Enhancement of Cu(II) adsorption on activated carbons by non-thermal plasma modification in O2, N2 and O2/N2 atmospheres

Activated carbon (AC) was modified by using non-thermal plasma in O-2, N-2 and O-2/N-2 atmospheres to increase its Cu(II) adsorption capacity and quantify the influences of the modifying atmospheres. SEM, BET, FT-IR and XPS were used to characterize the surface physical and chemical properties of AC. The results show that the AC modified by using plasma had significantly better Cu(II) adsorption performance than the raw AC. Among the O-2, N-2 and O-2/N-2 atmospheres, the AC with plasma modification in N-2 showed best Cu(II) adsorption performance and the Cu(II) adsorption capacity was 369.5% higher than the raw AC. The AC modified in O-2 atmosphere can form C-COOH groups, while the AC modified in N-2 atmosphere can form C-NH2 groups. These two groups are both beneficial for Cu(II) adsorption, where the -NH2 groups are more effective for Cu(II) adsorption compared to -COOH groups. The chemisorption dominated the Cu(II) adsorption on the plasma modified AC and the adsorption performance was dependent on the surface functional groups properties of AC.