Kinetic study of humic acid adsorption onto smectite: The role of individual and blend background electrolyte

Abstract

Many factors can affect the natural organic matter adsorption on clay, such as pH and ionic strength. Blended background electrolyte could be causing better simulation to natural effects. Therefore, kinetic study of humic acid (HA) adsorption onto smectite has been studied under various conditions. Impact of pH and individual and blend background electrolyte with different ionic strength concentration on the rate of adsorption has been investigated. The rate and amount of adsorbed HA on smectite improved with raised background electrolyte concentration, declining pH, and in existence Ca2+. The rate of adsorption order was in the presence of CaCl2 > blend (CaCl2 and KCl) > KCl. The adsorption isotherm was L-shap in the presence of CaCl2 and KCl while was S-shap in presence blend (CaCl2 and KCl). Moreover, the data revealed that the adsorption behavior of HA might be pronounced more obviously by Freundlich model than Langmuir. Two kinetic models were applied to assess the rate constants and kinetic data. The results clarified that HA adsorption on smectite was following to pseudo second order model under various conditions.

Keywords

• kinetics
• humic acid
• smectite
• adsorption
• background electrolyte