Recovery of Uranium from Philippine Wet Phosphoric Acid Using D2EHPA-TOPO Solvent Extraction

Botvinnik L. Palattao*, Jennyvi D. Ramirez, Estrellita U. Tabora,
Editha A. Marcelo, Edmundo P. Vargas, Socorro P. Intoy,
Reymar R. Diwa, and Rolando Y. Reyes

Philippine Nuclear Research Institute - Department of Science and Technology
Quezon City, Manila 1101 Philippines

*Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.



Recovery of uranium from Philippine wet phosphoric acid was studied using a synergistic mixture of 0.5 M D2EHPA - 0.125 M TOPO diluted in kerosene. Results from characterization of materials in phosphate processing revealed the presence of valuable elements such as uranium and rare earths in both raw materials and fertilizer products. Variation of operating parameters on extraction such as P2O5 content and optical density was found to be inversely proportional with the extraction efficiency. The reaction was found to establish rapid equilibrium and is exothermic in nature. Distribution coefficient for the extraction of uranium from 27% P2O5 phosphoric acid was determined to be at 10.71 at about 25°C. Analysis of the equilibrium data and McCabe-Thiele plot based on batch testing indicates a 92.59% recovery rate could be achieved in three-ideal extraction stages at an aqueous to organic phase volume ratio of 4:1.

Key words: D2EHPA-TOPO, Philippines, phosphate fertilizer, phosphoric acid, uranium extraction



Phosphate rocks contain a wide variety of useful elements apart from phosphorus used in making fertilizers. Among these elements that are of value contained in the mineral are uranium, thorium, radium, and rare earths elements (REE) (Preston et al. 1996; Kouraim et al. 2014; Emsbo et al. 2015; Ramos et al. 2016). In the wet processing of phosphate rock, the mineral is broken down by sulfuric acid, which then produces two intermediate products, namely phosphoric acid and phosphogypsum precipitate. During this process, trace elements like REE and naturally occurring radionuclides uranium, thorium, and radium contained in mineral distributes into these intermediate products. Majority of the uranium and thorium content in the rocks are reported to redistribute itself into the acid phase (Hodge & Popovici 1994; Rutherford et al. 1994; Singh et al. 2009; Haneklaus et al. 2017) while most of the rare earths, and along with radium, precipitates with the phosphogypsum (USEPA 1992; Sahu et al. 2014; Kulczycka et al. 2015). The phosphoric acid is then further converted into fertilizers and, in the process, transfers all valuable elements into the product that is then consequently lost during land application. These valuable elements, if left in fertilizers, are considered as heavy metal contaminants and may pose negative environmental impacts. However, if recovered from phosphoric acid prior to fertilizer production, it presents a huge opportunity to utilizing these strategic metals in technological applications and/or marketable way. Recovery of these valuable elements thus, is not only a means of maximizing the mineral potential but also a means of environmental stewardship.  . . . . . read more


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