Adsorption of Cd2+ in aqueous solutions using KMnO4-modified activated carbon derived from Astragalus residue

Abstract Activated carbon obtained from Astragalus residue was chemically activated by KOH and modified with KMnO 4 . The samples were characterized by N 2 adsorption, Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, and Boehm titration. Accordingly, the original and modified carbon materials were used for the removal of Cd 2+ from aqueous solution by batch adsorption experiments. Results showed that the contents of oxygen-containing functional groups increased, and MnO 2 was nearly uniformly deposited on the surface of activated carbon after modification by KMnO 4 . The adsorption kinetics was described by pseudo-second order model. Langmuir model fitted the adsorption-isotherm experimental data of Cd 2+ better than the Freundlich model. The maximum adsorption capacities of the activated carbon before and after modification for Cd 2+ were 116.96 and 217.00 mg/g, respectively. KMnO 4 considerably changed the physicochemical properties and surface texture of activated carbon and enhanced the adsorption capacity of activated carbon for Cd 2+ .