Distribution of potentially toxic elements in the Brazilian phosphogypsum and phosphate fertilizers

Abstract

The Brazilian phosphate fertilizer is obtained by wet reaction of the igneous phosphate rock with concentrated sulphuric acid, giving as final product phosphoric acid and dehydrated calcium sulphate (phosphogypsum) as by-product. Phosphoric acid is the raw material for the production of phosphate fertilizers (SSP, TSP, MAP and DAP). Phosphogypsum waste is stored in stacks, since its level of impurities (metals and radionuclides among others) prevent its safe reutilization. However, part of this waste is used to improve fertility of agricultural soils. The main aim of this paper is to determine the levels of potentially toxic elements in phosphate fertilizers and phosphogypsum produced in Brazil. The elements Co and Cr were analyzed by instrumental neutron activation analysis and As, Cd, Cu, Hg, Ni, Pb, Se and Zn were analyzed by ICP-OES. The results obtained are lower than the limits established by the Brazilian regulatory agency for metals in fertilizers and soil conditioner.

Keywords

• Phosphogypsum
• phosphate fertilizers
• metals