Adjacent hydroxyl groups (on adjacent silicon atoms) are very important for the adsorption of polar substances; isolating hydroxyl groups are mainly present on the surface of silica that removes moisture. The content of such hydroxyl groups is more in the gas phase method than in the precipitation method, and it is not easy to remove when the temperature is increased; the dihydroxy group has two hydroxyl groups connected to one silicon atom.

The groups on the surface of white carbon black have certain reactivity. The surface reactions include: water loss and hydrolysis reaction, reaction with acid chloride, reaction with active hydrogen, formation of hydrogen bonds, etc.

2. Adsorption on the surface of white carbon black
The surface of white carbon black has a strong chemisorption activity, which is related to the surface hydroxyl group. It can be combined with water in the form of hydrogen bonds to form a multi-molecular adsorption layer. In addition, it can also adsorb with many small organic molecules.

Polyfunctional amines or alcohols have higher adsorptivity than monofunctional ones, so polyfunctional compounds such as ethanolamine, ethylene glycol, and triethanolamine are commonly used as active agents in SiO2 compounds.

3． Thermal behavior
Heating white carbon black will release water, and the temperature will increase the amount of water released. Before 150 ~ 200 ℃, the most water is released, and after 200 ℃, it tends to be gentle with obvious turning points. Before the inflection point was mainly desorption of adsorbed water, after the inflection point, the surface hydroxyl group shrank.