Biochar, a promising material for environmental applications, is a carbon rich product obtained from biomass pyrolysis in a waste-to-resource process. This study focused on the evaluation of two biochars as adsorbents for lead removal. Biochar produced from almond hardwood (AB) and the modified material by oxidation with H2O2 (MAB) were characterized to document the chemical interactions controlling the adsorption process. The surface area increased from 55.61 to 101.42 m2g-1 after modification, with an increment of micropores higher than 300 %, as compared to the unmodified material. Results obtained from adsorption isotherms revealed that AB adsorption capacity was 40.32 mgg-1 while that of unmodified biochar was 24.81 mgg-1. Sequential extraction allowed to identify the mechanism of adsorption, showing that Pb+2 was mainly adsorbed on AB and MAB as non-bioavailable fraction (67.17% and 47.54%) indicating surface complexation; however, the acidic soluble fraction accounted for 45.26 in MAB, whereas only 28.08 % in AB, indicating that the modification promoted cation-π interactions instead of the preferred complexation, despite the increase in O-groups after modification (showed by Boehm titrations). The exchangeable fraction for both materials was between 4.76-7.19%, while the water-soluble fraction was insignificant, indicating that these materials show promise in various long-term environmental applications.

https://zoom.us/j/97592450412?pwd=eENVSmUvZFVoVE1GVVFaWG1waVc5UT09