A Review and Perspective on Analytical Methods of Critical Metal Elements
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ABSTRACT
BACKGROUNDStrategic critical metal mineral resources including rare, dispersed, rare earth and platinum group elements play an increasingly critical role in emerging industries such as new materials, new energy and information technology. With the deepening of the geological survey of key mineral resources in China, the critical metal elements present new challenges to analytical techniques due to their complex matrix, large differences in different mineral contents, and unstable chemical properties.OBJECTIVESTo introduce recent analytical techniques and applications for critical metal elements in different types of geological samples.METHODSBased on different chemical composition, the main matrices of critical metal elements were classified, mainly divided into silicate, carbonate, sulfate, tungstate, phosphate, oxide, sulfide and halide. For different types of rocks and minerals, chemical digestion was largely carried out by traditional dissolution methods such as the acid dissolution method (nitric acid-hydrofluoric acid combination, aqua regia) or alkali fusion methods.RESULTSThe characteristics and application of commonly used instruments including electronic probe microanalyzer, inductively coupled plasma-mass spectrometry, inductively coupled plasma-optical emission spectroscopy, and X-ray fluorescence spectroscopy were reviewed. The problems during critical metal analysis including incomplete dissolution, low recovery, oxides and isobaric interference, inconsistency between samples and standard matrices were reviewed and corresponding solutions were proposed.CONCLUSIONSIn situ microanalysis with the advantages of high efficiency, low cost, and high spatial resolution, and field on-site geoanalysis with its simple, fast and close to field work features are the main trends in the development of critical metal elements analytical techniques.
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