The pore size of activated carbon plays a crucial role in the adsorption of water pollutants. Activated carbon is a highly porous material with a large surface area, which makes it an excellent adsorbent for removing contaminants from water. The pore size distribution in activated carbon can be classified into three categories: micropores less than 2 nm , mesopores 2-50 nm , and macropores greater than 50 nm . The effectiveness of activated carbon in adsorbing water pollutants depends on the size and structure of the pores, as well as the size and properties of the pollutants.1. Micropores: These small pores are responsible for the majority of the adsorption capacity of activated carbon. They provide a large surface area for the adsorption of small molecules and ions, such as heavy metals, organic compounds, and some inorganic ions. Micropores are particularly effective in adsorbing pollutants with low molecular weights and small molecular sizes, as they can easily penetrate and be trapped within the micropores.2. Mesopores: These intermediate-sized pores are essential for the adsorption of larger molecules and particles, such as organic macromolecules, colloids, and suspended particles. Mesopores act as transport channels, allowing pollutants to access the micropores and the internal surface area of the activated carbon. They also provide additional adsorption sites for pollutants that are too large to enter the micropores.3. Macropores: These large pores primarily serve as transport channels for pollutants to access the mesopores and micropores. They do not contribute significantly to the adsorption capacity of activated carbon but are essential for the diffusion of pollutants within the adsorbent.The effectiveness of activated carbon in adsorbing water pollutants depends on the match between the pore size distribution and the size and properties of the pollutants. For example, activated carbon with a high proportion of micropores is more effective in adsorbing small molecules and ions, while activated carbon with a higher proportion of mesopores and macropores is more effective in adsorbing larger molecules and particles.In summary, the pore size of activated carbon affects the adsorption of water pollutants by determining the accessibility of pollutants to the adsorption sites, the surface area available for adsorption, and the compatibility between the pore size and the size of the pollutants. To optimize the adsorption performance of activated carbon, it is essential to select or modify the activated carbon with a suitable pore size distribution that matches the size and properties of the target pollutants.