Method of removing iron and calcium from a geothermal brine
This invention relates generally to processes for extracting iron and/or calcium from geothermal brines.
1. A method of depleting iron from a geothermal brine solution comprising:
(a) contacting the geothermal brine solution with an oxidizing agent, wherein said oxidizing agent oxidizes soluble iron in the solution to form an insoluble iron oxide precipitate;
(b) removing the iron oxide precipitate from the solution to form an iron-depleted geothermal brine solution; and
(c) contacting the iron-depleted geothermal brine solution with a QL reagent to create a reaction solution, wherein the QL reagent comprises a quaternary ammonium compound, a hydrogen ion exchange reagent and an organic solvent, wherein the reaction solution comprises an organic phase and an aqueous phase, and wherein the reaction solution is maintained at a temperature in the range of about 180° F. to about 230° F.
2. The method of claim 1 , wherein the soluble iron is oxidized from an oxidation state of Fe 2+ to Fe 3+ .
3. The method of claim 1 , wherein the oxidizing agent is sodium hypochlorite, sodium hydroxide, hydrogen peroxide, or chlorine gas.
4. The method of claim 1 , wherein the oxidizing agent is sodium hypochlorite.
5. The method of claim 4 , wherein the insoluble iron oxide precipitate is iron akageneite.
6. The method of claim 1 , wherein the oxidizing agent is combined with a buffer.
7. The method of claim 6 , wherein the buffer is sodium carbonate.
8. The method of claim 1 , wherein the pH of the geothermal brine solution remains in the range between about 1.5 and 5.
9. The method of claim 8 , wherein the oxidizing is performed over at least two stages of increasing pH.
10. The method of claim 9 , wherein a first stage is performed at a pH between about 1.7 and 1.8, a second stage is performed at a pH between about 2.3 and 2.4, and a third stage is performed at a pH of about 3.4.
11. The method of claim 1 , wherein the iron-depleted geothermal brine solution has a soluble iron concentration of less than about 10%.
12. The method of claim 11 , wherein the iron-depleted geothermal brine solution has a soluble iron concentration of less than about 8%.
13. The method of claim 12 , wherein iron-depleted geothermal brine solution has a soluble iron concentration of less than about 5%.
14. The method of claim 13 , wherein iron-depleted geothermal brine solution has a soluble iron concentration of less than about 3%.
15. The method of claim 13 , wherein iron-depleted geothermal brine solution has a soluble iron concentration of about 1%.
16. The method of claim 1 , further comprising:
(d) extracting one or more non-manganese impurities into the aqueous phase, wherein the organic phase becomes an impurity depleted solution; and
(e) separating the aqueous phase from the organic phase.
17. The method of claim 16 , wherein the non-manganese impurity is calcium.
18. The method of claim 16 , wherein the non-manganese impurity is zinc.
19. The method of claim 16 , further comprising:
(f) extracting manganese from the impurity depleted reaction solution, wherein the pH of the solution remains constant.
20. The method of claim 16 , further comprising:
(f) removing any remaining calcium from the impurity depleted solution by extracting the impurity depleted solution with an aqueous acidic scrubbing solution.
21. The method of claim 20 , wherein about 90% to about 100% of calcium is removed from the impurity depleted solution in the scrubbing step.
22. A method of depleting calcium from a geothermal brine solution comprising:
(a) contacting the geothermal brine solution with a QL reagent to create a reaction solution, wherein the QL reagent comprises a quaternary ammonium compound, a hydrogen ion exchange reagent and an organic solvent, wherein the reaction solution comprises an organic phase and an aqueous phase, and wherein the reaction solution is maintained at a temperature in the range of about 180° F. to about 230° F.;
(b) extracting calcium into the aqueous phase, wherein the organic phase becomes a calcium-depleted geothermal brine solution;
(c) separating the aqueous phase from the organic phase;
(d) removing any remaining calcium from the calcium-depleted geothermal brine solution by extracting the calcium-depleted geothermal brine solution with an aqueous acidic scrubbing solution to form a scrubbed organic phase.
23. The method of claim 22 , wherein the scrubbing solution is a manganese-rich scrubbing solution.