Water desalination using directional solvent extraction
Substantially pure water is produced via desalination using a directional solvent that directionally dissolves water but does not dissolve salt. The directional solvent is heated to dissolve water from the salt solution into the directional solvent. The remaining highly concentrated salt water is removed, and the solution of directional solvent and water is cooled to precipitate substantially pure water out of the solution.
1. A method for separating water from a saline solution using a directional solvent, the method comprising:
providing a directional solvent comprising a fatty acid and providing a saline solution comprising water and at least one salt at an initial salt concentration;
making an emulsion of the saline solution in the directional solvent in liquid form;
heating the directional solvent before or after contact with the saline solution to produce a first phase that includes the directional solvent and a concentration of water from the saline solution dissolved in the directional solvent, and a second phase that includes a highly concentrated remainder of the saline solution;
allowing the first phase to separate from the second phase;
extracting the first phase including the directional solvent and the dissolved water from the highly concentrated remainder of the saline solution or extracting the highly concentrated remainder of the saline solution from the first phase;
cooling the first phase after extraction to precipitate the water from the directional solvent, wherein the directional solvent is maintained in liquid form as the water is precipitated, wherein the water is precipitated with a salt concentration substantially less than the initial salt concentration of the saline solution, and wherein the concentration of water that dissolves in the directional solvent is at least 10 times greater than the concentration of the directional solvent in the precipitated water; and
removing the precipitated water from the directional solvent.
2. The method of claim 1 , wherein the fatty acid includes a carbon chain with a length from 6 to 13 carbon atoms.
3. The method of claim 1 , wherein the directional solvent is a solid at temperatures of 30° C. and below.
4. The method of claim 1 , further comprising mixing the directional solvent and the saline solution to produce the emulsion before heating the directional solvent and saline solution.
5. The method of claim 1 , further comprising mixing the directional solvent and the saline solution to produce the emulsion after heating the directional solvent.
6. The method of claim 1 , further comprising using dielectrophoresis to separate the precipitated water from the directional solvent.
7. The method of claim 1 , wherein the directional solvent is heated using energy from a mid-temperature heat source of no greater than 75° C.
8. The method of claim 1 , wherein the directional solvent is heated using energy from a low-temperature heat source of no greater than 40° C.
9. The method of claim 1 , wherein the directional solvent and the saline solution are heated using heat from another process or using terrestrial or solar heat.
10. The method of claim 1 , wherein the extracted precipitated water has a weight-to-weight salt content of less than 1.5%.
11. The method of claim 1 , wherein the extracted precipitated water has a weight-to-weight salt content of less than 0.14%.
12. The method of claim 1 , wherein the extracted precipitated water has a weight-to-weight salt content of less than 0.05%.
13. The method of claim 1 , wherein separation of the water from the saline solution using the directional solvent is a first stage in a multi-stage desalination process, the method further comprising subjecting the precipitated water, after extraction, to a second stage of desalination to reach a higher level of purity.
14. The method of claim 13 , wherein the second stage of desalination includes reverse osmosis or flash distillation.
15. The method of claim 1 , further comprising reusing the directional solvent to repeat the method of separating water from saline solution.
16. The method of claim 1 , wherein the water from the saline solution dissolves into the directional solvent at a concentration of at least about 1 volume-% of the directional solvent.
17. The method of claim 1 , wherein the water is precipitated from the directional solvent at a volume of at least about 0.5% of the volume of the directional solvent.
18. The method of claim 1 , wherein the salt concentration in the precipitated water is less than half of the initial salt concentration.
19. The method of claim 1 , wherein the salt concentration in the precipitated water is less than a fifth of the initial salt concentration.
20. The method of claim 1 , wherein the water is precipitated with a directional-solvent content of 0 to about 0.3 volume %.