A multi-level porous MgO/biochar composite for the highly efficient adsorption of Pb(II) and Cd(II) from water

• MgO/biochar composite (MBC) with multi-level pores was synthesized via MgCl2-NaOH co-impregnation of lavender stalks, achieving a 54-fold increase in specific surface area. • MBC-700 exhibited exceptional adsorption capacities of 520 mg/g for Cd(II) and 808 mg/g for Pb(II), following quasi-second-order kinetics. • Adsorption mechanisms include ion exchange, precipitation, electrostatic attraction, and surface complexation, with metallic lead recovery via biochar reduction at high temperatures. • The study offers a cost-effective and sustainable approach for heavy metal removal and biomass waste valorization.