Draw solutes, methods of forming draw solutes, and methods of using draw solutes to treat an aqueous liquid

Abstract

A method of treating an aqueous liquid. The method comprises providing an aqueous feed liquid comprising water and at least one solute to a first side of a membrane. A draw solution comprising water and a draw solute comprising at least one of a phosphazene compound and a triazine compound is provided to a second side of the membrane. At least a portion of the water of the aqueous feed liquid is osmosed across the membrane and into the draw solution to form a diluted draw solution comprising water and the draw solute. The water of the diluted draw solution is separated from the draw solute of the diluted draw solution to form a purified water product. Draw solutes comprising phosphazene compounds and draw solutes comprising triazine compounds are also disclosed, as are methods of forming the draw solutes.

1 . A draw solute comprising:
 at least one phosphazene compound comprising the following chemical structure:   
       
         
           
           
               
               
           
         
       
       where each X 1  independently comprises —O—, —S—, or —NH—; 
       each G independently comprises an alkylene group, an alkenylene group, an alkynylene group, an alicyclic group, an arylene group —CO—, —SO 2 —, —SO—, —PO—, —O—, —S—, and —NH—; 
       each R independently comprises a salt functional group; and 
       n comprises an integer of from 3 to 5. 
     
     
         2 . The draw solute of  claim 1 , wherein the salt functional group comprises one of the following structures: 
       
         
           
           
               
               
           
         
       
       where each M 1  independently comprises a mono-valent cationic counterion or a multi-valent cationic counterion. 
     
     
         3 . The draw solute of  claim 2 , wherein each M 1  independently comprises Li + , Na + , K + , NH 4   + , Ca 2+ , Mg 2+ , Zn 2+ , (R 1 ) 4 N + , or (R 1 ) 4 P + , wherein each R 1  independently comprises H, a substituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, an unsubstituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, a substituted aryl group comprising from carbon atoms to 8 carbon atoms, or an unsubstituted aryl group comprising from 5 carbon atoms to 8 carbon atoms. 
     
     
         4 . The draw solute of  claim 1 , wherein the salt functional group comprises one of the following structures: 
       
         
           
           
               
               
           
         
         where each R 1  independently comprises H, a substituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, an unsubstituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, a substituted aryl group comprising from 5 carbon atoms to 8 carbon atoms, or an unsubstituted aryl group comprising from 5 carbon atoms to 8 carbon atoms; and 
         each M 2  independently comprises a mono-valent anionic counterion or a multi-valent anionic counterion. 
       
     
     
         5 . The draw solute of  claim 1 , wherein the at least one phosphazene compound comprises at least one cyclic phosphazene compound. 
     
     
         6 . The draw solute of  claim 5 , wherein the at least one cyclic phosphazene compound comprises the following structure: 
       
         
           
           
               
               
           
         
       
     
     
         7 . The draw solute of  claim 1 , wherein the at least one phosphazene compound has the following structure: 
       
         
           
           
               
               
           
         
       
     
     
         8 . A draw solute comprising:
 at least one triazine compound comprising the following structure:   
       
         
           
           
               
               
           
         
       
       where each X 2  independently comprises —N—, —P—, —CH—, or —SiH—;
 each G independently comprises an alkylene group, an alkenylene group, an alkynylene group, an alicyclic group, an arylene group, —CO—, —SO 2 —, —SO—, —PO—, —O—, —S—, and —NH—; and 
 each R independently comprises a salt functional group. 
 
     
     
         9 . The draw solute of  claim 8 , wherein the salt functional group comprises one of the following structures: 
       
         
           
           
               
               
           
         
         where each M 1  independently comprises a mono-valent cationic counterion or a multi-valent cationic counterion. 
       
     
     
         10 . The draw solute of  claim 9 , wherein each M 1  independently comprises Li + , Na + , K + , NH 4   + , Ca 2+ , Mg 2+ , Zn 2+ , (R 1 ) 4 N + , or (R 1 ) 4 P + , wherein each R 1  independently comprises H, a substituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, an unsubstituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, a substituted aryl group comprising from 5 carbon atoms to 8 carbon atoms, or a unsubstituted aryl group comprising from 5 carbon atoms to 8 carbon atoms. 
     
     
         11 . The draw solute of  claim 8 , wherein the salt functional group comprises one of the following structures: 
       
         
           
           
               
               
           
         
         where each R 1  independently comprises H, a substituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, an unsubstituted alkyl group comprising from 1 carbon atom to 8 carbon atoms, a substituted aryl group comprising from 5 carbon atoms to 8 carbon atoms, or an unsubstituted aryl group comprising from 5 carbon atoms to 8 carbon atoms; and 
         each M 2  independently comprises a mono-valent anionic counterion or a multi-valent anionic counterion. 
       
     
     
         12 . The draw solute of  claim 8 , wherein the triazine compound has the following structure: 
       
         
           
           
               
               
           
         
       
     
     
         13 . A method of treating an aqueous liquid, the method comprising:
 providing an aqueous feed liquid comprising water and at least one solute to a first side of a membrane;   providing a draw solution comprising water and a draw solute comprising at least one of a phosphazene compound and a triazine compound to a second side of the membrane;   osmosing at least a portion of the water of the aqueous feed liquid across the membrane and into the draw solution to form a diluted draw solution comprising water and the draw solute; and   separating the water of the diluted draw solution from the draw solute of the diluted draw solution to form a purified water product.   
     
     
         14 . The method of  claim 13 , wherein providing the aqueous feed liquid comprises providing at least one of an aqueous saline solution, ocean water, brine, brackish water, mineralized water, and industrial waste water. 
     
     
         15 . The method of  claim 13 , wherein the phosphazene compound comprises a plurality of salt-terminated pendant groups bonded to phosphorus atoms of a plurality of phosphorus-nitrogen units. 
     
     
         16 . The method of  claim 13 , wherein the triazine compound comprises a plurality of salt-terminated pendant groups bonded to carbon atoms of a triazine ring. 
     
     
         17 . The method of  claim 13 , wherein the draw solute at least partially dissociates in water to produce from about three particles of the draw solute to about seven particles of the draw solute. 
     
     
         18 . The method of  claim 13 , wherein providing a draw solution further comprises adjusting at least one of an amount of the water in the draw solution and an amount of the draw solute in the draw solution such that the draw solution comprises a greater number of particles than a total number of particles in the aqueous feed liquid. 
     
     
         19 . The method of  claim 13 , wherein separating the water of the diluted draw solution from the draw solute of the diluted draw solution comprises filtering the diluted draw solution. 
     
     
         20 . The method of  claim 19 , wherein filtering the diluted draw solution comprises subjecting the diluted draw solution to at least one of microfiltration, ultrafiltration, and nanofiltration. 
     
     
         21 . A method of forming a draw solute, comprising:
 reacting a halogenated phosphazene compound with a nucleophilic compound to form a fully-substituted phosphazene compound;   hydrolyzing the fully-substituted phosphazene compound to form an acidic phosphazene compound comprising acid-terminated pendant groups; and   neutralizing the acidic phosphazene compound to form a phosphazene compound comprising salt-terminated pendant groups.