Surface modification, characterization and adsorptive properties of a coconut activated carbon

► A coconut activated carbon has been modified using nitric acid. ► Acidic functional groups of oxidized carbons were increased during oxidization process. ► BET surface area and pore volume were decreased. ► The oxidized carbons have higher adsorption capacity of sodium and formaldehyde. ► Chemical properties of activated carbon played an important role in adsorption of metal ions and organic pollutants.