The adsorption of aqueous cadmium ions (Cd(II)) have been investigated for modified activated carbon (AC-T) with oxygen-containing functional groups. The oxygen-containing groups of AC-T play an important role in Cd(II) ion adsorption onto AC-T. The modified activated carbon is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results of batch experiments indicate that the maximal adsorption could be achieved over the broad pH range of 4.5 to 6.5. Adsorption isotherms and kinetic study suggest that the sorption of Cd(II) onto AC-T produces monolayer coverage and that adsorption is controlled by chemical adsorption. And the adsorbent has a good reusability. According to the FT-IR and XPS analyses, electrostatic attraction and cation exchange between Cd(II) and oxygen-containing functional groups on AC-T are dominant mechanisms for Cd(II) adsorption. (C) 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.