Pore distribution structure and function of granular activated carbon

The pore structure of granular activated carbon is a three-disperse system, that is, the pore size is very uneven, mainly concentrated in the three dimensions of large, medium and micropores. Large holes, also known as large holes, refer to holes with a radius greater than 100-200mm. Macropores act as adsorption channels during the adsorption process.

The pore structure of granular activated carbon is a three-disperse system, that is, their pore sizes are very uneven and mainly concentrated in three size ranges: macropores, mesopores and micropores. Macropores, also called macropores, refer to pores with a radius greater than 100-200mm. There will be no condensation of vapor in large holes. There is no essential difference between the inner surface of macropores and the surface of non-porous carbon, and its proportion is very small, so its impact on the adsorption capacity can be ignored. The macropores function as adsorption channels during the adsorption process.

Mesopores are also called transition pores, which refer to pores in which capillary condensation of steam can occur, causing a hysteresis loop to appear in the adsorption isotherm. Its effective radius is usually between 2-100mm. The size of mesopores is much smaller than that of macropores. Although there is no essential difference between its inner surface and the non-porous carbon surface, its specific surface area accounts for a certain proportion, so it has a certain impact on the adsorption capacity. But in general, it mainly plays the role of coarse and fine adsorption channels. The micropores have an effective radius of the same order as the molecules of the adsorbed substance (less than 2mm). It is an important pore structure in activated carbon and determines its adsorption capacity. size. Because the inner surface of micropores relatively avoids overlapping of adsorption force fields, there is an essential difference between it and the non-porous carbon surface, thus affecting its adsorption mechanism.

Physical adsorption first occurs in micropores with smaller sizes and higher potential energy, and then gradually expands to micropores with larger sizes and lower potential energy. The adsorption of micropores does not proceed layer by layer along the surface, but is achieved by solvent filling, while macropores and mesopores are surface adsorption mechanisms. Therefore, the adsorption performance of activated carbon mainly depends on its pore structure, especially the microporous structure. The large number of mesopores also has a certain impact on adsorption.

Coconut shell activated carbon is made of coconut shell as raw material and refined through a series of processes. The appearance is black, granular, columnar, with developed gaps, good adsorption, high strength, easy to regenerate, economical and durable. Products are mainly used for purification, decolorization, dechlorination and deodorization of drinking water, purified water, wine, beverages and industrial wastewater. It can also be used to sweeten mercaptans in the oil refining industry. With the continuous development of the activated carbon industry, more and more industries and companies use activated carbon, and some companies have also entered the activated carbon industry.

Coconut shell activated carbon is often used for gas phase adsorption, usually by adsorbing airflow through an activated carbon layer. According to the state of the activated carbon layer in the adsorption device, the adsorption layer can be divided into a fixed layer, a mobile layer and a moving layer. But in small adsorbers, such as frost and car deodorizers, they rely on the absorption and diffusion of gases. In addition to granular activated carbon, activated carbon fibers and activated carbon shaped products are also increasingly used in gas phase adsorption. Coconut shell activated carbon can be used in the gases emitted from chemical plants, tanneries, paint factories and projects that use various organic solvents, which contain chemicals harmful to the environment, such as various organic solvents, metals and organic sulfides, hydrocarbons , chlorine, oil and mercury, and can be discharged after adsorption. The radioactive gas nitrogen, xenon, iodine and other substances emitted by the equipment must be adsorbed by activated carbon before being discharged. The smoke produced by the combustion of coal and heavy oil contains sulfur dioxide and nitrogen oxides, which are harmful components that pollute the air and form acid rain. They can also be removed by activated carbon adsorption.

Examples of coconut shell activated carbon used to purify gas include gas masks, cigarette filters, refrigerator deodorizers, car exhaust purifiers, etc. They all use the excellent adsorption properties of activated carbon to remove poisons, harmful substances or odorous substances in poisonous gases. For example, if 100 to 120 nanograms of activated carbon is added to the mouth of a cigarette filter, a large number of harmful substances in the smoke will be removed. In industries such as solvent recovery and oil and gas recovery, most choose columnar activated carbon or coconut shell granular activated carbon with a higher iodine value. Activated carbon made of different materials has different pore sizes and structures due to different production raw materials. Wooden activated carbon has larger pores, fruit shell activated carbon has smaller and more uniform pores, and coal-based activated carbon is somewhere in between. Therefore, for the organic waste gas generated by some special industries, activated carbon of different materials can be selected to achieve better treatment effects.