Adsorption of Eu(III) on oMWCNTs: effects of pH, ionic strength, solid-liquid ratio and water-soluble fullerene

The influences of pH, ionic strength, solid-liquid ratio, C60(C(COOH)2)n, and C60(OH)n on Eu(III) adsorption onto the oxidation multiwalled carbon nanotubes (oMWCNTs) were studied by using batch technique. The dynamic process showed that the adsorption of Eu(III) onto oMWCNTs could be in equilibrium for about 17 h and matched the quasi-second-order kinetics model. The sorption process was influenced strongly by pH changes and ionic strength. In the pH range of 1.0 to 4.0, the adsorption ratio increased with the increasing of pH values, then the adsorption of Eu(III) was almost saturated in the pH range of 4.0 to 10.0, and the adsorption ratio reached about 90%. The adsorption ratio decreased with the increasing of ionic strength. C60(C(COOH)2)2 could promote the adsorption process obviously, but C60(OH)n competed with Eu(III) for the adsorption sites, thus leading to the reducing of Eu(III) adsorption onto oMWCNTs. In the presence of C60(C(COOH)2)n or C60(OH)n, the adsorption of Eu(III) onto oMWCNTs could be affected obviously by solid-liquid ratio and the initial concentration of Eu(III).