Pore structure development of silica particles below the isoelectric point

The textural properties of amorphous silica play a fundamental role in its final properties and, therefore, in its possible applications. The aim of this study is to gain comprehensive understanding about how the process conditions influence the pore structure of silica synthesized below the isoelectric point and find possible solutions to tailor the final properties of nano-silica. This study was conducted using the mineral olivine as silica source and dissolving it in sulfuric acid. This synthesis method is an interesting and sustainable alternative to the existing commercial methods. This nano-silica exhibits a specific surface area in the range of 100–500 m²/g and a pore size distribution of 1–100 nm for silicas with a purity above 99%. At the beginning of the reaction, silica is microporous and mesoporous, showing no macroposity. As the reaction conversion progresses, silica particles become larger and macroporous, and internal porosity is developed. The process conditions have an important influence on the textural properties of nano-silica. By modifying the process conditions the small mesopores can be removed featuring no porosity below 9 nm and the large pores can be reduced to pore sizes as small as 30 nm. The possibility of tailoring the porosity of silica in this large range makes this material suitable for a wide range of applications.