172-8 Engineering Biochar and Bone Char for Selective Immobilization of Heavy Metals Under Controlled Conditions

Session: Environmental Geochemistry and Health (Part II)

Presenting Author:

Mauricio Peregrina-Llanes

Authors:

Peregrina-Llanes, Mauricio¹, González-Méndez, Blanca², Loredo-Portales, René³, Molina-Freaner, Francisco⁴

(1) Posgrado en Ciencias de la Tierra, Instituto de Geología UNAM Estación Regional Noroeste, Hermosillo, Sonora, Mexico, (2) Instituto de Geología, Secihti-Instituto de Geología UNAM Estación Regional Noroeste, Hermosillo, Sonora, Mexico, (3) Instituto de Geología, UNAM Institutio de Geologia Estacion Regional Noroeste, Hermosillo, Sonora, Mexico; UNAM-LANGEM, Laboratorio Nacional de Geoquímica y Mineralogía, Ciudad de México, Mexico, Mexico, (4) Ecología de la Biodiversidad, Instituto de Ecología UNAM, Hermosillo, Sonora, Mexico,

Abstract:

Biochar, a carbon-based material derived from organic residues, offers a promising route for remediation of soil and water systems through its capacity to bind heavy metals, an ability that can be further enhanced via activation treatments. This study examined how chemical and biological activation influence the performance of two biochars generated from arid-zone biomass byproducts: pecan-pruning orchard residue and bovine femur bones in improving heavy metals immobilization. Chemical activation involved NaOH impregnation (0.5, 1, and 2 M) for periods of 3 to 24 h, followed by a thermal treatment step. Bone char was subjected to biological activation using vermiwash, a liquid byproduct of vermicomposting, applying both fresh and 10-month-aged extracts at 6- and 24-h impregnation intervals. Adsorption capacity was assessed through batch experiments targeting Pb (single-element solution) and Cd, Cu, Mn, and Zn (multi-element solution), each at 100 mg L⁻¹, comparing treated versus untreated materials. The chemically activated biochar (0.5 M NaOH, 18 h, plus thermal treatment) achieved enhanced immobilization with the largest increases observed for Mn (15%) and Cd (20%); notably, Pb removal was greater in the unmodified material. Biologically activated bone char (aged vermiwash, 24 h) improved immobilization efficiency, driven by gains in surface area, porosity, and surface functional groups, with the strongest effects seen for Cu (29%) and Zn (17%). Together, these findings support the viability of regionally sourced pecan pruning and bovine bone as low-cost remediation materials in arid environments, while underscoring the added complexity of multi-element contamination and the potential benefit of combining both activated biochar and bone char for more robust, sustainable remediation outcomes.

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