Superior removal of Hg (II) ions from wastewater using hierarchically porous, functionalized carbon.

•A hierarchically porous carbon functionalized with Fe-Mn oxide was fabricated for superior removal of Hg(II) from water.•The composite exhibits high adsorption efficiency of 96.8% and fast adsorption rate for the removal of Hg(II).•The high efficiency is contributed by the synergy between physical and chemical adsorption.•The adsorption kinetics agrees with the pseudo-second order model, and isotherms are consistent with the Freundlich model.