Synergistic Se/S functionalization of biochar for effective immobilization of multi-target heavy metals in water and soil

Cadmium (Cd) and lead (Pb) contaminate aquatic environments and soil systems, threatening ecosystems and human health via bioaccumulation, while current remediation materials are often limited by insufficient adsorption capacity and restriction to a single medium. To address these challenges, a novel almond shell biochar co-functionalized with L -cysteine ( L -Cys) and selenium (Se) was prepared ( L -SeBC). This synergistic integration endows L -SeBC with abundant active sites for effective remediation. Adsorption thermodynamics demonstrated the maximum of 147.7 mg/g (Cd 2 + ) and 203.4 mg/g (Pb 2+ ). Density functional theory (DFT) calculations indicated that the enhanced adsorption occurred via chemisorption-physisorption synergy. In soil remediation experiments (5 % w/w L -SeBC application), the available Cd and Pb decreased by 45.1 % and 52.1 %. The addition of L -SeBC promoted soybean growth in contaminated soil, and reduced Cd and Pb contents in leaves (by 55.6 % and 68.9 %) and roots (by 28.6 % and 29.0 %). Furthermore, L -SeBC increased the activities of plant enzymes and soil enzymes, enhancing nutrient cycling and stress resistance of plants. Microbial analysis revealed that L -SeBC reshaped the soil microbiome by enriching functional genera (e.g., Pseudomonas spp.). Overall, the waste-derived, multifunctional adsorbent L -SeBC is cost-effective and eco-friendly, enables multi-scenario remediation, and exhibits great practical potential in sustainable pollution control.