How Does Activated Carbon Adsorb? — A Look at Its Microstructure

The fundamental reason activated carbon possesses adsorption capabilities lies in its unique microstructure.

I. Enormous Specific Surface Area

The interior of activated carbon is riddled with a dense network of tiny pores. Studies show that the specific surface area of ​​one gram of high-quality activated carbon can reach 1,000–1,500 square meters—roughly the size of a standard soccer field. This translates to a vast amount of space available for adsorption.

II. A Well-Developed Pore System

The pores in activated carbon are primarily categorized into three types:

Micropores (diameter < 2 nm): These account for the majority of the total pore volume and serve as the primary sites for adsorbing small-molecule pollutants.

Mesopores (diameter 2–50 nm): These are responsible for adsorbing medium-sized molecules.

Macropores (diameter > 50 nm): These act as transport channels, facilitating the rapid movement of molecules into the interior.

It is precisely this hierarchical structure—ranging from macropores to micropores—that enables activated carbon to efficiently capture and trap various impurity molecules.

III. Predominantly Physical Adsorption

In the vast majority of cases, activated carbon relies on physical adsorption (van der Waals forces) to capture molecules from gases or liquids into its pores. Since this type of adsorption is reversible, activated carbon can be regenerated and reused.