Effect of anions in commercial phosphoric acid on the extraction of uranium by DEHPA /TOPO

Abstract

Extraction of uranium from commercial phosphoric acid by DEHPA/TOPO process is a well-developed process on the commercial and pilot plant scale. Commercial phosphoric acid contains certain anions such as Cl − , F − and SO 2− 4 in varying concentrations. The presence of such anions could have a negative effect on the extraction process.This paper investigated the effect of Cl − , F − and SO 2−4 anions present in commercial wet phosphoric acid on the uranium extraction process. The effect of adding SiO 2 which complexes with F − and other anions was also studied. The results obtained showed that these anions formed complexes with UO 2+ 2 and therefore had a negative influence on the extraction of uranium from laboratory and commercial phosphoric acids. This effect was strong in the case of F − followed by SO 2− 4 and much less for Cl − . Addition of SiO 2 was found to negate the effect of F − and other anions and to exert a positive effect on uranium extraction. KeywordsExtraction · uranium · DEHPA/TOPO · anions · phosphoric acid AcknowledgementThe authors would like to express their thanks to the General

Characteristics of uranium recovery from phosphoric acid by an aminophosphonic resin and application to wet process phosphoric acid

“…Several techniques have been developed to separate and recover uranium ions from wet process phosphoric acid including chemical precipitation [3], emulsion liquid membrane [4][5][6][7][8], liquid-liquid extraction [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and solid phase extraction. The conventional extraction methods viz., solvent extraction or precipitation and emulsion liquid membrane are not completely satisfactory because these processes have several disadvantages like finite aqueous solubility of extractants and dilutions.…”

Recovery of Uranium from Wet Phosphoric Acid by Solvent Extraction Processes

“…This phenomenon was attributed to the formation of (UO 2 X a ) (2−a) complexes with X = Cl − , SO 4 2− , or F − . 35 …”

“…One indication that this is true is that the distribution ratio of uranium(VI) between phosphoric acid and D2EHPA/TOPO diluted in kerosene is significantly affected by the presence of F − , SO 4 2− , or Cl − in phosphoric acid, while the presence of HSO 4 − in WPA has no impact on uranium(VI) speciation in phosphoric acid. 35,65,112,113 These anions have a negative impact, and the magnitude of the decrease of the uranium(VI) distribution ratio follows the order Cl − < SO 4 2− < F − . This phenomenon was attributed to the formation of (UO 2 X a ) (2−a) complexes with X = Cl − , SO 4 2− , or F − .…”

“…This phenomenon was attributed to the formation of (UO 2 X a ) (2−a) complexes with X = Cl − , SO 4 2− , or F − . 35 Several studies concerned the extraction of uranium(VI) by D2EHPA/TOPO from phosphoric acid, but only a few of them were focused on the speciation in the organic phase and the equilibria involved in the recovery of uranium(VI) from concentrated phosphoric acid (4−8 mol L −1 ). The addition of TOPO into D2EHPA increases significantly the distribution ratio of uranium(VI) between the extraction solvent and phosphoric acid (Figure 17).…”