Cloud point extraction assisted spectrophotometric quantification of trace boron impurity in uranium-based nuclear fuels

Abstract

The separation of boron in nuclear fuels by cloud point extraction (CPE) has been a challenge due to high acidity of digested sample solutions. High acidity hampers the coacervation of micelles. As a result, the cloud point temperature increases and thus could cause the inevitable loss of boron as volatile species. Herein we have proposed a novel CPE-assisted colorimetric method for the quantification of traces of boron (B) in uranium-based fuels. A 1:1 mixture of 2-ethyl hexane-1,3-diol (EHD) and curcumin dispersed in Triton X-114 surfactant was used in the proposed CPE process. We had investigated several compounds to act as micelle surface modifiers. Among them, only bromine water (Br2) was found not only to lower the cloud point temperature (CPT, from 80 °C to 42 ± 2 °C) but also resulted in the quantitative recovery of boron (≥95%). The CPE of boron from uranium matrix in a 2.0 mol L−1 HCl medium was suitable for direct chemical quality assurance of routine uranium-based fuels. The molar extinction coefficient of the boron-EHD-curcumin complex was found to be 4.75 × 105 L mol−1 cm−1 (λmax at 458 nm) in N,N-dimethyl formamide medium. The linear dynamic range and detection limit of the proposed analytical procedure were calculated to be 10–150 ng mL−1 and 0.8 ng mL−1 respectively. The proposed analytical methodology was validated by analysis of three in-house working reference materials of uranium. Determination of traces of boron in two uranium dioxide and two metallic uranium samples were found to demonstrate the applicability of the method. The relative standard deviation of the proposed method was found to be of 3–5%.