The influence of process conditions and Ostwald ripening on the specific surface area of olivine nano-silica

The production of porous amorphous nano-silica by the olivine route is an interesting alternative to the existing commercial production methods because of the much lower energy requirements of this process. The produced olivine nano-silica has a specific surface area between 100-400 m2/g and primary particles between 10 to 25 nm (agglomerated in clusters). The process conditions of the dissolution of olivine and the subsequent ripening treatment influence the specific surface area of the nano-silica in the following ways. 1) The cleaner the nano-silica is, the higher the specific surface area is. Thus, high-purity silicas presents an SSA between 300 and 400 m2/g. 2) The higher the filtration pressure is, the higher the surface area will be. 3) The ripening treatment can diminish the specific surface of nano-silica by three quarters and reduce the microporous surface area by 90%. A 99% pure nano-silica with specific surface area controlled between 90 and 400 m2/g can be synthesized by ripening treatment in an alkaline solution at room temperature. Therefore, tailored olivine nano-silica can provide additional environmental and economic benefits over the current commercial products.