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- Author or Editor: V. Crespi Caramella x
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Abstract
We studied the preparation of some specific adsorbers capable of isolating and concentrating actinides. Bases of the 8-hydroxyquinoline family, diphosphineamine and tribenzylamine, salted by benzohydroxamic, benzylic or phthalic acid, are able to complex actinides in different oxidation states. As a result of the presence of the benzene rings, all the compounds are easily incorporated into active charcoal to obtain adsorbers with a highly specific surface. The adsorption behaviors of uranyl U(VI) ion, thorium(IV) and Eu(III) were studied by evaluating their distribution coefficients, K d. Results show that all the prepared salts can adsorb the ions in the III and IV oxidation state from weak acid solutions, whereas uranyl ion is adsorbed mainly from weak basic solutions. The prepared compounds can be used successfully to absorb and concentrate actinides from nearly neutral solutions, such as natural waters. The 8-hydroxyquinoline salt of the benzylic anion showed the highest adsorption values and thus seems to be the most appropriate salt to use in the analysis of actinides in water.
Characterisation of lead rhodizonate as barium and radium adsorber from fresh water
I. Preparation and characterisation of lead rhodizonate
Abstract
A new adsorber for concentrating barium and radium from diluted solutions and from fresh waters was prepared. It consists of basic lead rhodizhonate, namely [Pb(OH)]2C6O6·PbC6O6·H2O, supported on activated charcoal. It was named LEHRO. Preparation conditions, solubility and barium, or radium, adsorption from solutions of different pH were investigated.
Abstract
The dietetic contribution of some bioelements, namely sodium, potassium, chromium, manganese, copper, zinc, bromine and lanthanum from rice grains was investigated by destructive neutron activation analysis. Three different species of rice grains, all grown in the Po river valley, were studied on account of different industrial treatments they had been submitted to. Radiochemical separations were carried out by means of inorganic adsorbers such as hydrated antimony pentoxide, metallic cadmium, tin dioxide and manganese dioxide. Results are presented and discussed. Precision and accuracy of the method is discussed as well. A depletion of the mineral content of the rice grains related to the different industrial treatments was established together with an enrichment of bromine in the treated grains.
Abstract
The adsorption conditions of uranium, neptunium, thorium, europium on the adsorbers containing the benzylate salts of the 8-hydroxyquinoline (adsorber B), and of 2-methyl- 8-hydroxyquinoline (adsorber R), were prepared, supported onto charcoal and compared with an adsorber, containing the benzylic acid, (G), stabilized with d-glucoseamine, and adsorbed onto charcoal as well. Thorium, protoactinium, and europium are adsorbed nearly completely from aqueous solutions at a large pH range, even in low acid medium, whereas uranium and neptunium are completely adsorbed only from basic solutions of pH 9. The actinides are preferentially adsorbed with respect to other ions, which are present in natural waters, such as calcium or magnesium. This feature make the analysis of most actinides in natural waters easily to be performed without changing the pH of the original system. The uranium (neptunium) analysis indeed may be accomplished after adjusting the original pH to a fairly basic value (about to 9). The adsorption experiments from real samples showed that the analysis of the actinides dispersed in natural water systems may be successfully performed after previous concentration on the adsorbers prepare.
Characterisation of lead rhodizonate as barium and radium adsorber from fresh water
II. Adsorption behavior of earth alkaline ions
Abstract
Batchwise measurement of distribution coefficients of earth alkaline metals, on LERHO, lead rhodizonate supported on charcoal, were studied. The adsorption appears to be related to solubility of barium and lead rhodizonates. Preliminary column experiments were carried out as well to check that LERHO is suitable for achieve the preconcentration of radium from extremely diluted solutions. The overall behavior was studied in order to apply it to radiochemical separations.
Abstract
The adsorption of about 50 ions on molybdenum dibromide, (Mo6Br8)Br4·2H2O, in nitric acid was investigated. The preparation of the adsorber and its characterization is presented and discussed. Adsorption mechanism studies were carried out for some noble metals and chromium. Sorption cannot be ascribed to ion exchange mechanism but to formation of insoluble species, and to settlement of few ions into surface sorption sites or into a limited number of cavities in the cluster crystal structure of the adsorber.
Abstract
Neutron activation analysis of palladium, iridium, platinum, gold, silver and copper in different matrices was carried out by using inorganic adsorbers such as molybdenum dibromide, zinc ferrocyanide and cadmium metal for their radiochemical separation. The matrices chosen to show the versatility of the method were: high-purity copper and nickel metals, NBS standard reference material SRM 1571 (Orchard leaves), Pultusk meteorite and the U. S. Geological Survey standard rock W-1. The method elaborated is very simple as it involves only a few steps and it has been shown to be accurate and capable of yielding reliable results.
Abstract
Copper, iridium, platinum and gold content was determined in 15 italian chondritic meteorites by destructive neutron activation analysis. The chemical procedure involves few steps: sample dissolution, group separation of noble metals on inorganic adsorbers and gamma-ray spectrometry. Element content and atomic abundances (Si=106 atoms) are presented and discussed. Precision and accuracy of the analytical method are given as well. Copper, platinum and gold content is within the reported ranges for ordinary chondrites, whereas the iridium content is located on the low side of reported values.
