Treatment of phosphogypsum waste produced from phosphate ore processing

Abstract

Phosphogypsum (PG), primary byproduct from phosphoric acid production, is accumulated in large stockpiles and occupies vast areas of land. Phosphogypsum is a technologically enhanced naturally occurring radioactive material (TE-NORM) that contains radionuclides from (238)U and (232)Th decay series which are of most radio-toxicity. The reduction in concentration of radionuclides content from PG was based on leaching of (226)Ra, (210)Pb, (238)U and (40)K 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 (226)Ra, (210)Pb, (238)U and (40)K 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 (∑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.