Sorption Of Cu(Ⅱ), Eu(Ⅲ), Th(Ⅳ) And U(Ⅵ) On Oxidized Multi-walled Carbon Nanotube And Oxidized Activated Carbon

Carbon nanotubes have a good application prospect in many fields because of their unique feature of structures. Many studies have found that oxidized carbon nanotubes are efficient sorbents for heave metal ions and are expected to be applied to liquid radioactive waste treatment. Whether sorption of heave metal ions on oxidized carbon nanotubes is related to its unique tubular structure is a significant topic, because some studies have shown that carbon nanotubes have higher sorption capacities than that of activated carbon under the same conditions.Oxidized activated carbon (AC-x) was prepared with nitric acid and characterized by FT-IR, SEM and X-ray photoelectron spectroscopy (XPS). It was found that the amounts of oxygen-containing functional groups of AC-x was increased by oxidation, specific surface areas, pore volume and pore diameter were decreased.The sorption of Cu(Ⅱ), Eu(Ⅲ),Th(Ⅳ) and U(Ⅵ) on AC-66%and MWCNT-66%was studied as a function of pH, ionic strength and concentration. It was found that the oxidation level of MWCNTs-x had a significant influence on Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) adsorption. The adsorption of Eu(Ⅲ) on AC-x increased with increasing pH and decreased with the increase of ionic strength. The Eu(Ⅲ) adsorption isotherms could be fitted by Freundlich equation.The sorption of Cu(Ⅱ), Th(Ⅳ) and U(Ⅵ) on AC-66%was strongly dependent on pH values, and decreased with the increase of ionic strength, respectively, independent of ionic strength on MWCNT-66%. The sorption isotherms of Cu(Ⅱ), Th(Ⅳ) and U(Ⅵ) were well described by the Langmuir model. The presence of salicylic acid (SA) resulted in strong enhancement of Cu(Ⅱ) adsorption at low pH values and obvious decrease of sorption at high pH values.The present work suggests that AC-x have higher sorption capacities for Cu(Ⅱ), Th(Ⅳ) and U(Ⅵ) than oxidized carbon nanotube.