Methods for Removing Potassium, Rubidium, and Cesium, Selectively or in Combination, From Brines and Resulting Compositions Thereof

Abstract

The invention generally relates to methods of removing potassium, rubidium, and/or cesium, selectively or in combination, from brines using tetrafluoroborates. Also disclosed are methods of producing potassium, rubidium, and/or cesium chlorides using ionic liquids and exchange media. This invention also generally relates to treated geothermal brine compositions containing reduced concentrations of silica, iron, and potassium compared to the untreated brines. Exemplary compositions of the treated brine contain a concentration of silica ranging from about 0 mg/kg to about 15 mg/kg, a concentration of iron ranging from about 0 mg/kg to about 10 mg/kg, and a concentration of potassium ranging from about 300 mg/kg to about 8500 mg/kg. Other exemplary compositions of the treated brines also contain reduced concentrations of elements like rubidium, cesium, and lithium.

We claim: 
     
         1 . A method for extracting potassium, rubidium and/or cesium from a brine solution, the method comprising the steps of:
 providing a brine solution containing potassium, rubidium and/or cesium dissolved therein;   contacting the brine solution with a tetrafluoroborate compound to produce a tetrafluoroborate precipitate containing potassium, rubidium and/or cesium and an aqueous layer; and   separating the tetrafluoroborate precipitate containing potassium, rubidium and/or cesium from the aqueous layer.   
     
     
         2 . The method of  claim 1 , wherein the brine solution is heated to a temperature of between about 70° C. and 100° C. 
     
     
         3 . The method of  claim 1 , wherein the tetrafluoroborate compound is an acid or salt comprising tetrafluoroborate anions. 
     
     
         4 . The method of  claim 1 , wherein the tetrafluoroborate compound is fluoroboric acid. 
     
     
         5 . The method of  claim 1 , wherein the tetrafluoroborate compound is an alkali metal or alkaline earth metal tetrafluoroborate. 
     
     
         6 . The method of  claim 1 , wherein the tetrafluoroborate compound is ammonium tetrafluoroborate. 
     
     
         7 . The method of  claim 1 , wherein the tetrafluoroborate compound is supplied to the brine solution in an amount between about 35 and 80 grams for each liter of brine. 
     
     
         8 . The method of  claim 1 , wherein the brine solution comprises potassium. 
     
     
         9 . The method of  claim 1 , wherein the brine solution comprises rubidium. 
     
     
         10 . The method of  claim 1 , wherein the brine solution comprises cesium. 
     
     
         11 . A method for preparing potassium chloride, rubidium chloride and/or cesium chloride from potassium, rubidium and/or cesium tetrafluoroborate, the method comprising the steps of:
 contacting potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate with an ionic liquid containing chloride anions to produce a tetrafluoroborate/ionic liquid solution;   heating the tetrafluoroborate/ionic liquid solution to produce a tetrafluoroborate layer and an aqueous layer containing potassium chloride, rubidium chloride, and/or cesium chloride;   separating the tetrafluoroborate layer from the aqueous layer containing potassium chloride, rubidium chloride, and/or cesium chloride; and   evaporating the aqueous layer to produce potassium chloride, rubidium chloride, and/or cesium chloride.   
     
     
         12 . The method of  claim 11 , wherein the ionic liquid containing chloride anions is a quaternary ammonium chloride. 
     
     
         13 . The method of  claim 11 , wherein the ionic liquid containing chloride anions is a phosphonium chloride. 
     
     
         14 . The method of  claim 11 , wherein the potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate is supplied to the ionic liquid containing chloride anions in an amount between about 10 and 80 grams of tetrafluoroborate for each liter of ionic liquid solution. 
     
     
         15 . The method of  claim 11 , wherein the ionic liquid solution is heated to a temperature of between about 70° C. and 100° C. 
     
     
         16 . A method for preparing potassium chloride, rubidium chloride and/or cesium chloride from a solution containing potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate, the method comprising the steps of:
 contacting potassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesium tetrafluoroborate with an aqueous solution containing an ion-exchange media containing chloride to produce a tetrafluoroborate/ion-exchange media mixture;   heating the tetrafluoroborate/ion-exchange media mixture to produce an ion-exchange media layer and an aqueous layer containing potassium chloride, rubidium chloride and/or cesium chloride;   separating the aqueous layer containing potassium chloride, rubidium chloride and/or cesium chloride from the ion-exchange media layer; and   evaporating the aqueous layer to produce potassium chloride, rubidium chloride, and/or cesium chloride.   
     
     
         17 . The method of  claim 16 , wherein the tetrafluoroborate solution comprises potassium. 
     
     
         18 . The method of  claim 16 , where in the ion-exchange media is quaternary ammonium functional-terminated chloride terminated resin beads. 
     
     
         19 . The method of  claim 17 , wherein the potassium tetrafluoroborate is added to the ion-exchange media mixture in an amount between about 0.5 to 10 grams of potassium tetrafluoroborate for every 100 grams of exchange media mixture. 
     
     
         20 . The method of  claim 16 , wherein the tetrafluoroborate/ion-exchange media mixture is heated to a temperature of between about 70-100° C.