Automated in-line extraction of uranium(VI) from raffinate streams with on-line detection by cathodic stripping voltammetry
- Univ. of Liverpool (United Kingdom)
- BNFL, Cumbria (United Kingdom)
An automated method for on-site monitoring of uranium(VI) in raffinate streams originating from nuclear fuel reprocessing plants is described. An in-line stripping procedure (based on liquid/liquid extraction) was developed to extract U(VI) from this stream, a solvent mixture of 20% tributyl phosphate and nitric acid in kerosene, into an aqueous sodium sulfate solution. Degradation products in the solvent mixture, especially dibutyl phosphate, give rise to very strong complexes and are responsible for moderate but constant U(VI) recoveries (nearly 50%). Optimal conditions for in-line stripping comprise a mixing ratio of extractant (0.5 M sodium sulfate in water)/solvent mixture of nearly 3 and a pumping rate of nearly 0.4 mL min{sup -} of the solvent mixture. The determination of U(VI) was by on-line cathodic stripping voltammetry (CSV), preceded by adsorptive collection of the U(VI) as an oxine complex onto a hanging mercury drop electrode. Quantities of 1-2 mL of the aqueous extract were pumped into the voltammetric cell and diluted (1/5 to 1/10) with a background electrolyte containing 0.1 M PIPES buffer, 2 x 10{sup -4} M oxine, 10{sup -4} M EDTA, and 0.2 M hydrazine hydrate (pH 9.0). The CSV peak for U(VI) was obtained at -0.68 V with a detection limit of 20 nM in the raffinate stream using an adsorption time of 120 s. 11 refs., 7 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 159709
- Journal Information:
- Analytical Chemistry (Washington), Vol. 67, Issue 21; Other Information: PBD: 1 Nov 1995
- Country of Publication:
- United States
- Language:
- English
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