Acid-base titrations of oxidized multiwall carbon nanotubes (MWCNTs), Sr(II) and Eu(III) adsorptions onto oxidized MWCNTs were conducted to investigate the Surface charge characteristics of oxidized MWCNTs and the surface complexation interactions between Sr(II)/Eu(III) and oxidized MWCNTs. The results suggested that Sr(II) and Eu(III) adsorptions onto oxidized MWCNTs increased with increasing pH, and decreased with increasing ionic strength, and the affinity of oxidized MWCNTs for Eu(III) was much higher than that for Sr(II). The diffuse layer model (DLM) fitted the experimental data of Sr(II) and Eu(III) adsorptions well with the aid of FITEQL 3.2. (C) 2008 Elsevier Inc. All rights reserved.