Apparatus and process for separation and selective recomposition of ions

A process for capacitive desalination of an electrolyte solution such as seawater by selective removal and depletion of ions therefrom, the process comprising the steps of:

• a) providing an apparatus for capacitive desalination of an electrolyte solution such as seawater, the apparatus comprising:
• i) a plurality of spaced apart ion exchange membranes arranged adjacent to one another forming a stack defining a plurality of compartments, wherein the ion exchange membranes are arranged in pairs of cation and anion ion exchange membranes;
• ii) a first Electric Double Layer Capacitor (EDLC) positioned on one side of the stack and a second EDLC positioned on the other side of the stack, a first end compartment being defined between the first EDLC and the ion exchange membrane closest to the first EDLC and a second end compartment being defined between the second EDLC and the ion exchange membrane closest to the second EDLC, wherein the stack is arranged between the first and second end compartments;
• iii) a frame for compressing and scaling together the EDLCs and the stacked ion exchange membranes, the frame comprising a nonconductive, insulating material;
• iv) a plurality of input and output passages leading into and out of the frame and each compartment, each passage including a control valve for regulating the flow of electrolyte solution into and out of the device;
• and
• v) a direct current electric power supply capable of polarity reversal for charging the EDLCs and establishing a potential difference between the EDLCs and thus causing the passage of electric current through the apparatus;
• b) filling the end compartments and the plurality of middle compartments via the plurality of input passages with an electrolyte solution such as seawater, each of the middle compartments being differentiated into either a concentrate compartment or a diluate compartment when the electrolyte solution is acted upon by an electric field, each concentrate compartment created by receiving positive ions passing through the cation exchange membrane and by receiving negative ions passing through the anion exchange membrane, each diluate compartment created by passage of positive and negative ions into adjacent concentrate compartments;
• c) applying an electric potential difference between the EDLCs to create an electric field between the EDLCs and to cause passage of electric current through the end compartments and the plurality of middle compartments and causing the formation of the concentrate and diluate compartments, the electric field further creating an inner internal capacitor and an outer internal capacitor at each end compartment, each of the inner and outer internal capacitors connected in series through the electrolyte solution between them, each inner internal capacitor being formed between the EDLC and ions collected on and in close proximity to the EDLC, each outer internal capacitor being formed between ions collected on the inner surface of its end compartment and distributed charges in the outside environment, wherein the formation of each outer internal capacitor leads to capacitive collection, concentration and voltage buildup of excess charges on the inner surface of its end compartment;
• and
• d) extracting desalinated solution from the diluate compartments and concentrated solution from the concentrate compartments via the output passages.