It will be shown that for a solution of salt dissolved in water in contact with a metallic or dielectric wall, the concentration of salt ions (both positive and negative) near the wall can be large enough to exceed the salt's solubility limit, as a result of electrical image charge forces. In addition, since the dielectric constant of water increases from 2.1 at the wall to 81 at about 1 nm from a solid wall, there will be an attractive image potential near the plane on which this increase of the dielectric constant occurs. Such large ion concentrations could possibly be used in water desalination.

• Received 16 August 2019
• Revised 31 October 2019

DOI:https://doi.org/10.1103/PhysRevE.101.013110