Methods for treating a liquid using draw solutions

1. A method of treating a liquid, the method comprising:

converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form;

contacting one side of a membrane with the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in the polar form and an opposite side of the membrane with a feed liquid comprising at least one solvent and at least one solute; and

osmosing the at least one solvent of the feed liquid across the membrane and into the draw solution to form a diluted draw solution and a concentrated feed liquid.

2. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises contacting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form with a switching agent.

3. The method of claim 2 , further comprising removing the switching agent from the diluted draw solution to form a multiple-phase solution comprising the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form and the at least one solvent.

4. The method of claim 3 , further comprising separating the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form and the at least one solvent.

5. The method of claim 4 , further comprising recovering the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form.

6. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises converting the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form to an aminium salt of the at least one N-cyclicalkyl-cycloalkylamine.

7. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises converting the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form to an aminium carbonate of the at least one N-cyclicalkyl-cycloalkylamine.

8. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises exposing the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in the nonpolar form to carbon dioxide.

9. The method of claim 1 , wherein osmosing the at least one solvent of the feed liquid across the membrane and into the draw solution to form a diluted draw solution and a concentrated feed liquid comprises osmosing the at least one solvent of the feed liquid across the membrane and into the draw solution to form a diluted draw solution on the one side of the membrane and a concentrated feed liquid on the opposite side of the membrane.

10. The method of claim 1 , wherein osmosing the at least one solvent of the feed liquid across the membrane and into the draw solution to form a diluted draw solution and a concentrated feed liquid comprises forming the concentrated feed liquid comprising the at least one solute and the diluted draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in the polar form.

11. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine comprising the chemical structure:

wherein n is 0, 1, or 2, n′ is 0, 1, or 2, and each of R 1 -R 6 is independently selected from the group consisting of an alkyl group, an alkoxy group, an acetyl group, an aryl group, a hydrogen group, a hydroxyl group, and a phosphorus-containing group.

12. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises converting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine into a draw solution comprising a bicarbonate form of the at least one N-cyclicalkyl-cycloalkylamine.

13. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises converting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine into a draw solution comprising the chemical structure:

wherein n is 0, 1, or 2, n′ is 0, 1, or 2, each of R 1 -R 6 is independently selected from the group consisting of an alkyl group, an alkoxy group, an acetyl group, an aryl group, a hydrogen group, a hydroxyl group, and a phosphorus-containing group, and X is an anionic counterion.

14. The method of claim 1 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine in a nonpolar form into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form comprises converting a draw solution comprising 1 -cyclohexylpiperidine into a draw solution comprising a bicarbonate form of 1 -cyclohexylpiperidine.

15. A method of treating a liquid, the method comprising:

converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine having the chemical structure:

wherein n is 0, 1, or 2, n′ is 0, 1, or 2, and each of R 1 -R 6 is independently selected from the group consisting of an alkyl group, an alkoxy group, an acetyl group, an aryl group, a hydrogen group, a hydroxyl group, and a phosphorus-containing group, into a draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a polar form;

contacting one side of a membrane with the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in the polar form and an opposite side of the membrane with a feed liquid comprising at least one solvent and at least one solute; and

osmosing the at least one solvent of the feed liquid across the membrane and into the draw solution to form a diluted draw solution and a concentrated feed liquid.

16. The method of claim 15 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine comprises converting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine where is 1 and n′ is 1.

17. The method of claim 15 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine comprises converting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine wherein each of R 1 and R 2 is independently selected from the group consisting of an alkyl group, an alkoxy group, an acetyl group, an aryl group, a hydroxyl group, and a phosphorus-containing group and each of R 3 -R 6 is a hydrogen group.

18. The method of claim 15 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine comprises converting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine in a secondary solvent.

19. The method of claim 15 , wherein converting a draw solution comprising at least one N-cyclicalkyl-cycloalkylamine comprises converting the draw solution comprising the at least one N-cyclicalkyl-cycloalkylamine into the polar form, the polar form of the at least one N-cyclicalkyl-cycloalkylamine being miscible with the secondary solvent.