Green efficient dual-strategy for critical metal recovery from spent LIBs: Nipa palm shell-derived cellulose and [C4H9NH3][Cyanex 272] ionic liquid extraction

Green and environmentally friendly natural adsorbents are prominent value-added products from agricultural waste materials. Herein, microcrystalline cellulose (MCC) was produced from nipa palm shells (with a purity of 96.2 %), and its application in the metal ion recovery was investigated. The surface morphology and chemical properties of the synthesized MCC were characterized using scanning electron microscopy and spectroscopic methods. While the as-synthesized MCC demonstrated effective metal adsorption capability, it exhibited low selectivity for nickel (II) ion (Ni²⁺) and cobalt (II) ion (Co²⁺). To overcome this limitation, we suggest the simultaneous use of the synthesized MCC as an adsorbent for lithium ion (Li⁺) and a n-butylamine phosphinate ionic liquid [C₄H₉NH₃][Cyanex 272] as an organic extractant for the efficient recovery of Ni²⁺ and Co²⁺ contained in spent lithium-ion batteries. Various parameters affecting the efficiency of the extraction process were optimized, including pH, reagent ratios and extraction time. The results revealed that using both MCC and [C₄H₉NH₃][Cyanex 272] ionic liquid considerably improved the metal extraction efficiency, especially for Co²⁺. The Ni²⁺ and Co²⁺ separation efficiency by the ionic liquid was found to be higher than 90 %, highlighting the potential of this combined strategy for recycling valuable metals from spent batteries.