Determination of main rare earth oxides in rare earth alloy slag by microwave digestion-inductively coupled plasma atomic emission spectrometry
XU Jing, LI Zong-an, LI Ming-lai, LI Kuo-she, WANG Zhi-qiang, YU Dun-bo
National Engineering Research Center for Rare Earth Materials, General Research Institute for Nonferrous Metals, and Grirem Advanced Materials Co., Ltd., Beijing 100088, China
Abstract： An analysis method of simultaneous determination of the main rare earth oxides such as lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide and dysprosium oxide in rare earth alloy slag by microwave digestion - inductively coupled plasma atomic emission spectrometry (ICP-AES) was put forward. Four different digestion reagent systems were examined, digestion parameters were optimized and the appropriate analytical line was selected. The results showed that the digestion effect of samples was best under the following conditions: HNO3-HCl-HF-H2O2 (V (HNO3)∶V (HCl)∶V (HF)∶V (H2O2)=4∶2∶2∶1) as a digestion reagent, four steps of temperature digestion process, the minimum temperature of 160℃, the minimum pressure of 1.5 MPa, the maximum temperature of 225℃, and the maximum pressure of 3.5 MPa, the maximum temperature difference of each step not exceeding 25℃, and the maximum differential pressure not more than 1 MPa. Under selected instrument parameters, using the spectral line of wavelength 408.671 nm, 413.765 nm,390.843 nm,401.255 nm,359.260 nm and 353.171 nm as the analytical line of La, Ce, Pr, Nd, Sm, Dy respectively, and with rare earth oxide to prepare the calibration curve, the rare earth oxides above in digestion solution were determined by ICP-AES. The relative standard deviation of the measured results was in the range of 0.44% to 0.98%, and the recovery rate was between 94% to 106%.
