Adsorption of pesticides from aqueous solution onto banana stalk activated carbon

Activated carbon was prepared from banana stalk by potassium hydroxide (KOH) and carbon dioxide (CO2) activation and its ability to remove the pesticides, 2,4-dichlorophenoxyacetic acid (2,4-D) and bentazon was explored. The banana stalk activated carbon (BSAC) was characterized by Fourier transform infrared spectroscopy (FT-IR) analysis. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first-order and pseudo-second-order models. The adsorption kinetics was better represented by the pseudo-second-order model. The equilibrium adsorption data obtained at 30, 40 and 50 °C were analyzed by Langmuir and Freundlich isotherm models and results showed that it was better described by the Freundlich model. Higher adsorption capacity observed for 2,4-D than bentazon were attributed to the presence of electron-withdrawing –Cl groups on the aromatic ring and smaller molecular size of 2,4-D. The thermodynamic parameters, ΔG°, ΔH° and ΔS° determined, showed that the adsorption of 2,4-D and bentazon onto BSAC was feasible, spontaneous and exothermic. The results showed that BSAC is an efficient adsorbent for the adsorptive removal of 2,4-D and bentazon from aqueous solutions.

► Banana stalk activated carbon (BSAC) was prepared by activation using KOH and CO2.
► BSAC exhibited higher adsorption capacity for 2,4-D than bentazon.
► The adsorption system followed the pseudo-second-order kinetic model platform.
► Equilibrium data were better described by the Freundlich isotherm model.
► Adsorption capacities of BSAC were high compared to other activated carbon.