Functionalized carbon nanotubes for selective lithium recovery from spent lithium-ion batteries: a sustainable approach to resource recycling

The intensive use of lithium-ion batteries (LIBs) has led to a surge in battery waste, which is a valuable secondary resource for metal recovery. Discarded LIBs, rich in critical metals like lithium and cobalt, offer a concentrated and economically attractive source, addressing supply limitations and environmental protection. The current study presents a novel, low-cost method for selectively recovering lithium ions from both synthetic solutions and LIB waste. Using a newly created adsorbent, mesoporous carbon nanotubes functionalized with aminomethylenephosphonic acid (CNT-AMP), lithium ions were selectively extracted. Extensive characterization of the structural and functional features of CNT-AMP and/or CNT-AMP/Li was carried out utilizing a variety of techniques, including FT-IR, XPS, BET, magnetization investigations, TEM, ¹H-NMR, ¹³C-NMR, and GC-MS. The ideal lithium recovery (299 mg g^-1) was obtained at 500 mg L^-1 lithium ions, 0.08 g CNT-AMP, pH 12, 25 °C, and 100 minutes of contact time. The adsorption behavior was highly consistent with the Langmuir and D-R models, indicating that chemisorption is the primary driving force behind the process. In an ideal setting, the recovery procedure produced 99.5% pure lithium carbonate (Li₂CO₃), which is confirmed by XRD and SEM, with a recovery efficiency of 95.76%. The results demonstrate that CNT-AMP can be utilized as a high-performance adsorbent for the sustainable recovery of lithium as a valuable recycling metal from battery waste. This helps conserve resources and promote environmental sustainability.