How stable is colloidal silica with large particle size in different environments?

The stability of colloidal silica with large particle size varies in different environments due to a variety of factors. In aqueous media,  colloidal silica with large particle size has a lower surface energy than small-particle colloids due to its larger particle size, which leads to poor dispersibility in water and easy agglomeration. As the pH value decreases or the salt concentration increases, the electrostatic repulsion between colloidal silica particles weakens, the stability of the particles decreases, and the risk of precipitation or aggregation increases.
In aqueous solutions, when the ionic strength is high, the electrolytes in the solution neutralize the charge on the surface of the colloid, weaken the electrostatic repulsion between the particles, and thus accelerate the aggregation of the particles. To solve this problem, surfactants or modifiers are often used to stabilize the particles. These additives can form a protective film by adsorbing on the surface of the particles, reducing direct contact between the particles, thereby improving the dispersibility and stability of the particles.
In organic solvents, the stability of  colloidal silica with large particle size is affected by the polarity of the solvent and the surface characteristics of the colloid. For polar organic solvents, such as alcohols and ketones, the stability of colloidal silica is usually poor, because the interaction between the silica surface and these solvent molecules is not strong, which easily leads to particle aggregation. In non-polar solvents, the dispersion of the particles will be worse due to the weak interaction between the silica particle surface and the solvent. In this case, surface modification becomes an effective way to improve stability.
Temperature also has an important effect on the stability of  colloidal silica with large particle size. Generally,  colloidal silica with large particle size is more stable in high temperature environments, especially in anhydrous or dry environments, because high temperature does not cause hydration of silica particles and the attraction between particles is relatively small. However, if the temperature is too high, it may cause sintering between silica particles, resulting in changes in particle size, thereby affecting its performance.
In acidic and alkaline environments, the stability of  colloidal silica with large particle size is significantly affected by pH. Under low pH conditions, the surface of silica particles will have a strong positive charge, which is easy to interact with negative ions in the solution to form hydrogen bonds or van der Waals forces, thereby promoting particle aggregation. At the same time, low pH values ​​will also affect the ionization of silica surface groups, further reducing its stability. On the contrary, under high pH conditions, the surface of silica particles may have negative charges, which enhances the electrostatic repulsion between particles and promotes the dispersion of particles. In order to improve the stability of colloidal silica with large particle size in acidic and alkaline environments, the dispersibility of particles can be optimized by adjusting the pH value, and the surface modifier can be appropriately selected to avoid particle aggregation or precipitation under extreme pH conditions.