Performance and mechanism of MnCO3/NaOH co-activated corncob-derived biochar for humic acid removal: XDLVO and DFT calculation

Abstract

In this study, waste corncobs were used as raw materials to prepare biochar (BC). Under the condition of activator (MnCO3 and NaOH) and pyrolysis (900℃), BC with high specific surface area (1161.99 m2/g) possessed satisfactory performance for the removal of humic acid (HA) in water, with a maximum adsorption capacity of 68.49 mg/g as determined by fitting Freundlich model. HA adsorption capacity was almost unaffected by initial solution pH (1 ∼ 9) and coexisting ions (i.e., Na+, K+, Ca2+, Mg2+, Al3+, CO32–, HCO3–, Cl−, SO42−). The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory suggested that the van der Waals interaction contributed to attraction between HA and BC, and the density functional theory (DFT) calculation visualized the hydrogen bonding and π-π interaction between HA and BC. Meanwhile, combined with characterization and factor experiments, pore filling and electrostatic interaction also were involved in the adsorption process. This study demonstrated the potential of using waste corncobs for producing BC, providing an effective solution for removing HA and highlighting the importance of waste material utilization in water purification.