Content and Signature of Rare Earth Elements in Phosphate Fertilizers Marketed in Brazil.

The rare earth elements (REE's) are a group of 17 chemical elements that have unique characteristics and are frequently associated with phosphate minerals, resulting in their presence in most of single or formulated phosphate fertilizers. This study aimed to: i) quantify the contents of REE's in Araxá rock phosphate and phosphate fertilizers marketed in Brazil; and, ii) evaluate formulated NPK fertilizers, in order to discover, through standardization with standards chondrites Post-Archean Average Australian Sedimentary rock (PAAS) and North American Shale Composite (NASC), the source of phosphates used for their production. For identification and quantification of RRE's we used alkaline fusion of samples followed by later determination with ICP-MS. Subsequently, the data were normalized using the standards PAAS and NASC. The contents of RRE's in formulated phosphate fertilizers are dependent on their content of P₂O₅ and the phosphate rock (or concentrate) used in their production. Furthermore, we found that the processing of phosphate rock can contribute to lower levels of REE's, since the smallest value for the sum of ETR's was observed for the MAP, while the highest value was observed in the phosphate rock. The two chondrites used for RRE´s normalization showed no difference, and 00:18:18 and 05:36:00 fertilizer has shown the same REE's signature as Araxá rock phosphate. Sponsored by FAPEMIG, CNPq and Vale.