Electroosmotic flow and transport of ionic species through a slit soft nanochannel filled with general electrolytes

A numerical study is presented of the electroosmotic flow (EOF) and transport of ionic species through a slit soft nanochannel filled with general electrolytes. The rigid walls of the undertaken channel are coated with ion and fluid penetrable charged polyelectrolyte layers (PELs). The physico-chemical properties of the surface PELs grafted on the lower and upper walls are considered to be either similar or dissimilar in nature. A nonlinear model based on the coupled Poisson-Boltzmann equation for electrostatics and the modified Stokes equation for hydrodynamics is adopted. Based on the Debye-Huckel limit under a low potential approximation a closed form solution for the induced potential and axial velocity is derived. However throughout our present study a sophisticated numerical technique is adopted to consider a wide range of pertinent parameters governing the problem. It is observed that the EOF and transport of ionic species strongly depends on the choice of the PEL-charge and the background electrolyte solution. In addition we have shown that the selectivity of mobile electrolyte ions can be actively tuned by regulating the physicochemical properties of the surface PELs and the background aqueous medium.