Interactions between Pb(II) and Cassava Residue Biochar: Adsorption, Complexation, and In Situ Application

The production of biochar through slow pyrolysis under controlled conditions represents a promising strategy for converting agro-industrial residues into functional materials for environmental remediation. This approach contributes to sustainability by providing an alternative to the disposal of waste with no specific application. In this context, the present study aimed to evaluate the interaction of cassava peel-derived biochars, produced at different pyrolysis temperatures (350 °C, 450 °C, 500 °C, and 550 °C), with lead (PbII) ions and to investigate their efficiency in removing this contaminant under environmentally relevant conditions. The biochars were characterized by elemental analysis. To assess their performance in Pb-(II) removal, adsorption isotherms, equilibrium time, complexation capacity, and in situ application tests were conducted. Elemental analysis revealed a clear influence of the pyrolysis temperature on the physicochemical properties of the biochars. Among the adsorption isotherm models tested, the Langmuir model provided the best fit to the experimental data, indicating that Pb-(II) adsorption occurs on a homogeneous monolayer surface without interactions between adsorbed ions. The maximum adsorption capacity for Pb-(II) reached 37.27 mg g^-1, a relatively high value compared to similar studies, and was obtained with biochar produced at the highest pyrolysis temperature (550 °C). The complexation capacity ranged from 37.60 to 39.11 mg g^-1. In the in situ application, the biochar produced at 550 °C using 200 mg exhibited the highest Pb-(II) retention (15.56 mg g^-1). Overall, cassava peel-derived biochars demonstrate considerable potential as low-cost, environmentally friendly materials for mitigating Pb-(II) contamination in aquatic environments.