A new procedure of phosphogypsum purification in order to diminish the content of radionuclides

Abstract

Phosphogypsum obtained by "wet procedure" for phosphoric acid production is actually calcium-sulphate dihydrate, CaSO 4 ·2H 2 O, which contains a high percent of impurities as well as radionuclides, originating from the basic raw material. Technology of phosphoric acid production by "wet process" intends for phosphogypsum to be a "sponge" that absorbs all impurities from phosphoric acid (except uranium) and to be left in deposits as an unnecessary burden. As an enormous amount of phosphogypsum results from phosphoric acid production (the ratio is 5:1), phosphogypsum deposits are a burden per se, from the view of environmental protection, because they occupy large areas and may contaminate the air, ground water, but also surface water that receive phosphogypsum in the form of dilute suspension. By the proposed procedure, phosphogypsum is transformed into hemihydrate, CaSO 4 ·1/2H 2 O. Im the process of removing radionuclides with barium-sulphate, 226 Ra isotope content decreases below the permitted concentration, but this process is directly dependent on the type of the phosphate utilized in phosphoric acid production.