L. Maggi

Copper hexacyanoferate(II) and (III) as trace cesium adsorbers from natural waters

A description is given of the preparation of copper hexacyanoferrate(II) supported on silica granules. The material in this form is suitable for use as adsorber in batch for concentrating trace cesium from cea water. A modified procedure for collecting cesium from large volumes of river water consists in the use of a column filled with the absorber that is oxidized to copper hexacyanoferrate(III) prior to use.

A novel approach to Ca-Sr separation in the determination of90Sr using inorganic exchangers: An application to environmental samples

A procedure for90Sr determination in calcium rich samples is presented. It is based on the precipitation of calcium oxalate in homogeneous solution and under controlled conditions to minimize the coprecipitation of strontium. The latter is subsequently separated as carbonate and radiochemical purification is completed by ion exchange chromatography on two inorganic exchangers: PRTD (partially reduced tin dioxide) and CUCR (copper chromate). The procedure was applied to environmental samples such as ashed sediment, fish and vegetable and results are reported.

Separation of traces of thorium from large amounts of uranium, by adsorption on lanthanum–ammonium oxalate

Abstract The separation of small amounts of thorium from large amounts of uranium was achieved by chromatographic columns loaded with ammonium–lanthanum oxalate LAOX, previously prepared and characterized. Good separation yields were obtained; the recovery of the elements was often greater then 95%. 234 Th , naturally occurring in uranium samples, was used as a tracer of 232 Th in order to study the behavior of thorium. The separation and preparation of a 234 Th carrier free solution was also investigated. During thorium adsorption, trace amounts of uranium may be reduced to the +4 oxidation state. The adsorption step and the washing of the column, before thorium elution, were, therefore, run in the presence of a dilute H2O2 solution in order to prevent uranium reduction.

Thorium adsorption behaviour on mixed ammonium lanthanum oxalate, LAOX

Abstract The cation-exchange properties of mixed ammonium lanthanum oxalate, LAOX, were studied by batch equilibration as a function of the concentration of some cations, such as alkaline earths or ammonium and of some anions and acids. The distribution coefficients for thorium are high, while U(VI) is not adsorbed over a large acidity range. Thus, the separation of thorium from uranium may be successfully carried out. The experimental conditions of adsorption, elution and recovery of thorium were investigated as well, by using chromatographic columns filled with LAOX, in order to set best the separation conditions from uranyl ions. Instrumental neutron activation analysis, ICP emission spectrometry and the UV spectrometry were used to evaluate the thorium, uranium and lanthanum concentrations.

Characterization of a partially reduced tin(IV) oxide and of its cation exchange properties

A novel type of tin oxide and its cation exchange properties are described. The preparation of the oxide is rather unusual and consists in the precipitation of SnO·xH2O in the presence of sodium nitroprusside and its digestion in the presence of sodium nitrite. The final product is a partially reduced tin dioxide (PRTD) with one out of eight atoms of metal in the lower oxidation state of +2 and a great part of the bound water hydrogen replaced by sodium. Usual applications of commercially available tin dioxide exchangers can be extended to PRTD with remarkable advantages.

Adsorption of actinides by chelating agents containing benzene rings, fixed on charcoal

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, Kd. 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.

Metal-Humic and Fulvic Acid Interactions in Fresh Water Ultrafiltrate Fractions

Abstract Fresh water samples from Po river (Northern Italy) were filtered and characterized by measuring the most important physico-chemical parameters. The samples were subsequently submitted to ultrafiltration to separate and fractionate the colloidal particle range from > 104 to < 103 M.W. Two different types of ultrafiltration cells were tested; they yielded quite different results due to systematic errors introduced when using the cell operating under pressure. It was found that the largest share of any metal considered was associated with the finest (< 103 M.W.) particle fraction. Correlation analysis applied to analytical data showed that manganese is associated to organic matter in the 103–104 M.W. particle fraction. Positive correlations existing between copper and Apparent Complexing Capacity (ACC) and between cadmium content and Total Organic Carbon (TOC) in the < 103 M.W. particle fraction were also discussed.

Separation of U(IV) and U(VI) by ion exchange chromatography on lanthanum ammonium oxalate

Abstract A new inorganic exchanger consisting of lanthanum ammonium oxalate (LAOX) has been prepared and studied, and application to the separation of U(IV) and U(VI) has been explored after measuring, by the batch exchange method, the distribution coefficients. A hydrochloric acid-acetic acid mixture represents the most appropriate medium, among those tested, for performing the separation. Sorption is negligible for U(VI) but is relevant for U(IV) and it can be ascribed to the formation of an insoluble lanthanum uranium and ammonium oxalate. Desorption is possible only by using as eluent a hot solution of EDTA.

Ion exchange chromatography on a new form of tin dioxide for the isolation of strontium radioisotopes from fission products: an application to milk samples

An amorphous, partially-reduced tin dioxide, having properties of an inorganic exchanger, was tested for application to fission product separations. Due to the good sorption of both strontium and barium the application of the exchanger to radiostrontium isolation from fission product mixtures is subject to important restrictions. An application to 90Sr determination in milk is proposed.

Use of radiotracers in the study of the distribution of manganese and zinc in the ultrafiltrate fractions of fresh waters

The distribution of manganese and zinc in the ultrafiltrate fractions of natural waters can be determined by spiking samples with radioisotopes prior to ultrafiltration, and determining the activity of the filtrate by gamma counting. This technique is very powerful when coupled with other methods of trace analysis. A comparison of the results obtained by gamma counting with those obtained by atomic absorption spectrometry showed that the optimum time interval between spiking and ultrafiltration was 2 h, indicating that this was the time required for equilibration between the stable and radioisotopes. This optimum time interval was unaffected by either chemical or physico-chemical transformations due to prior ageing. Sorption equilibria at the outer surface of natural colloids were considered to be the predominant processes determining the radioisotope and trace metal distributions.