正渗透离子截留性能的分子动力学模拟

Molecular dynamics simulation on the ion rejection performance of forward osmosis

正渗透离子截留性能的分子动力学模拟可为纳米孔材料的优化设计提供理论依据和技术指导。文章采用正渗透膜纳米通道模型,运用分子动力学模拟方法,模拟了不同孔径和亲水性纳米通道对离子的截留行为,分析了通道内离子截留率与离子水化数、离子水化半径及平均力势间的关系。结果表明:离子进入纳米通道需克服的能量势垒是由离子水化物的脱水引起,随纳米通道孔径的增大,离子水化物需脱去的水分子数减少;Na+和Cl-的截留率随孔径的增大而降低,当孔径≥1.356 nm时,二者均可通过膜纳米通道;离子进入纳米通道需克服的能量势垒、膜纳米通道对离子的截留率均随亲水性的增强而降低。

Molecular dynamics simulations of ion rejection performance in forward osmosis offer basic theoretical insights and guidance for the optimal design of nano-porous materials.This study,carbon nano-tube is modeled as a single channel of forward osmosis membrane.Molecular dynamics simulations are conducted on ion rejection behaviors across the nano-tubes with different pore diameters and different hydrophilic properties.It examines the relationships among the efficiency of ion rejection in nano-tubes and hydration number of ions,radius of hydrated ions,and the potential of mean force.The simulation results demonstrate that the ion energy barrier for hydrated ions entering into nano-tubes from the draw solution is caused by the dehydration of hydrated ions,and the dehydration number of hydrated ions decreases with the increasing pore diameter.The rejection efficiencies of sodium ions and chlorine ions decrease with the increasing pore diameter.When the diameter reaches or exceeds 1.356 nm,both the sodium ions and chlorine ions can pass through the nano-tubes of membrane.Additionally,the ion energy barrier and the efficiency of ion rejection decrease as the hydrophilic property of the nano-tube increases.