Apparatus and process for separation and selective recomposition of ions

1. A process for capacitive desalination of a saline water solution by selective removal and depletion of ions therefrom, the process comprising the steps of:

a) providing an apparatus for capacitive desalination of a saline water solution, the apparatus comprising:

i) a plurality of spaced apart cation and anion exchange membranes arranged adjacent to one another in pairs, thereby forming a stack defining a plurality of middle compartments;

ii) a first capacitive electrode positioned within a first end compartment on one side of the stack and a second capacitive electrode positioned within a second end compartment on the other side of the stack, the first end compartment being defined between the first capacitive electrode and the ion exchange membrane closest to the first capacitive electrode and the second end compartment being defined between the second capacitive electrode and the ion exchange membrane closest to the second capacitive electrode, wherein the stack is arranged between the first and second end compartments;

iii) a frame for compressing and sealing the stack and the end compartments together;

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 the saline water solution into and out of the device; and

v) a direct current electric power supply for passage of electric current through the apparatus, wherein the power supply is capable of polarity reversal and is electrically connected to the first and second capacitive electrodes;

b) filling the end compartments and the plurality of middle compartments via the plurality of input passages with the saline water solution;

c) applying an electric current via the power supply, wherein the passage of electric current through the apparatus causes the plurality of middle compartments to differentiate into alternating concentrate and diluate compartments, each of the concentrate compartments receiving both positive and negative ions from adjacent diluate compartments via the cation and anion exchange membranes, each of the diluate compartments conveying positive and negative ions to adjacent concentrate compartments via the cation and anion exchange membranes;

d) determining when the potential difference between each capacitive electrode and its adjacent electrolyte solution reaches the point of initiating electrode reactions;

e) based on the determination in step (d) regarding the initiation of electrode reactions, reversing the polarity of the power supply to prevent occurrence of electrode reactions, wherein the reversal of polarity causes the plurality of middle compartments which were previously diluate compartments to become concentrate compartments and the plurality of middle compartments which were previously concentrate compartments to become diluate compartments; and

f) extracting desalinated solution from the diluate compartments and concentrated solution from the concentrate compartments via the output passages.

2. A process for capacitive desalination of a saline water solution by selective removal and depletion of ions therefrom, the process comprising the steps of:

a) providing an apparatus for capacitive desalination of a saline water solution, the apparatus comprising:

i) a first capacitive electrode positioned within a first end compartment;

ii) a second capacitive electrode positioned within a second end compartment;

iii) a first stack comprising a first plurality of spaced apart cation and anion exchange membranes arranged adjacent to one another in pairs, the first stack defining a first plurality of middle compartments;

iv) a second stack comprising a second plurality of spaced apart cation and anion exchange membranes arranged adjacent to one another in pairs, the second stack defining a second plurality of middle compartments;

v) a divider placed between and separating the first and second stacks, wherein the first and second stacks are arranged next to one another and in opposite orientation to one another between the first and second end compartments, the first end compartment being defined between the first capacitive electrode and the ion exchange membranes of the first and second stacks closest to the first capacitive electrode and the second end compartment being defined between the second capacitive electrode and the ion exchange membranes of the first and second stacks closest to the second capacitive electrode;

vi) a frame for compressing and sealing the stacks and the end compartments together;

vii) 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 the saline water solution into and out of the device; and

viii) a direct current electric power supply for passage of electric current through the apparatus, wherein the power supply is capable of polarity reversal and is electrically connected to the first and second capacitive electrodes;

b) filling the end compartments and the first and second plurality of middle compartments via the plurality of input passages with the saline water solution;

c) applying an electric current via the power supply between the first and second capacitive electrodes to create an electric field through the first and second plurality of middle compartments;

d) removing the saline water solution from one of the plurality of compartments of the second stack, thereby directing the passage of electric current through the first stack only, wherein the electric current causes the first plurality of middle compartments to differentiate into alternating concentrate and diluate compartments, each of the concentrate compartments receiving both positive and negative ions from adjacent diluate compartments via the cation and anion exchange membranes, each of the diluate compartments conveying positive and negative ions to adjacent concentrate compartments via the cation and anion exchange membranes;

e) following step (d), determining when the potential difference between each capacitive electrode and its adjacent electrolyte solution reaches the point of initiating electrode reactions;

f) following step (e), removing the saline water solution from one of the plurality of compartments of the first stack;

g) following step (f), reversing the polarity of the power supply;

h) following step (g), filling the previously emptied compartment of the second stack with the saline water solution, thereby directing the passage of electric current through the second stack only, wherein the reversal of polarity causes the second plurality of middle compartments to differentiate into alternating concentrate and diluate compartments, each of the concentrate compartments receiving both positive and negative ions from adjacent diluate compartments via the cation and anion exchange membranes, each of the diluate compartments conveying positive and negative ions to adjacent concentrate compartments via the cation and anion exchange membranes; and

i) extracting desalinated solution from the diluate compartments and concentrated solution from the concentrate compartments of both the first and the second stack via the output passages.