Determination of Total Rare Earth Contents of Baotou Rare Earth Concentrates by ICP-AES

According to the technological process of extracting rare earth in Bao Tou Mine, the content of total rare earth ranges from x%-xx%. The national standard of the oxalate gravimetric method is applied to detecting high content of rare earth, which yields between 20% and 80%, but the operation of the method separating interference elements is complex. In fact, Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) could quickly determine each rare earth element content, and avoid complicated separating steps. However, it was difficult to obtain accurate results by ICP-AES, as a consequence of unfavourable precision for high contents rare earth. The method of alkali fusion combined with ICP-AES was applied to overcome problems of complex components and difficult decomposition in acid for rare earth ores from Bao Tou Mine and is reported herein. The sample was melted by sodium hydroxide and sodium peroxide, and leached with deionized water, in order to transfer all kinds of elements into solution as forms of ions or hydroxide. The interference of elements in the solution was reduced by filtering aluminum, silicon, phosphorus, and a mass of sodium ion. During determination of rare earth contents with ICP-AES, the instrument stability and matrix effect were adjusted by adding an internal standard with scandium. When rare earth content in the sample was 2%, RSD was less than 1.2%. When rare earth content in the sample was between 30% and 50%, the method was successfully used with RSD < 0.7%. The recoveries were in the range of 98.0%-103.3%. The method is simpler than the national standard. Compared with ICP-AES reported in the literatur, the precision of the method was significantly improved. Rare earth content in Bao Tou Mine between 2%-50% was quickly and accurately measured using this method.