Tailored activation of biochar and bone char for targeted removal of potentially toxic elements under controlled conditions

Abstract Biochar, a carbon-rich material produced from organic waste, has shown promise for soil remediation due to its ability to adsorb potentially toxic elements, with adsorption performance enhanced through activation processes. This study evaluated the effects of chemical and biological activation on two biochars produced from arid-zone biomass residues: pecan-pruning and bovine bones to assess potentially toxic elements removal improvement. Chemical activation was performed using NaOH (0.5, 1 and 2 M) at impregnation times ranging from 3–24 h, followed by thermal treatment. Bone char was biological activated using vermiwash, a vermicompost-derived solution. Both fresh and 10-month-stored extracts were applied with impregnation times of 6 and 24 h. Batch adsorption experiments assessed the removal of As, Pb (single-element systems), and Cd, Cu, Mn, and Zn (multi-element system) at concentrations of 100 mg L −1 , comparing activated and unmodified biomaterials. Chemical activation (0.5 M NaOH, 18 h, with thermal treatment) increased removal efficiency by up to 99%, with notable improvements for Mn (15%) and Cd (20%), although Pb removal was higher in unmodified biochar. Biological activation using stored vermiwash (10-month, 24 h) enhanced bone char’s removal efficiency by 91%, improving surface area, porosity, and functional groups, with the highest removal observed for Zn (17%) and Cu (29%). These results demonstrate the potential of locally sourced pecan pruning and bovine bones for potentially toxic elements remediation in arid regions and highlight the complexity of mixed-polluted systems, suggesting that combined use of activated biochar and bone char may provide a more effective and sustainable remediation strategy.