Distribution of uranium in the production of triple superphosphate (TSP) fertilizer and phosphoric acid

Abstract

In this study the distribution of uranium, which is one of the radioactive elements present in phosphate fertilizers was investigated in different steps of the triple superphosphate (TSP) production process. The uranium in phosphate rock, phosphoric acid, phosphogypsum and TSP was extracted into the organic phase by using the TOPO extraction method. The uranium contents of these materials were determined by measuring the absorbance of the formed (pH 7.6) uranyl bromo-PADAP [uranyl(2-(5-bromo-2-pyridylazo)-5-diethylaminophenol)] complex solutions at 574 nm against blank. It was found that 50% of the uranium is dissolved in the acid during the production of phosphoric acid while the remainder is precipitated with phosphogypsum residue. The observations showed that in the second step, the sum of uranium in phosphate rock and phosphoric acid completely passed into TSP in the TSP manufacturing process.