基于分子动力学的钠离子与纳米二氧化硅表面的相互作用过程模拟

Simulation of Interaction Process between Sodion and the Surface of Nano Silicon Dioxide Based on Molecular Dynamics

张凤娟 张 磊 吕振虎 麦尔耶姆古丽·安外尔 余维初 王牧群 董景锋 庄为杰

ZHANG Fengjuan ZHANG Lei LYU Zhenhu MELYAMGULI Anwaier YU Weichu WANG Muqun DONG Jingfeng ZHUANG Weijie

认识盐水中的Na+对纳米SiO2的作用过程，可为优化纳米SiO2在石油开采领域的应用参数提供依据。以无定形纳米 SiO2粒子为研究对象，构建了一种既有饱和稳定的硅醇基团，又有脱质子化的硅醇基团的纳米 SiO2粒子模型。通过分子模拟方法，刻画了Na+在纳米 SiO2表面的运移特征、扩散行为、对氢键的影响以及体系中的相互作用能。结果表明，在纳米 SiO2-NaCl 溶液体系中，当 Na+运移至距纳米 SiO2粒子表面6.540 ?时，短程力开始起作用；当Na+运移至距纳米 SiO2粒子表面2～3 ?时，二者发生电荷交换，Na+产生振荡运动。在 NaCl 质量浓度为3 g/L 时，Na+与水分子主要进行水合作用，形成稳定的溶剂化层，Na+与纳米SiO2粒子之间的作用力弱，Na+更易在溶液中扩散。随着NaCl 质量浓度增至7 g/L，Na+突破溶剂化层，和水分子一起被吸附到纳米SiO2粒子的表面，发生电荷置换，Na+的运移能力减弱，扩散系数由1.39×10-4 ?2/ps 下降至3.75×10-5 ?2/ps，斯特恩层的厚度由0.88 ?下降至0.72 ?，亥姆霍兹层的厚度由0.64 ?下降至0.20 ?，纳米SiO2与Na+之间的相互作用能由-14 000 kcal/mol变为-22 000 kcal/mol，纳米 SiO2的稳定性逐渐被破坏。Na+与纳米 SiO2粒子的静电相互作用是影响纳米 SiO2粒子表面性质的主要作用力，氢键和范德华力则是次要作用力。研究结果可为纳米SiO2材料在油气开采领域及其他相关行业的应用提供基础理论认识。

It can more effectively regulate the parameters of application of nano SiO2 in the field of oil production by understanding the interaction process of Na+ on the surface of nano SiO2 in saline water. In this paper，the amorphous nano SiO2 particles was taken as an object of study，so that a nano SiO2 particle model with both saturated stable silanol groups and deprotonated silanol groups was constructed. By using the molecular dynamics simulation experiments，this paper studied the interaction process between nano-SiO2 particles and Na+ with different concentrations，including transportation，diffusion，recombination of hydrogen bonds， and the interaction energy. The results showed that in the system of nano-SiO2 and NaCl solution，when Na+ migrated to a distance of 6.540 ? away from the surface of nano SiO2 particles，the short-range force began to affect the movement of Na+ . When Na+ migrated to a distance of 2—3 ? away from the surface of nano SiO2 particles，the charge exchange occurred between Na+ and the surface of nano SiO2 particles，resulting in an oscillation motion of Na+ . At a NaCl concentration of 3 g/L，most Na+ underwent hydration with water molecules，which could form a stable solvation layer. The interaction between Na+ and nano SiO2 particles was weak，so Na+ was more likely to diffuse in the solution. As the concentration of NaCl increased to 7 g/L，Na+ could break through the solvation layer. And then Na+ along with water molecules could be adsorbed on the surface of nano-SiO2 particles. The migration ability of Na+ was weakened，the thickness of the double electric layer on the surface of nano-SiO2 particles was narrowed，the interaction energy between nano-SiO2 and Na + was enhanced，and then the stability of nano-SiO2 was gradually destroyed. The diffusion coefficient of Na+ decreased from 1.39×10-4 ?2/ps to 3.75×10-5 ?2/ps. The thickness of the Stern layer on the surface of nano-SiO2 decreased from 0.88 ? to 0.72 ?. The thickness of the Helmholtz layer on the surface of nano-SiO2 decreased from 0.64 ? to 0.20 ?. The interaction energy between nano SiO2 and Na + changed from -14 000 kcal/mol to -22 000 kcal/mol. The electrostatic interaction between Na + and nano SiO2 particles was the main force to affect the surface properties of nano SiO2 particles，while hydrogen bonding and van der Waals forces were secondary forces. The research conclusion could provide a basic theoretical understanding for the application of nano SiO2 materials in the field of oil and gas drilling and other related industries.

10.19346/j.cnki.1000-4092.2024.03.016