Kinetic study for copper adsorption onto soil minerals in the absence and presence of humic acid

Equilibrium and kinetics of Cu2+ adsorption onto soil minerals (kaolinite and hematite) in the absence and presence of humic acid have been investigated under various conditions. The influences of ionic strength, pH and solution cations on the rate of the adsorption have been studied. The rate and the amount of adsorbed Cu2+ onto soil minerals in the absence or the presence of humic acid increased with decreasing ionic strength, increasing pH and in the presence of the background electrolyte K+ rather than Ca2+. Humic acid enhanced the rate and the amount of adsorbed Cu2+ onto soil minerals. The adsorption equilibrium data showed that adsorption behavior of Cu2+ could be described more reasonably by Langmiur adsorption isotherm than Freundlich isotherm in the absence or presence of humic acid. Pseudo first and pseudo second order models were used to evaluate the kinetic data and the rate constants. The results indicated that the adsorption of Cu2+ onto hematite and kaolinite in the absence and presence of humic acid is more conforming to pseudo second order kinetics. (C) 2013 Elsevier Ltd. All rights reserved.