地质样品中贵金属元素的预处理方法研究进展

本文评述了近年来地质样品中贵金属元素分析预处理技术的研究现状和应用进展,对样品分解过程中常用的火试金法、碱熔融法、酸分解法以及样品分离富集过程中的吸附法、碲共沉淀法、离子交换法、溶剂萃取法、蒸馏法、生物吸附法等手段进行了归纳总结,分析了各方法的特点与不足,展望了技术方法未来发展方向。分解方法中的火试金法经分析工作者不断探索及改进,已成为分解贵金属的最佳手段,但其仍存在试剂消耗量大、成本高、流程长等缺点;碱熔融法虽可分解几乎所有地质样品,但其处理后的溶液存在大量钠盐,需经进一步的纯化;酸分解法主要以高压密闭和卡洛斯管的消解方式为主,但受到样品性质的制约。而不同分离富集的手段都具有较强的针对性,如:吸附法多用于Au、Pt、Pd的富集,蒸馏法仅适用于Os、Ru的分析。由于贵金属元素具有颗粒效应强、赋存形式复杂多样以及超痕量等特殊性,需要针对样品的类型特点选择相适应的预处理方法。本文提出,应当在现有的贵金属分解方法基础上,结合当前新的实验设备及实验条件,寻求更加高效、快捷的分解技术,严格控制流程的本底及各个环节的污染问题,实现多技术、多方法联用,满足贵金属分析的要求。

Research Progress on Pretreatment Methods for Analysis of Precious Metal Elements in Geological Samples

BACKGROUND: This article reviewed the research progress of pretreatment techniques for the analysis of precious metal elements in geological samples in recent years. The fire assay, alkali fusion, acid decomposition and adsorption methods used in the separation and enrichment of samples and absorption, tellurium co-precipitation, ion exchange, solvent extraction, distillation, and biosorption methods commonly used for sample decomposition were reviewed. The characteristics and deficiencies of each method were investigated, and the future development direction of the method is prospected.
OBJECTIVES: In order to make the analysis results accurate and reliable, it is necessary to select the appropriate means of sample decomposition and separation and enrichment to ensure complete sample decomposition, effectively eliminate the interference of co-existing ions and matrix effect, enhance the precious metal element test signal, and improve the signal-to-noise ratio.
METHODS: The fire assay method used for sample decomposition has been continuously explored and improved by analysts, and has become the best method to decompose precious metals. However, it still has the disadvantages of large reagent consumption, high cost, and long procedure. Although the alkali fusion method can decompose almost all geological samples, the resulted solution contained a large amount of sodium salt, which needed to be further purified. The acid decomposition method was mainly based on the high-pressure sealed Carius tube digestion, but it was limited by the nature of the sample. Different separation and enrichment methods were highly targeted. For example, the adsorption method was mostly used for the enrichment of Au, Pt, and Pd. The distillation method was only suitable for the analysis of Os and Ru.
RESULTS: Precious metal elements had features such as strong particle effects, complex and diverse forms, and ultra-trace amounts, so it was necessary to choose a suitable pretreatment method according to the type of samples.
CONCLUSIONS: Based on the existing precious metal decomposition methods, in combination with the current new experimental equipment and conditions, more efficient and rapid decomposition technologies should be sought and the background of the procedure and pollution problems in each step strictly controlled, realizing multi-technology and multi-method integration and meeting the requirements of precious metal analysis.