Electrophoresis of ions and electrolyte conductivity: From bulk to nanochannels.

The article focuses on revisiting and advancing the theoretical understanding of the electrophoretic mobility of ions and the resulting electrical conductivity of monovalent electrolyte solutions, both in bulk and when confined within narrow micro- and nanochannels. It derives improved analytical expressions for ion mobility and bulk conductivity valid up to molar concentrations, clarifying the limitations of classical models such as the Stokes drag-based mobility and Kohlrausch's empirical law. The theory incorporates salt-dependent reductions in ion zeta potentials and extends to describe conductivity enhancements in charged channels, distinguishing between thick and thin channel modes and accounting for electrostatic boundary conditions. Validation against experimental data for NaCl solutions shows excellent agreement, and the work highlights open problems including the treatment of ions with differing radii, highly concentrated or multivalent electrolytes, and the unique transport mechanisms of hydrogen and hydroxyl ions.