Adsorption of 2, 4-dichlorophenoxyacetic acid onto date seeds activated carbon: Equilibrium, kinetic and thermodynamic studies

Abstract

Adsorption isotherm and kinetics of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide on activated carbon prepared from Barhi date seeds were determined from batch tests. The effects of contact time, initial herbicide concentration and solution temperature were investigated. The adsorption equilibrium data were processed in accordance with the three most widely used adsorption isotherms: Langmuir, Freundlich and Temkin isotherm models. The equilibrium data were best represented by Langmuir isotherm model, showing maximum monolayer adsorption capacity of 175.4 mg/g. The kinetic data were also examined with the pseudo-first-order and pseudo-second-order models, and was found to follow closely the pseudo-second-order kinetic model. Thermodynamic parameters such as standard enthalpy (ΔHo), standard entropy (ΔSo) and standard free energy (ΔGo) were evaluated. The adsorption interaction was found to be endothermic in nature.