Effect of Carbon–Oxygen and Carbon–Nitrogen Surface Complexes on the Adsorption of Cations by Activated Carbons

Abstract

Adsorption studies of Na⁺, Cs⁺, Ag⁺, Sr²⁺ and Co²⁺ from aqueous solutions by surface-treated activated carbons are reported. Carbon–oxygen and carbon–nitrogen surface complexes were formed on an activated carbon from almond shells by treating it with either oxidizing reagents or ammonia. In order to discover the surface acidity and/or basicity of each carbon, selective neutralization techniques were carried out. Both Na⁺ and Cs⁺ are adsorbed by only those carbons containing strong acidic functional groups; however, Ag⁺, Sr²⁺ and Co²⁺ are adsorbed not only by these latter carbons but also by those with predominance of basic groups. The results suggest that some of these carbons can be used to remove, separate and pre-concentrate all the cations studied.