A recyclable method for production of pure silica from rice hull ash

A recyclable technology was proposed for preparation of silica powder using rice hull ash and NH4F. The silica in rice hull ash was dissolved into NH4F solution to produce (NH4)2SiF6 and NH3. The silica powder was precipitated when (NH4)2SiF6 solution was added to NH3·H2O. The microstructure and morphology analysis of the precipitated silica powders were characterized using transmission electron microscopy (TEM). The preparation conditions and the recyclable process were explored experimentally. The yield of silica reached up to 94.6% and the particles were spherical with the diameter of 50–60 nm. Most importantly, all the reactants and byproducts were recyclable in this process.