Evaluation and application of Diffusive Gradients in Thin Films (DGT) technique using Chelex®-100, Metsorb™ and Diphonix® binding phases in uranium mining environments

A new resin- Diphonix (R) in Diffusive Gradients in Thin Films (DGT) technique for the determination of uranium was investigated and compared with previously used binding phases for uranium, Chelex (R)-100 and Metsorb (TM). The DGT gel preparation and the elution procedure were optimized for the new resin. The U uptake on Diphonix (R) resin gel was 97.4 +/- 1.5% (batch method; [U] = 20 mu g L-1; 0.01 M NaNO3; pH = 7.0 +/- 0.2). The optimal eluent was found to be 1 M 1-hydroxyethane-1, 1-diphosphonic acid (HEDPA) with an elution efficiency of 80 +/- 4.2%. Laboratory DGT study on U accumulation using a DGT samplers with Diphonix (R) resin showed a very good performance across a wide range of pH (3-9) and ionic strength (0.001-0.7 M NaNO3). Diffusion coefficients of uranium at different pH were determined using both, a diffusion cell and the DGT time-series, demonstrating the necessity of the implementation of the effective diffusion coefficients into U-DGT calculations. Diphonix (R) resin gel exhibits greater U capacity than Chelex (R)-100 and Metsorb (TM) binding phase gels (a Diphonix (R) gel disc is not saturated, even with loading of 10.5 mu mol U). Possible interferences with Ca2+ (up to 1.33 x 10(-2) M), PO43- (up to 1.72 x 10(-4) M), SO42- (up to 4.44 x 10(-3) M) and HCO3- (up to 8.20 x 10(-3) M) on U-DGT uptake ([U] = 20 mu g L-1) were investigated. No effect or minor effect of Ca2+, PO43-, SO42-, and HCO3- on the quantitative measurement of U by Diphonix (R)-DGT was observed. The results of this study demonstrated the DGT technique with Diphonix (R) resin is a reliable and robust method for the measurement of labile uranium species under laboratory conditions. (C) 2015 Elsevier B.V. All rights reserved.