The adsorption of activated carbon is not only physical adsorption, but also chemical adsorption. The adsorbability of activated carbon depends on both the pore structure and the chemical composition. Activated carbon not only contains carbon, but also contains a small amount of oxygen and hydrogen that are chemically combined and functional groups, such as carbonyl groups, carboxyl groups, phenols, lactones, quinones, and ethers. Some of the oxides and complexes contained on the surface are derived from raw materials, and some are generated by the action of air or water vapor during and after activation. Sometimes surface sulfides and chlorides are generated. In the activation, the minerals contained in the raw materials are concentrated in the activated carbon to become ash. The main components of the ash are the salts of alkali metals and alkaline earth metals, such as carbonates and phosphates. These ash contents can be reduced by washing or pickling.
activated carbon is accompanied by catalytic reactions in many adsorption processes, showing the activity of the catalyst. For example, activated carbon adsorbs sulfur dioxide and becomes sulfur trioxide through catalytic oxidation. Due to the existence of specific oxygen-containing compounds or complexes on the surface of activated carbon, it has catalyst activity for many reactions, such as the formation of phosgene from chlorine and carbon monoxide. Complexes are formed between activated carbon and the support. Chemical catalysts greatly increase the catalytic activity. For example, activated carbon supporting palladium salt, even if there is no copper salt catalyst, the oxidation reaction of olefins can be catalyzed, and the speed is high and the selectivity is high. Because activated carbon has a developed pore structure, a huge internal surface area and good heat resistance, acid resistance, and alkali resistance, it can be used as a catalyst carrier. For example, in the reactions of hydrogenation, dehydrocyclization, and isomerization in organic chemistry, activated carbon is an excellent carrier for platinum and palladium catalysts.