A preparation method of SiO2 aerogels, comprising the following steps:
- (1). Mixing an inorganic silicon source with pure water in a container to form a mixed solution;
- (2). hydrolyzing the mixed solution via a cation exchange resin to obtain a silicic acid solution;
- (3). Adding an alkaline catalyst into the silicic acid solution to obtain a wet gel;
- (4). Crushing the wet gel;
- (5). Adding an alcohol solvent into the crushed wet gel to perform aging for one to twelve hours;
- (6). Performing solvent replacement on the aged wet gel, wherein the solvent replacement is divided into two stage operations, wherein in the first stage, the aged wet gel is placed in a reaction container containing an alcohol solvent, and the water content within pores of the wet gel is exchanged with the alcohol solvent;
- and wherein in the second stage, an organic solvent is added in the reaction container having the wet gel after the first stage, so as to exchange the alcohol solvent within the pores of the wet gel with the organic solvent;
- (7). Carrying out surface modification of the wet gel that has undergone solvent replacement, wherein a mixed solution having a siloxane modifier and an organic solvent is added into the reaction container having the wet gel that has undergone solvent replacement so that the wet gel is modified to be hydrophobic;
- (8). Adopting atmospheric drying to dry the modified hydrophobic wet gel so as to prepare SiO2 aerogels;
- characterized in that:
- in step (6), continuous circulation filtration is adopted for the step of adding the alcohol solvent and for the step of adding the organic solvent, wherein a liquid inlet from a liquid pipe above the reaction container containing the wet gel communicates with the reaction container, and the bottom of the reaction container is disposed with a discharge pipe via a discharge outlet, and the discharge outlet is disposed with a filtration device, and the discharge pipe communicates with a solvent storage tank, and a power source is disposed between the solvent storage tank and the liquid pipe, and the power source provides a sucking effect on the discharge pipe and a pushing effect on the liquid pipe, and proper solvent content is stored in the solvent storage tank, and with the effect of the power source, solvent is circulated in the reaction container, the discharge pipe, the solvent storage tank, the power source and the liquid pipe, and the water content (of the first stage) and the alcohol solution of the second stage contained within the wet gel is separated and removed.