The invention belongs to the technical field of
silicon dioxide, and particularly relates to a preparation method for low-refractive-index high-transparency
silicon dioxide. The preparation method comprises the following steps: S1, preparing a water glass solution, and performing standing and heat preservation to obtain a water glass
sol seed crystal; S2, taking the water glass
sol seed crystal, and adding water to dilute the water glass
sol seed crystal and prepare a water glass base solution; S3, adding the water glass base solution and a
sodium sulfate solution into a reaction kettle, and performing uniform stirring and heating; S4, simultaneously adding the water glass sol seed
crystal and a
sulfuric acid solution dropwise, controlling the pH in the process, and after addition of the water glass sol seed
crystal is completed, continuing to add the
sulfuric acid solution dropwise till the final pH; S5, stopping stirring, keeping the temperature, performing aging, and performing pressure
filtration, washing,
drying and crushing on formed
silicon dioxide precipitates to obtain the
silicon dioxide. The preparation method is simple, stable in process, low in production cost and less in
pollution; the prepared
silicon dioxide has high transparency under a low
refractive index, and is applied to a transparent
toothpaste formula, the using amount of water can be increased, and the using amount of a
wetting agent is reduced, so that the production cost is reduced.