离子交换树脂法分离沉积物中锶和钕的影响因素研究

Sr和Nd同位素是地质学研究中经典的同位素定年和示踪体系。传统沉积物中Sr和Nd分离方法通常是利用AG50W-X8树脂分离Sr与稀土元素(REEs),再用Sr和Ln特效树脂分别对Sr和Nd纯化,但对于Fe元素含量较高的沉积物样品,该方法对REEs的洗脱率偏低,仅有50%。另外,AG50W-X8树脂高度、洗脱酸种类、Sr特效树脂淋洗酸体积以及Ln特效树脂过柱方式对Sr和Nd分离都有影响。为分析上述因素对Sr和Nd分离效果的影响,本文以水系沉积物标准物质GBW07309为例进行了研究,结果表明:(1)高含量的Fe会显著影响Sr和Nd的分离效果,而AG1-X8树脂可以有效去除Fe;(2)当AG50W-X8树脂高度为1 m L,硝酸作为洗脱酸时,Sr和REEs的分离效果较好;(3)Sr特效树脂淋洗酸中硝酸淋洗体积达到15 m L时可以有效分离Sr和Rb;(4)Ln特效树脂采用重力过柱方式时Sr和Nd分离效果较好,没有拖尾现象。本研究解决了Fe对分离Sr和Nd的干扰,K、Na、Ca、Mg、Fe、Rb、Sm去除率达到99%以上,完全满足Sr和Nd同位素分析的要求,为离子交换树脂法分离沉积物中Sr和Nd提供了较详细的前处理经验数据。

Study on the Factors Influencing the Separation of Sr and Nd in Sediments by Ion Exchange Resin

BACKGROUND: In geological studies, Sr and Nd isotopes are classical isotopic dating and tracer systems.OBJECTIVES: The traditional separation method usually uses the AG50W-X8 resin to elute and separate Sr and REEs in sediments, and then uses Sr-special resin and Ln-special resin to purify Sr and Nd, respectively. However, this method has lower recovery of REEs (only 50%) for sediments with high Fe content.METHODS: In addition, height and elution acid species of AG50W-X8 resin, Sr resin elution acid volume, and Ln resin washing ways have impacts on the separation of Sr and Nd. In this work, in order to investigate the effect of these factors on the separation of Sr and Nd in detail, we took river sediment (GBW07309) as an example.RESULTS: The results showed that (1) high Fe content significantly affected the separation effect of Sr and Nd, and AG1-X8 resin could effectively remove Fe; (2) using 1 mL AG50W-X8 resin and HNO₃ as the eluting acid, the separation effect of Sr and REEs was the best; (3) Sr and Rb could be effectively separated when the elution acid volume of Sr-special resin reaches 15 mL; (4) Nd was separated well without trailing phenomenon when gravity column method was used to wash the Ln-special resin.CONCLUSIONS: This method solves the Fe interference during separation of Sr and Nd. More than 99% of K, Na, Ca, Mg, Fe, Rb, and Sm were removed, which fully satisfied the requirements for the analysis of Sr and Nd isotopes. This paper provides more detailed empirical data for the separation of Sr and Nd isotopes in sediments by ion exchange resin method.