Methods for producing and using alkaline aqueous ferric iron carbonate solutions

Abstract

A method for producing and using an alkaline aqueous ferric iron carbonate solution is disclosed. The method broadly comprises reacting at least one ferric iron salt reagent with at least one alkali metal carbonate salt reagent and forming an alkaline aqueous ferric iron carbonate solution comprising an aqueous-soluble, ferric iron carbonate complex. The reacting generally includes reacting a solid with an aqueous solution. The reacting may include reacting a solid comprising one or both of the ferric iron salt reagent and alkali metal carbonate salt reagent with an aqueous solution. A method for removing reduced sulfur compounds from a reduced sulfur-containing fluid is also disclosed.

What is claimed is: 
     
         1 . A method for removal of reduced sulfur compounds from a fluid comprising:
 (a) contacting an alkaline aqueous ferric iron salt solution that contains anionic ferric iron-carbonate complexes with a reduced sulfur-containing fluid comprising reduced sulfur compounds,
 (i) wherein the alkaline aqueous ferric iron salt solution comprises ferric ions (Fe 3+ ), potassium ions (K + ), carbonate ions (CO 3   2− ) and bicarbonate ions (HCO 3   − ) and optionally one or more organic additives, 
 (ii) wherein the alkaline aqueous ferric iron salt solution has a pH of at least 8; 
   (b) producing, due to the contacting, a reduced alkaline iron solution, wherein the producing comprises:
 (i) forming one or more iron sulfide compounds in the alkaline aqueous ferric iron solution to thereby remove at least a portion of the reduced sulfur compounds from the reduced sulfur-containing fluid; and 
 (ii) oxidizing at least a portion of the reduced sulfur compounds and reducing at least a portion of the ferric ions to ferrous ions (Fe 2+ ). 
   
     
     
         2 . The method of  claim 1 , wherein the alkaline aqueous ferric iron salt solution is free of ferric iron-based particles. 
     
     
         3 . The method of  claim 1 , wherein the alkaline aqueous ferric iron salt solution is free of iron oxide particles and iron oxyhydroxide particles. 
     
     
         4 . The method of  claim 1 , wherein the alkaline aqueous ferric iron salt solution has a pH of at least 8.5. 
     
     
         5 . The method of  claim 1 , wherein a molar ratio of the potassium ions to the ferric ions is at least 1.0. 
     
     
         6 . The method of  claim 1 , wherein a molar ratio of the potassium ions to the ferric ions is at least 2.0. 
     
     
         7 . The method of  claim 1 , wherein a molar ratio of the potassium ions to the ferric ions is at least 5.0. 
     
     
         8 . The method of  claim 1 , further comprising, after removal of at least a portion of the reduced sulfur compounds from the reduced sulfur-containing fluid,
 (c) oxidizing at least a portion of the ferrous iron formed in the reduced alkaline iron solution to at least in part regenerate the alkaline aqueous ferric iron solution with concomitant oxidation of at least a portion of the sulfide of iron sulfide in the reduced alkaline aqueous iron solution to elemental sulfur.   
     
     
         9 . The method of  claim 8 , wherein oxidizing at least a portion of the ferrous iron comprises exposing the reduced alkaline iron solution to an oxidizing agent to oxidize at least a portion of the ferrous ions therein to ferric ions, thereby producing a regenerated alkaline aqueous ferric iron salt solution, and wherein the exposing comprises producing elemental sulfur. 
     
     
         10 . The method of  claim 1 , wherein the forming one or more iron sulfide compounds comprises forming a black precipitate comprising ferrous sulfide. 
     
     
         11 . A method for producing an aqueous-soluble, ferric iron carbonate complex, comprising:
 (a) reacting at least one ferric iron salt reagent with at least one alkali metal carbonate salt reagent and forming an alkaline aqueous ferric iron solution comprising the aqueous-soluble, ferric iron carbonate complex; and
 (i) wherein the at least one alkali metal carbonate salt reagent comprises potassium carbonate, potassium bicarbonate or a combination thereof; and 
 (ii) wherein the aqueous-soluble, ferric iron carbonate complex comprises ferric ions (Fe 3+ ), potassium ions (K + ), wherein the molar ratio of the potassium ions to the ferric ions is at least 1.0; 
   (b) optionally removing water from the alkaline aqueous ferric iron solution.   
     
     
         12 . The method of  claim 11 , wherein:
 (i) a solid comprises the at least one ferric iron salt reagent,   (ii) an aqueous solution comprises the at least one alkali metal carbonate salt reagent, and   (iii) the reacting comprises combining the solid with the aqueous solution.   
     
     
         13 . The method of  claim 11 , wherein:
 (i) an aqueous solution comprises the at least one ferric iron salt reagent,   (ii) a solid comprises the at least one alkali metal carbonate salt reagent, and   (iii) the reacting comprises combining the solid with the aqueous solution.   
     
     
         14 . The method of  claim 11 , wherein:
 (i) a solid comprises the at least one ferric iron salt reagent and the at least one alkali metal carbonate salt reagent; and   (ii) the reacting comprises adding an aqueous solution to the solid.   
     
     
         15 . The method of  claim 11 , wherein the optionally removing water from the alkaline aqueous ferric iron solution step comprises drying the alkaline aqueous ferric iron solution, thereby forming a ferric iron-containing solid material. 
     
     
         16 . The method of  claim 15 , wherein the method comprises rehydrating the ferric iron-containing solid material, wherein the rehydrating comprises mixing the ferric iron-containing solid material with an aqueous solution. 
     
     
         17 . The ferric iron-containing solid material of  claim 15 . 
     
     
         18 . The method of  claim 11 , wherein the at least one ferric iron salt reagent comprises ferric nitrate. 
     
     
         19 . The method of  claim 11 , wherein the method comprises diluting the alkaline aqueous ferric iron solution. 
     
     
         20 . The method of  claim 11 , wherein the alkaline aqueous ferric iron carbonate solution comprises carbonate ions (CO 3   2− ), bicarbonate ions (HCO 3   − ), hydroxide ions (OH − ), optionally nitrate ions (NO 3   − ), wherein:
 (i) a molar ratio of the potassium ions to the ferric ions is at least 5.0;   (ii) ferric iron is complexed with carbonate, bicarbonate or both to form a water-soluble complex that is anionic in nature and highly soluble in the alkaline aqueous ferric iron carbonate solution at pH above 8.5; and   (iii) a pH of the alkaline aqueous ferric iron carbonate solution is at least 8.5.