Modified Biochar for Lead Removal from Water: A Critical Review on Synthesis, Characterization, Evaluation, and Unveiling the Adsorption Mechanisms Through Molecular Simulations

Anthropogenic activities release lead (Pb) into natural and engineered water systems, affecting water quality. Biochar has been widely studied as an adsorbent for the removal of Pb from water. However, pristine biochar often exhibits low efficiencies in remediating Pb. To enhance its performance for Pb removal, biochar modification techniques such as surface oxidation, surface reduction, mineral impregnation, and physical modification have been explored to amend its physicochemical characteristics. This review critically evaluates the adsorption of Pb onto modified biochar (MBC), including influencing parameters and removal mechanisms. Density functional theory (DFT) calculations and molecular dynamics (MD) simulation were employed to examine the interactions between Pb2+ and MBC at the molecular scale. This review emphasized the implication of molecular simulations (DFT and MD) for screening and designing MBCs for experimental studies to remove Pb from water. Molecular simulations play a critical role in revealing the molecular-scale interactions involved in heavy metal removal by MBCs, offering valuable insights for developing MBCs with superior adsorption performance to address heavy metal pollution in water. Moreover, the challenges and issues related to the process scalability of MBC for treating Pb-contaminated water were critically discussed.