The Relationship Between Specific Surface Area and Adsorption Capacity of Activated Carbon

{"news_id":8964,"is_preview":0,"news_info":{"id":8964,"company_id":176,"user_id":411,"author":"","website_id":781,"pub_date":"2024-06-25 12:02:41","urla":"relationship-between-activated-carbon-surface-area-and-adsorption-capacity","description":"It's generally believed that the larger the specific surface area, the stronger the adsorption capacity of activated carbon. However, in practice,  is not so simple.","image_url":"https:\/\/oss.matchpages.cn\/matchpages\/common\/2024\/0319\/2146\/65f9475284a71\/ACarbon%C2%AE-Activated-Carbon-Products.webp","image_alt":"ACarbon\u00ae-Activated-Carbon-Products","title":"The larger the specific surface area of activated carbon, the stronger the adsorption capacity must be?","content":"<p><span style=\"color: #000000;\">As an important adsorption material, activated carbon is widely used in water treatment, air purification, food processing and chemical industry. One of its core characteristics is the specific surface area, i.e. the total surface area per unit mass of activated carbon. It is generally believed that the larger the specific surface area, the stronger the adsorption capacity of activated carbon. However, in practice, the relationship between specific surface area and adsorption capacity is not so simple. We will discuss the relationship between specific surface area of activated carbon and its adsorption capacity in detail to help you understand activated carbon more comprehensively.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><strong><span style=\"color: #000000;\">1.Measurement and Meaning of Specific Surface Area<\/span><\/strong><\/h2>\n<p><span style=\"color: #000000;\">Specific surface area is usually measured by the BET (Brunauer-Emmett-Teller) method, which uses adsorption data of nitrogen or butane to calculate the total surface area of activated carbon. This method provides a basic reference for assessing the potential adsorption capacity of activated carbon. However, the BET specific surface area is only a total parameter and does not fully reflect the adsorption effect of activated carbon in practical applications.<\/span><\/p>\n<h3><strong><span style=\"color: #000000;\">Pore structure and adsorption performance<\/span><\/strong><\/h3>\n<p><span style=\"color: #000000;\">The pore structure of activated carbon is complex, mainly divided into three types: macropores, mesopores and micropores. Different pore sizes have different effects on the adsorption of molecules of different sizes:<\/span><\/p>\n<p><span style=\"color: #236fa1;\">Macropores (&gt;50nm): mainly used as adsorption channels, the actual adsorption capacity is weak.<\/span><\/p>\n<p><span style=\"color: #236fa1;\">Mesopore (2-50nm): suitable for adsorption of larger molecules, especially some organic molecules and pollutants with complex structures, especially in the liquid phase adsorption process.<\/span><\/p>\n<p><span style=\"color: #236fa1;\">Microporous (&lt;2nm): strong adsorption capacity for small molecules, such as nitrogen and carbon dioxide in gas phase adsorption.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><strong><span style=\"color: #000000;\">2.Specific surface area and adsorption capacity in liquid phase adsorption<\/span><\/strong><\/h2>\n<p><span style=\"color: #000000;\">In liquid phase adsorption, the adsorption capacity of activated carbon usually increases with the increase of molecular weight (molecular size) of the adsorbent until the molecules are so large that they cannot enter the pore size. For example, the presence of mesopores is particularly important in the adsorption of large organic molecules, as they provide sufficient space for macromolecules to enter and adsorb. Micropores, although numerically superior, are limited in their effectiveness for macromolecular adsorbates.<\/span><\/p>\n<p><span style=\"color: #000000;\">Therefore, for liquid-phase applications, the most desirable counting party activated carbon should have a large number of pore sizes that are just slightly larger than the molecules of the adsorbate. A pore size that is too small hinders the entry of the adsorbent, and one that is too large leads to a reduction in the surface area per unit volume, which reduces the adsorption efficiency. This is why, when selecting activated carbon for a particular liquid-phase adsorption application, it is not sufficient to rely solely on the BET specific surface area, but the pore size distribution and the specific properties of the adsorbate molecules need to be taken into account as well.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><strong><span style=\"color: #000000;\">3.Specific surface area and adsorption capacity in gas phase adsorption<\/span><\/strong><\/h2>\n<p><span style=\"color: #000000;\">In gas-phase adsorption, small molecules are usually adsorbed into micropores, so the concept of total surface area is more applicable in this case. Micropores provide a large amount of surface area and adsorption sites, allowing activated carbon to efficiently adsorb gas-phase pollutants such as volatile organic compounds (VOCs) and hazardous gases.<\/span><\/p>\n<p><span style=\"color: #000000;\">However, even in gas-phase adsorption, an excessive pursuit of a high specific surface area may not always be optimal. The pore size distribution and surface chemistry of the micropores also have an important influence on the adsorption effect. For example, for certain gas molecules, moderate pore sizes and specific chemical functional groups can significantly enhance the adsorption efficiency, and these details are not always revealed by the BET specific surface area.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><strong><span style=\"color: #000000;\">4.The difference between chemical adsorption and physical adsorption<\/span><\/strong><\/h2>\n<p><span style=\"color: #000000;\">The adsorption process of activated carbon can be divided into two categories: physical adsorption and chemical adsorption:<\/span><\/p>\n<p><span style=\"color: #236fa1;\"><a href=\"activated-carbon-knowledge\" data-page_id=\"21061\" data-page_name=\"Activated Carbon Knowledge\" data-page_type=\"menuPage\"><strong><span style=\"color: #2dc26b;\">Physical adsorption<\/span><\/strong><\/a>: adsorption mainly relies on van der Waals forces and is usually directly related to the specific surface area. Most gas-phase and liquid-phase adsorption processes fall into this category.<\/span><\/p>\n<p><span style=\"color: #236fa1;\">Chemisorption: involves the formation of chemical bonds, e.g. the adsorption of metal complexes by activated carbon. This adsorption process is not only dependent on the surface area, but is also closely related to the chemical properties of the activated carbon surface.<\/span><\/p>\n<p><span style=\"color: #000000;\">During chemisorption, the specific surface area is of relatively low importance and depends more on the presence and distribution of chemical functional groups on the surface of the activated carbon. For example, oxygen-containing functional groups (e.g., carboxyl groups, hydroxyl groups, etc.) are able to form coordination bonds with metal ions, thus enhancing the adsorption of metal complexes. Therefore, for chemical adsorption applications, the surface chemistry of CNAC should be examined rather than simply pursuing a high specific surface area.<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><strong><span style=\"color: #000000;\">5. Balance and optimisation in practical applications<\/span><\/strong><\/h2>\n<p><span style=\"color: #000000;\">In practical applications, in order to obtain the best adsorption effect, it is necessary to strike a balance between specific surface area, pore size distribution and surface chemistry. Example:<\/span><\/p>\n<p><span style=\"color: #236fa1;\"><a href=\"activated-carbon-for-chloramine-removal\" data-page_id=\"19574\" data-page_name=\"Activated Carbon for Chloramine Removal\uff5cACC\" data-page_type=\"menuPage\"><strong><span style=\"color: #2dc26b;\">Water treatment<\/span><\/strong><\/a>: In water treatment, activated carbon is often used to remove organic pollutants and odourous substances. In this case, it is necessary to choose activated carbon with appropriate mesopore and micropore distribution in order to efficiently adsorb organic molecules of different sizes.<\/span><\/p>\n<p><span style=\"color: #236fa1;\"><a href=\"activated-carbon-for-rng-and-biogas\" data-page_id=\"19572\" data-page_name=\"Activated Carbon for RNG\/Biogas\uff5cACC\" data-page_type=\"menuPage\"><span style=\"color: #2dc26b;\"><strong>Air purification<\/strong><\/span><\/a>: In air purification, activated carbon is mainly used for the adsorption of volatile organic compounds (VOCs) and harmful gases. For these applications, activated carbons with a high specific surface area of micropores are often preferred, while the adsorption capacity of the surface functional groups for specific gases should also be considered.<\/span><\/p>\n<p><span style=\"color: #236fa1;\"><a href=\"resin-based-spherical-activated-carbon\" data-page_id=\"21460\" data-page_name=\"Resin Based Spherical Activated Carbon\" data-page_type=\"menuPage\"><strong><span style=\"color: #2dc26b;\">Pharmaceutical<\/span><\/strong><\/a>: In the pharmaceutical field, activated carbon is used for drug purification and toxin adsorption. In this case, it is necessary to select the activated carbon with the appropriate pore size and surface chemistry according to the properties of the specific drug or toxin molecule.<\/span><\/p>\n<h2><br \/><strong><span style=\"color: #000000;\">Conclusion<\/span><\/strong><\/h2>\n<p><span style=\"color: #000000;\">In summary, there is a complex relationship between the specific surface area of activated carbon and its adsorption capacity. Although in general the larger the specific surface area, the stronger the adsorption capacity, the pore size distribution and surface chemistry need to be considered comprehensively in specific applications. It is through the optimisation of the balance of comparative surface area, pore size structure and surface chemistry that the most suitable activated carbon for a specific application can be selected to achieve the best adsorption effect. Future research should focus more on the comprehensive evaluation of multidimensional parameters to guide the development and application of activated carbons and enhance their adsorption performance in various fields.<\/span><\/p>\n<p>&nbsp;<\/p>","discuss":0,"seo_title":"The Relationship Between Specific Surface Area and Adsorption Capacity of Activated Carbon","seo_keyword":"specific surface area of activated carbon, activated carbon adsorption capacity, factors affecting activated carbon adsorption, selection of activated carbon, optimization of activated carbon properties","seo_describe":"How pore structure, surface chemistry plus surface area influence carbon's adsorption. Balancing these factors optimizes capacity across uses, with guidelines for comprehensive evaluation.","track_code":"","viewer":"","source_copy_id":0,"sort":25,"status":0,"data_time":"2024-06-25 12:02:41","create_time":"2024-06-25 11:11:09","update_time":"2025-04-02 09:56:43","type_items":[{"id":2083,"website_id":781,"name":"Activated Carbon","urla":""}],"tag_items":[{"id":6851,"website_id":781,"name":"specific surface area of activated carbon"},{"id":6852,"website_id":781,"name":"adsorption capacity "}]}}

<p><span style="color: #000000;">As an important adsorption material, activated carbon is widely used in water treatment, air purification, food processing and chemical industry. One of its core characteristics is the specific surface area, i.e. the total surface area per unit mass of activated carbon. It is generally believed that the larger the specific surface area, the stronger the adsorption capacity of activated carbon. However, in practice, the relationship between specific surface area and adsorption capacity is not so simple. We will discuss the relationship between specific surface area of activated carbon and its adsorption capacity in detail to help you understand activated carbon more comprehensively.</span></p>
<p> </p>
<h2><strong><span style="color: #000000;">1.Measurement and Meaning of Specific Surface Area</span></strong></h2>
<p><span style="color: #000000;">Specific surface area is usually measured by the BET (Brunauer-Emmett-Teller) method, which uses adsorption data of nitrogen or butane to calculate the total surface area of activated carbon. This method provides a basic reference for assessing the potential adsorption capacity of activated carbon. However, the BET specific surface area is only a total parameter and does not fully reflect the adsorption effect of activated carbon in practical applications.</span></p>
<h3><strong><span style="color: #000000;">Pore structure and adsorption performance</span></strong></h3>
<p><span style="color: #000000;">The pore structure of activated carbon is complex, mainly divided into three types: macropores, mesopores and micropores. Different pore sizes have different effects on the adsorption of molecules of different sizes:</span></p>
<p><span style="color: #236fa1;">Macropores (>50nm): mainly used as adsorption channels, the actual adsorption capacity is weak.</span></p>
<p><span style="color: #236fa1;">Mesopore (2-50nm): suitable for adsorption of larger molecules, especially some organic molecules and pollutants with complex structures, especially in the liquid phase adsorption process.</span></p>
<p><span style="color: #236fa1;">Microporous (<2nm): strong adsorption capacity for small molecules, such as nitrogen and carbon dioxide in gas phase adsorption.</span></p>
<p> </p>
<h2><strong><span style="color: #000000;">2.Specific surface area and adsorption capacity in liquid phase adsorption</span></strong></h2>
<p><span style="color: #000000;">In liquid phase adsorption, the adsorption capacity of activated carbon usually increases with the increase of molecular weight (molecular size) of the adsorbent until the molecules are so large that they cannot enter the pore size. For example, the presence of mesopores is particularly important in the adsorption of large organic molecules, as they provide sufficient space for macromolecules to enter and adsorb. Micropores, although numerically superior, are limited in their effectiveness for macromolecular adsorbates.</span></p>
<p><span style="color: #000000;">Therefore, for liquid-phase applications, the most desirable counting party activated carbon should have a large number of pore sizes that are just slightly larger than the molecules of the adsorbate. A pore size that is too small hinders the entry of the adsorbent, and one that is too large leads to a reduction in the surface area per unit volume, which reduces the adsorption efficiency. This is why, when selecting activated carbon for a particular liquid-phase adsorption application, it is not sufficient to rely solely on the BET specific surface area, but the pore size distribution and the specific properties of the adsorbate molecules need to be taken into account as well.</span></p>
<p> </p>
<h2><strong><span style="color: #000000;">3.Specific surface area and adsorption capacity in gas phase adsorption</span></strong></h2>
<p><span style="color: #000000;">In gas-phase adsorption, small molecules are usually adsorbed into micropores, so the concept of total surface area is more applicable in this case. Micropores provide a large amount of surface area and adsorption sites, allowing activated carbon to efficiently adsorb gas-phase pollutants such as volatile organic compounds (VOCs) and hazardous gases.</span></p>
<p><span style="color: #000000;">However, even in gas-phase adsorption, an excessive pursuit of a high specific surface area may not always be optimal. The pore size distribution and surface chemistry of the micropores also have an important influence on the adsorption effect. For example, for certain gas molecules, moderate pore sizes and specific chemical functional groups can significantly enhance the adsorption efficiency, and these details are not always revealed by the BET specific surface area.</span></p>
<p> </p>
<h2><strong><span style="color: #000000;">4.The difference between chemical adsorption and physical adsorption</span></strong></h2>
<p><span style="color: #000000;">The adsorption process of activated carbon can be divided into two categories: physical adsorption and chemical adsorption:</span></p>
<p><span style="color: #236fa1;"><a href="activated-carbon-knowledge" data-page_id="21061" data-page_name="Activated Carbon Knowledge" data-page_type="menuPage"><strong><span style="color: #2dc26b;">Physical adsorption</span></strong></a>: adsorption mainly relies on van der Waals forces and is usually directly related to the specific surface area. Most gas-phase and liquid-phase adsorption processes fall into this category.</span></p>
<p><span style="color: #236fa1;">Chemisorption: involves the formation of chemical bonds, e.g. the adsorption of metal complexes by activated carbon. This adsorption process is not only dependent on the surface area, but is also closely related to the chemical properties of the activated carbon surface.</span></p>
<p><span style="color: #000000;">During chemisorption, the specific surface area is of relatively low importance and depends more on the presence and distribution of chemical functional groups on the surface of the activated carbon. For example, oxygen-containing functional groups (e.g., carboxyl groups, hydroxyl groups, etc.) are able to form coordination bonds with metal ions, thus enhancing the adsorption of metal complexes. Therefore, for chemical adsorption applications, the surface chemistry of CNAC should be examined rather than simply pursuing a high specific surface area.</span></p>
<p> </p>
<h2><strong><span style="color: #000000;">5. Balance and optimisation in practical applications</span></strong></h2>
<p><span style="color: #000000;">In practical applications, in order to obtain the best adsorption effect, it is necessary to strike a balance between specific surface area, pore size distribution and surface chemistry. Example:</span></p>
<p><span style="color: #236fa1;"><a href="activated-carbon-for-chloramine-removal" data-page_id="19574" data-page_name="Activated Carbon for Chloramine Removal｜ACC" data-page_type="menuPage"><strong><span style="color: #2dc26b;">Water treatment</span></strong></a>: In water treatment, activated carbon is often used to remove organic pollutants and odourous substances. In this case, it is necessary to choose activated carbon with appropriate mesopore and micropore distribution in order to efficiently adsorb organic molecules of different sizes.</span></p>
<p><span style="color: #236fa1;"><a href="activated-carbon-for-rng-and-biogas" data-page_id="19572" data-page_name="Activated Carbon for RNG/Biogas｜ACC" data-page_type="menuPage"><span style="color: #2dc26b;"><strong>Air purification</strong></span></a>: In air purification, activated carbon is mainly used for the adsorption of volatile organic compounds (VOCs) and harmful gases. For these applications, activated carbons with a high specific surface area of micropores are often preferred, while the adsorption capacity of the surface functional groups for specific gases should also be considered.</span></p>
<p><span style="color: #236fa1;"><a href="resin-based-spherical-activated-carbon" data-page_id="21460" data-page_name="Resin Based Spherical Activated Carbon" data-page_type="menuPage"><strong><span style="color: #2dc26b;">Pharmaceutical</span></strong></a>: In the pharmaceutical field, activated carbon is used for drug purification and toxin adsorption. In this case, it is necessary to select the activated carbon with the appropriate pore size and surface chemistry according to the properties of the specific drug or toxin molecule.</span></p>
<h2><br /><strong><span style="color: #000000;">Conclusion</span></strong></h2>
<p><span style="color: #000000;">In summary, there is a complex relationship between the specific surface area of activated carbon and its adsorption capacity. Although in general the larger the specific surface area, the stronger the adsorption capacity, the pore size distribution and surface chemistry need to be considered comprehensively in specific applications. It is through the optimisation of the balance of comparative surface area, pore size structure and surface chemistry that the most suitable activated carbon for a specific application can be selected to achieve the best adsorption effect. Future research should focus more on the comprehensive evaluation of multidimensional parameters to guide the development and application of activated carbons and enhance their adsorption performance in various fields.</span></p>
<p> </p>