Fungal hyphae upcycling: A green bio-adsorbent for sustainable lithium recovery from salt lake brines

Lithium is indispensable to national new energy strategy, with widespread applications in batteries, ceramics, pharmaceuticals, construction, and nuclear energy. Efficient extraction of lithium ion (Li(I)) from salt-lake brine using bio-based adsorbents is crucial for environmental protection and sustainable resource utilization. Comparative analyses of diverse fungal hyphae, combined with alkali-extracted chitin assays, have conclusively identified chitin as the critical functional component responsible for Li(I) adsorption. Nevertheless, the commercial application of biological adsorbents remains constrained by poorly understood adsorption mechanisms. Here, we systematically evaluated the adsorption performance of fungal hyphae under various physicochemical conditions. Physical and chemical properties of materials were characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Adsorption equilibrium was best described by the Langmuir model, yielding a maximum Li(I) adsorption capacity of 60.2 mg g ‒1 by the fungal hyphae. Kinetic data adhered to the pseudo-second-order model, confirming chemisorption as the primary mechanism. Cycling stability tests demonstrated 82.8% retention of initial adsorption capacity after seven adsorption-desorption cycles, highlighting outstanding regenerability. Molecular electrostatic potential (MEP) and molecular dynamics (MD) simulations further demonstrated that chitin, a key component in the hyphal cell wall, adsorbs Li(I) via electrostatic interactions, coordination with -OH and -NH 2 moieties, and multi-site hydrogen bonding. This work developed a cost-effective, high-performance bio-adsorbent for Li(I) and elucidated its multiscale adsorption mechanisms thereby providing a theoretical basis and practical guidance for the rational design of next-generation bio-adsorbents.