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

• Humic acid enhanced the rate and amount of adsorbed Cu2+ onto soil minerals.
• Total active sites were calculated for humic acid–soil minerals complex.
• Copper adsorption increased with increasing pH and decreasing ionic strength.
• K+ as background electrolyte enhanced copper adsorption in comparison to Ca2+.
• Influence of solution cations on the rate of Cu2+ adsorption is firstly studied.

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.

Mechanisms and kinetics study of interaction between soil minerals and heavy metal cation in the absence and presence of humic acid.Figure optionsDownload as PowerPoint slide