RADIOACTIVITY AND ELEMENTAL COMPOSITION OF PHOSPHOGYPSUM PRODUCED FROM 3 PHOSPHATE ROCK SOURCES

Phosphogypsum, a by-product of phosphate fertilizer production, is pro duced in large quantities worldwide. Most phosphogypsum is stockpiled while lesser quantities are recycled or dumped into water. Phosphogyps um is primarily CaSO4 . 2H(2)O, but also contains impurities of enviro nmental concern such as residual acids, fluoride, heavy metals and nat urally-occurring radionuclides. Impurity composition within phosphogyp sum can vary greatly depending on the source of phosphate rock used in phosphoric acid production. This study was undertaken to obtain detai led information on the composition of phosphogypsum produced from the processing of rock from Florida, Togo and Idaho, to define more clearl y the chemical issues of importance to management and use of the by-pr oduct. All freshly produced phosphogypsum had sufficiently high fluori de levels that leaching and decomposition of silicate minerals beneath repositories might occur. Phosphogypsum from Idaho rock had elevated Ag, Cd and Se concentrations, and the greatest Ra-226 activity concent rations (up to 1780 Bq kg(-1)). Radon-222 emanation coefficients range d between 12-51%.