Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7686573 | Talanta | 2012 | 7 Pages |
Abstract
A new diffusive gradients in a thin film (DGT) technique for measuring dissolved uranium (U) in freshwater is reported. The new method utilises a previously described binding phase, Metsorb (a titanium dioxide based adsorbent). This binding phase was evaluated and compared to the well-established Chelex-DGT method. Batch experiments showed quantitative uptake (100±3%) of dissolved U by Metsorb and an elution efficiency of 95% was obtained using a mixed eluent of 1 mol Lâ1 NaOH/1 mol Lâ1 H2O2. The mass of U accumulated by Metsorb was linear (R2â¥0.98) with time across the pH range 3.0-8.1, validating the DGT measurement. The measured effective diffusion coefficients were highly dependent on pH, ranging from 2.74-4.81Ã10â6 cm2 sâ1, which were in reasonable agreement with values from the literature. Ionic strength showed no effect on the uptake of U, and thereby on diffusion coefficients, at NaNO3 concentrations â¤0.01 mol Lâ1, but caused the U concentration to be underestimated by 18% and 24% at 0.1 mol Lâ1 NaNO3 and 0.7 mol Lâ1 NaNO3, respectively. Deployment of Metsorb-DGT in synthetic freshwater resulted in reliable measurement of the dissolved U concentration (CDGT/CSol=1.05), whereas Chelex-DGT significantly underestimated the dissolved U concentration (CDGT/CSol=0.76). Metsorb-DGT was found to give reliable results after 8 h deployments in synthetic seawater but experienced competition effects with longer deployments. The Chelex-DGT was unable to measure U at all in synthetic seawater. A field deployment in a freshwater stream (Coomera River) confirmed the utility of the Metsorb-DGT method for measuring U in natural freshwaters, but performance of field deployments may require further evaluation due to the possibility of major changes in uranium speciation with pH and water composition. We recommend a filtered sample, of any water in which DGT measurements are to be made, be used to determine the appropriate diffusion coefficient under controlled laboratory conditions.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Colin M. Hutchins, Jared G. Panther, Peter R. Teasdale, Feiyue Wang, Ryan R. Stewart, William W. Bennett, Huijun Zhao,