Method for preparing dispersible ultra-fine silicon dioxide

The invention discloses a method for preparing dispersible ultra-fine silicon dioxide. The method is characterized by comprising the following steps of: adding a liquid surface modifier into a precipitated silicon dioxide filter cake raw material; coating the surfaces of silicon dioxide particles in the precipitated silicon dioxide filter cake to form coating liquid by using the liquid surface modifier with strong stirring; and drying and activating the coating liquid to prepare a dispersible ultra-fine silicon dioxide powder product, wherein the surface modifier accounts for 1 to 50 percent of the mass of the silicon dioxide of the precipitated silicon dioxide filter cake. Experiment results show that: according to an SEM image of the dispersible ultra-fine silicon dioxide dispersed in an organic medium, the particle sizes of silicon dioxide particles are between 100 nm and 10 mu m; and the particle sizes of the silicon particles are between 100 and 400 nm and are distributed uniformly when a boric acid ester coupling agent is adopted.