With the ongoing development and utilization of nuclear energy, uranium pollution has become an increasingly serious issue. Although many adsorbents are able to remove hexavalent uranium (U(VI)) from aqueous solution, the development of a high capacity adsorbent exhibiting superior stability would be beneficial. Grafting poly(amidoxime) (PAO) onto reduced graphene oxide (rGO) provides suitable U(VI) adsorption performance but the PAO is prone to agglomeration. The present work used density functional theory calculations to predict that PAO would bond with pyrrolic N atoms in nitrogen-doped rGO (N-rGO). To confirm this, PAO-grafted rGO (PAO-rGO) and PAO-grafted N-rGO (PAO-N-rGO) were prepared and characterized and the successful grafting of PAO on N-rGO was demonstrated. Adsorption experiments demonstrated that PAO-N-rGO exhibit superb U(VI) adsorption performance compared with the original PAO-rGO under acidic conditions. As for competing metal ions, Cu²⁺, Al³⁺, and Ca²⁺ have a greater impact on U(VI) adsorption than Na⁺, Mg²⁺, and K⁺ both for PAO-rGO and PAO-N-rGO. The maximum adsorption capacities of PAO-rGO and PAO-N-rGO for U(VI) were calculated to be 1500.26 and 1545.95 mg g⁻¹, respectively. The mechanism of nitrogen doping promoting uranium(VI) adsorption can be attributed to enhanced PAO grafting and improvement of adsorption performance of the rGO. This work demonstrates that nitrogen doping is a viable strategy for enhancing the U(VI) adsorption performance of PAO-rGO.

中文翻译：

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使用氮掺杂策略增强铀 (VI) 吸附的理论和实验研究

随着核能的不断开发利用，铀污染问题日益突出。尽管许多吸附剂能够从水溶液中去除六价铀 (U( VI ))，但开发具有优异稳定性的高容量吸附剂将是有益的。在还原氧化石墨烯 (rGO) 上接枝聚 (脒) (PAO) 可提供合适的 U( VI )) 吸附性能，但 PAO 容易结块。目前的工作使用密度泛函理论计算来预测 PAO 将与氮掺杂 rGO (N-rGO) 中的吡咯 N 原子结合。为了证实这一点，制备并表征了 PAO 接枝的 rGO (PAO-rGO) 和 PAO 接枝的 N-rGO (PAO-N-rGO)，并证明了 PAO 在 N-rGO 上的成功接枝。吸附实验表明，与原始 PAO-rGO 在酸性条件下相比，PAO-N-rGO 表现出极好的 U( VI ) 吸附性能。对于竞争金属离子，Cu ²⁺、Al ³⁺和Ca ²⁺对U( VI )吸附的影响大于Na ⁺、Mg ²⁺和K ⁺适用于 PAO-rGO 和 PAO-N-rGO。PAO-rGO 和 PAO-N-rGO 对 U( VI ) 的最大吸附容量计算为分别为 1500.26 和 1545.95 mg g ^-1。氮掺杂促进铀( VI )吸附的机制可归因于增强的PAO接枝和rGO吸附性能的提高。这项工作表明，氮掺杂是提高 PAO-rGO 对 U( VI ) 吸附性能的可行策略。