well-known strong off-odor can interfere during further processing of the deodorization distillates, and this must be taken into account when deciding what is to become of them. Similarly, the results of this work open the possibility of recovering phenolic compounds from the “second centrifugation olive oils” by adding a new washing step prior to the refining process. By including this new step, the most polar polyphenols, hydroxytyrosol and tyrosol, will diffuse from oil to water and a concentration of up to 1400 mg/L of hydroxytyrosol may be achieved.