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_4^2- 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_4^2- 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_4^2- 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.