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Different types of activated carbon have different production processes. During the manufacturing of activated carbon, after volatile organic compounds are removed, the voids that form between the crystal lattices create numerous pores of various shapes and sizes. The total surface area of these pore walls (i.e., the specific surface area) is generally as high as 500–1700 m2/g, which is the main reason for the strong adsorption capacity of activated carbon. The pore structure varies depending on the raw material, activation method, and activation conditions. Generally, it can be divided into 3 types based on the pore radius: 1. Macro-pores: with a radius of 1000–100,000 Å ； 2. Transition hole: 20～2000 μm ； 3. Small micropores: approximately 20 ?. Generally, activated carbon produced from coal as a raw material is activated using physical methods with water vapor or carbon dioxide gas as the medium. The product is mainly in granular form, with a pore size distribution dominated by micropores, making it more suitable for adsorbing substances with low molecular weight and small molecular diameter in both liquid and gas phases. The adsorption performance is typically indicated by the methylene blue adsorption value and the iodine adsorption value. Beijing coal-based activated carbon and shell activated carbon: Activated carbon produced from wood chips is usually activated using chemical methods. The product is generally in powder form, and its pore size distribution can be controlled by adjusting the ratio of chemical activators, which provides flexibility; it is possible to produce products with a pore size distribution dominated by micropores or those with a higher proportion of mesopores (transition pores). The latter type is more suitable for adsorbing substances with larger molecular weights and diameters in liquid phases. The adsorption performance is indicated by the caramel decolorization rate. Activated carbon produced from fruit peels is typically activated using physical methods with water vapor or carbon dioxide as the medium. The product is mainly in granular form, and due to its unique material properties, its pore size distribution falls between that of the two types of activated carbon mentioned above; as a result, it has a wider range of applications. The downside is that, due to limitations in domestic raw materials, its cost is relatively high.