Modeling of copper ions adsorption onto oxidative-modified activated carbons

In this work, the adsorption of copper ions onto activated carbons that oxidatively modified with H2O2 and HNO3 was studied. The prepared sorbents with the surface area of 275-780 m(2)/g contain 0.53-3.77 mmol/g of oxygen-containing groups. It was found that the oxidized activated carbon effectively adsorbs Cu2+ ions from aqueous solutions. For the most efficient activated carbon-HNO3-30 sorbent, the percentage removal of copper ions from solutions of varying concentration is high. In the concentration range from 1.5 to 6 x 10(-4) M of Cu2+, it reaches >55%. At the concentrations lower than 1.5 x 10(-4) M, the expected removal is above 80%. The experimental equilibrium adsorption data were modeled with 2- and 3-parameter isotherms. The analysis of adsorption modeling results accounting for the surface heterogeneity effect was provided. The data fit well to the Dubinin-Radushkevich model. Presumably, the complexation of Cu2+ with oxygen-containing groups passes within micropores. We found the correlation between the sorption capacity for Cu2+ and the concentration of surface groups. The presence of the carboxyl, anhydride, and lactone groups make a major impact on the adsorption.