I've extract pure silica from rice husk by acid leaching. I want to get silica nano particle by base extraction with sodium hydroxide and acid precipitation. I've dissolve extracted silica rice husk in sodium hydroxide solution then boiled it for 4 hours and neutralize the solution with sulfuric acid. After I aged it for 6 hours, I still didn't get precipitate nano silica.
What's wrong with the method I do? Can you provide accurate method to make nano silica from extracted silica rice husk?