Studies Of The Matrix Effect On XRF Of Bayan Obo Ores

Bayan Obo mine plays an important role in the development of rare earth industry. Arapid, accurate, and nondestructive method for analysis REE content is desirable. X-rayfluorescence (XRF) analysis provides such a technology that is simple, and can detect widerange of elements (Na to U) in either rocks or powders with high accuracy.When XRF used in analysis of multi metal mineral, matrix effect on REE causes theintensity of REE XRF not linearly related to the grade, thus correction of matrix effect isnecessary in order to calculate REE grade from XRF intensity. In general, XRF analysisrequires standard samples to calibrate the instruments. However, such standard samples forBayan Obo minerals are hard to get because there are numerous elements contained in BayanObo ores with highly variable grades. This report describes a method for correction ofempirical coefficients that are used to calculate REE grade from measured intensity ofEDXRF (Energy Dispersive XRF).To determine the correction to the empirical coefficients, a series of artificial sampleswere made with increasing concentration of Fe2O3(or CaO) while CaO (or Fe2O3) keptconstant and CeO decreasing accordingly. With the artificial samples, the corrections fromenhancement effect of Fe and absorption effect of Ca were determined. A equation expressesthe content-XRF relationship for Ce was established by combining those corrections withthe un-corrected empirical coefficient in the grade-XRF equation for Ce. XRF analysis usingour equation was able to measure the Ce content in Bayan Obo ore with error less than10%.The matrix effects from other elements, e.g. Si, were not considered because their XRF peaksare far away from L series. Since the ratio of Ce/La was stable in Bayan Obo ores and Ceand La count the majority of total REE, our method is also useful for measurement of totalREE in Bayan Obo ores.