The invention relates to a device and a process for the desalination of NaCl solutions employing a three-chamber electrochemical cell separated by relative ion exchange membranes, namely a succession of a cathode chamber (16; 116), a cation exchange membrane (28; 128), a central chamber (12; 112) for the saline solution, an anion exchange membrane (26; 126) and an anode chamber (14; 114). The oxidation of OH- and the reduction of H3O+ under the formation of OH- and H2 causes the passage of Na+ and Cl- ions from the central chamber to the other chambers, thereby reducing the salt concentration. The feeding of the cathode chamber can be managed in a circuit with the insertion of a carbonation reactor (50) to reduce the concentration of NaOH and eliminate CO2 from the air. Under certain conditions, the chlorides entering the anode chamber undergo oxidation and the chlorine formed therein reacts with water to produce HCl and HClO.