According to the different forces between the activated carbon molecules and the contaminant molecules in the adsorption process, the adsorption can be divided into two categories: physical adsorption and chemical adsorption (also known as active adsorption). In the adsorption process, when the force between the activated carbon molecule and the contaminant molecule is van der Waals force (or electrostatic attraction), it is called physical adsorption; when the interaction between the activated carbon molecule and the contaminant molecule is a chemical bond, it is called chemical adsorption. . The adsorption strength of physical adsorption is mainly related to the physical properties of activated carbon, and has nothing to do with the chemical properties of activated carbon. Because van der Waals force is weak, it has little effect on the structure of pollutant molecules. This force is the same as the intermolecular cohesion, so the physical adsorption can be compared to the aggregation phenomenon. The chemical nature of the contaminants remains unchanged during physical adsorption.