Geopolymer is an amorphous cementitious material produced by geopolymerization using minerals or industrial waste as the main raw material under the action of activators. It can be used for safe treatment of heavy metal and radioactive pollution. This study applied molecular dynamics simulation to investigate the transport behaviour of uranyl nitrate in nanochannel of geopolymer, and focused on the influence of changes in the Si/Al ratio of geopolymer on the adsorption and diffusion of ions and water molecules. The simulation results described by density distribution, radial distribution function (RDF), hydrogen bonding network structure, mean square displacement (MSD) and diffusion coefficient. The density distribution shows that geopolymer has the strongest adsorption capacity for UO22+, followed by NO3−, and finally H2O. The results also indicate that the changes in molecular composition of geopolymer have a significant impact on kinetic characteristics of UO22+, NO3− and H2O. As the Si/Al ratio decreases, the adsorption capacity of geopolymer shows an upward trend, with the most significant improvement in the adsorption of UO22+. In addition, when the Si/Al ratio reduces, the migration rate of UO22+ and NO3− slows down. It could hinder the diffusion of ions in nanopores of geopolymer. The work could optimize the preparation of geopolymer adsorbent, and reveal the transport mechanism of uranyl nitrate in nanopore of geopolymer with different Si/Al ratios at the atomic scale.

中文翻译：

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不同Si/Al比地质聚合物纳米孔中硝酸铀酰的输运机理：分子动力学模拟


地聚合物是以矿物或工业废料为主要原料，在活化剂作用下，通过地聚合反应生产的非晶态胶凝材料。可用于重金属、放射性污染的安全治理。本研究应用分子动力学模拟研究了硝酸铀酰在地质聚合物纳米通道中的输运行为，重点研究了地质聚合物Si/Al比的变化对离子和水分子吸附和扩散的影响。模拟结果通过密度分布、径向分布函数（RDF）、氢键网络结构、均方位移（MSD）和扩散系数来描述。密度分布表明，地质聚合物对UO22+的吸附能力最强，其次是NO3−，最后是H2O。结果还表明，地质聚合物分子组成的变化对UO22+、NO3−和H2O的动力学特性有显着影响。随着Si/Al比的降低，地聚合物的吸附能力呈现上升趋势，其中对UO22+的吸附提高最为显着。此外，当Si/Al比降低时，UO22+和NO3−的迁移速率减慢。它可以阻碍离子在地质聚合物纳米孔中的扩散。该工作可以优化地质聚合物吸附剂的制备，并在原子尺度上揭示硝酸铀酰在不同Si/Al比地质聚合物纳米孔中的传输机制。