Preparation and characterization of activated carbon from acorn shell by physical activation with H2O-CO2 in two-step pretreatment

► Activated carbon was produced from acorn shell by physical activation with H2O-CO2. ► Two-step pretreatment including ZnCl2-HCl applied to acorn shell at 850 °C. ► BET surface area of the best produced activated carbon was 1779 m2/g. ► The characterization of activated carbon was determined by FTIR, SEM and BET. ► Adsorption capacity was demonstrated by the iodine numbers.