The difference between modified activated carbon and ordinary activated carbon

Modification of activated carbon refers to changing the properties of activated carbon and adding surface functional groups through alkali treatment or acid treatment to give it certain catalytic properties. Usually, modified activated carbon is mostly used in the field of special purposes or high-value products.

Activated carbon modification mainly changes its pore structure, changes its surface acidity and alkalinity through physical and chemical treatment, or introduces or removes certain functional groups on its surface to make activated carbon have special adsorption performance and catalytic characteristics. In addition, different activation methods or different activators can also be used to prepare activated carbons with different pore size distributions and different surface chemical properties.

(1) Modification of surface physical properties: The modification of the surface structure of activated carbon is mainly to change the specific surface area and pore size distribution of activated carbon through physical or chemical methods, expand or reduce the pore size, and achieve the purpose of changing the surface structure of activated carbon, thus mentioning the properties of activated carbon. Adsorption capacity.

(2) Modification of surface chemical properties: The change of surface chemical properties of activated carbon is mainly to change the functional groups on the surface of activated carbon and the ions and compounds loaded on the surface through certain methods, thereby changing the chemical properties of its surface to improve the adsorption capacity of activated carbon. The following are several methods for modifying surface chemical properties:

① Surface oxidation modification: Activated carbon is oxidized and modified by oxidants under appropriate conditions to increase the content of oxygen-containing functional groups and enhance the adsorption capacity of polar substances. Different oxidants have different types and quantities of functional groups on the surface after modification. Generally, the higher the degree of oxidation, the more oxygen-containing functional groups. Commonly used oxidants include: HNO3, HClO, H2SO4, Cl2, H2O2, (NH4)S2O8, etc.

②Surface reduction modification: The surface of activated carbon is reduced and modified by reducing agents under appropriate conditions to increase the content of basic groups, enhance the non-polarity of the surface, and thereby improve the adsorption capacity of activated carbon for non-polar substances. Commonly used reduction modification methods are high-temperature treatment of activated carbon with inert gases such as H2 and N2 to obtain more basic groups, and immersion treatment in NH3??H20 water to obtain rich nitrogen-containing functional groups.

③ Loaded atom modification: Loaded atom modification is based on the adsorption and reducibility of activated carbon, immersing the activated carbon in a certain solution, introducing specific atoms and compounds on the surface of the activated carbon through liquid phase deposition, and invading metal ions into the activated carbon. The surface of activated carbon mainly uses the reducing property of activated carbon to reduce metal ions into elemental or low-valence ions.

④ Surface acid-base modification: The acid-base modification method uses acids, alkali and other substances to treat activated carbon, and adjusts the functional groups on the surface of activated carbon to the required number according to actual needs. Usually acid-base modification of activated carbon is to improve the adsorption effect of activated carbon on metal ions. Commonly used modifiers include HCl, NaOH, HNO3, HClO, H2SO4, H2O2, NH3H20, citric acid, etc.