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WU Shi-tou,WANG Ya-ping,SUN De-zhong,WEN Hong-li,XU Chun-xue,WANG Wei.Determination of 15 Rare Earth Elements in Rare Earth Ores by Inductively Coupled Plasma-Atomic Emission Spectrometry:A Comparison of Four Different Pretreatment Methods[J].Rock and Mineral Analysis,2014,33(1):12-19
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Determination of 15 Rare Earth Elements in Rare Earth Ores by Inductively Coupled Plasma-Atomic Emission Spectrometry:A Comparison of Four Different Pretreatment Methods
Received:March 11, 2013  Revised:March 22, 2013
DOI:
Key words: ion adsorption-type rare earth ore  mineral lattice-type rare earth ore  rare earth elements  acid digestion  alkali fusion  Inductively Coupled Plasma-Atomic Emission Spectrometry
Author NameAffiliationE-mail
WU Shi-tou National Research Centre for Geoanalysis, Beijing 100037, China
Faculty of Material Science and Chemistry, China University of Geosciences (Wuhan), Wuhan 430074, China 
 
WANG Ya-ping National Research Centre for Geoanalysis, Beijing 100037, China wypsm@yeah.net 
SUN De-zhong National Research Centre for Geoanalysis, Beijing 100037, China  
WEN Hong-li National Research Centre for Geoanalysis, Beijing 100037, China  
XU Chun-xue National Research Centre for Geoanalysis, Beijing 100037, China  
WANG Wei National Research Centre for Geoanalysis, Beijing 100037, China  
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Abstract:
      Rare earth elements (REEs) in ore have many different forms, mainly ion adsorption and mineral lattice types. The occurrence state of rare earth elements has a great impact on accurate analysis. In this study, the effects of different pretreatment methods in REEs analysis are discussed from the perspective of REEs occurrence states in ore. Four pretreatment methods including HCl-HNO3-HF-HClO4 under normal pressure (the open acid digestion), HCl-HNO3-HF-HClO4-H2SO4 under normal pressure (the open acid digestion, adding sulfuric acid), HF-HNO3 in confining pressure (the pressurized acid digestion) as well as NaOH-Na2O2 alkali fusion were conducted for REEs ores. 15 rare earth elements were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The results of the open HCl-HNO3-HF-HClO4 acid digestion for the two National Standard Substances (GBW 07161, GBW 07188) which are ion adsorption-type rare earth ores, are significantly lower, mostly 10%-20% lower than certified values. Meanwhile, the results from the pressurized acid digestion, the open HCl-HNO3-HF-HClO4-H2SO4 acid digestion and alkaline fusion are in agreement with certified values. For the two Baiyun Ebo REEs ore samples (SS-1 and BY-1) which are mineral lattice-type, results from all three acid digestions are lower than those from alkaline fusion. The results of the open HCl-HNO3-HF-HClO4 acid digestion are the lowest, approximately 20% lower than those from alkaline fusion, and results of the open HCl-HNO3-HF-HClO4-H2SO4 acid digestion and the pressurized acid digestion essentially are as low as approximately 5%-15%. In summary, for ion adsorption-type rare earth ores, the the open HCl-HNO3-HF-HClO4-H2SO4 acid digestion and pressurized acid digestion could replace the traditional alkaline fusion, while for mineral lattice-type rare earth ores, the most suitable pretreatment method is still alkaline fusion.