  The theory of electrokinetic ion transport in cylindrical channels of a fixed
surface charge density is revisited. Attention is focused on impact of the
hydrophobic slippage and mobility of adsorbed surface charges. We formulate
generalised Onsager relations for a cylinder of an arbitrary radius and then
derive exact expressions for the mean electro-osmotic mobility and
conductivity. To employ these expressions we perform additional electrostatic
calculations, with the special focus on the non-linear electrostatic effects.
Our theory provides a simple explanation of a giant enhancement of the
electrokinetic mobility and conductivity of hydrophobic nanotubes by
highlighting the role of appropriate electrostatic and hydrodynamic length
scales and their ratios. We also propose a novel interpretation of zeta
potentials of cylindrical channels.
