Targeted sequestration of antimony via adsorption-induced topological transformation on supramolecular...

The simultaneous and deep sequestration of multivalent antimony (Sb(III) and Sb(V)) from aquatic environments is strictly hindered by the "site-shielding effect", where the random agglomeration of functional groups limits active site accessibility. To address this, a novel supramolecular microcrystal-functionalized biochar (CPPB) was engineered by anchoring L-cysteine and polyethyleneimine onto a lignin-derived biochar matrix. Structural analysis confirmed the in-situ growth of well-ordered hexagonal L-cystine microcrystals within the hierarchical pores. CPPB exhibited exceptional maximum adsorption capacities of 513.5 mg/g for Sb(III) and 500.9 mg/g for Sb(V), with > 90% of the total capacity achieved within 10 min. The material maintained robust performance across a pH range of 3.0-8.0 and demonstrated high selectivity in complex wastewater matrices. Mechanistic investigations, integrating density functional theory calculations and multiscale spectroscopic analyses, unveiled a unique adsorption-induced topological transformation. Specifically, the intense coordination affinity between Sb species and active sites overcomes the lattice energy, triggering a transition of L-cystine from long-range ordered crystalline domains to short-range disordered open networks. This dynamic reconstruction effectively exposes previously shielded high-density sites (-SH, -NH, and -COO⁻) for multidentate coordination. Furthermore, the Sb-saturated CPPB was successfully upcycled into an SbPO₄/C composite via in-situ carbonization; as a sodium-ion battery anode, this recovered material delivered a stable capacity of 261.0 mA h/g after 60 cycles. This work provides a transformative strategy to unlock the latent thermodynamic potential of biochar-based materials and establishes a sustainable "waste-to-resource" closed-loop for heavy metal remediation.