Lead, a commonly found heavy metal in contaminated soil, is highly mobilized in acidic conditions resulting to rapid soil leaching. This study investigated the effectiveness of biochar derived from Talisay ( Terminalia catappa ) seed husks employing the long-term immobilization of Lead in an artificially contaminated soil using simulated acid rain water meant for 100 years of rain with 5% amendment rate. Before immobilization, the heating temperatures were varied at 400, 500 and 600°C to determine its optimal pyrolysis temperature. The biochar was pyrolyzed under three different temperatures: with 1-hour residence time. SEM images revealed that the degree of porosity of the biochar produced increased as the temperature increased. In addition, the biochar produced at 600°C has the highest % fixed carbon and % elemental carbon indicating stability. It then shows that Talisay seed husks are feasible materials for biochar production that can be used for the amendment of lead contaminated soil. The Freundlich and Langmuir models were used to describe the heavy metal sorption equilibrium of the biochar. Results showed that the biochar best fitted the pseudo-second-order models and Langmuir isotherm models and that the biochar displayed a favorable adsorption. Also, the immobilization experiment showed that the soil amended with biochar immobilized Pb decreasing its concentration by 99.47%. Therefore, the produced biochar is suitable for Pb remediation in contaminated soils.
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