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红土镍矿样品前处理方法和分析测定技术研究进展

Research Progress on Sample Preparation Methods and Analytical Techniques for Nickel Laterite

  • 摘要: 随着常规镍来源的硫化镍矿资源的日益枯竭, 可直接生产氧化镍、镍锍和镍铁等产品的红土镍矿倍受关注.对于红土镍矿中主量、次量、痕量元素的检测, 相同的检测项目存在多种测试方法, 且部分相同原理的测试方法存在细节上的差异, 使得检测者选择合适的检测方法变得困难.本文综述了近年来红土镍矿中24种元素测定的样品前处理方式及分析技术研究进展.样品前处理方式依据目标元素及后续的分析方法进行选择, 其中酸溶法和碱熔法用途最广.酸溶法引入的盐分少, 操作简单, 但是分解过程中易导致挥发元素As、Sb、Bi、Hg的损失, Cr易随高氯酸冒烟损失.碱熔法分解能力强, 适合分析Cr、Si、全铁等项目, 但会引入大量的盐类和因坩埚材料损耗而带入其他杂质, 给后续分析带来困难.红土镍矿的分析技术依据实验室条件及目标元素的性质和浓度进行选择.电感耦合等离子体发射光谱法(ICP-AES)是主量、次量元素的主要分析方法, 适合于分析含量为10-5~30%级别的金属元素; X射线荧光光谱法主要用于分析含量为10-3~1级别的元素, 尤其适合于测定Al、Si、Ti、V和P, 由于该方法的准确性依赖于一套高质量的标准样品, 故更适合炉前检测或检测大批红土镍矿样品.电感耦合等离子体质谱法(ICP-MS)最适合于分析10-4含量以下的重元素, 特别是稀土和贵金属元素.原子吸收光谱法(AAS)适合于分析10-4~10-2级别的Ca、Mg、Ni、Co、Zn、Cr、Mn等低沸点、易原子化元素.分光光度法主要用于分析Ni和P.原子荧光光谱法(AFS)主要用于分析As、Bi、Sb等易形成气态氢化物的元素.容量法主要用于分析Al、Fe、Mg和SiO2等主含量元素.尽管AAS、分光光度法、AFS法和容量法检测周期长, 但所用仪器为实验室常规配置, 可满足缺乏相应大型仪器实验室的日常检测.本文认为, 针对各种检测方法的适用性及存在问题, 应从开发微波消解法、固体进样直接测汞法、ICP-MS法以及Cr与其他元素同时分析的快速分析方法等方面开展研究, 建立灵敏、准确的检测方法, 从而更好地服务于红土镍矿的贸易、检验和综合利用.

     

    Abstract: With the depletion of common sulphide nickel resources, nickel laterite is becoming more attractive as nickel oxide, nickel matte and nickel-iron, amongst others, can be produced directly. For the determination of major, minor and trace elements in laterite nickel ore, many kinds of measurement methods for a given element and many differences of details between detection methods based on the same principle are available, making it difficult to select the appropriate method. Recent research in the pretreatment method and technology of the detection of a number of elements (Al, As, Bi, C, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Hg, Mg, Mn, Ni, P, Pb, S, Sb, Sc, Si, Ti, Zn) in laterite nickel is reviewed in this paper. The proper pretreatment methods were selected according to the target elements and detection method. Acid dissolution and alkali fusion as the pretreatment methods are most widely used now. Although acid dissolution introduces less salt and operates more simply, the volatile elements such as As, Sb, Bi and Hg are often lost in the decomposition process, while Cr is frequently lost by smoking with perchloric acid. Alkali fusion has better decomposition ability for Cr, Si and total iron, while the subsequent analysis is difficult, because impurities as well as many other salts are introduced due to the loss of crucible material and the melting process. The determination techniques of nickel laterite are chosen on the basis of character and concentration of target elements and the equipment in the laboratory. Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), which is suitable for the determination of elements content from 10-5 to 30%, is the main analysis method of major, minor and trace elements. X-ray Fluorescence Spectrometry (XRF) is used to analysis elements content of 10-3-1 in samples, especially for the detection of Al, Si, Ti, V and P. This method whose accuracy relies on a set of high quality standard sample is suitable for spot detection and determination of the large numbers of laterite nickel ore samples. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is appropriate for determining heavy elements with the content of less than 10-4 in samples, especially for the rare earth and noble metal elements. Atomic Absorption Spectrometry (AAS) is adopted in the determination of the low boiling point elements with the content level ranging from 10-4 to 10-2 which are liable to atomization, such as Ca, Mg, Ni, Co, Zn, Cr and Mn. Spectrophotometry is mainly used for detecting the Ni and P, while Atomic Fluorescence Spectrometry (AFS) for the measurement of elements which were easily to form gaseous hydride such as As, Bi and Sb. Some main content elements, like Al, Fe, Mg and SiO2, are analyzed by Volumetry. Although the detection period is a little longer, AAS, Spectrophotometry, AFS and Volumetry which just need common equipment meet the daily determination in the laboratory which lacks large scale equipment. In order to solve the applicability and other existing problems, it is necessary to study the microwave digestion method, direct mercury analysis method, ICP-MS method, and rapid determination of Cr and other elements. The progress in establishing appropriate detection methods is certain to serve the trade, analysis and comprehensive utilization of laterite nickel ore.

     

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