Humulus scandens-Derived Biochars for the Effective Removal of Heavy Metal Ions: Isotherm/Kinetic Study, Column Adsorption and Mechanism Investigation

Humulus scandens was first adopted as a biomass precursor to prepare biochars by means of a facile molten salt method. The optimized biochar exhibits a high specific surface area of ~450 m(2)/g, a rich porous structure and abundant oxygen functional groups, which demonstrate excellent adsorption performance for heavy metal ions. The isotherm curves fit well with the Langmuir models, indicating that the process is governed by the chemical adsorption, and that the maximum adsorption capacity can reach 748 and 221 mg/g for Pb2+ and Cu2+, respectively. In addition, the optimized biochar demonstrates good anti-interference ability and outstanding removal efficiency for Cu2+ and Pb2+ in simulated wastewater. The mechanism investigation and DFT calculation suggest that the oxygen functional groups play dominant roles in the adsorption process by enhancing the binding energy towards the heavy metal ions. Meanwhile, ion exchange also serves as the main reason for the effective removal.

Automated summary

Humulus scandens was used as a biomass precursor to prepare biochars with high adsorption performance for heavy metal ions. The optimized biochar demonstrated excellent removal efficiency for Cu2+ and Pb2+ in simulated wastewater, with oxygen functional groups playing a dominant role in the adsorption process.