  The comprehensive depiction of the many-body effects governing nanoconfined
electrolytes is an essential step for the conception of nanofluidic devices
with optimized performance. By incorporating self-consistently multivalent
charges into the Poisson-Boltzmann equation dressed by a background monovalent
salt, we investigate the impact of strong-coupling electrostatics on the
nanofluidic transport of electrolyte mixtures. We find that the experimentally
observed negative streaming currents in anionic nanochannels originate from the
collective effect of the Cl attraction by the interfacially adsorbed
multivalent cations, and the no-slip layer reducing the hydrodynamic
contribution of these cations to the net current. The like-charge current
condition emerging from this collective mechanism is shown to be the reversal
of the average potential within the no-slip zone. Applying the formalism to
surface-coated membrane nanoslits located in the giant dielectric permittivity
regime, we reveal a new type of streaming current activated by attractive
polarization forces. Under the effect of these forces, the addition of
multivalent ions into the KCl solution sets a charge separation and generates a
counterion current between the neutral slit walls. The adjustability of the
current characteristics solely via the valency and amount of the added
multivalent ions identifies the underlying process as a promising mechanism for
nanofluidic ion separation purposes.
