Separation and quantification of 238U, 232Th and rare earths in monazite samples by ion chromatography coupled with on-line flow scintillation detector.
An alternative procedure has been described for efficient separation and quantitative determination of uranium (U), thorium (Th) and rare earth elements (REEs) in monazite mineral by high performance ion chromatographic system (IC). Different variables affecting the distribution coefficient, the retention and hence separation efficiency such as eluent flow rate and concentrations of HCI and ammonium sulfate (NH4)2SO4 containing the mobile phase were studied. The developed separation protocol of U, Th and REEs was optimized using an Ion Pac CS5 separation column followed by post-column derivatization reaction with Arsenaso III and UV-VIS spectrophotometric detection. Comparative evaluation of U, Th and REEs concentration in monazite mineral was demonstrated using two different on-line detection modes including flow through cell scintillation detector (FSD) and UV-VIS spectrophotometer. Response of the FSD was found to be linear over the full range of activities investigated (4-100 Bq). The lower limits of detection (LLD) for the investigated radionuclides were 3.0+0.1 Bq for 238U and 6.0 +/- 0.1 Bq for 232Th. The detection of 238U and 232Th by FSD shows good agreement with the corresponding determination by UV-VIS spectrophotometer. The content of ThO2 and U3O8 in monazite sample were found to be 4.7 +/- 0.1% and 0.42 +/- 0.04% using UV-VIS detector and 4.3 +/- 0.1% and 0.45 +/- 0.1% using FSD, respectively.
SOLID-LIQUID PHASE EXTRACTION OF THORIUM (IV) FROM NITRATE LEACH LIQUORS USING AMINE FUNCTIONALIZED GLYCIDYL METHACRYLATE RESINS
Thorium adsorption from low concentration nitrate leach liquors was studied using glycidyl methacrylate/divinyl benzene/amine polymers. RI and RII resins were prepared by the reaction of GMA/ DVB copolymers with ethylenediamine and diethylenediamine, respectively. The thermal stability of the resins was studied thermogravimetrically. The prepared resins were applied for the adsorption of thorium from synthetic and real samples. The results indicated that; the adsorption of Th(IV) increased as the solution pH increased and the maximum metal adsorption was 50 and 64 mg/g for RI and RII, respectively. Thorium (IV) adsorbed per mass unit of RI and RII resins increased from 50 to 64 and from 66 to 88 mg/g by increasing the temperature from 293 o to 323 o K respectively. The obtained results indicated the applicability of RI and RII for Th(IV) adsorption. Finally, RI and RII resins were used for the separation of Th(IV) from three granite samples leach liquors.
Determination of uranium in natural groundwaters using high-performance liquid chromatography
A procedure using high-performance liquid chromatography (HPLC) and trace enrichment techniques has been developed to measure trace levels of uranium in solutions containing high concentrations of dissolved salts. This procedure is required to support research into the feasibility of deep geological disposal of used nuclear fuel, which includes studying the leaching of uranium from fuel by natural groundwater. After conditioning, several milliliters of sample are passed through a small reversed-phase enrichment of cartridge, where the uranium is concentrated and separated from the bulk of other constituents. The uranium is then back flushed from the column onto a reversed-phase analytical column where further separation is achieved. The separated species are monitored spectrophotometrically after postcolumn reaction with the chromogenic reagent Arsenazo III. Analysis of simulated ground waters has shown the procedure to be free from major interferences. Automation of the system using automatic switching valves and an automated sample injector allows approximately 40 samples per day to be analyzed with a measurement precision of about 4%. Detection limits are in the 1-2 ng/times/mL/sup /minus/1/ range.