Selective Removal of Silica from Silica Containing Brines
This invention relates to a method for selective removal of silica and silicon containing compounds from solutions that include silica and silicon containing compounds, including geothermal brines.
1 . A method for selectively removing silica from a brine solution that comprises silica, the method comprising the steps of:
providing a brine solution that comprises silica;
maintaining the pH of the brine solution at an adjusted pH of between about 4 and 7 and contacting said brine solution with activated alumina at the adjusted pH such that silica present in the brine solution selectively binds to the activated alumina; and
recovering an aqueous product stream from the contacting step, said aqueous product stream having a reduced silica concentration relative to the brine solution.
2 . The method of claim 1 , further wherein the brine solution at the adjusted pH is contacted with the activated alumina in a column.
3 . The method of claim 1 , further comprising maintaining the pH of the brine solution at between 4.8 and 5.3 during the contacting step.
4 . The method of claim 1 , wherein the brine solution that comprises silica is a geothermal brine.
5 . A method for removing silica from an aqueous brine solution that comprises silica, the method comprising the steps of:
providing an aqueous brine solution that comprises silica and an iron (II) salt;
oxidizing the iron (II) salt to iron (III) hydroxide;
maintaining the pH of the brine solution at between about 4.5 and 6;
contacting the silica and the iron (III) hydroxide for a time sufficient for the silica to attach to the iron (III) hydroxide and form a silica/iron precipitate;
separating the silica/iron precipitate from the aqueous brine solution; and
recovering an aqueous product stream from the separation step, said aqueous product stream having a reduced silica concentration relative to the aqueous brine solution.
6 . The method of claim 5 wherein the aqueous brine solution is a geothermal brine.
7 . The method of claim 5 wherein the iron (II) salt is iron (II) chloride.
8 . The method of claim 5 further wherein the step of oxidizing the iron (II) salt comprises sparging the aqueous brine solution with air.
9 . The method of claim 5 wherein the pH of the aqueous brine solution is maintained at a predetermined pH by the addition of base.
10 . The method of claim 5 wherein the pH of the aqueous brine solution is maintained at a predetermined pH by the addition of base selected from calcium oxide or calcium hydroxide.
11 . The method of claim 5 wherein the pH of the aqueous brine solution is maintained at between about 4.75 and 5.5.
12 . The method of claim 5 wherein the pH of the aqueous brine solution is maintained at between about 4.9 and 5.3.
13 . The method of claim 5 wherein the silica concentration of the aqueous product stream is less than 20 ppm.
14 . The method of claim 5 further comprising the steps of:
maintaining the pH of the aqueous product stream at between about 4 and 7;
supplying the aqueous product stream to a column charged with activated alumina at a pH of between about 4 and 7 such that silica present in the aqueous product stream selectively binds to the activated alumina; and
recovering a column product stream having a reduced silica concentration relative to the aqueous product stream.
15 . The method of claim 5 further comprising supplying the aqueous product stream to means for recovering at least one metal selected from lithium, zinc and manganese from said aqueous brine solution.
16 . A method for removing silica from a brine solution comprising silica, the method comprising the steps of:
providing a brine solution that comprises silica;
contacting the brine solution with an aqueous solution that comprises aluminum chloride to produce a second aqueous solution, said second aqueous solution comprising brine and aluminum chloride;
adjusting and maintaining the pH of the second aqueous solution such that the pH is between about 4.5 and 5.5 to form an aluminosilicate precipitate;
removing the aluminosilicate precipitate that forms from the second aqueous solution; and
recovering an aqueous product stream, said aqueous product stream having a reduced silica concentration relative to the brine solution.
17 . The method of claim 16 wherein the brine solution is a geothermal brine.
18 . The method of claim 16 further comprising adding an amorphous aluminosilicate solid to the second solution.
19 . The method of claim 18 wherein at least 0.25% by weight of the aluminosilicate solid is added to the second solution.
20 . The method of claim 16 wherein the pH of the second aqueous solution is maintained at between about 4.85 and 5.15.