Effects of ion-ion correlations on surface charge inversion in mixture electrolyte solutions

As the structure of electrical double layer(EDL)is crucial for the transport properties of ions in micro/nanochannels,to demonstrate the effects of the ion-ion correlations on EDL structures in mixture electrolyte solutions,the interaction forces between two mica surfaces immersed in different volume fractions of LaCl3/KCl and LaCl3/MgCl2 mixture solutions with a total ionic strength of 10^-4 mol/L were measured using a surface forces apparatus(SFA).The results reveal that the surface charge of mica surfaces can be inversed at a critical concentration of La^3+ions in electrolyte solutions,due to the correlations between La^3+ions.The addition of monovalent has negligible effects on ion-ion correlations,while the charge inversion was slightly suppressed by introducing the divalent ions.The mechanism of charge inversion in mixture electrolyte solutions was analyzed based on the strongly correlated liquid(SCL)theory.These findings provide implications for understanding the effects of ion-ion correlations on EDL structures,surface charge properties,and ion transportation.

纳米通道中电渗流的分子动力学模拟

采用分子动力学(MD)方法,模拟了纳米通道中NaC l溶液的电渗现象。模拟结果表明,与上下两板带同性电荷相比,当纳米通道的上下壁面所带电荷电性相反时,通道中水的浓度分布大致相同,而离子浓度分布,水的速度及通道中的电势分布相差很大。具体表现在:Na+主要聚集在带负电的硅板附近,C l-主要聚集在带正电的硅板附近,通道中部出现电荷倒置现象;在通道下部的区域水的速度为负值,而在上部区域速度为正值;电势在硅板附近呈指数分布,其值在下硅板附近为正,在上硅板附近为负,在模拟区域中段,电势在通道下部区域由正值变为负值,在通道上部区域由负值变为正值。此外,模拟结果还表明:纳米通道中的速度流型随通道壁面电荷分布的改变而改变。