Eco-friendly approach for the effective leaching of valuable metals (Ni, Co, Mn) from spent lithium-ion batteries employing natural reductants

Abstract

The widespread utilization of lithium-ion batteries (LIBs) in energy storage systems has led to an accumulation of discarded LIBs. Recycling has been implemented as a novel approach to alleviate the detrimental impacts of battery waste and facilitate the recovery of precious metals. This innovative method utilizes an eco-friendly hydrometallurgical process for metal leaching, employing biodegradable mixed organic acids, specifically citric acid (C.A.) and tartaric acid (T.A.), alongside sugarcane bagasse, an agricultural byproduct. These experiments indicate that around 84% of Ni, 88% of Co, 95% of Li, and 93% of Mn were extracted under optimal circumstances of 1.5 : 1.5 mol L⁻¹ mixed acids (C.A. : T.A.) concentration, 0.6 g g⁻¹ bagasse dose, 15 g L⁻¹ slurry density, 50 °C temperature, 50 minutes leaching duration, and 400 rpm agitation speed. Moreover, experimental findings validated that organic compounds in bagasse improved the leaching efficiencies of precious metals. The leaching kinetics governed by chemical reactions are accurately represented by an Avrami model, which provides apparent activation energies of 47 kJ mol⁻¹ for Co, 44 kJ mol⁻¹ for Li, 46 kJ mol⁻¹ for Mn, and 45 kJ mol⁻¹ for Ni. This process turns agricultural waste into a valuable asset, reducing the environmental impact of discarded lithium-ion batteries.