Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, People's Republic of China.
School of Chemical Engineering, Dalian University of Technology, Dalian 116024, People's Republic of China.
Environ Sci Technol. 2023 Jul 18;57(28):10339-10347. doi: 10.1021/acs.est.3c01026. Epub 2023 Jul 3.
Using molecular dynamics simulations, this work targets a molecular understanding on the rigidity and flexibility of fulvic acid (FA) in uranyl sorption on graphene oxide (GO). The simulations demonstrated that both rigid Wang's FA (WFA) and flexible Suwannee River FA (SRFA) can provide multiple sites to cooperate with GO for uranyl sorption and act as "bridges" to connect uranyl and GO to form GO-FA-U (type B) ternary surface complexes. The presence of flexible SRFA was more beneficial to uranyl sorption on GO. The interactions of WFA and SRFA with uranyl were primarily driven by electrostatics, and the electrostatic interaction of SRFA-uranyl was significantly stronger owing to the formation of more complexes. The flexible SRFA could markedly enhance the bonding strength of uranyl with GO by folding itself to provide more sites to coordinate with uranyl. The rigid WFAs tended to be adsorbed on the GO surface in parallel due to π-π interactions, whereas the flexible SRFAs took more slant configurations resulting from intermolecular hydrogen bonds. This work provides new insights into the sorption dynamics, structure, and mechanism and addresses the effect of molecular rigidity and flexibility, with great significance for FA-based remediation strategies of uranium-contaminated sites.
本工作采用分子动力学模拟，针对富里酸（FA）在氧化石墨烯（GO）上吸附铀时的刚性和柔性的分子理解。模拟表明，刚性的 Wang 氏 FA（WFA）和柔性的苏湾河 FA（SRFA）都可以提供多个位点与 GO 配合进行铀吸附，并作为“桥梁”将铀和 GO 连接起来形成 GO-FA-U（B 型）三元表面络合物。存在柔性的 SRFA 更有利于 GO 上的铀吸附。WFA 和 SRFA 与铀的相互作用主要是由静电驱动的，由于形成了更多的配合物，SRFA-铀的静电相互作用明显更强。柔性的 SRFA 可以通过自身折叠提供更多的位点与铀配位，从而显著增强铀与 GO 的键合强度。刚性的 WFA 由于π-π 相互作用而倾向于在 GO 表面平行吸附，而柔性的 SRFA 由于分子间氢键的存在而采取更多的倾斜构象。这项工作为吸附动力学、结构和机制提供了新的见解，并解决了分子刚性和柔性的影响，对于基于 FA 的铀污染场地修复策略具有重要意义。
