Manufacture and recovery of monodisperse silica sols from a geothermal brine

摘要

The invention provides a method of manufacture and recovery of a monodisperse silica sol from a geothermal brine. The brine is cooled from a temperature above to a selected nucleation temperature below its silica saturation temperature at a rate such that no significant polymerisation of the silica takes place during this cooling. The brine undergoes a primary ageing at about the selected temperature to cause nucleation of the silica and to fix the number density of the silica particles formed by the nucleation which thereby determines the final particle size of the sol. The brine then undergoes a secondary ageing, preferably with cooling, the conditions being such that substantially no further nucleation occurs but growth of the silica particles does occur to form a colloidal suspension of monodisperse silica particles in the brine. These particles are concentrated by ultrafiltration to provide a concentrated monodisperse silica sol. Options include adding one or more stabilising agents to the brine to prevent aggregation of the silica particles and diafiltration of the sol to lower the concentration of unwanted ions.