Activated carbon is used in everyday life. Although it is composed of very fine carbon particles, it has a large surface area, and within these particles, there are even finer pores known as capillaries. These capillaries possess strong adsorption capabilities, and activated carbon utilizes these pores to achieve its吸附 function. Generally, the adsorption of activated carbon can be divided into chemical adsorption and physical adsorption.

Chemical Adsorption

Activated carbon not only contains carbon but also has a small amount of oxygen in the form of chemically bonded functional groups on its surface, such as carboxyl, hydroxyl, phenolic, lactone, quinone, and ether groups, among others. These surface oxides or complexes can undergo chemical reactions with the adsorbed substances, thereby binding and aggregating with the adsorbed materials onto the surface of the activated carbon.

Physical Adsorption

In addition to chemical adsorption, activated carbon also exhibits physical adsorption. This primarily occurs during the process of activated carbon removing impurities from both liquid and gaseous phases. The porous structure of activated carbon provides a vast surface area, making it highly effective in absorbing and collecting impurities. Just like a magnet, all molecules possess intermolecular attractions. Consequently, the numerous molecules on the walls of activated carbon's pores can generate a strong gravitational force, attracting impurities within the medium into the pores.

It must be noted that the molecular diameter of the adsorbed impurities must be smaller than the pore size of the activated carbon to ensure that the impurities can be absorbed into the pores. This is why we continuously modify the raw materials and activation conditions to create activated carbon with varying pore structures, making it suitable for various applications in impurity absorption.

When the adsorption and desorption rates of activated carbon in a solution are equal, i.e., the amount of activated carbon adsorbed per unit time equals the amount desorbed, the concentration of the adsorbed substance in the solution and on the surface of the activated carbon no longer change and reach equilibrium. At this point, the dynamic equilibrium is referred to as the activated carbon adsorption equilibrium, and the concentration of the adsorbed substance in the solution at this time is called the equilibrium concentration.