High-efficiency synthesis of colloidal silica via suppression of foam layer

•By adding defoaming substances to inhibit the foam layer, the reaction conversion rate is increased in a short time.•The initial reaction conversion was increased from 54.8 % to 85 % within 4 h.•It provides a new development strategy for efficient chemical synthesis of colloidal silica. As an important fundamental material, colloidal silica is widely used in many fields. Hydrolysis of elemental silicon is an important method for the preparation of colloidal silica. This method has been widely studied because of its simple process, low cost, easy control of colloidal particle size and good stability. However, this method has the problem of low reaction conversion rate (RCR). This paper proposed an efficient method to increase RCR of colloidal silica by inhibiting the formation of a foam layer. After the size of the silicon powder particle, reaction time, and the defoamer types were optimized, the defoamer of hydrophobic fumed silica could effectively inhibit the increase of foam layer and improve the yield of colloidal silica, the RCR was significantly increased from 54.8 % to 85 % within 4 h. This research provides an innovative strategy for the efficient chemical synthesis of colloidal silica.