Method and system for decreasing molybdenum and/or tungsten concentration in aqueous solutions

Abstract

A method and system for decreasing the concentration of at least one metal in an aqueous solution. The metal may be molybdenum, tungsten, or both. An aqueous solution is introduced into at least one reaction zone, and at least one source of hydroxide ions is provided into the at least one reaction zone in an amount sufficient to precipitate at least some of the mass of the at least one metal. The aqueous solution includes a mass of the at least one metal and a mass of at least one reducing agent. The at least one reducing agent includes at least ferrous iron from at least one source of the at least one reducing agent. A composition of tungsten ferrite or molybdenum tungsten ferrite may be formed. The method may be used for purifying water, for the refining of metals, or to facilitate a chemical analytical determination.

1 - 19 . (canceled)  
   
   
       20 . A water purification system comprising at least one reactor having at least one reaction zone and configured to receive an aqueous solution in said at least one reaction zone, said aqueous solution comprising: 
 a) at least one metal comprising molybdenum or tungsten; and    b) at least one reducing agent comprising at least ferrous iron;    wherein said at least one reactor is configured to receive at least one source of hydroxide ions into said at least one reaction zone in an amount sufficient to precipitate at least some of said mass of said at least one metal.    
   
   
       21 . The system of  claim 20 , wherein said source of said at least one reducing agent is selected from a group consisting of ferrous sulfate, ferrous chloride, metallic iron, and combinations thereof.  
   
   
       22 . The system of  claim 20 , wherein said at least one metal comprises said molybdenum.  
   
   
       23 . The system of  claim 22 , wherein the mass of said ferrous iron in said aqueous solution is at least about three times the mass of said molybdenum that is desired to be precipitated from said aqueous solution.  
   
   
       24 . The system of  claim 22 , wherein the mass of said ferrous iron in said aqueous solution is at least about six times the mass of said molybdenum that is desired to be precipitated from said aqueous solution.  
   
   
       25 . The system of  claim 20 , wherein said at least one metal comprises said tungsten.  
   
   
       26 . The system of  claim 25 , wherein the mass of said ferrous iron in said aqueous solution is at least about 1.5 times the mass of said tungsten that is desired to be precipitated from said aqueous solution.  
   
   
       27 . The system of  claim 25 , wherein the mass of said ferrous iron in said aqueous solution is at least about three times the mass of said tungsten that is desired to be precipitated from said aqueous solution.  
   
   
       28 . The system of  claim 20 , wherein said at least one reaction zone is maintained at a pH in a range from about 6 to about 14.  
   
   
       29 . The system of  claim 20 , wherein said at least one reaction zone is maintained at a temperature in a range from about 0° C. to about 100° C.  
   
   
       30 . The system of  claim 20 , wherein said at least one reactor is selected from a group consisting of a continuous tank reactor, a continuous tubular reactor, a batch reactor, or combinations thereof.  
   
   
       31 . The system of  claim 20 , wherein said at least one source of hydroxide ions is selected from a group consisting of sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, calcium carbonate, potassium carbonate, or combinations thereof.  
   
   
       32 . The system of  claim 20 , wherein a byproduct of the precipitation is a compound comprising said at least one metal.  
   
   
       33 . The system of  claim 32 , further comprising at least one recovery device for recovering at least some of said compound.  
   
   
       34 . The system of  claim 33 , wherein said at least one recovery device comprises a device for settling, filtration, centrifugation, magnetic separation, or combinations thereof.  
   
   
       35 . The system of  claim 20 , wherein said at least one metal comprises said tungsten and said molybdenum.  
   
   
       36 - 38 . (canceled)