Synthesis, structural characterization and Pb(II) adsorption behavior of K- and H-birnessite samples

► The presence of NO3− in birnessite samples is of academic importance. ► NO3− in birnessite could be utilized as an exchangeable site for other anions. ► H+ treatment increases total pore volume, which does not come from the increase in micropores. ► The works related to Pb(II) adsorption on birnessite are scarce. ► The change in the intensity of Mn-O band is also linked to Pb(II) adsorption.