Potential of chemically activated and raw charcoals of Melocanna baccifera for removal of Ni(II) and Zn(II) from aqueous solutions

► Activated charcoal with KOH showed highest adsorption for Ni(II) and Zn(II). ► FTIR spectra revealed involvement of different functional groups in metal adsorption. ► Raw and activated charcoals surface area is 6.26 m2/g and 222.81 m2/g respectively. ► pH, dose, contact, metal concentrations and desorption investigated in batch mode. ► Langmuir, Freundlich and D-R isotherms were used for calculation.