Characterization of oxidized activated carbon obtained from Astragalus residue and its adsorption application for Cu²⁺ from aqueous solution

The activated carbon prepared by Astragalus residue was chemically modified with KMnO₄. The samples before and after modification were characterized by N₂ adsorption, XRD, SEM and Boehm titration. Accordingly, the original and modified-carbon materials were used for adsorption of Cu²⁺ from aqueous solution. The results showed that the numbers of oxygen-containing functional groups increased and MnO₂ was almost uniformly deposited on the surface of activated carbon after modification by KMnO₄. The Langmuir isotherm provided the well description of the equilibrium adsorption giving a maximum uptake capacity for Cu²⁺ as 127.71mg/g and 196.46mg/g, respectively for activated carbon before and after modification. KMnO₄ changed the physicochemical properties and surface texture of activated carbon significantly and enhanced adsorption capacity for Cu²⁺. (paper)