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 (SU = 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.

•Au/CeO2 catalysts were prepared via incipient wetness impregnation method.•Both (110) and (100) surface of ceria have strong interaction with gold.•The high Ce3+/Ce4+ and Auδ+/Au0 of 0.5%Au/CeO2NT contributes to its high activity.•The reaction could reach 100% CO conversion over 0.5%Au/CeO2NT at 70 °C.CeO2 show excellent performance in catalysis due to its oxygen vacancies, high oxygen storage capacity and easy conversation between Ce3+ and Ce4+ oxidation states. The ceria nano-materials with different morphologies were prepared with hydrothermal methods in the present work. It is found that the gold particles on ceria prepared via incipient wetness impregnation method are smaller and more uniform than those prepared via deposition-precipitation method (Applied Surface Science 2017, 416, 183–190). The incipient wetness impregnation method prepared samples also show better catalytic performance for CO oxidation than the samples prepared via deposition-precipitation method. Characterization results reveal that the small sizes as well as the oxidation states of the gold nanoparticles contribute to the higher activity than the deposition-precipitation samples. For the incipient wetness impregnation samples, the 0.5%Au/CeO2NT could reach 100% CO conversion at 70 °C, which shows much better activity and stability than the 0.5%Au/CeO2rod and 0.5%Au/CeO2NC. XPS results indicates that this is because the higher Ce3+/Ce4+ and Auδ+/Au0 of 0.5%Au/CeO2NT than 0.5%Au/CeO2rod and 0.5%Au/CeO2NC, since the presence of a specific Auδ+-Ce3+ structure promotes the adsorption of molecular oxygen and further favors the oxidation of CO. In addition, the gold nanoparticle could grow into larger particles on the ceria nanocubes and leads to the deactivition of the catalysts. In contrast the ceria nanorod and nanotube supported catalysts show excellent stability.Download full-size image

Gold supported on various bentonites was prepared using hydrothermal and co-precipitation methods. The catalysts were characterized by FT-IR, BET, XRD, TEM, SEM, XPS and ICP and tested for CO oxidation reaction. It was found that the Au–Al–Ce pillared bentonite, Au–Al–Ce/Na-LBen (CP) and Au–Al–Ce/Na-LBen (HT), have better catalytic activity and stability than Au/Na-Lben and Au/Al–Ce–Na-LBen. Characterization results show that gold nanoparticles could move into the interlayer spaces of bentonite, which contributes to the high stability of the Au–Al–Ce/Na-LBen (HT) and Au–Al–Ce/Na-LBen (CP) samples. Ce oxide is distributed on the surface of Au–Al–Ce/Na-LBen (HT), while it stays in the interlayers of the bentonite in the Au–Al–Ce/Na-LBen (CP) sample. The pillaring process could increase the d(001) space of the bentonite since the Ce and Au species could move into the interlayer space of the bentonite. The acid-activation process clearly increases the surface area of the bentonite, while the pillaring process increases the surface area of the samples slightly.