Adsorption of heavy metals by activated carbon: effect of natural organic matter and regeneration methods of the adsorbent

Abstract

At present, global water resources are seriously polluted by heavy metals. It is necessary to take timely measures to remove heavy metals from wastewater. In this study, the effect of natural organic matter (NOM) on the adsorption of heavy metals by activated carbon was confirmed, and the optimal regeneration method of activated carbon was obtained. The results showed that the order of adsorp-tion capacities of activated carbon for five heavy metals was Cu(II) > Cr(VI) > Pb(II) > Zn(II) > Cd(II). NOM, which is widely present in wastewater, affected the adsorption capacities of heavy met-als. The equilibrium adsorption capacities of activated carbon for Pb(II), Zn(II), Cd(II) and Cu(II) increased by 0.031, 0.023, 0.001 and 0.012 mmol/g respectively, while the equilibrium adsorp-tion capacity for Cr(VI) decreased by 0.020 mmol/g when the concentration of NOM was 1 mg/L. With the raise of NOM concentration, the promoting effect of NOM on the removal of Pb(II) and Zn(II) was gradually reduced, and the promoting degree of Cd(II) adsorption and the inhibiting degree of Cr(VI) adsorption were correspondingly enhanced. At the same time, the influence of high concentration of NOM on the removal of Cu(II) was changed from promotion to inhibi-tion. In addition, HCl solution of 0.1 mol/L was confirmed to be the best regeneration reagent for desorbing metal ions on activated carbon through regeneration experiments. After six adsorption– regeneration cycles, the high adsorption performance of activated carbon could still be maintained.