Determination of Rare Earth Oxides in Bauxite by Inductively Coupled Plasma-Optical Emission Spectrometry

Abstract

BACKGROUND When the rare earth oxides in bauxite are determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), acid dissolution often results in incomplete dissolution of samples, and a large amount of fluxes at high temperature alkali fusion will reduce the emission intensity of rare earth elements. Moreover, due to the low content of rare earth oxides (0.0010%-0.050%) and the matrix interferences such as aluminum and iron, accurate determination of them is difficult. OBJECTIVES To develop an accurate method to determine the contents of rare earth oxides in bauxite by ICP-OES. METHODS The bauxite was fused with sodium hydroxide, and the melt was extracted with hot water. A triethanolamine solution was used to eliminate the interferences of aluminum and iron, and ethylenediamine tetraacetate disodium solution was used to complex with calcium, magnesium and other elements. Rare earth hydroxide was retained in the precipitation, which was dissolved into the liquid hydrochloric acid digestion. Rare earth elements can be effectively separated from fluxes and matrix elements by the proposed procedure. RESULTS The standard solution did not need matrix matching. The linear correlation coefficient of calibration curve was not less than 0.9999, and the detection limits were 0.0002%-0.0015%. The relative standard deviations of rare earth elements in the sample were 2.0%-4.6%, and recoveries were 85.2%-104.4%. CONCLUSIONS There are no obvious differences for analytical results between ICP-OES and inductively coupled plasma-mass spectrometry (ICP-MS).

Keywords

• bauxite
• rare earth oxide
• sodium hydroxide melting
• precipitation separation
• matrix interference
• inductively coupled plasma-optical emission spectrometry