Treatment of phosphogypsum waste produced from phosphate ore processing

Phosphogypsum (PG), primary byproduct from phosphoric acid production, is accumulated in large stock-piles and occupies vast areas of land. Phosphogypsum is a technologically enhanced naturally occurring radioactive material (TE-NORM) that contains radionuclides from U-238 and Th-232 decay series which are of most radio-toxicity. The reduction in concentration of radionuclides content from PG was based on leaching of Ra-226, Pb-210, U-238 and K-40 using tri-butyl phosphate (TBP) and tri-octyl phosphine oxide (TOPO) in kerosene. The factors which affect the leaching process such as contact time, concentration of the solvent and temperature were optimized. Based on the experimental results, about 92.1, 88.9, 83.4, 94.6% of Ra-226, Pb-210, U-238 and K-40 respectively were successfully removed from the PG. The reduction in the concentration of radionuclides was accompanied by reduction in the concentration of rare earth elements (Sigma REE) equals to 80.1%. Using the desired organic extractant under optimum conditions for treatment of the PG waste leads to obtain a decontaminated product that can be safely used in many industrial applications. (c) 2012 Elsevier B.V. All rights reserved.