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The retention behavior of U and Th as their 2,6-pyridine dicarboxylic acid (PDCA) complexes on a cation exchange column was investigated under low pH conditions. Based on the observed retention characteristics, an ion chromatographic method for the rapid separation of uranium and thorium in isocratic elution mode using 0.08 mM PDCA and 0.24 M KNO(3) in 0.22 M HNO(3) as the eluent was developed. Both uranium and thorium were eluted as their PDCA complexes within 2 min, whereas the transition and lanthanide metal cations were eluted as an unresolved broad peak after thorium. Under the optimized conditions both U and Th have no interference either from alkali and alkaline earth elements up to a concentration ratio of 1:500 or from other elements up to 1:100. The detection limits (LOD) of U and Th were calculated as 0.04 and 0.06 ppm, respectively (S/N=3). The precision in the measurement of peak area of 0.5 ppm of both U and Th was better than 5% and a linear calibration in the concentration range of 0.25-25 ppm of U and Th was obtained. The method was successfully applied to determine U and Th in effluent water samples.

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Bentonite is the candidate buffer and backfill material in the deep geological repositories. Montmorillonite (Mt) is the major clay minerals of bentonite. Over a long period of time, the interaction of corrosion products from overpack and/or cansister with clay minerals is expected to result in formation of Fe(III)-Mt, a plausible alterated product. In this context, it is important to understand the properties of Fe-Mt in comparison with original clay mineral, Na-Mt. In the present study, sorption behavior of Cs(I), long lived fission product (135Cs, t1/2 = 2.3 × 106 years; 137Cs, t1/2 = 30.1 years) with high fission yield, on Fe(III)-Mt is investigated. Batch sorption studies are conducted at varying pH (3–9), ionic strength (0.001–1 M) and Cs(I) concentration (10−10 to 0.05 M). The distribution coefficient (Kd) of Cs(I) on Fe(III)-Mt was found to be independent of pH except at low pH, indicating ion exchange mechanism as dominant interaction mode for Cs(I). It was further verified by ionic strength variation which depicted decrease in Cs(I) sorption with increasing ionic strength. Adsorption isotherm of Cs(I) was found to be linear over the concentration range of 10−10 to 10−3 M Cs(I). The Fe released from Fe(III)-Mt during the Cs(I) sorption was found to be not more than 0.2 ppm. However, on lowering the pH and increasing the ionic strength, the Fe release increased. Furthermore, the apparent diffusion coefficient for Cs(I) in Fe(III)-Mt has been determined.

Identification of various soluble organic acids formed during the pyrohydrolysis of uranium-plutonium mixed carbide [(U,Pu)C] was carried out using ion chromatography. This has significant importance as the soluble organic acids can cause severe interferences during the ion chromatography separation and determination of Cl − and F − in the pyrohydrolysis distillate of (U,Pu)C. Determination of Cl and F is important in the chemical quality control of nuclear materials as these two elements can cause corrosion and hence, their concentrations in all nuclear materials are restricted to certain specified values. Since the pyrohydrolysis distillates contain both inorganic and organic acid anions, for the sake of separating and identifying organic acid anions from the common inorganic anions, three independent isocratic elutions using varying concentrations of NaOH eluent were employed for the separation of weakly, moderately and strongly retained anions. It was observed that pyrohydrolysis of (U,Pu)C also produced soluble organic acids as in the case of nitric acid dissolution of UC. The present investigation revealed the presence of formic, acetic, propionic, butyric, oxalic acid anions in the pyrohydrolysis distillate of (U,Pu)C in trace or ultra-trace concentrations. The presence of each organic acid identified in the chromatogram was confirmed with spike addition as well as by separating them by capillary electrophoresis method. The presence of lower aliphatic acids viz. formic and acetic acids was reconfirmed by carrying out an independent separation with tetraborate eluent. It is suggested that nitric acid being formed during pyrohydrolysis could be responsible for the formation of organic acids. Based on the findings, an ion chromatography separation method has been proposed for the interferencefree determination of chloride and fluoride in pyrohydrolysis distillate of (U,Pu)C.

Retention behavior of U(VI) and Th(IV) as their 2,6-pyridine dicarboxylic acid (PDCA) complexes on reversed phase and ion exchange (cation, anion and mixed ion exchange) columns was studied and based on the results, a simple ion chromatography method for the determination of trace level thorium in uranium oxide using 0.075 mM 2,6-pyridine dicarboxylic acid (PDCA) and 1 M KNO 3 in 1.2 M HNO 3 as eluent (flow rate 1 mL/min) was proposed. The advantage of the developed method is that the separation of uranium matrix is not required prior to the ion chromatographic determination of trace Th. Separation was carried out on a mixed ion exchange stationary phase and a 10 −4 M arsenazo (III) solution was used as post column reagent for detecting the separated metal ions. The separation of Th from uranium using PDCA in the present investigation is attributed through cation exchange mechanism. A calibration plot was constructed by following the standard addition method over the concentration range of 0.25 to 10 ppm of Th in the presence of uranium matrix, which resulted in a linear regression coefficient of 0.9978. The precision of the method was better than 5% and the LOD for Th was found to be 0.1 ppm (S/N = 3). The method has been validated by comparing the results with the results obtained from ICP-MS analysis where the Th is separated from the uranium matrix. The proposed method is simple, rapid, accurate and cost effective compared to techniques like ICP-MS or ICP-AES and is suitable for the routine kind of analysis.