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 preventing silica scale in geothermal brine reinjection wells by selectively removing silica from a geothermal brine solution, the method comprising the steps of:
obtaining a geothermal brine solution comprising silica from a geothermal well;
maintaining the pH of the geothermal brine solution at an adjusted pH of between 4.75 and 6.25;
contacting the geothermal brine solution at adjusted pH with activated alumina at a temperature of 90° C. to 110° C., such that silica present in the geothermal brine solution selectively binds to the activated alumina;
recovering an aqueous brine product stream from the contacting step, said aqueous product stream having a reduced silica concentration relative to the geothermal brine solution; and
injecting the aqueous brine product stream into the geothermal well.
2. The method of claim 1 , further wherein the geothermal brine solution maintained at the adjusted pH is contacted with the activated alumina in a column.
3. The method of claim 1 , wherein the adjusted pH is between 4.8 and 5.3.
4. The method of claim 1 wherein the geothermal brine solution has a silica concentration of between about 150 ppm and 250 ppm.
5. The method of claim 1 further comprising, prior to injecting the aqueous brine product stream into the geothermal well, supplying at least a portion of the aqueous brine product stream to a recovery process for the recovery of at least one metal selected from the group consisting of lithium, manganese and zinc.