Radiological characterization and treatment of contaminated phosphogypsum waste

Preparation of uncontaminated phosphogypsum (PG) produced by wet-process phosphoric acid plant for its safe use in industry was investigated. PG is mainly composed of calcium sulfate and contains enhanced natural radioactivity. The activity of 238U, 226Ra, 210Pb, 232Th, and 40K in PG samples was measured by γ-ray spectrometry. The values of radiation hazard indices, calculated to evaluate the environmental impacts of PG samples, were higher than the permissible safe levels. Therefore, the PG should be treated before use in agriculture and/or building materials. This involves the leaching of PG with organic extractant such as TOPO in kerosene. Reduction in the radionuclide concentration was accompanied by a decrease in the concentration of total rare earth elements (ΣREE). Extraction treatment of PG waste under optimum conditions allows preparation of a decontaminated product that can be safely used in many branches of industry.