Adsorption of cadmium ions from aqueous solutions by activated carbon with oxygen-containing functional groups

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.

XPS spectra of activated carbon (AC), modified activated carbon (AC-T) and AC-T after Cd(II) adsorption (AC-T-Cd): C 1s spectra (a) and O 1s spectra (b).The adsorption for aqueous cadmium ions (Cd(II)) were investigated for modified activated carbon (AC-T) with oxygen-containing functional groups. The oxygen-containing groups play an important role in Cd(II) ion adsorption. According to XPS analyses of AC, AC-T and AC-T-Cd, some typical oxygen-containing functional groups on the surface of AC-T are phenolic hydroxyl group and carboxyl group, which are responsible for the Cd(II) adsorption. Additionally, it indicates the formation of C–O–Cd and carboxyl-Cd species in Cd(II) adsorption. Thus electrostatic attraction and cation exchange between Cd(II) and oxygen-containing functional groups on AC-T are the dominant mechanisms for Cd(II) adsorption.Figure optionsDownload as PowerPoint slide