Water with Switchable Ionic Strength

Abstract

A method and system for reversibly converting water between an initial ionic strength and an increased ionic strength, using a switchable additive, is described. The disclosed method and system can be used, for example, in distillation-free removal of water from solvents, solutes, or solutions. Following extraction of a solute from a medium by dissolving it in water, the solute can then be isolated from the aqueous solution or “salted-out” by converting the water to a solution having an increased ionic strength. The solute then separates from the increased ionic strength solution as a separate phase. Once the solute is, for example, decanted off, the increased ionic strength aqueous solution can be converted back to water having its original ionic strength and reused. Switching from lower to higher ionic strength is readily achieved using low energy methods such as bubbling with CO 2 , CS 2 or COS. Switching from higher to lower ionic strength is readily achieved using low energy methods such as bubbling with air, heating, agitating, introducing a vacuum or partial vacuum, or any combination or thereof.

We claim: 
     
         1 . A system for controlling the amount of dissolved salt in an aqueous mixture comprising:
 an ionizing trigger;   a switchable water, which comprises water and a switchable additive which reversibly converts to a salt upon contact with the ionizing trigger in the presence of water, the switchable additive having the general formula (1):   
       
         
           
           
               
               
           
         
       
       where R 1 , R 2 , and R 3  are independently:
 H; 
 a substituted or unsubstituted C 1  to C 8  aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {—Si(R 10 ) 2 —O—} up to and including 8 C being replaced by 8 {—Si(R 10 ) 2 —O—}; 
 a substituted or unsubstituted C n Si m  group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8; 
 a substituted or unsubstituted C 4  to C 8  aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {—Si(R 10 ) 2 —O—}; 
 a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {—Si(R 10 ) 2 —O—}, wherein aryl is optionally heteroaryl; 
 a —(Si(R 10 ) 2 —O) p — chain in which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or unsubstituted C 1  to C 8  aliphatic and/or aryl group; or a substituted or unsubstituted (C 1  to C 8  aliphatic)-(C 4  to C 8  aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {—Si(R 10 ) 2 —O—}; 
 wherein R 10  is a substituted or unsubstituted C 1  to C 8  aliphatic group, a substituted or unsubstituted C 1  to C 8  alkoxy, a substituted or unsubstituted C 4  to C 8  aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and 
 wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl; Si(alkyl) 3 ; Si(alkoxy) 3 ; halo; alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester; phosphonato; phosphina to; cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate; sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties; thioester; or a combination thereof; 
 wherein said ionizing trigger is capable of dissolving in said switchable water; 
 wherein said switchable water is switchable between (i) a high ionic strength form in which the ionizing trigger is present in said mixture at an amount sufficient to convert the switchable additive to, and/or to maintain the switchable additive in, its protonated form; and (ii) a low ionic strength form, in which the ionizing trigger is absent or present in said mixture at an amount insufficient to convert the switchable additive to, or maintain the switchable additive in, its protonated form. 
 
     
     
         2 . The system of  claim 1 , further comprising:
 means for exposing the increased ionic strength switchable water to (i) heat, (ii) a flushing gas, (iii) a vacuum or partial vacuum, (iv) agitation, or (v) any combination thereof, thereby reducing the amount of the ionizing trigger   to an amount insufficient to convert the switchable additive to, or to maintain the switchable additive in, its protonated form.   
     
     
         3 . The system of  claim 1 , further comprising:
 solid material comprising at least one selected compound,   wherein at least a portion of the at least one selected compound becomes associated with the switchable water to form an aqueous solution when the ionizing trigger is present in said mixture at an amount that is insufficient to convert the switchable additive to, or maintain the switchable additive in, its protonated form; and   a two-phase liquid mixture is formed when the switchable additive is in its protonated form, said two-phase liquid mixture having a first liquid phase comprising the at least one selected compound, and a second liquid phase comprising an increased ionic strength switchable water.   
     
     
         4 . The system of  claim 3 ,
 wherein the solid material comprises solid particles that are contaminated by the at least one selected compound, wherein the solid particles are insoluble in the switchable water containing the non-protonated switchable additive, and   wherein the system comprises means for isolating the solid particles therefrom; and   optionally comprising means for collecting the at least one selected compound from the first liquid phase.   
     
     
         5 . The system of  claim 4 , wherein isolated solid particles are substantially free of the at least one selected compound. 
     
     
         6 . The system of  claim 4 , wherein the at least one selected compound collected from the first liquid phase is substantially pure. 
     
     
         7 . The system of  claim 3 ,
 wherein the at least one selected compound is one or more components of a chemical reaction, and the system additionally comprises:   means for adding reagents of the chemical reaction to the system; and   means for collecting the one or more components of the chemical reaction from the first liquid phase.   
     
     
         8 . A system for modulating an osmotic gradient across a membrane, comprising:
 a semi-permeable membrane;   a switchable water on one side of said semi-permeable membrane, said switchable water comprising a switchable additive and having a switchable ionic strength;   means for contacting the semi-permeable membrane with a feed stream; and   means for contacting the switchable water with an ionizing trigger to ionize the switchable additive and thereby increase solute concentration in the switchable water and modulate the osmotic gradient.   
     
     
         9 . The system of  claim 8  for use in a desalination process or a wastewater remediation process. 
     
     
         10 . A desalination system comprising:
 a semi-permeable membrane that is selectively permeable for water;   a draw solution comprising a switchable additive and water, said draw solution having switchable ionic strength;   means for introducing an ionizing trigger to the draw solution to ionize the switchable additive;   means for contacting the semi-permeable membrane with a feed stream of an aqueous salt solution to permit flow of water from the aqueous salt solution through the semi-permeable membrane into the draw solution comprising the ionized switchable additive; and   optionally, means for separating the switchable additive from the water.   
     
     
         11 . A system for concentrating a dilute aqueous solution, comprising:
 a semi-permeable membrane that is selectively permeable for water;   a draw solution comprising a switchable additive and water, said draw solution having switchable ionic strength;   means for introducing an ionizing trigger to the draw solution to ionize the switchable additive;   means for contacting the semi-permeable membrane with a feed stream of the dilute aqueous solution to permit flow of water from the dilute aqueous solution through the semi-permeable membrane into the draw solution comprising the ionized switchable additive; and   optionally, means for separating the switchable additive from the water.   
     
     
         12 . The system of  claim 11 , wherein the dilute aqueous solution is wastewater. 
     
     
         13 . The system of  claim 10 , wherein the means for separating the switchable additive from the water comprises a reverse osmosis system. 
     
     
         14 . The system of  claim 10 , wherein the means for separating the switchable additive from the water comprises:
 means for expelling the ionizing trigger from the mixture of the draw solution and water to deprotonate the switchable additive; and   means for separating the deprotonated switchable additive from the mixture.   
     
     
         15 . The system of  claim 14 , wherein the means for separating the deprotonated switchable additive from the mixture comprises:
 means for separating the deprotonated switchable additive by decanting if the deprotonated switchable additive is immiscible with water; or   means for filtering the deprotonated switchable additive if the deprotonated switchable additive is insoluble in water.   
     
     
         16 . The system of  claim 15 , additionally comprising:
 means for removal of residual switchable additive remaining after decantation or filtration.   
     
     
         17 . The system of  claim 16 , wherein the means for removal of residual switchable additive comprises a reverse osmosis or nanofiltration system. 
     
     
         18 . The system of  claim 1 , wherein the ionizing trigger is CO 2 . 
     
     
         19 - 68 . (canceled) 
     
     
         69 . The system of  claim 11 , wherein the means for separating the switchable additive from the water comprises a reverse osmosis system. 
     
     
         70 . The system of  claim 11 , wherein the means for separating the switchable additive from the water comprises:
 means for expelling the ionizing trigger from the mixture of the draw solution and water to deprotonate the switchable additive; and   means for separating the deprotonated switchable additive from the mixture.   
     
     
         71 . The system of  claim 70 , wherein the means for separating the deprotonated switchable additive from the mixture comprises:
 means for separating the deprotonated switchable additive by decanting if the deprotonated switchable additive is immiscible with water; or   means for filtering the deprotonated switchable additive if the deprotonated switchable additive is insoluble in water.   
     
     
         72 . The system of  claim 71 , additionally comprising:
 means for removal of residual switchable additive remaining after decantation or filtration.   
     
     
         73 . The system of  claim 72 , wherein the means for removal of residual switchable additive comprises a reverse osmosis or nanofiltration system. 
     
     
         74 . The system of  claim 1 , further comprising a solute,
 wherein protonation of the switchable additive causes separation of two components: a first component that comprises the protonated form of the switchable additive and water; and a second component that comprises the solute,   wherein the solute is not reactive with the switchable additive, ionizing trigger, or a combination thereof, and the ionizing trigger is CO 2 , COS, CS 2 , or a combination thereof.   
     
     
         75 . The system of  claim 1 , further comprising a water-immiscible or water-insoluble ingredient,
 wherein protonation of the switchable additive causes separation of two components: a first component that comprises the water-immiscible or water-insoluble ingredient, and a second component that comprises water and the protonated form of the switchable additive;   wherein the ionizing trigger is CO 2 , COS, CS 2 , or a combination thereof.   
     
     
         76 . The system of  claim 1 , further comprising a hydrophobic liquid,
 wherein protonation of the switchable additive causes separation of two components: a first component that comprises the protonated form of the switchable additive and water; and a second component that comprises the hydrophobic liquid;   wherein the hydrophobic liquid is not reactive with the switchable additive, ionizing trigger, or a combination thereof, and the ionizing trigger is CO 2 , COS, CS 2 , or a combination thereof.   
     
     
         77 . The system of  claim 1 , wherein the switchable additive is:
 MDEA (N-methyl diethanol-amine);   TMDAB (N,N,N′,N′-tetramethyl-1,4-diaminobutane);   TEDAB (N,N,N′,N′-tetraethyl-1,4-diaminobutane);   EPDAB (N,N′-diethyl-N,N′-dipropyl-1,4-diaminobutane);   THEED (N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine);   DMAPAP (1-[bis[3-(dimethylamino)]propyl]amino]-2-propanol);   HMTETA (1,1,4,7,10,10-hexamethyl triethylenetetramine);   MeSpe (N 1 ,N 1′ -(butane-1,4-diyl)bis(N 1 ,N 3 ,N 3 -trimethylpropane-1,3-diamine);   Methylated polyethyleneimine; or   CHTDMA (1,1′,1″-(cyclohexane-1,3,5-triyl)tris(N,N,-dimethylmethanamine).