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  • Author or Editor: P. Lopez-de-Alba x
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Abstract  

The reactions of uranium(VI) and thorium(IV) ions with carminic acid have been investigated. These ions react with carminic acid in neutral medium, forming colored complexes. The dark purple or red wine complexes show a high absorption in the visible region (597 nm U(VI) and 616 nm Th(IV)). Chemical variables that affect the reaction have been optimized. The spectral overlapping of the color of complexes has been resolved by first-derivative spectrophotometry. The simultaneous determination of uranium(VI) and thorium(IV) mixtures is accomplished by taking the derivative signal (zero crossing) at 597 nm for U(VI) determination and at 616 nm for Th(IV) determination, respectively. The method has been applied to Tyuyamonite ore, containing in the matrix both ions.

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Abstract  

Salicylaldehyde-semicarbazone /SAS/ forms a complex with uranyl ion at pH 3.8±0.1 which has been studied spectrophotometrically. The results of Job's and moral ratio methods indicate 14 composition for the complex which at 230 nm obeys Beer's law in the range of 1 to 2500 ppb of uranium/VI/.

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Abstract  

A bivariate calibration method, has been applied to the simultaneous determination of U(VI) and Th(IV) ions as complexes with carminic acid by visible absorption spectrophotometry. The bivariate calibration method was applied satisfactorily to the determination of these ions in synthetic solutions simulating sulfuric acid leach solution obtained from uranium-thorium ores and the results were compared with those given by first derivative spectrophotometry. No significant advantages of any method were found.

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Abstract  

Two multivariate calibration methods, partial least squares types 1 and 2 (PLS-1 and PLS-2) have been applied to the simultaneous determination of U(VI) and Th(IV) ions as complexes with carminic acid by visible absorption spectrophotometry. The results obtained by application of different chemometric approaches are discussed. No significant advantages were found between the methods. The proposed methods were applied satisfactorily to the determination of these ions in synthetic solutions simulating sulfuric acid leach solutions obtained from uranium-thorium ores.

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Abstract  

The precipitation of uranyl ion with 2-hydroxy-1-naphthaldehyde /2H–1N=HL/ was studied. The solid complex /orange crystals/ was characterized by IR, UV-Vis spectra. Uranium was determined as U3O8 after calcination of the complex at 850°C /37.78% U experimental, 36.64% U calculated for C22H14O6U, UO2L2/. Using a statistical experimental design, the best conditions for quantitative precipitation were obtained. A gravimetric method for the determination of UO 2 2+ is proposed by weighing the complex after drying at 110°C.

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Abstract  

A multivariate calibration method, Partial Least Squares Type 1 (PLS-1), is proposed for simultaneous spectrophotometric determination of uranium and thorium ions as their complexes with arsenazo III in hydrochloric acid medium. Several data characteristics are taking into account in order to minimize the optimum number of factors required for the construction of calibration model, while using various statistical criterions of selection. Finally, the evaluated calibration model is satisfactorily applied to determination of these ions in samples that resemble sulfuric acid leach solution obtained from a uranium ore.

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Abstract  

Collection of uranium by salicyliden and glutariliden chitosans /Schiff's Bases/ was investigated to obtain information on uranium recovery from ores, especially carnotites. The collection of uranium by salicyliden /SDQ/ and glutariliden /GDQ/ chitosans was very rapid during the first 20 min and was affected by the pH of the solution, contact time and temperature. Uranium collected on SDQ and GDQ was easily eluted with diluted sodium bicarbonate solution. Also uranyl and vanadyl ions were separated from each other by using these biopolymers.

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