Guanidine compounds for removal of oxyanions from aqueous solutions and for carbon dioxide capture

Abstract

Methods for removing oxyanions from water according to the following steps: (i) dissolving an oxyanion precipitating compound into the aqueous source to result in precipitation of an oxyanion salt of the oxyanion precipitating compound; and (ii) removing the oxyanion salt from the water containing the oxyanion to result in water substantially reduced in concentration of the oxyanion; wherein the oxyanion precipitating compound has the following composition: wherein A is a ring-containing moiety and X m− is an anionic species with a magnitude of charge m. The invention employs bis-iminoguanidinium compounds according to Formula (1a) as well as neutral precursor compounds according to Formula (1), which can be used for removing undesirable species from aqueous solutions or air, such as removal of sulfate from water and carbon dioxide from air.

What is claimed is: 
     
         1 . A compound having the following composition: 
       
         
           
           
               
               
           
         
         wherein A is a ring-containing moiety; one or more of the hydrogen atoms in Formula (1) may be replaced with one or more methyl groups; and wherein Formula (1) optionally further comprises salt forms of the structure of Formula (1). 
       
     
     
         2 . The compound of  claim 1 , wherein the compound of Formula (1) is a salt form having the following composition: 
       
         
           
           
               
               
           
         
         wherein: 
         A is a ring-containing moiety; 
         X m−  is an anionic species with a magnitude of charge m, where m is an integer of at least 1; and 
         n is an integer of at least 1; 
         provided that n×m=2. 
       
     
     
         3 . The compound of  claim 1 , wherein A is a monocyclic ring. 
     
     
         4 . The compound of  claim 3 , wherein said monocyclic ring is a five-membered, six-membered, or seven-membered ring. 
     
     
         5 . The compound of  claim 1 , wherein A is a carbocyclic ring or ring system. 
     
     
         6 . The compound of  claim 5 , wherein said carbocyclic ring or ring system is unsaturated. 
     
     
         7 . The compound of  claim 6 , wherein A comprises a benzene ring. 
     
     
         8 . The compound of  claim 1 , wherein A is a heterocyclic ring or ring system. 
     
     
         9 . The compound of  claim 8 , wherein said heterocyclic ring or ring system is unsaturated. 
     
     
         10 . The compound of  claim 8 , wherein said heterocyclic ring or ring system contains at least one nitrogen ring atom. 
     
     
         11 . The compound of  claim 10 , wherein A comprises a pyridine ring. 
     
     
         12 . The compound of  claim 2 , wherein X m−  is a halide or nitrate. 
     
     
         13 . The compound of  claim 2 , wherein X m−  is sulfate. 
     
     
         14 . The compound of  claim 2 , wherein X m−  is carbonate or bicarbonate. 
     
     
         15 . A method for removing an oxyanion from an aqueous source containing said oxyanion, the method comprising:
 (i) dissolving an oxyanion precipitating compound into said aqueous source to result in precipitation of an oxyanion salt of said oxyanion precipitating compound; and   (ii) removing said oxyanion salt from said water containing the oxyanion to result in water substantially reduced in concentration of said oxyanion;   wherein said oxyanion precipitating compound has the following composition:   
       
         
           
           
               
               
           
         
         wherein: 
         A is a ring-containing moiety; 
         one or more of the hydrogen atoms in Formula (1) may be replaced with one or more methyl groups; 
         X m−  is an anionic species with a magnitude of charge m, where m is an integer of at least 1, provided that X m−  is an anionic species exchangeable with the oxyanion in said aqueous source before said oxyanion precipitating compound contacts said oxyanion in step (i), and X m−  is said oxyanion in the oxyanion salt of said oxyanion precipitating compound; and 
         n is an integer of at least 1; 
         provided that n×m=2. 
       
     
     
         16 . The method of  claim 15 , wherein said oxyanion is selected from the group consisting of sulfate, nitrate, chromate, selenate, phosphate, arsenate, carbonate, bicarbonate, and perchlorate. 
     
     
         17 . The method of  claim 15 , wherein said oxyanion is sulfate. 
     
     
         18 . The method of  claim 15 , wherein A is a monocyclic ring. 
     
     
         19 . The method of  claim 15 , wherein said monocyclic ring is a five-membered, six-membered, or seven-membered ring. 
     
     
         20 . The method of  claim 15 , wherein A is a carbocyclic ring or ring system. 
     
     
         21 . The method of  claim 20 , wherein said carbocyclic ring or ring system is unsaturated. 
     
     
         22 . The method of  claim 21 , wherein A comprises a benzene ring. 
     
     
         23 . The method of  claim 15 , wherein A is a heterocyclic ring or ring system. 
     
     
         24 . The method of  claim 23 , wherein said heterocyclic ring or ring system is unsaturated. 
     
     
         25 . The method of  claim 23 , wherein said heterocyclic ring or ring system contains at least one nitrogen ring atom. 
     
     
         26 . The method of  claim 25 , wherein A comprises a pyridine ring. 
     
     
         27 . A method for removing carbon dioxide from a gaseous source, the method comprising:
 (i) contacting said gaseous source with an aqueous solution containing a carbon dioxide complexing compound to result in precipitation of a carbonate or bicarbonate salt of said carbon dioxide complexing compound; and   (ii) removing said carbonate or bicarbonate salt from said aqueous solution;   wherein said carbon dioxide complexing compound has the following composition:   
       
         
           
           
               
               
           
         
         wherein: 
         A is a ring-containing moiety; 
         one or more of the hydrogen atoms in Formula (1) may be replaced with one or more methyl groups; 
         X m−  is an anionic species with a magnitude of charge m, where m is an integer of at least 1, provided that X m−  is hydroxide in said carbon dioxide complexing compound before said carbon dioxide complexing compound is contacted with carbon dioxide in step (i), and X m−  is carbonate or bicarbonate in said carbonate or bicarbonate salt; and 
         n is an integer of at least 1; 
         provided that n×m=2. 
       
     
     
         28 . The method of  claim 27 , wherein A is a monocyclic ring. 
     
     
         29 . The method of  claim 28 , wherein said monocyclic ring is a five-membered, six-membered, or seven-membered ring. 
     
     
         30 . The method of  claim 27 , wherein A is a carbocyclic ring or ring system. 
     
     
         31 . The method of  claim 30 , wherein said carbocyclic ring or ring system is unsaturated. 
     
     
         32 . The method of  claim 31 , wherein A comprises a benzene ring. 
     
     
         33 . The method of  claim 27 , wherein A is a heterocyclic ring or ring system. 
     
     
         34 . The method of  claim 33 , wherein said heterocyclic ring or ring system is unsaturated. 
     
     
         35 . The method of  claim 33 , wherein said heterocyclic ring or ring system contains at least one nitrogen ring atom. 
     
     
         36 . The method of  claim 33 , wherein A comprises a pyridine ring.