Thermo-responsive draw solute for forward osmosis and method for water desalination and purification using the same
The present invention relates to a thermo-responsive draw solute that can be applied to water desalination and purification based on forward osmosis. The thermo-responsive draw solute has a molar mass of 50 to 3000 g/mol and undergoes a phase transition at a temperature of 0° C. to 70° C. The thermo-responsive draw solute creates optimum conditions for the desalination of seawater and the purification of contaminated water based on forward osmosis. The present invention also relates to a method for water desalination and purification using the thermo-responsive draw solute. The method consumes little energy for water desalination or purification, is simple to apply to water desalination or purification, and enables separation of the draw solute in a very easy manner.
1. A method for water desalination and purification using a thermo-responsive draw solute for forward osmosis, the method comprising:
1) bringing unpurified water into contact with a draw solution comprising the thermo-responsive draw solute at a higher concentration than the unpurified water through a semi-permeable membrane;
2) allowing clean water to flow from the unpurified water into the draw solution through the semi-permeable membrane by forward osmosis;
3) adjusting the temperature of the draw solution to or above the critical solution temperature of the thermo-responsive draw solute to cause a lower critical solution temperature (LCST) phase separation of the thermo-responsive draw solute from the draw solution; and
4) separating the clean water from the thermo-responsive draw solution.
2. The method according to claim 1 , wherein the thermo-responsive draw solute for forward osmosis has a molar mass of 50 to 3000 g/mol and undergoes a LCST phase transition at a temperature of 0° C. to 70° C.
3. The method according to claim 1 , wherein the thermo-responsive draw solute for forward osmosis is selected from the group consisting of:
and mixtures thereof.
4. The method according to claim 1 , wherein the semi-permeable membrane is a cellulose acetate or polyether sulfone semi-permeable membrane.
5. The method according to claim 1 , wherein the unpurified water is water comprising ions, colloids, microbes, water soluble molecules, insoluble organic molecules, or mixtures thereof.
6. The method according to claim 1 , wherein the draw solution is formed by dissolving phase-separated thermo-responsive draw solute.
7. A method for water desalination and purification using a thermo-responsive draw solute for forward osmosis, the method comprising:
1) bringing unpurified water into contact with a draw solution comprising the thermo-responsive draw solute at a higher concentration than the unpurified water through a semi-permeable membrane;
2) allowing clean water to flow from the unpurified water into the draw solution through the semi-permeable membrane by forward osmosis;
3) adjusting the temperature of the draw solution to or below the critical solution temperature of the thermo-responsive draw solute to cause an upper critical solution temperature (UCST) phase separation of the thermo-responsive draw solute from the draw solution;
and
4) separating the clean water from the thermo-responsive draw solution.
8. The method according to claim 7 , wherein the thermo-responsive draw solute has a molar mass of 50 to 3000 g/mol and undergoes an UCST phase transition at a temperature of 0° C. to 70° C.
9. The method according to claim 7 , wherein the thermo-responsive draw solute is selected from the group consisting of:
and mixtures thereof.
10. The method according to claim 7 , wherein the semi-permeable membrane is a cellulose acetate or polyether sulfone semi-permeable membrane.
11. The method according to claim 7 , wherein the unpurified water is water comprising ions, colloids, microbes, water soluble molecules, insoluble organic molecules, or mixtures thereof.
12. The method according to claim 7 , wherein the draw solution is formed by dissolving phase-separated thermo-responsive draw solute.
13. A method for water desalination and purification using a thermo-responsive draw solute for forward osmosis, the method comprising:
1) bringing unpurified water into contact with a draw solution comprising the thermo-responsive draw solute at a higher concentration than the unpurified water through a semi-permeable membrane;
2) allowing clean water to flow from the unpurified water into the draw solution through the semi-permeable membrane by forward osmosis;
3) adjusting the temperature of the draw solution to or below the critical solution temperature of the thermo-responsive draw solute to cause a phase transition of the thermo-responsive draw solute from the draw solution; and
4) separating the clean water from the draw solution,
wherein the thermo-responsive draw solute is selected from the group consisting of:
and mixtures thereof.
14. The method according to claim 13 , wherein the phase transition in element 3) results in phase separation of the thermo-responsive draw solute.