微波消解-电感耦合等离子体质谱法测定粉煤灰中铀

粉煤灰是一种宝贵的铀资源,为了满足我国日益增长的核电对铀的需求,必须加大对粉煤灰中铀的综合回收利用,因此准确测定粉煤灰中铀含量意义重大。采用HNO₃-HF-HClO₄体系微波消解样品,选择¹⁸⁷Re为内标元素,²³⁸U为铀测定同位素,建立了微波消解-电感耦合等离子体质谱法(ICP-MS)准确快速测定粉煤灰中铀的分析方法。对溶样条件进行了优化,确定溶样酸用量为5.0mL HNO₃、3.0mL HF、0.50mL HClO₄,消解程序如下所示:消解功率为800W,15min从室温升到150℃,保温10min,15min从150℃升到200℃,保温30min。实验表明,当铀的质量浓度范围为0.5~20ng/mL时,铀的质量浓度与其对应的信号强度呈线性关系,线性相关系数为0.9999,方法检出限为0.05μg/g。将实验方法应用于粉煤灰实际样品分析,测定结果的相对标准偏差(RSD,n=6)为3.2%,加标回收率为95%~104%。选取来自不同地方燃煤电厂的粉煤灰,按照实验方法进行铀的测定,并与激光荧光法进行对比,两种方法测定结果基本一致。

Determination of uranium in coal fly ash by inductively coupled plasma mass spectrometry with microwave digestion

The coal fly ash was a kind of valuable uranium resource. The comprehensive recovery and use of uranium in coal fly ash must be strengthened in order to meet the increasing demands of uranium in nuclear power industry. Therefore, the accurate determination of uranium content in coal fly ash was of great significance. The sample was treated by microwave digestion in nitric acid-hydrofluoric acid-perchloric acid system. An accurate and rapid determination method of uranium in coal fly ash by inductively coupled plasma mass spectrometry (ICP-MS) with microwave digestion was established with ¹⁸⁷Re as the internal standard element and ²³⁸U as the determination isotope. The sample dissolution conditions were optimized. The acid dosage was selected as follows: 5.0mL of nitric acid, 3.0mL of hydrofluoric acid and 0.50mL of perchloric acid. The digestion procedures were listed as follows: the digestion power was 800W; the temperature was increased from room temperature to 150℃ in 15min and kept for 10min; then the temperature was increased from 150℃ to 200℃ in 15min and kept for 30min. The experimental results showed that the mass concentration of uranium in range of 0.5-20ng/mL was linear to its corresponding signal intensity with linear correlation coefficient of 0.9999. The detection limit of method was 0.05μg/g. The proposed method was applied for the analysis of coal fly ash actual sample. The relative standard deviation (RSD, n=6) of the results was 3.2%. The spiked recoveries were between 95% and 104%. Various coal fly ash samples from different coal-fired power plants were determined according to the experimental method. The found results were basically consistent with those obtained by laser fluorescence method