Liang Ying,Xia Meng,Yu Qiuhan,Li Yongpeng,Sui Zhuyin,Yuan Yihui,Hu Xin-Ming,Chen Qi,Wang Ning
Uranium, which was abundant in the ocean but existed in the form of uranyl tricarbonate ([UO 2 (CO 3 ) 3 ] 4− ) with an extremely low concentration of 3.3 ppb, was a significant element of nuclear energy. It is of immediate significance to the research into uranium extraction by the exploration of adsorbents for environment and resource sustainability. Herein, the new ionic covalent organic frameworks (iCOFs) named COF-DG containing the guanidine groups was designed and synthesized via Schiff base reaction between diaminoguanidine hydrochloride and 1,3,5-triformylphloroglucinol. The adsorption performance indicated that the COF-DG possessed an uptake capacity of 65.6 mg g −1 toward the [UO 2 (CO 3 ) 3 ] 4− , attributed to the chemical interaction and anion exchange between [UO 2 (CO 3 ) 3 ] 4− and the cationic COF-DG with Cl − , as well as the electrostatic attraction. Besides, the COF-DG exhibited a higher affinity and selectivity toward [UO 2 (CO 3 ) 3 ] 4− in the presence of the competing anions. Furthermore, the COF-DG displayed an antibacterial rate of 82% against Gram-negative bacteria Escherichia coli owing to the guanidine groups. This work contributes new insights into the further development of iCOFs, for applying as a potential candidate in uranium extraction from seawater in practical engineering. Graphical abstract The new ionic covalent organic frameworks named COF-DG was designed and exploited via Schiff base reaction, which exhibited a higher affinity and selectivity toward the [UO 2 (CO 3 ) 3 ] 4− .
Polyamidoxime fibers have been widely studied for uranium extraction from seawater, but improving the amidoxime (AO) group utilization and increasing the selectivity toward uranium remain challenging. Herein, a hyperbranched macromolecular cross-linking strategy was employed to construct hyperbranched polyethylenimine (PEI) among the molecular chains of polyamidoxime nanofibers (PAN/PEI-AO nanofibers). This approach simultaneously suppressed chain entanglement and effectively reduced hydrogen bond formation between amidoxime groups, thereby significantly enhancing the utilization efficiency of AO groups. Moreover, the PEI structure also facilitated the dissociation of CO32– from uranyl tricarbonate ([UO2(CO3)3]4–) and comprised amino groups as assistant groups for enhanced uranium uptake. The above cross-linking effect by PEI was confirmed by experimental data and theoretical calculation, resulting in high uranium uptake (474.8 mg g–1) alongside good deep removal capability (kd = 7.7 × 105 mL g–1) from [UO2(CO3)3]4– solution. Moreover, PAN/PEI-AO nanofibers also exhibited good selectivity and reusability toward uranium and showed a uranium extraction capacity of 8.24 mg g–1 after 20 days’ testing from natural seawater. The obtained adsorption performance of PAN/PEI-AO nanofibers exceeded traditional polyamidoxime nanofibers and many reported uranium adsorbents. Overall, this work offers a strategy to improve the performance of polyamidoxime fibers, which possess the potential to extract real uranium species from natural seawater.
危险品化学品经营许可证（带存储）