聚酰胺复合正渗透膜扩散过程分子动力学模拟

Molecular dynamics simulation of diffusion process of polyamide composite forward osmosis membrane

水通量较低的问题限制了正渗透技术的大规模应用,在聚酰胺复合正渗透膜的支撑层和活性层中引入纳米材料是正渗透膜水通量提升的重要方式.采用Materials Studio(MS)软件对H_(2)O分子、Na^(+)和Cl^(-)等在正渗透膜活性层和支撑层内的扩散过程进行模拟,研究了纳米材料的添加对水分子和离子渗透的影响.结果表明,相较于支撑层,活性层具有较小的水分子和离子扩散系数及自由体积;活性层较低的自由体积结构是限制正渗透膜水通量的主要因素.在活性层中添加纳米材料可增加活性层聚合物的自由体积,相较于在支撑层中的添加,可更有效地提高正渗透膜的水通量.

The low water permeability of polyamide composite forward osmosis membrane limits its larger-scale applications.The introduction of nano-materials in both active layer and support layer is an important way to mitigate this issue.In this work,the Materials Studio(MS)software was applied to simulate the diffusion process of water molecules and salt ions in polyamide composite forward osmosis membrane.The results indicated that the diffusion coefficients and free volume of the active layer were smaller than those of the polysulfone support layer.The structure of the active layer with lower free volume was the main factor limited the forward osmosis membrane water permeability.Therefore,the forward osmosis membrane water permeability can be improved by adding nano-materials into the active layer increasing the active layer molecules free volume.