三步离子交换方法用于粘土沉积物酸溶相中硼同位素测定

Sample Preparation for Isotope Determination of Boron in Clay Sediments by Three-step Ion-exchange Method

在采用酸溶法进行粘土沉积物中硼同位素组成测定时,大量存在的Al、Fe、稀土等元素在较高p H溶液中会形成能强烈吸附硼的氢氧化物沉淀,对硼的提取和硼同位素的测定产生较大影响。有效去除这些干扰元素一直是测定粘土沉积物酸溶相中硼同位素组成的瓶颈。本实验采用三步离子交换法萃取和纯化粘土沉积物中的硼,以AG 50W×8阳离子树脂柱去除所有能生成水不溶性氢氧化物的Al、Fe、稀土等元素,再采用Amberlite IRA 743硼特效树脂柱提取硼,最后采用Ion-exchangerⅡ与AG 50W×8组成的阴阳离子混合树脂柱进一步纯化硼提取液。结果表明,采用以上三步离子交换法提取粘土沉积物中硼的回收率高于90%,未观察到明显的硼同位素分馏,可满足粘土沉积物酸溶相中硼同位素组成高精度测定的需要。

When clay sediments were dissolved by hydrochloric acid, there will form large amounts of water insoluble hydroxide precipitation of A1, Fe and rare earth elements which can absorb boron strongly in high pH solutions. The hydroxide precipitation will greatly affect the extraction of boron and the determination of boron isotope. In this experiment, a new three-step ion-exchange method for the separation and purification of boron was proposed. Firstly, all the A1, Fe and rare earth elements which can generate water insoluble hydroxide, were removed by cation resin column with AG 50 W x 8. Next, boron in the sample solutions without A1, Fe and rare earth elements was extracted by boron special resin column with Amberlite IRA 743. Finally, the boron solutions were further purified by anion and cation resin mixed with Ion-exchanger II and AG 50 W x 8. The experimental results showed that the recovery of boron was more than 90% and no obvious boron isotope fractionation could be achieved using this three-step ion-exchange method. Therefore, this method could meet the needs of the high-precision determination of boron isotope of clay sediments.