Highly selective adsorption of uranium in strong HNO3 media achieved on a phosphonic acid functionalized nanoporous polymer

Abstract

The competition between uranium and other metal ions is one of the greatest challenges for recovery of uranium in strong HNO₃ media. In this study, a novel nanoporous organic polymer adsorbent P(EGDMA-VPA) (POP-EDVP) was designed and synthesized by a solvothermal strategy, showing highly selective adsorption of uranium in strong HNO₃ media containing 16 co-existing cations. The outstanding selectivity (S_U = 94.2%) for the adsorption of uranium on the polymer is reasonably attributed to the presence of PO groups in the polymer skeleton, where the PO groups have a strong complexation with UO₂(NO₃)₂, as evidenced by their XPS results and supported by the density functional theory (DFT) calculation. Very importantly, the polymer shows a maximum adsorption capacity of uranium as high as 215.9 mg g⁻¹ at 298 K in a 4 M HNO₃ solution. Even after recycling seven times, there is not any noticeable loss of its sorption capacity. This work shows a simple route to prepare a polymer adsorbent for highly selective adsorption of uranium in strong HNO₃ media, which is very significant for recovery of uranium in strongly acidic media.