高压密闭消解-电感耦合等离子体质谱法测定锰矿石中的稀土元素前处理方法研究

吴磊; 刘义博; 王家松; 吴良英; 张楠; 王娜

doi:10.15898/j.cnki.11-2131/td.201712060189

高压密闭消解-电感耦合等离子体质谱法测定锰矿石中的稀土元素前处理方法研究

Sample Treatment Methods for Determination of Rare Earth Elements in Manganese Ore by High-pressure Closed Digestion-Inductively Coupled Plasma-Mass Spectrometry

摘要

摘要: 高压密闭消解因称样量小、用酸量少、空白低等优点成为测定稀土元素前处理的主要方法。但锰矿石组分复杂，锰含量差别较大且具有多种不同价态，常含有伴（共）生金属和其他杂质，该方法采用常规酸溶体系很难将其消解完全，造成ICP-MS测试结果不准确。本文从样品前处理消解效果出发，选择锰矿石标准物质GBW07261、GBW07263、GBW07266和一个锰矿石样品，试验了三种酸溶前处理方法对锰矿石稀土元素测试的影响。结果表明：方法一（氢氟酸-硝酸密闭消解，硝酸复溶提取）不能将锰矿石样品完全消解，测定值偏低0.28%~61.31%；方法二（氢氟酸-硝酸-双氧水密闭消解，硝酸-双氧水复溶，硝酸提取）和方法三（氢氟酸-硝酸密闭消解，盐酸复溶，硝酸提取）均可将锰矿石样品消解完全，用ICP-MS测定稀土元素的数据较为接近，与传统的过氧化钠熔融ICP-MS法测定值吻合。但实验过程中发现对于锰含量较高的样品，方法三需多次重复加入盐酸复溶后方可将样品消解完全，而方法二复溶一次即可。因此，方法二对锰矿石样品的消解效率更高，精密度好（0.96%~2.68%），加标回收率在95.0%~107.0%之间，更适用于锰矿石中稀土元素的分析。

Abstract:
BACKGROUNDWith advantages of small sample quantity, less acid, and low blank, high-pressure closed digestion-Inductively Coupled Plasma-Mass Spectrometry became the main method in the determination of rare earth elements. However, the composition of manganese ore is complex with varying manganese contents and different valence states of Mn, often with accompanying (co)producing metals and other impurities. The ore is difficult to digest completely using conventional acid-soluble systems, resulting in inaccurate ICP-MS analytical results.
OBJECTIVESTo optimize the acid-solution system condition of the high-pressure closed digestion method, in order to completely and effectively digest the manganese ore with complex components and improve the accuracy of the results.
METHODSThree standards GBW07261, GBW07263, GBW07266 and an unknown sample of manganese ore were digested using three different acid-solution systems of high-pressure closed digestion:Hydrofluoric acid-nitric acid closed digestion, extracted with nitric acid (Method 1); Hydrofluoric acid-nitric acid-hydrogen peroxide closed digestion, redissolved with nitric acid-hydrogen peroxide, extracted with nitric acid (Method 2); Hydrofluoric acid-nitric acid closed digestion, redissolved with hydrochloric acid, extracted with nitric acid (Method 3). The contents of rare-earth elements were then determined by ICP-MS.
RESULTSMethods 2 and Methods 3 can completely digest manganese ore samples. The results of rare-earth elements by ICP-MS were similar, and were consistent with the results of conventional sodium peroxide fusion. However, during the experimental process, for samples with high manganese content, Method 3 required repeated additions of hydrochloric acid before the samples were completely digested, whereas Method 2 need only one repeat. The precision of Method 2 was 0.96%-2.68%, and the recovery was 95.0%-107.0%.
CONCLUSIONSFor different manganese ore samples, Method 2 can completely digest the samples. The determination of rare earth elements was reliable by ICP-MS. Method 2 was the most suitable sample digestion method for the determination of rare earth elements in manganese ores.

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