Recycling spent lithium-ion battery as adsorbents to remove aqueous heavy metals: Adsorption kinetics, isotherms, and regeneration assessment

Proper disposal and resource recovery of spent batteries are crucial for environmental protection and sustainability. This study evaluated the adsorption performances of spent lithium iron phosphate (SLFP) and spent lithium manganate (SLMO) cathodes as adsorbents toward heavy metals in water. The effects of adsorption time, initial adsorbate concentrations, and co-existing ions on adsorption kinetics were examined. SLFP and SLMO demonstrated outstanding adsorption capacities for heavy metals that were higher than or comparable with other reported adsorbents. SLFP shows adsorption capacities of 44.28, 39.54, 25.63, and 27.34 mg g⁻¹ for Cu²⁺, Pb²⁺, Cd²⁺ and Zn²⁺, respectively, SLMO achieved similar adsorption capacities (32.51, 31.83, 26.24 and 25.25 mg g⁻¹, respectively). Among different adsorption kinetics model, the pseudo-second-order model described heavy metals adsorption kinetics best with R² over 0.99, implying that chemisorption may be the predominant adsorption mechanism. The adsorption data at equilibrium well fitted the Langmuir isotherm model with R² over 0.96, suggesting that the adsorption process could be endothermic. Cathode materials from of SLIBs may be recycled as adsorbents for heavy metal removal from water, which supports the “waste to treat waste” concept.