Activated carbon (AC) has been used widely as an adsorbent in environmental treatment thanks to their low-cost and high surface area. To enhance the adsorption capacity to heavy metal ions (HM) in water, the surface of AC is usually functionalized with various organic functional groups that have a high chelating affinity to HM such as hydroxyl, carboxyl, amino, and thiol. Grafting polyethyleneimine (PEI) onto the surface of various absorbents has been demonstrated to increase their HM removal efficiencies. However, the effects of PEI grafting on the performance of AC have not been fully explored yet. Herein, we grafted PEI onto the surface of oxidized activated carbon (oAC) and compared their porous structure and the adsorption properties toward Cu(II). Nitrogen adsorption–desorption analysis shows that PEI grafting reduces both the surface area and porous volume of the adsorbent by nearly 50%. Nevertheless, the PEI grafting makes the adsorption sites on the adsorbent’s surface more homogeneous and increases the adsorption maximum to Cu(II) by 26%. The constradict effects of PEI grafting demonstrated herein could be beneficial to developing AC-based materials for HM removal.
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