Sustainable Recovery of Spent Lithium–Ion Batteries using Green Solvents

Abstract

This study tackles both environmental and economic concerns by developing a sustainable, eco-friendly approach for recovering valuable metals from spent lithium-ion batteries (LIBs). Owing to their compact size, high energy density, and exceptional electrochemical properties, LIBs are widely used in electronic devices and electric vehicles. However, their end-of-life disposal poses significant environmental challenges. To address this, two green leaching systems were explored, utilizing citric acid as the lixiviant and fruit peel waste, specifically, blueberry lixiviant and citron peel powder as natural reductants, along with hydrogen peroxide (H 2 O 2 ) as an auxiliary reducing agent. Leaching efficiencies for cobalt (Co), lithium (Li), and manganese (Mn) using the blueberry-based lixiviant were optimized through key parameters: lixiviant concentration (5 g), citric acid concentration (1.5 M), temperature (70°C), reaction time (4 hours), and slurry density (25 g/mL). Among the two, citron peel exhibited superior overall performance. The reducing power of the fruit peel-based lixiviants was validated using 3,5-dinitrosalicylic acid (DNS) assays. Maximum recovery rates achieved were 46.44% for Co and 31.19% for Li, facilitated by selective precipitation in the citric acid system. Importantly, the solid residues generated during the process exhibited minimal cytotoxicity when tested on three human cell lines, indicating their environmental safety. This innovative green method not only advances sustainable recycling of LIBs using biodegradable fruit waste but also contributes to reducing the ecological footprint of electronic and organic waste, promoting circular economy principles and green chemistry initiatives.